Various scroll area fixes

9 files changed, 2672 insertions, 0 deletions

diff --git a/TODO b/TODO
new file mode 100644
index 0000000..fab63d0
--- /dev/null
+++ b/TODO
@@ -0,0 +1,4 @@
+- Think of a better name than oppress 
+  	- Populst?
+	- Demagogue?
+
diff --git a/backingstore.c b/backingstore.c
new file mode 100644
index 0000000..5e040c4
--- /dev/null
+++ b/backingstore.c
@@ -0,0 +1,263 @@
+#include "backingstore.h"
+
+struct BackingStore
+{
+    GdkPixmap *pixmap;
+    GdkRegion *update_region;
+    int width;
+    int height;
+};
+
+BackingStore *
+backing_store_new (GdkWindow *window,
+		   int        width,
+		   int        height)
+{
+    BackingStore *store = g_new0 (BackingStore, 1);
+    GdkRectangle rect = { 0, 0, width, height };
+    
+    store->pixmap = gdk_pixmap_new (window, width, height, -1);
+    store->update_region = gdk_region_rectangle (&rect);
+    store->width = width;
+    store->height = height;
+
+    return store;
+}
+
+void
+backing_store_free (BackingStore *store)
+{
+    g_object_unref (store->pixmap);
+    gdk_region_destroy (store->update_region);
+    g_free (store);
+}
+
+void
+backing_store_scroll (BackingStore *store,
+		      int           dx,
+		      int           dy)
+{
+    GdkGC *gc = gdk_gc_new (store->pixmap);
+    GdkRectangle rect;
+    
+    gdk_draw_drawable (store->pixmap, gc, store->pixmap,
+		       0, 0, dx, dy,
+		       store->width, store->height);
+
+    gdk_region_offset (store->update_region, dx, dy);
+    
+    /* Invalidate vertically */
+    rect.x = 0;
+    rect.width = store->width;
+
+    if (dy > 0)
+    {
+	rect.y = 0;
+	rect.height = dy;
+    }
+    else
+    {
+	rect.y = store->height + dy;
+	rect.height = -dy;
+    }
+
+    gdk_region_union_with_rect (store->update_region, &rect);
+    
+    /* Invalidate horizontally */
+    rect.y = 0;
+    rect.height = store->height;
+
+    if (dx > 0)
+    {
+	rect.x = 0;
+	rect.width = dx;
+    }
+    else
+    {
+	rect.x = store->width + dx;
+	rect.width = -dx;
+    }
+
+    gdk_region_union_with_rect (store->update_region, &rect);
+}
+
+static void
+print_region (const char *header, GdkRegion *region)
+{
+    GdkRectangle *rects;
+    int n_rects;
+    int i;
+    
+    g_print ("%s\n", header);
+    
+    gdk_region_get_rectangles (region, &rects, &n_rects);
+    for (i = 0; i < n_rects; ++i)
+    {
+	GdkRectangle *rect = &(rects[i]);
+	g_print ("  %d %d %d %d\n",
+		 rect->x, rect->y, rect->width, rect->height);
+    }
+
+    g_free (rects);
+}
+
+void
+backing_store_invalidate_rect (BackingStore *store,
+			       GdkRectangle *rect)
+{
+    g_return_if_fail (store != NULL);
+    g_return_if_fail (rect != NULL);
+    
+    gdk_region_union_with_rect (store->update_region, rect);
+}
+
+void
+backing_store_invalidate_region (BackingStore *store,
+				 GdkRegion    *region)
+{
+    g_return_if_fail (store != NULL);
+    g_return_if_fail (region != NULL);
+    
+    gdk_region_union (store->update_region, region);
+}
+
+void
+backing_store_invalidate_all (BackingStore *store)
+{
+    GdkRectangle rect;
+
+    g_return_if_fail (store != NULL);
+    
+    gdk_region_destroy (store->update_region);
+    
+    rect.x = 0;
+    rect.y = 0;
+    rect.width = store->width;
+    rect.height = store->height;
+
+    store->update_region = gdk_region_rectangle (&rect);
+}
+
+static void
+simple_draw_drawable (GdkDrawable *dst,
+		      GdkDrawable *src,
+		      int	   src_x,
+		      int	   src_y,
+		      int          dst_x,
+		      int          dst_y,
+		      int          width,
+		      int          height)
+{
+    GdkGC *gc = gdk_gc_new (dst);
+
+    gdk_draw_drawable (dst, gc, src, src_x, src_y, dst_x, dst_y, width, height);
+
+    g_object_unref (gc);
+}
+
+void
+backing_store_resize (BackingStore    *store,
+		      int              width,
+		      int              height)
+{
+    GdkPixmap *pixmap;
+    GdkRegion *old, *invalid;
+    GdkRectangle r;
+
+    width = MAX (width, 1);
+    height = MAX (height, 1);
+
+    pixmap = gdk_pixmap_new (store->pixmap, width, height, -1);
+    
+    /* Unfortunately we don't know in which direction we were resized,
+     * so we just assume we were dragged from the south-east corner.
+     *
+     * Although, maybe we could get the root coordinates of the input-window?
+     * That might just work, actually. We need to make sure metacity uses
+     * static gravity for the window before this will be useful.
+     */
+    simple_draw_drawable (pixmap, store->pixmap, 0, 0, 0, 0, -1, -1);
+
+    g_object_unref (store->pixmap);
+
+    store->pixmap = pixmap;
+
+    r.x = r.y = 0;
+    r.height = store->height;
+    r.width = store->width;
+    
+    old = gdk_region_rectangle (&r);
+    
+    store->width = width;
+    store->height = height;
+
+    r.height = store->height;
+    r.width = store->width;
+    
+    invalid = gdk_region_rectangle (&r);
+
+    gdk_region_subtract (invalid, old);
+
+    backing_store_invalidate_region (store, invalid);
+
+    gdk_region_destroy (old);
+    gdk_region_destroy (invalid);
+}
+
+
+static void
+cclip_to_region (cairo_t *cr, GdkRegion *region)
+{
+    int n_rects;
+    GdkRectangle *rects;
+
+    gdk_region_get_rectangles (region, &rects, &n_rects);
+
+    cairo_new_path (cr);
+    while (n_rects--)
+    {
+	GdkRectangle *rect = &(rects[n_rects]);
+
+	cairo_rectangle (cr, rect->x, rect->y, rect->width, rect->height);
+    }
+    cairo_clip (cr);
+
+    g_free (rects);
+}
+
+void
+backing_store_draw (BackingStore *store, 
+		    GdkDrawable  *dest,
+		    GdkRegion    *clip,
+		    int           dest_x,
+		    int           dest_y)
+{
+    GdkGC *gc = gdk_gc_new (dest);
+
+    gdk_gc_set_clip_region (gc, clip);
+
+    gdk_draw_drawable (dest, gc, store->pixmap,
+		       0, 0, dest_x, dest_y, store->width, store->height);
+    g_object_unref (gc);
+}
+
+void
+backing_store_process_updates (BackingStore       *store,
+			       BackingPaintFunc    func,
+			       gpointer            data)
+{
+    cairo_t *cr = gdk_cairo_create (store->pixmap);
+    GdkRegion *region = store->update_region;
+    store->update_region = gdk_region_new ();
+
+    cclip_to_region (cr, region);
+
+    cairo_set_source_rgb (cr, g_random_double(), 0, 0);
+
+    cairo_paint (cr);
+    
+    func (cr, region, data);
+
+    gdk_region_destroy (region);
+    cairo_destroy (cr);
+}
diff --git a/backingstore.h b/backingstore.h
new file mode 100644
index 0000000..2d39214
--- /dev/null
+++ b/backingstore.h
@@ -0,0 +1,35 @@
+#include <gtk/gtk.h>
+#include <gdk/gdk.h>
+#include <cairo.h>
+
+typedef struct BackingStore BackingStore;
+
+typedef void     (* BackingPaintFunc) (cairo_t   *cr,
+				       GdkRegion *region,
+				       gpointer   data);
+typedef gboolean (* BackingInputFunc) (gpointer   input_data,
+				       gpointer   user_data);
+
+BackingStore *backing_store_new                   (GdkWindow       *window,
+						   int              width,
+						   int              height);
+void	      backing_store_free                  (BackingStore    *store);
+void          backing_store_draw                  (BackingStore    *store, 
+						   GdkDrawable     *dest,
+						   GdkRegion       *clip,
+						   int              dest_x,
+						   int              dest_y);
+void          backing_store_scroll                (BackingStore    *store,
+						   int              dx,
+						   int              dy);
+void          backing_store_invalidate_rect       (BackingStore    *store,
+						   GdkRectangle    *rect);
+void          backing_store_invalidate_region     (BackingStore    *store,
+						   GdkRegion       *region);
+void          backing_store_invalidate_all        (BackingStore    *store);
+void          backing_store_resize                (BackingStore    *store,
+						   int              width,
+						   int              height);
+void          backing_store_process_updates       (BackingStore    *store,
+						   BackingPaintFunc func,
+						   gpointer         data);
diff --git a/build.sh b/build.sh
new file mode 100755
index 0000000..b6662d6
--- /dev/null
+++ b/build.sh
@@ -0,0 +1,8 @@
+gcc -Wall -g						\
+    `pkg-config --cflags --libs gtk+-2.0 libglade-2.0`	\
+    -DGLADE_FILE=\"oppress.glade\"			\
+							\
+    scrollarea.c					\
+    foo-marshal.c					\
+    main.c						\
+    backingstore.c
\ No newline at end of file
diff --git a/deck.h b/deck.h
new file mode 100644
index 0000000..f457f35
--- /dev/null
+++ b/deck.h
@@ -0,0 +1,7 @@
+typedef struct Deck Deck;
+typedef struct Slide Slide;
+
+Deck * deck_new           (void);
+int    deck_get_n_slides  (Deck *deck);
+Slide *deck_get_nth_slide (Deck *deck,
+			   int   n);
diff --git a/main.c b/main.c
new file mode 100644
index 0000000..88fd969
--- /dev/null
+++ b/main.c
@@ -0,0 +1,114 @@
+#include <gtk/gtk.h>
+#include <glade/glade.h>
+#include <glib/gprintf.h>
+#include <stdlib.h>
+#include <string.h>
+#include <math.h>
+#include "scrollarea.h"
+
+typedef struct
+{
+    GladeXML *		xml;
+    GtkWidget *		main_area;
+    GtkWidget *		thumbnails;
+} App;
+
+static void *
+get_widget (App *app, const char *name)
+{
+    void *result = glade_xml_get_widget (app->xml, name);
+
+    if (!result)
+	g_error ("Could not find widget %s\n", name);
+
+    return result;
+}
+
+static void
+on_thumbs_paint (FooScrollArea *scroll_area,
+	       cairo_t	     *cr,
+	       GdkRectangle  *extents,
+	       GdkRegion     *region,
+	       gpointer       data)
+{
+    g_print ("paint thumbs\n");
+}
+	
+
+static void
+on_main_paint (FooScrollArea *scroll_area,
+	       cairo_t	     *cr,
+	       GdkRectangle  *extents,
+	       GdkRegion     *region,
+	       gpointer       data)
+{
+    g_print ("paint %d %d %d %d\n", extents->x, extents->y, extents->width, extents->height);
+}
+
+static void
+set_size (GtkWindow *window)
+{
+    GdkScreen *screen;
+    int monitor_num;
+    GdkRectangle monitor;
+    int width, height;
+    GtkWidget *widget = GTK_WIDGET (window);
+    
+    screen = gtk_widget_get_screen (widget);
+    monitor_num = gdk_screen_get_monitor_at_window (screen, widget->window);
+    
+    gdk_screen_get_monitor_geometry (screen, monitor_num, &monitor);
+    
+    width = monitor.width * 3 / 4;
+    height = monitor.height * 3 / 4;
+    
+    gtk_window_resize (window, width, height);
+}
+
+static void
+on_viewport_changed (FooScrollArea *scroll_area, 
+                     GdkRectangle  *viewport,
+                     GdkRectangle  *old_viewport)
+{
+    foo_scroll_area_set_size (scroll_area, 800, 30);
+}
+
+int
+main (int argc, char **argv)
+{
+    App *app;
+    
+    gtk_init (&argc, &argv);
+
+    app = g_new0 (App, 1);
+    app->xml = glade_xml_new (GLADE_FILE, NULL, NULL);
+    
+    app->main_area = foo_scroll_area_new();
+    app->thumbnails = foo_scroll_area_new();
+
+    gtk_container_add (
+	GTK_CONTAINER (get_widget (app, "main_area_scrolled_window")),
+	app->main_area);
+
+    gtk_container_add (
+	GTK_CONTAINER (get_widget (app, "thumbnails_scrolled_window")),
+	app->thumbnails);
+
+    foo_scroll_area_set_size (app->main_area, 80, 30);
+    foo_scroll_area_set_min_size (app->thumbnails, 200, -1);
+
+    g_signal_connect (app->main_area, "paint",
+		      G_CALLBACK (on_main_paint), app);
+#if 0
+    g_signal_connect (app->main_area, "viewport_changed",
+		      G_CALLBACK (on_viewport_changed), app);
+#endif
+    
+    g_signal_connect (app->thumbnails, "paint",
+		      G_CALLBACK (on_thumbs_paint), app);
+
+    set_size (get_widget (app, "main_window"));
+    gtk_widget_show_all (get_widget (app, "main_window"));
+    
+    gtk_main ();
+}
diff --git a/oppress.glade b/oppress.glade
new file mode 100644
index 0000000..43c3412
--- /dev/null
+++ b/oppress.glade
@@ -0,0 +1,429 @@
+<?xml version="1.0" standalone="no"?> <!--*- mode: xml -*-->
+<!DOCTYPE glade-interface SYSTEM "http://glade.gnome.org/glade-2.0.dtd">
+
+<glade-interface>
+
+<widget class="GtkWindow" id="main_window">
+  <property name="visible">True</property>
+  <property name="title" translatable="yes">Oppress</property>
+  <property name="type">GTK_WINDOW_TOPLEVEL</property>
+  <property name="window_position">GTK_WIN_POS_NONE</property>
+  <property name="modal">False</property>
+  <property name="resizable">True</property>
+  <property name="destroy_with_parent">False</property>
+  <property name="decorated">True</property>
+  <property name="skip_taskbar_hint">False</property>
+  <property name="skip_pager_hint">False</property>
+  <property name="type_hint">GDK_WINDOW_TYPE_HINT_NORMAL</property>
+  <property name="gravity">GDK_GRAVITY_NORTH_WEST</property>
+  <property name="focus_on_map">True</property>
+  <property name="urgency_hint">False</property>
+
+  <child>
+    <widget class="GtkVBox" id="vbox1">
+      <property name="visible">True</property>
+      <property name="homogeneous">False</property>
+      <property name="spacing">0</property>
+
+      <child>
+	<widget class="GtkMenuBar" id="menubar1">
+	  <property name="visible">True</property>
+	  <property name="pack_direction">GTK_PACK_DIRECTION_LTR</property>
+	  <property name="child_pack_direction">GTK_PACK_DIRECTION_LTR</property>
+
+	  <child>
+	    <widget class="GtkMenuItem" id="menuitem1">
+	      <property name="visible">True</property>
+	      <property name="label" translatable="yes">_File</property>
+	      <property name="use_underline">True</property>
+
+	      <child>
+		<widget class="GtkMenu" id="menu1">
+
+		  <child>
+		    <widget class="GtkImageMenuItem" id="new1">
+		      <property name="visible">True</property>
+		      <property name="label">gtk-new</property>
+		      <property name="use_stock">True</property>
+		      <signal name="activate" handler="on_new1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+
+		  <child>
+		    <widget class="GtkImageMenuItem" id="open1">
+		      <property name="visible">True</property>
+		      <property name="label">gtk-open</property>
+		      <property name="use_stock">True</property>
+		      <signal name="activate" handler="on_open1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+
+		  <child>
+		    <widget class="GtkImageMenuItem" id="save1">
+		      <property name="visible">True</property>
+		      <property name="label">gtk-save</property>
+		      <property name="use_stock">True</property>
+		      <signal name="activate" handler="on_save1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+
+		  <child>
+		    <widget class="GtkImageMenuItem" id="save_as1">
+		      <property name="visible">True</property>
+		      <property name="label">gtk-save-as</property>
+		      <property name="use_stock">True</property>
+		      <signal name="activate" handler="on_save_as1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+
+		  <child>
+		    <widget class="GtkSeparatorMenuItem" id="separatormenuitem1">
+		      <property name="visible">True</property>
+		    </widget>
+		  </child>
+
+		  <child>
+		    <widget class="GtkImageMenuItem" id="quit1">
+		      <property name="visible">True</property>
+		      <property name="label">gtk-quit</property>
+		      <property name="use_stock">True</property>
+		      <signal name="activate" handler="on_quit1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+		</widget>
+	      </child>
+	    </widget>
+	  </child>
+
+	  <child>
+	    <widget class="GtkMenuItem" id="menuitem2">
+	      <property name="visible">True</property>
+	      <property name="label" translatable="yes">_Edit</property>
+	      <property name="use_underline">True</property>
+
+	      <child>
+		<widget class="GtkMenu" id="menu2">
+
+		  <child>
+		    <widget class="GtkImageMenuItem" id="cut1">
+		      <property name="visible">True</property>
+		      <property name="label">gtk-cut</property>
+		      <property name="use_stock">True</property>
+		      <signal name="activate" handler="on_cut1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+
+		  <child>
+		    <widget class="GtkImageMenuItem" id="copy1">
+		      <property name="visible">True</property>
+		      <property name="label">gtk-copy</property>
+		      <property name="use_stock">True</property>
+		      <signal name="activate" handler="on_copy1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+
+		  <child>
+		    <widget class="GtkImageMenuItem" id="paste1">
+		      <property name="visible">True</property>
+		      <property name="label">gtk-paste</property>
+		      <property name="use_stock">True</property>
+		      <signal name="activate" handler="on_paste1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+
+		  <child>
+		    <widget class="GtkImageMenuItem" id="delete1">
+		      <property name="visible">True</property>
+		      <property name="label">gtk-delete</property>
+		      <property name="use_stock">True</property>
+		      <signal name="activate" handler="on_delete1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+		</widget>
+	      </child>
+	    </widget>
+	  </child>
+
+	  <child>
+	    <widget class="GtkMenuItem" id="menuitem3">
+	      <property name="visible">True</property>
+	      <property name="label" translatable="yes">_View</property>
+	      <property name="use_underline">True</property>
+
+	      <child>
+		<widget class="GtkMenu" id="menu3">
+		</widget>
+	      </child>
+	    </widget>
+	  </child>
+
+	  <child>
+	    <widget class="GtkMenuItem" id="menuitem4">
+	      <property name="visible">True</property>
+	      <property name="label" translatable="yes">_Help</property>
+	      <property name="use_underline">True</property>
+
+	      <child>
+		<widget class="GtkMenu" id="menu4">
+
+		  <child>
+		    <widget class="GtkMenuItem" id="about1">
+		      <property name="visible">True</property>
+		      <property name="label" translatable="yes">_About</property>
+		      <property name="use_underline">True</property>
+		      <signal name="activate" handler="on_about1_activate" last_modification_time="Wed, 04 Jun 2008 03:11:49 GMT"/>
+		    </widget>
+		  </child>
+		</widget>
+	      </child>
+	    </widget>
+	  </child>
+	</widget>
+	<packing>
+	  <property name="padding">0</property>
+	  <property name="expand">False</property>
+	  <property name="fill">False</property>
+	</packing>
+      </child>
+
+      <child>
+	<widget class="GtkHBox" id="hbox1">
+	  <property name="visible">True</property>
+	  <property name="homogeneous">False</property>
+	  <property name="spacing">0</property>
+
+	  <child>
+	    <widget class="GtkToolbar" id="toolbar1">
+	      <property name="visible">True</property>
+	      <property name="orientation">GTK_ORIENTATION_VERTICAL</property>
+	      <property name="toolbar_style">GTK_TOOLBAR_BOTH_HORIZ</property>
+	      <property name="tooltips">True</property>
+	      <property name="show_arrow">False</property>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton2">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes">Text</property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton1">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes">Curve</property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		  <property name="group">radiotoolbutton2</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton3">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes">New slide</property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		  <property name="group">radiotoolbutton2</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton4">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes"></property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		  <property name="group">radiotoolbutton2</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton5">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes"></property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		  <property name="group">radiotoolbutton2</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton6">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes"></property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		  <property name="group">radiotoolbutton2</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton7">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes"></property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		  <property name="group">radiotoolbutton2</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton8">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes"></property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		  <property name="group">radiotoolbutton2</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton9">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes"></property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		  <property name="group">radiotoolbutton2</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+
+	      <child>
+		<widget class="GtkRadioToolButton" id="radiotoolbutton10">
+		  <property name="visible">True</property>
+		  <property name="label" translatable="yes"></property>
+		  <property name="use_underline">True</property>
+		  <property name="visible_horizontal">True</property>
+		  <property name="visible_vertical">True</property>
+		  <property name="is_important">False</property>
+		  <property name="active">False</property>
+		  <property name="group">radiotoolbutton2</property>
+		</widget>
+		<packing>
+		  <property name="expand">False</property>
+		  <property name="homogeneous">True</property>
+		</packing>
+	      </child>
+	    </widget>
+	    <packing>
+	      <property name="padding">0</property>
+	      <property name="expand">False</property>
+	      <property name="fill">False</property>
+	    </packing>
+	  </child>
+
+	  <child>
+	    <widget class="GtkScrolledWindow" id="main_area_scrolled_window">
+	      <property name="visible">True</property>
+	      <property name="can_focus">True</property>
+	      <property name="hscrollbar_policy">GTK_POLICY_AUTOMATIC</property>
+	      <property name="vscrollbar_policy">GTK_POLICY_AUTOMATIC</property>
+	      <property name="shadow_type">GTK_SHADOW_NONE</property>
+	      <property name="window_placement">GTK_CORNER_TOP_LEFT</property>
+
+	      <child>
+		<placeholder/>
+	      </child>
+	    </widget>
+	    <packing>
+	      <property name="padding">0</property>
+	      <property name="expand">True</property>
+	      <property name="fill">True</property>
+	    </packing>
+	  </child>
+
+	  <child>
+	    <widget class="GtkScrolledWindow" id="thumbnails_scrolled_window">
+	      <property name="visible">True</property>
+	      <property name="can_focus">True</property>
+	      <property name="hscrollbar_policy">GTK_POLICY_NEVER</property>
+	      <property name="vscrollbar_policy">GTK_POLICY_ALWAYS</property>
+	      <property name="shadow_type">GTK_SHADOW_NONE</property>
+	      <property name="window_placement">GTK_CORNER_TOP_LEFT</property>
+
+	      <child>
+		<placeholder/>
+	      </child>
+	    </widget>
+	    <packing>
+	      <property name="padding">0</property>
+	      <property name="expand">False</property>
+	      <property name="fill">True</property>
+	    </packing>
+	  </child>
+	</widget>
+	<packing>
+	  <property name="padding">0</property>
+	  <property name="expand">True</property>
+	  <property name="fill">True</property>
+	</packing>
+      </child>
+    </widget>
+  </child>
+</widget>
+
+</glade-interface>
diff --git a/scrollarea.c b/scrollarea.c
new file mode 100644
index 0000000..c4a6954
--- /dev/null
+++ b/scrollarea.c
@@ -0,0 +1,1705 @@
+#include <gdk/gdkprivate.h> /* For GDK_PARENT_RELATIVE_BG */
+#include <gdk/gdkx.h>
+#include <X11/Xlib.h>
+#include "scrollarea.h"
+#include "foo-marshal.h"
+#include "backingstore.h"
+
+
+G_DEFINE_TYPE (FooScrollArea, foo_scroll_area, GTK_TYPE_CONTAINER);
+
+static GtkWidgetClass *parent_class;
+
+typedef struct InputPath InputPath;
+typedef struct InputRegion InputRegion;
+typedef struct AutoScrollInfo AutoScrollInfo;
+
+struct InputPath
+{
+    gboolean			is_stroke;
+    cairo_fill_rule_t		fill_rule;
+    double			line_width;
+    cairo_path_t	       *path;		/* In canvas coordinates */
+
+    FooScrollAreaEventFunc	func;
+    gpointer			data;
+
+    InputPath		       *next;
+};
+
+/* InputRegions are mutually disjoint */
+struct InputRegion
+{
+    GdkRegion *region;		/* the boundary of this area in
+				 * canvas coordinates
+				 */
+    InputPath *paths;
+};
+
+struct AutoScrollInfo
+{
+    int				dx;
+    int				dy;
+    int				timeout_id;
+    int				begin_x;
+    int				begin_y;
+    double			res_x;
+    double			res_y;
+    GTimer		       *timer;
+};
+
+struct FooScrollAreaPrivate
+{
+    int				width;
+    int				height;
+    
+    GtkAdjustment	       *hadj;
+    GtkAdjustment	       *vadj;
+    int			        x_offset;
+    int				y_offset;
+    
+    int				min_width;
+    int				min_height;
+
+    GPtrArray		       *input_regions;
+    
+    AutoScrollInfo	       *auto_scroll_info;
+    
+    /* During expose, this region is set to the region
+     * being exposed. At other times, it is NULL
+     *
+     * It is used for clipping of input areas
+     */
+    InputRegion		       *current_input;
+    
+    gboolean			grabbed;
+    FooScrollAreaEventFunc	grab_func;
+    gpointer			grab_data;
+
+    BackingStore	       *store;
+    
+    guint32			motion_notify_time;
+};
+
+enum
+{
+    VIEWPORT_CHANGED,
+    PAINT,
+    INPUT,
+    LAST_SIGNAL,
+};
+
+static guint signals [LAST_SIGNAL] = { 0 };
+
+static void     foo_scroll_area_size_request           (GtkWidget        *widget,
+							GtkRequisition   *requisition);
+static gboolean foo_scroll_area_expose                 (GtkWidget        *widget,
+							GdkEventExpose   *expose);
+static void     foo_scroll_area_size_allocate          (GtkWidget        *widget,
+							GtkAllocation    *allocation);
+static void     foo_scroll_area_set_scroll_adjustments (FooScrollArea    *scroll_area,
+							GtkAdjustment    *hadj,
+							GtkAdjustment    *vadj);
+static void     foo_scroll_area_realize                (GtkWidget        *widget);
+static void     foo_scroll_area_unrealize              (GtkWidget        *widget);
+static void     foo_scroll_area_map                    (GtkWidget        *widget);
+static void     foo_scroll_area_unmap                  (GtkWidget        *widget);
+static gboolean foo_scroll_area_button_press           (GtkWidget        *widget,
+							GdkEventButton   *event);
+static gboolean foo_scroll_area_button_release         (GtkWidget        *widget,
+							GdkEventButton   *event);
+static gboolean foo_scroll_area_motion                 (GtkWidget        *widget,
+							GdkEventMotion   *event);
+static gboolean foo_scroll_area_crossing               (GtkWidget        *widget,
+							GdkEventCrossing *event);
+
+
+static void
+foo_scroll_area_map (GtkWidget *widget)
+{
+    FooScrollArea *area = FOO_SCROLL_AREA (widget);
+    
+    GTK_WIDGET_CLASS (parent_class)->map (widget);
+    
+#if 0
+    if (area->priv->input_window)
+	gdk_window_show (area->priv->input_window);
+#endif
+}
+
+static void
+foo_scroll_area_unmap (GtkWidget *widget)
+{
+    FooScrollArea *area = FOO_SCROLL_AREA (widget);
+    
+#if 0
+    if (area->priv->input_window)
+	gdk_window_hide (area->priv->input_window);
+#endif
+    
+    GTK_WIDGET_CLASS (parent_class)->unmap (widget);
+}
+
+static void
+foo_scroll_area_finalize (GObject *object)
+{
+    FooScrollArea *scroll_area = FOO_SCROLL_AREA (object);
+    
+    g_object_unref (scroll_area->priv->hadj);
+    g_object_unref (scroll_area->priv->vadj);
+    
+    g_ptr_array_free (scroll_area->priv->input_regions, TRUE);
+    
+    g_free (scroll_area->priv);
+
+    G_OBJECT_CLASS (foo_scroll_area_parent_class)->finalize (object);
+}
+
+static void
+foo_scroll_area_class_init (FooScrollAreaClass *class)
+{
+    GObjectClass *object_class = G_OBJECT_CLASS (class);
+    GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
+    
+    object_class->finalize = foo_scroll_area_finalize;
+    widget_class->size_request = foo_scroll_area_size_request;
+    widget_class->expose_event = foo_scroll_area_expose;
+    widget_class->size_allocate = foo_scroll_area_size_allocate;
+    widget_class->realize = foo_scroll_area_realize;
+    widget_class->unrealize = foo_scroll_area_unrealize;
+    widget_class->button_press_event = foo_scroll_area_button_press;
+    widget_class->button_release_event = foo_scroll_area_button_release;
+    widget_class->motion_notify_event = foo_scroll_area_motion;
+    widget_class->enter_notify_event = foo_scroll_area_crossing;
+    widget_class->leave_notify_event = foo_scroll_area_crossing;
+    widget_class->map = foo_scroll_area_map;
+    widget_class->unmap = foo_scroll_area_unmap;
+    
+    class->set_scroll_adjustments = foo_scroll_area_set_scroll_adjustments;
+    
+    parent_class = g_type_class_peek_parent (class);
+    
+    signals[VIEWPORT_CHANGED] =
+	g_signal_new ("viewport_changed",
+		      G_OBJECT_CLASS_TYPE (object_class),
+		      G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION,
+		      G_STRUCT_OFFSET (FooScrollAreaClass,
+				       viewport_changed),
+		      NULL, NULL,
+		      foo_marshal_VOID__BOXED_BOXED,
+		      G_TYPE_NONE, 2,
+		      GDK_TYPE_RECTANGLE,
+		      GDK_TYPE_RECTANGLE);
+    
+    signals[PAINT] =
+	g_signal_new ("paint",
+		      G_OBJECT_CLASS_TYPE (object_class),
+		      G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION,
+		      G_STRUCT_OFFSET (FooScrollAreaClass,
+				       paint),
+		      NULL, NULL,
+		      foo_marshal_VOID__POINTER_BOXED_POINTER,
+		      G_TYPE_NONE, 3,
+		      G_TYPE_POINTER,
+		      GDK_TYPE_RECTANGLE, 
+		      G_TYPE_POINTER);
+    
+    widget_class->set_scroll_adjustments_signal =
+	g_signal_new ("set_scroll_adjustments",
+		      G_OBJECT_CLASS_TYPE (object_class),
+		      G_SIGNAL_RUN_LAST | G_SIGNAL_ACTION,
+		      G_STRUCT_OFFSET (FooScrollAreaClass,
+				       set_scroll_adjustments),
+		      NULL, NULL,
+		      foo_marshal_VOID__OBJECT_OBJECT,
+		      G_TYPE_NONE, 2,
+		      GTK_TYPE_ADJUSTMENT,
+		      GTK_TYPE_ADJUSTMENT);
+}
+
+static GtkAdjustment *
+new_adjustment (void)
+{
+    return GTK_ADJUSTMENT (gtk_adjustment_new (0.0, 0.0, 0.0, 0.0, 0.0, 0.0));
+}
+
+static void
+foo_scroll_area_init (FooScrollArea *scroll_area)
+{
+#if 0
+    GTK_WIDGET_SET_FLAGS (scroll_area, GTK_NO_WINDOW);
+#endif
+    
+    gtk_widget_set_redraw_on_allocate (GTK_WIDGET (scroll_area), FALSE);
+    
+    scroll_area->priv = g_new0 (FooScrollAreaPrivate, 1);
+    scroll_area->priv->width = 0;
+    scroll_area->priv->height = 0;
+    scroll_area->priv->hadj = g_object_ref_sink (new_adjustment());
+    scroll_area->priv->vadj = g_object_ref_sink (new_adjustment());
+    scroll_area->priv->x_offset = 0.0;
+    scroll_area->priv->y_offset = 0.0;
+    scroll_area->priv->min_width = -1;
+    scroll_area->priv->min_height = -1;
+    scroll_area->priv->auto_scroll_info = NULL;
+    scroll_area->priv->input_regions = g_ptr_array_new ();
+
+    gtk_widget_set_double_buffered (GTK_WIDGET (scroll_area), FALSE);
+}
+
+static void
+translate_cairo_device (cairo_t       *cr,
+			int            x_offset,
+			int            y_offset)
+{
+    cairo_surface_t *surface = cairo_get_target (cr);
+    double dev_x;
+    double dev_y;
+    
+    cairo_surface_get_device_offset (surface, &dev_x, &dev_y);
+    dev_x += x_offset;
+    dev_y += y_offset;
+    cairo_surface_set_device_offset (surface, dev_x, dev_y);
+}
+
+#if 0
+static void
+print_region (const char *header, GdkRegion *region)
+{
+    GdkRectangle *rects;
+    int n_rects;
+    int i;
+    
+    g_print ("%s\n", header);
+    
+    gdk_region_get_rectangles (region, &rects, &n_rects);
+    for (i = 0; i < n_rects; ++i)
+    {
+	GdkRectangle *rect = &(rects[i]);
+	g_print ("  %d %d %d %d\n",
+		 rect->x, rect->y, rect->width, rect->height);
+    }
+}
+#endif
+
+typedef void (* PathForeachFunc) (double  *x,
+				  double  *y,
+				  gpointer data);
+
+static void
+path_foreach_point (cairo_path_t     *path,
+		    PathForeachFunc   func,
+		    gpointer	      user_data)
+{
+    int i;
+    
+    for (i = 0; i < path->num_data; i += path->data[i].header.length)
+    {
+	cairo_path_data_t *data = &(path->data[i]);
+	
+	switch (data->header.type)
+	{
+	case CAIRO_PATH_MOVE_TO:
+	case CAIRO_PATH_LINE_TO:
+	    func (&(data[1].point.x), &(data[1].point.y), user_data);
+	    break;
+	    
+	case CAIRO_PATH_CURVE_TO:
+	    func (&(data[1].point.x), &(data[1].point.y), user_data);
+	    func (&(data[2].point.x), &(data[2].point.y), user_data);
+	    func (&(data[3].point.x), &(data[3].point.y), user_data);
+	    break;
+	    
+	case CAIRO_PATH_CLOSE_PATH:
+	    break;
+	}
+    }
+}
+
+typedef struct
+{
+    double x1, y1, x2, y2;
+} Box;
+
+#if 0
+static void
+update_box (double *x, double *y, gpointer data)
+{
+    Box *box = data;
+    
+    if (*x < box->x1)
+	box->x1 = *x;
+
+    if (*y < box->y1)
+	box->y1 = *y;
+
+    if (*y > box->y2)
+	box->y2 = *y;
+    
+    if (*x > box->x2)
+	box->x2 = *x;
+}
+#endif
+
+#if 0
+static void
+path_compute_extents (cairo_path_t *path,
+		      GdkRectangle *rect)
+{
+    if (rect)
+    {
+	Box box = { G_MAXDOUBLE, G_MAXDOUBLE, G_MINDOUBLE, G_MINDOUBLE };
+
+	path_foreach_point (path, update_box, &box);
+
+	rect->x = box.x1;
+	rect->y = box.y1;
+	rect->width = box.x2 - box.x1;
+	rect->height = box.y2 - box.y1;
+    }
+}
+#endif
+
+static void
+input_path_free_list (InputPath *paths)
+{
+    if (!paths)
+	return;
+
+    input_path_free_list (paths->next);
+    cairo_path_destroy (paths->path);
+    g_free (paths);
+}
+
+static void
+input_region_free (InputRegion *region)
+{
+    input_path_free_list (region->paths);
+    gdk_region_destroy (region->region);
+
+    g_free (region);
+}
+
+static void
+get_viewport (FooScrollArea *scroll_area,
+	      GdkRectangle  *viewport)
+{
+    GtkWidget *widget = GTK_WIDGET (scroll_area);
+    
+    viewport->x = scroll_area->priv->x_offset;
+    viewport->y = scroll_area->priv->y_offset;
+    viewport->width = widget->allocation.width;
+    viewport->height = widget->allocation.height;
+}
+
+static void
+allocation_to_canvas (FooScrollArea *area,
+		      int           *x,
+		      int           *y)
+{
+    *x += area->priv->x_offset;
+    *y += area->priv->y_offset;
+}
+
+static void
+clear_exposed_input_region (FooScrollArea *area,
+			    GdkRegion *exposed)	/* in canvas coordinates */
+{
+    int i;
+    GdkRegion *viewport_reg;
+    GdkRectangle viewport;
+
+    get_viewport (area, &viewport);
+    
+    viewport_reg = gdk_region_rectangle (&viewport);
+    gdk_region_subtract (viewport_reg, exposed);
+    
+    for (i = 0; i < area->priv->input_regions->len; ++i)
+    {
+	InputRegion *region = area->priv->input_regions->pdata[i];
+
+	gdk_region_intersect (region->region, viewport_reg);
+
+	if (gdk_region_empty (region->region))
+	{
+	    input_region_free (region);
+	    g_ptr_array_remove_index_fast (area->priv->input_regions, i--);
+	}
+    }
+
+    gdk_region_destroy (viewport_reg);
+}
+
+static void
+setup_background_cr (GdkWindow *window,
+		     cairo_t   *cr,
+		     int        x_offset,
+		     int        y_offset)
+{
+    GdkWindowObject *private = (GdkWindowObject *)window;
+    
+    if (private->bg_pixmap == GDK_PARENT_RELATIVE_BG && private->parent)
+    {
+	x_offset += private->x;
+	y_offset += private->y;
+	
+	setup_background_cr (GDK_WINDOW (private->parent), cr, x_offset, y_offset);
+    }
+    else if (private->bg_pixmap &&
+	     private->bg_pixmap != GDK_PARENT_RELATIVE_BG &&
+	     private->bg_pixmap != GDK_NO_BG)
+    {
+	gdk_cairo_set_source_pixmap (cr, private->bg_pixmap, -x_offset, -y_offset);
+    }
+    else
+    {
+	gdk_cairo_set_source_color (cr, &private->bg_color);
+    }
+}
+
+static void
+canvas_to_window (FooScrollArea *area,
+		  GdkRegion *region)
+{
+    GtkWidget *widget = GTK_WIDGET (area);
+    
+    gdk_region_offset (region,
+		       -area->priv->x_offset,
+		       -area->priv->y_offset);
+}
+
+static void
+window_to_canvas (FooScrollArea *area,
+		  GdkRegion *region)
+{
+    GtkWidget *widget = GTK_WIDGET (area);
+
+    gdk_region_offset (region,
+		       area->priv->x_offset,
+		       area->priv->y_offset);
+}
+
+static void
+canvas_to_store (FooScrollArea *area,
+		 GdkRegion *region)
+{
+    gdk_region_offset (region, -area->priv->x_offset, -area->priv->y_offset);
+		       
+}
+
+static void
+store_to_canvas (FooScrollArea *area,
+		 GdkRegion *region)
+{
+    gdk_region_offset (region, area->priv->x_offset, area->priv->y_offset);
+}
+
+static gboolean paint_updates = FALSE;
+
+static void
+paint_region (FooScrollArea *area, GdkRegion *region, double r, double g, double b, double a)
+{
+    cairo_t *cr = gdk_cairo_create (GTK_WIDGET (area)->window);
+    gdk_cairo_region (cr, region);
+    cairo_clip (cr);
+    
+    cairo_set_source_rgba (cr, r, g, b, a);
+    
+    cairo_paint (cr);
+    
+    cairo_destroy (cr);
+}
+
+static void
+do_exposes (cairo_t *cr,
+	    GdkRegion *store_region,
+	    gpointer data)
+{
+    FooScrollArea *scroll_area = data;
+    GdkRegion *region;
+    GdkRectangle rect;
+    GdkRegion *r;
+
+    /* Paint background */
+    setup_background_cr (GTK_WIDGET (scroll_area)->window, cr, 0, 0);
+    cairo_paint (cr);
+
+    if (paint_updates)
+	paint_region (scroll_area, store_region, 0.2, 0.2, 0.8, 0.4);
+    
+    /* Note that this function can be called at a time
+     * where the adj->value is different from x_offset. 
+     * Ie., the GtkScrolledWindow changed the adj->value
+     * without emitting the value_changed signal. 
+     *
+     * Hence we must always use the value we got 
+     * the last time the signal was emitted, ie.,
+     * priv->{x,y}_offset.
+     */
+    region = gdk_region_copy (store_region);
+
+    store_to_canvas (scroll_area, region);
+
+    /* Set up input areas */
+    clear_exposed_input_region (scroll_area, region);
+    
+    scroll_area->priv->current_input = g_new0 (InputRegion, 1);
+    scroll_area->priv->current_input->region = gdk_region_copy (region);
+    scroll_area->priv->current_input->paths = NULL;
+    g_ptr_array_add (scroll_area->priv->input_regions,
+		     scroll_area->priv->current_input);
+
+    /* Set up cairo context and emit the signal */
+    translate_cairo_device (cr,
+			    -scroll_area->priv->x_offset,
+			    -scroll_area->priv->y_offset);
+
+    /* Restrict to the actual canvas */
+    rect.x = 0;
+    rect.y = 0;
+    rect.width = scroll_area->priv->width;
+    rect.height = scroll_area->priv->height;
+
+    r = gdk_region_rectangle (&rect);
+    gdk_region_intersect (region, r);
+    gdk_region_destroy (r);
+    
+    if (!gdk_region_empty (region))
+    {
+	gdk_region_get_clipbox (region, &rect);
+
+	g_signal_emit (scroll_area, signals[PAINT], 0, cr, &rect, region);
+    }
+    
+    scroll_area->priv->current_input = NULL;
+    gdk_region_destroy (region);
+}
+
+static gboolean
+foo_scroll_area_expose (GtkWidget *widget,
+			GdkEventExpose *expose)
+{
+    FooScrollArea *area = FOO_SCROLL_AREA (widget);
+
+    backing_store_process_updates (area->priv->store, do_exposes, area);
+
+    if (paint_updates)
+    {
+	paint_region (area, expose->region, 0.8, 0.2, 0.2, 0.4);
+    
+	gdk_flush ();
+	g_usleep (70000);
+    }
+    
+    backing_store_draw (area->priv->store, widget->window,
+			expose->region, 0, 0);
+
+    return TRUE;
+}
+
+void
+foo_scroll_area_get_viewport (FooScrollArea *scroll_area,
+			      GdkRectangle  *viewport)
+{
+    g_return_if_fail (FOO_IS_SCROLL_AREA (scroll_area));
+    
+    if (!viewport)
+	return;
+    
+    get_viewport (scroll_area, viewport);
+}
+
+static void
+process_event (FooScrollArea	       *scroll_area,
+	       FooScrollAreaEventType	input_type,
+	       int			x,
+	       int			y,
+	       int			button);
+
+static void
+emit_viewport_changed (FooScrollArea *scroll_area,
+		       GdkRectangle  *new_viewport,
+		       GdkRectangle  *old_viewport)
+{
+    int px, py;
+
+    g_signal_emit (scroll_area, signals[VIEWPORT_CHANGED], 0, 
+		   new_viewport, old_viewport);
+
+    if (new_viewport->x != old_viewport->x		||
+	new_viewport->y != old_viewport->y		||
+	new_viewport->width != old_viewport->width	||
+	new_viewport->height != old_viewport->height)
+    {
+	gdk_window_get_pointer (GTK_WIDGET (scroll_area)->window, &px, &py, NULL);
+	
+	process_event (scroll_area, FOO_MOTION, px, py, 0);
+    }
+}
+
+static void
+clamp_adjustment (GtkAdjustment *adj)
+{
+    double old_value = adj->value;
+    
+    if (adj->upper >= adj->page_size)
+	adj->value = CLAMP (adj->value, 0.0, adj->upper - adj->page_size);
+    else
+	adj->value = 0.0;
+    
+    if (old_value != adj->value)
+	gtk_adjustment_value_changed (adj);
+    
+    gtk_adjustment_changed (adj);
+}
+
+static gboolean
+set_adjustment_values (FooScrollArea *scroll_area)
+{
+    GtkAllocation *allocation = &GTK_WIDGET (scroll_area)->allocation;
+    
+    GtkAdjustment *hadj = scroll_area->priv->hadj;
+    GtkAdjustment *vadj = scroll_area->priv->vadj;
+    
+    /* Horizontal */
+    hadj->page_size = allocation->width;
+    hadj->step_increment = 0.1 * allocation->width;
+    hadj->page_increment = 0.9 * allocation->width;
+    hadj->lower = 0.0;
+    hadj->upper = scroll_area->priv->width;
+    
+    /* Vertical */
+    vadj->page_size = allocation->height;
+    vadj->step_increment = 0.1 * allocation->height;
+    vadj->page_increment = 0.9 * allocation->height;
+    vadj->lower = 0.0;
+    vadj->upper = scroll_area->priv->height;
+    
+    clamp_adjustment (hadj);
+    clamp_adjustment (vadj);
+    
+    return TRUE;
+}
+
+static void
+foo_scroll_area_realize (GtkWidget *widget)
+{
+    FooScrollArea *area = FOO_SCROLL_AREA (widget);
+    GdkWindowAttr attributes;
+    gint attributes_mask;
+
+    g_print ("realizing\n");
+    
+    GTK_WIDGET_SET_FLAGS (widget, GTK_REALIZED);
+    
+    attributes.window_type = GDK_WINDOW_CHILD;
+    attributes.x = widget->allocation.x;
+    attributes.y = widget->allocation.y;
+    attributes.width = widget->allocation.width;
+    attributes.height = widget->allocation.height;
+    attributes.wclass = GDK_INPUT_OUTPUT;
+    attributes.event_mask = gtk_widget_get_events (widget);
+    attributes.event_mask |= (GDK_BUTTON_PRESS_MASK |
+			      GDK_BUTTON_RELEASE_MASK |
+			      GDK_BUTTON1_MOTION_MASK |
+			      GDK_BUTTON2_MOTION_MASK |
+			      GDK_BUTTON3_MOTION_MASK |
+			      GDK_POINTER_MOTION_MASK |
+			      GDK_EXPOSURE_MASK |
+			      GDK_ENTER_NOTIFY_MASK |
+			      GDK_LEAVE_NOTIFY_MASK);
+    attributes.visual = gtk_widget_get_visual (widget);
+    attributes.colormap = gtk_widget_get_colormap (widget);
+    
+    attributes_mask = GDK_WA_X | GDK_WA_Y | GDK_WA_VISUAL | GDK_WA_COLORMAP;
+    
+    widget->window = gdk_window_new (gtk_widget_get_parent_window (widget),
+				     &attributes, attributes_mask);
+    gdk_window_set_user_data (widget->window, area);
+    
+    area->priv->store = backing_store_new (widget->window, widget->allocation.width,
+					   widget->allocation.height);
+
+    widget->style = gtk_style_attach (widget->style, widget->window);
+
+    gtk_style_set_background (widget->style, widget->window, GTK_STATE_NORMAL);
+}
+
+static void
+foo_scroll_area_unrealize (GtkWidget *widget)
+{
+    FooScrollArea *area = FOO_SCROLL_AREA (widget);
+    
+#if 0
+    if (area->priv->input_window)
+    {
+	gdk_window_set_user_data (area->priv->input_window, NULL);
+	gdk_window_destroy (area->priv->input_window);
+	area->priv->input_window = NULL;
+    }
+#endif
+
+    backing_store_free (area->priv->store);
+    
+    GTK_WIDGET_CLASS (parent_class)->unrealize (widget);
+}
+
+static void
+allocation_to_canvas_region (FooScrollArea *area,
+			     GdkRegion *region)
+{
+    gdk_region_offset (region, area->priv->x_offset, area->priv->y_offset);
+}
+			     
+
+static void
+foo_scroll_area_size_allocate (GtkWidget     *widget,
+			       GtkAllocation *allocation)
+{
+    FooScrollArea *scroll_area = FOO_SCROLL_AREA (widget);
+    GdkRectangle new_viewport;
+    GdkRectangle old_viewport;
+    GdkRegion *old_allocation;
+    GdkRegion *invalid;
+
+    get_viewport (scroll_area, &old_viewport);
+    
+    widget->allocation = *allocation;
+    
+    if (GTK_WIDGET_REALIZED (widget))
+    {
+	gdk_window_move_resize (widget->window,
+				allocation->x, allocation->y,
+				allocation->width, allocation->height);
+
+	/* FIXME: We should possibly restrict the size of the
+	 * backing store to be not more than the size of
+	 * the area itself. The only problem with that is that
+	 * we still need to paint the background of the exposed
+	 * areas outside the area.
+	 */
+	backing_store_resize (scroll_area->priv->store,
+			      widget->allocation.width,
+			      widget->allocation.height);
+    }
+
+    set_adjustment_values (scroll_area);
+    
+    get_viewport (scroll_area, &new_viewport);
+
+    emit_viewport_changed (scroll_area, &new_viewport, &old_viewport);
+}
+
+static void
+emit_input (FooScrollArea *scroll_area,
+	    FooScrollAreaEventType type,
+	    int			   x,
+	    int			   y,
+	    int			   button,
+	    FooScrollAreaEventFunc func,
+	    gpointer		data)
+{
+    FooScrollAreaEvent event;
+    
+    if (!func)
+	return;
+
+    if (type != FOO_MOTION)
+	emit_input (scroll_area, FOO_MOTION, x, y, button, func, data);
+    
+#if 0
+    x += scroll_area->priv->x_offset;
+    y += scroll_area->priv->y_offset;
+#endif
+    
+    event.type = type;
+    event.x = x;
+    event.y = y;
+    event.button = button;
+    
+    func (scroll_area, &event, data);
+}
+
+#if 0
+static void
+print_path (const char *header,
+	    cairo_path_t *path)
+{
+    int i;
+
+    g_print ("%s\n", header);
+
+    for (i=0; i < path->num_data; i += path->data[i].header.length)
+    {
+	cairo_path_data_t *data = &(path->data[i]);
+	
+	switch (data->header.type)
+	{
+	case CAIRO_PATH_MOVE_TO:
+	    g_print ("move to:    %f, %f\n", data[1].point.x, data[1].point.y);
+	    break;
+	    
+	case CAIRO_PATH_LINE_TO:
+	    g_print ("line to:    %f, %f\n", data[1].point.x, data[1].point.y);
+	    break;
+	    
+	case CAIRO_PATH_CURVE_TO:
+	    g_print ("curve to:   %f, %f\n", data[1].point.x, data[1].point.y);
+	    g_print ("            %f, %f\n", data[1].point.x, data[1].point.y);
+	    g_print ("            %f, %f\n", data[1].point.x, data[1].point.y);
+	    break;
+	    
+	case CAIRO_PATH_CLOSE_PATH:
+	    break;
+	}
+    }
+}
+#endif
+
+static void
+process_event (FooScrollArea	       *scroll_area,
+	       FooScrollAreaEventType	input_type,
+	       int			x,
+	       int			y,
+	       int			button)
+{
+    GtkWidget *widget = GTK_WIDGET (scroll_area);
+    int i;
+
+    allocation_to_canvas (scroll_area, &x, &y);
+    
+    if (scroll_area->priv->grabbed)
+    {
+	emit_input (scroll_area, input_type, x, y, button,
+		    scroll_area->priv->grab_func,
+		    scroll_area->priv->grab_data);
+	return;
+    }
+
+    
+#if 0
+    x += widget->allocation.x;
+    y += widget->allocation.y;
+#endif
+
+#if 0
+    g_print ("number of input regions: %d\n", scroll_area->priv->input_regions->len);
+#endif
+    
+    for (i = 0; i < scroll_area->priv->input_regions->len; ++i)
+    {
+	InputRegion *region = scroll_area->priv->input_regions->pdata[i];
+
+#if 0
+	g_print ("%d ", i);
+	print_region ("region:", region->region);
+#endif
+	
+	if (gdk_region_point_in (region->region, x, y))
+	{
+	    InputPath *path;
+	    int n_paths = 0;
+
+	    path = region->paths;
+	    while (path)
+	    {
+		cairo_t *cr;
+		gboolean inside;
+
+		cr = gdk_cairo_create (widget->window);
+		cairo_set_fill_rule (cr, path->fill_rule);
+		cairo_set_line_width (cr, path->line_width);
+		cairo_append_path (cr, path->path);
+
+		if (path->is_stroke)
+		    inside = cairo_in_stroke (cr, x, y);
+		else
+		    inside = cairo_in_fill (cr, x, y);
+
+		cairo_destroy (cr);
+		
+		if (inside)
+		{
+		    emit_input (scroll_area, input_type,
+				x, y, button,
+				path->func,
+				path->data);
+		    return;
+		}
+		
+		path = path->next;
+		n_paths++;
+	    }
+
+	    /* Since the regions are all disjoint, no other region
+	     * can match. Of course we could be clever and try and
+	     * sort the regions, but so far I have been unable to
+	     * make this loop show up on a profile.
+	     */
+	    return;
+	}
+    }
+}
+
+static void
+process_gdk_event (FooScrollArea *scroll_area,
+		   int		  x,
+		   int	          y,
+		   GdkEvent      *event)
+{
+    FooScrollAreaEventType input_type = FOO_BUTTON_PRESS;
+    int button = 0;
+    
+    if (event->type == GDK_BUTTON_PRESS)
+    {
+	input_type = FOO_BUTTON_PRESS;
+	button = event->button.button;
+    }
+    else if (event->type == GDK_BUTTON_RELEASE)
+    {
+	input_type = FOO_BUTTON_RELEASE;
+	button = event->button.button;
+    }
+    else if (event->type == GDK_MOTION_NOTIFY	||
+	     event->type == GDK_LEAVE_NOTIFY	||
+	     event->type == GDK_ENTER_NOTIFY)
+    {
+	input_type = FOO_MOTION;
+	button = 0;
+    }
+    
+    process_event (scroll_area, input_type, x, y, button);
+}
+
+static gboolean
+foo_scroll_area_button_press (GtkWidget *widget,
+			      GdkEventButton *event)
+{
+    FooScrollArea *area = FOO_SCROLL_AREA (widget);
+    
+    process_gdk_event (area, event->x, event->y, (GdkEvent *)event);
+    
+    return TRUE;
+}
+
+static gboolean
+foo_scroll_area_button_release (GtkWidget *widget,
+				GdkEventButton *event)
+{
+    FooScrollArea *area = FOO_SCROLL_AREA (widget);
+
+    process_gdk_event (area, event->x, event->y, (GdkEvent *)event);
+    
+    return FALSE;
+}
+
+typedef struct
+{
+    Window	window;
+    guint32	last_motion_time;
+    gboolean	stop_compressing;
+} EventScannerData;
+
+static Bool
+get_motion_time (Display  *dpy,
+		 XEvent   *xevent,
+		 XPointer  arg)
+{
+    EventScannerData *esd = (EventScannerData *)arg;
+  
+    if (esd->stop_compressing)
+	return FALSE;
+
+    if (esd->window != xevent->xany.window)
+    {
+	esd->stop_compressing = TRUE;
+	return FALSE;
+    }
+
+    if (xevent->type == MotionNotify)
+    {
+	esd->last_motion_time = xevent->xmotion.time;
+	return FALSE;
+    }
+
+    if (xevent->type == EnterNotify		||
+	xevent->type == LeaveNotify)
+    {
+	esd->last_motion_time = xevent->xcrossing.time;
+	return FALSE;
+    }
+    
+    return FALSE;
+}
+
+static gboolean
+use_this_motion_notify (GdkWindow *window,
+			guint32    event_time,
+			guint32	  *motion_notify_time)
+{
+    if (*motion_notify_time)
+    {
+	if (event_time == *motion_notify_time)
+	{
+	    *motion_notify_time = 0;
+
+	    return TRUE;
+	}
+	else
+	{
+	    /* There are more motion events already queued up */
+	    
+	    return FALSE;
+	}
+    }
+    else
+    {
+	Display *dpy = gdk_x11_get_default_xdisplay();
+	EventScannerData esd = { GDK_WINDOW_XWINDOW (window), 0, FALSE };
+	XEvent dummy;
+    
+	XCheckIfEvent (dpy, &dummy, get_motion_time, (XPointer)&esd);
+	
+	if (esd.last_motion_time == 0)
+	{
+	    return TRUE;
+	}
+	else
+	{
+	    *motion_notify_time = esd.last_motion_time;
+	    return FALSE;
+	}
+    }
+}
+
+static gboolean
+foo_scroll_area_motion (GtkWidget *widget,
+			GdkEventMotion *event)
+{
+    FooScrollArea *area = FOO_SCROLL_AREA (widget);
+
+    if (use_this_motion_notify (event->window,
+				event->time,
+				&(area->priv->motion_notify_time)))
+    {
+	process_gdk_event (area, event->x, event->y, (GdkEvent *)event);
+    }
+    
+    return TRUE;
+}
+
+static gboolean
+foo_scroll_area_crossing (GtkWidget *widget,
+			  GdkEventCrossing *event)
+{
+    FooScrollArea *area = FOO_SCROLL_AREA (widget);
+
+    if (use_this_motion_notify (event->window,
+				event->time,
+				&(area->priv->motion_notify_time)))
+    {
+	process_gdk_event (area, event->x, event->y, (GdkEvent *)event);
+    }
+    
+    return TRUE;
+}
+
+void
+foo_scroll_area_set_size_fixed_y (FooScrollArea	       *scroll_area,
+				  int			width,
+				  int			height,
+				  int			old_y,
+				  int			new_y)
+{
+    int dy = new_y - old_y;
+    
+    scroll_area->priv->width = width;
+    scroll_area->priv->height = height;
+    
+#if 0
+    g_print ("diff: %d\n", new_y - old_y);
+#endif
+    
+    scroll_area->priv->vadj->value += dy;
+    
+    set_adjustment_values (scroll_area);
+    
+    if (dy != 0)
+	gtk_adjustment_value_changed  (scroll_area->priv->vadj);
+}
+
+void
+foo_scroll_area_set_size (FooScrollArea	       *scroll_area,
+			  int			width,
+			  int			height)
+{
+    g_return_if_fail (FOO_IS_SCROLL_AREA (scroll_area));
+    
+    /* FIXME: Default scroll algorithm should probably be to
+     * keep the same *area* outside the screen as before.
+     *
+     * For wrapper widgets that will do something roughly
+     * right. For widgets that don't change size, it
+     * will do the right thing. Except for idle-layouting
+     * widgets.
+     *
+     * Maybe there should be some generic support for those
+     * widgets. Can that even be done?
+     *
+     * Should we have a version of this function using 
+     * fixed points?
+     */
+    
+    scroll_area->priv->width = width;
+    scroll_area->priv->height = height;
+    
+    set_adjustment_values (scroll_area);
+}
+
+static void
+foo_scroll_area_size_request (GtkWidget      *widget,
+			      GtkRequisition *requisition)
+{
+    FooScrollArea *scroll_area = FOO_SCROLL_AREA (widget);
+    
+    requisition->width = scroll_area->priv->min_width;
+    requisition->height = scroll_area->priv->min_height;
+    
+#if 0
+    g_print ("request %d %d\n", requisition->width, requisition->height);
+#endif
+}
+
+static void
+foo_scrollbar_adjustment_changed (GtkAdjustment *adj,
+				  FooScrollArea *scroll_area)
+{
+    GtkWidget *widget = GTK_WIDGET (scroll_area);
+    gint dx = 0;
+    gint dy = 0;
+    GdkRectangle old_viewport, new_viewport;
+
+    /* FIXME: When dragging diagonally, this function will be called
+     * twice, causing two separate scrolls in the backing store.
+     *
+     * On the other hand with the constant time scrolling, it shouldn't
+     * really matter.
+     */
+    get_viewport (scroll_area, &old_viewport);
+    
+    if (adj == scroll_area->priv->hadj)
+    {
+	/* FIXME: do we treat the offset as int or double, and,
+	 * if int, how do we round?
+	 */
+	dx = (int)adj->value - scroll_area->priv->x_offset;
+	scroll_area->priv->x_offset = adj->value;
+    }
+    else if (adj == scroll_area->priv->vadj)
+    {
+	dy = (int)adj->value - scroll_area->priv->y_offset;
+	scroll_area->priv->y_offset = adj->value;
+    }
+    else
+    {
+	g_assert_not_reached ();
+    }
+    
+    if (GTK_WIDGET_REALIZED (widget) && (dx || dy))
+    {
+	backing_store_scroll (scroll_area->priv->store, -dx, -dy);
+
+	gtk_widget_queue_draw (GTK_WIDGET (scroll_area));
+    }
+    
+    get_viewport (scroll_area, &new_viewport);
+    
+    emit_viewport_changed (scroll_area, &new_viewport, &old_viewport);
+}
+
+static void
+set_one_adjustment (FooScrollArea *scroll_area,
+		    GtkAdjustment *adjustment,
+		    GtkAdjustment **location)
+{
+    g_return_if_fail (location != NULL);
+    
+    if (adjustment == *location)
+	return;
+    
+    if (!adjustment)
+	adjustment = new_adjustment ();
+    
+    g_return_if_fail (GTK_IS_ADJUSTMENT (adjustment));
+    
+    if (*location)
+    {
+	g_signal_handlers_disconnect_by_func (
+	    *location, foo_scrollbar_adjustment_changed, scroll_area);
+	
+	g_object_unref (*location);
+    }
+    
+    *location = adjustment;
+    
+    g_object_ref_sink (*location);
+    
+    g_signal_connect (*location, "value_changed",
+		      G_CALLBACK (foo_scrollbar_adjustment_changed),
+		      scroll_area);
+}
+
+static void
+foo_scroll_area_set_scroll_adjustments (FooScrollArea *scroll_area,
+					GtkAdjustment *hadjustment,
+					GtkAdjustment *vadjustment)
+{
+    set_one_adjustment (scroll_area, hadjustment, &scroll_area->priv->hadj);
+    set_one_adjustment (scroll_area, vadjustment, &scroll_area->priv->vadj);
+    
+    set_adjustment_values (scroll_area);
+}
+
+FooScrollArea *
+foo_scroll_area_new (void)
+{
+    return g_object_new (FOO_TYPE_SCROLL_AREA, NULL);
+}
+
+void
+foo_scroll_area_set_min_size (FooScrollArea *scroll_area,
+			      int		   min_width,
+			      int            min_height)
+{
+    scroll_area->priv->min_width = min_width;
+    scroll_area->priv->min_height = min_height;
+    
+    /* FIXME: think through invalidation.
+     *
+     * Goals: - no repainting everything on size_allocate(),
+     *        - make sure input boxes are invalidated when
+     *          needed
+     */
+    gtk_widget_queue_resize (GTK_WIDGET (scroll_area));
+}
+
+#if 0
+static void
+warn_about_adding_input_outside_expose (const char *func)
+{
+    static gboolean warned = FALSE;
+    
+    if (!warned)
+    {
+	g_warning ("%s() can only be called "
+		   "from the paint handler for the FooScrollArea\n", func);
+	
+	warned = TRUE;
+    }
+}
+#endif
+
+static void
+user_to_device (double *x, double *y,
+		gpointer data)
+{
+    cairo_t *cr = data;
+    
+    cairo_user_to_device (cr, x, y);
+}
+
+static void
+add_path (FooScrollArea *area,
+	   cairo_t *cr,
+	   gboolean is_stroke,
+	   FooScrollAreaEventFunc func,
+	   gpointer data)
+{
+    InputPath *path = g_new0 (InputPath, 1);
+#if 0
+    double x1, y1, x2, y2;
+    GdkRectangle r;
+
+    if (is_stroke)
+	cairo_stroke_extents (cr, &x1, &y1, &x2, &y2);
+    else
+	cairo_fill_extents (cr, &x1, &y1, &x2, &y2);
+
+    cairo_user_to_device (cr, &x1, &y1);
+    cairo_user_to_device (cr, &x2, &y2);
+    
+    r.x = x1 - 1;
+    r.y = y1 - 1;
+    r.width = x2 - x1 + 1;
+    r.height = y2 - y1 + 1;
+
+    if (gdk_region_rect_in (area->priv->current_input->region, &r) != GDK_OVERLAP_RECTANGLE_OUT)
+    {
+#endif
+	path->is_stroke = is_stroke;
+	path->fill_rule = cairo_get_fill_rule (cr);
+	path->line_width = cairo_get_line_width (cr);
+	path->path = cairo_copy_path (cr);
+	path_foreach_point (path->path, user_to_device, cr);
+	path->func = func;
+	path->data = data;
+	path->next = area->priv->current_input->paths;
+	area->priv->current_input->paths = path;
+#if 0
+    }
+#endif
+    
+    return path;
+}
+
+/* FIXME: we probably really want a
+ *
+ *	foo_scroll_area_add_input_from_fill (area, cr, ...);
+ * and
+ *      foo_scroll_area_add_input_from_stroke (area, cr, ...);
+ * as well.
+ */
+void
+foo_scroll_area_add_input_from_fill (FooScrollArea           *scroll_area,
+				     cairo_t	             *cr,
+				     FooScrollAreaEventFunc   func,
+				     gpointer                 data)
+{
+    g_return_if_fail (FOO_IS_SCROLL_AREA (scroll_area));
+    g_return_if_fail (cr != NULL);
+    g_return_if_fail (scroll_area->priv->current_input);
+
+    add_path (scroll_area, cr, FALSE, func, data);
+}
+
+void
+foo_scroll_area_add_input_from_stroke (FooScrollArea           *scroll_area,
+				       cairo_t	                *cr,
+				       FooScrollAreaEventFunc   func,
+				       gpointer                 data)
+{
+    g_return_if_fail (FOO_IS_SCROLL_AREA (scroll_area));
+    g_return_if_fail (cr != NULL);
+    g_return_if_fail (scroll_area->priv->current_input);
+
+    add_path (scroll_area, cr, TRUE, func, data);
+}
+
+void
+foo_scroll_area_invalidate_region (FooScrollArea *area,
+				   GdkRegion     *region)
+{
+    g_return_if_fail (FOO_IS_SCROLL_AREA (area));
+
+    if (GTK_WIDGET_REALIZED (area))
+    {
+	canvas_to_store (area, region);
+	backing_store_invalidate_region (area->priv->store, region);
+	store_to_canvas (area, region);
+
+	canvas_to_window (area, region);
+	gdk_window_invalidate_region (GTK_WIDGET (area)->window, region, TRUE);
+	window_to_canvas (area, region);
+    }
+}
+
+void
+foo_scroll_area_invalidate_rect (FooScrollArea *scroll_area,
+				 int	        x,
+				 int	        y,
+				 int	        width,
+				 int	        height)
+{
+    GdkRectangle rect = { x, y, width, height };
+    GdkRegion *region;
+    
+    g_return_if_fail (FOO_IS_SCROLL_AREA (scroll_area));
+
+    region = gdk_region_rectangle (&rect);
+
+    foo_scroll_area_invalidate_region (scroll_area, region);
+
+    gdk_region_destroy (region);
+}
+
+void
+foo_scroll_area_invalidate (FooScrollArea *scroll_area)
+{
+    GtkWidget *widget = GTK_WIDGET (scroll_area);
+
+    foo_scroll_area_invalidate_rect (scroll_area,
+				     scroll_area->priv->x_offset, scroll_area->priv->y_offset,
+				     widget->allocation.width,
+				     widget->allocation.height);
+}
+
+void
+foo_scroll_area_begin_grab (FooScrollArea *scroll_area,
+			    FooScrollAreaEventFunc func,
+			    gpointer       input_data)
+{
+    g_return_if_fail (FOO_IS_SCROLL_AREA (scroll_area));
+    g_return_if_fail (!scroll_area->priv->grabbed);
+    
+    scroll_area->priv->grabbed = TRUE;
+    scroll_area->priv->grab_func = func;
+    scroll_area->priv->grab_data = input_data;
+    
+    /* FIXME: we should probably take a server grab */
+    /* Also, maybe there should be support for setting the grab cursor */
+}
+
+void
+foo_scroll_area_end_grab (FooScrollArea *scroll_area)
+{
+    g_return_if_fail (FOO_IS_SCROLL_AREA (scroll_area));
+    
+    scroll_area->priv->grabbed = FALSE;
+    scroll_area->priv->grab_func = NULL;
+    scroll_area->priv->grab_data = NULL;
+}
+
+gboolean
+foo_scroll_area_is_grabbed (FooScrollArea *scroll_area)
+{
+    return scroll_area->priv->grabbed;
+}
+
+void
+foo_scroll_area_set_viewport_pos (FooScrollArea  *scroll_area,
+				  int		  x,
+				  int		  y)
+{
+    int x_changed;
+    int y_changed;
+    GtkAdjustment *hadj, *vadj;
+
+    hadj = scroll_area->priv->hadj;
+    vadj = scroll_area->priv->vadj;
+
+    x_changed = (int)hadj->value != x;
+    y_changed = (int)vadj->value != y;
+
+    hadj->value = x;
+    vadj->value = y;
+
+    set_adjustment_values (scroll_area);
+
+    if (x_changed && hadj->upper >= hadj->page_size)
+    {
+#if 0
+	g_print ("changed x\n");
+#endif
+	gtk_adjustment_value_changed (hadj);
+    }
+    
+    if (y_changed && vadj->upper >= vadj->page_size)
+    {
+#if 0
+	g_print ("changed y\n");
+#endif
+	gtk_adjustment_value_changed (vadj);
+    }
+}
+
+static gboolean
+rect_contains (const GdkRectangle *rect, int x, int y)
+{
+    return (x >= rect->x		&&
+	    y >= rect->y		&&
+	    x  < rect->x + rect->width	&&
+	    y  < rect->y + rect->height);
+}
+
+static void
+stop_scrolling (FooScrollArea *area)
+{
+#if 0
+    g_print ("stop scrolling\n");
+#endif
+    if (area->priv->auto_scroll_info)
+    {
+	g_source_remove (area->priv->auto_scroll_info->timeout_id);
+	g_timer_destroy (area->priv->auto_scroll_info->timer);
+	g_free (area->priv->auto_scroll_info);
+	
+	area->priv->auto_scroll_info = NULL;
+    }
+}
+
+static gboolean
+scroll_idle (gpointer data)
+{
+    GdkRectangle viewport, new_viewport;
+    FooScrollArea *area = data;
+    AutoScrollInfo *info = area->priv->auto_scroll_info;
+#if 0
+    int dx, dy;
+#endif
+    int new_x, new_y;
+    double elapsed;
+    
+    get_viewport (area, &viewport);
+    
+#if 0
+    g_print ("old info: %d %d\n", info->dx, info->dy);
+    
+    g_print ("timeout (%d %d)\n", dx, dy);
+#endif
+    
+#if 0
+    viewport.x += info->dx;
+    viewport.y += info->dy;
+#endif
+    
+#if 0
+    g_print ("new info %d %d\n", info->dx, info->dy);
+#endif
+
+    elapsed = g_timer_elapsed (info->timer, NULL);
+
+    info->res_x = elapsed * info->dx / 0.2;
+    info->res_y = elapsed * info->dy / 0.2;
+
+#if 0
+    g_print ("%f %f\n", info->res_x, info->res_y);
+#endif
+    
+    new_x = viewport.x + info->res_x;
+    new_y = viewport.y + info->res_y;
+
+#if 0
+    g_print ("%f\n", elapsed * (info->dx / 0.2));
+#endif
+    
+#if 0
+    g_print ("new_x, new_y\n: %d %d\n", new_x, new_y);
+#endif
+    
+    foo_scroll_area_set_viewport_pos (area, new_x, new_y);
+#if 0
+				      viewport.x + info->dx,
+				      viewport.y + info->dy);
+#endif
+
+    get_viewport (area, &new_viewport);
+
+    if (viewport.x == new_viewport.x		&&
+	viewport.y == new_viewport.y		&&
+	(info->res_x > 1.0			||
+	 info->res_y > 1.0			||
+	 info->res_x < -1.0			||
+	 info->res_y < -1.0))
+    {
+	stop_scrolling (area);
+	
+	/* stop scrolling if it didn't have an effect */
+	return FALSE;
+    }
+    
+    return TRUE;
+}
+
+static void
+ensure_scrolling (FooScrollArea *area,
+		  int		 dx,
+		  int		 dy)
+{
+    if (!area->priv->auto_scroll_info)
+    {
+#if 0
+	g_print ("start scrolling\n");
+#endif
+	area->priv->auto_scroll_info = g_new0 (AutoScrollInfo, 1);
+	area->priv->auto_scroll_info->timeout_id =
+	    g_idle_add (scroll_idle, area);
+	area->priv->auto_scroll_info->timer = g_timer_new ();
+    }
+    
+#if 0
+    g_print ("setting scrolling to %d %d\n", dx, dy);
+#endif
+
+#if 0
+    g_print ("dx, dy: %d %d\n", dx, dy);
+#endif
+    
+    area->priv->auto_scroll_info->dx = dx;
+    area->priv->auto_scroll_info->dy = dy;
+}
+
+void
+foo_scroll_area_auto_scroll (FooScrollArea *scroll_area,
+			     FooScrollAreaEvent *event)
+{
+#define SCROLL_MARGIN 4
+    
+    GdkRectangle viewport;
+
+    get_viewport (scroll_area, &viewport);
+
+    viewport.x += SCROLL_MARGIN;
+    viewport.y += SCROLL_MARGIN;
+    viewport.width -= 2 * SCROLL_MARGIN;
+    viewport.height -= 2 * SCROLL_MARGIN;
+
+    if (rect_contains (&viewport, event->x, event->y))
+    {
+#if 0
+	g_print ("in viewport\n");
+#endif
+	
+	stop_scrolling (scroll_area);
+    }
+    else
+    {
+	int dx, dy;
+	
+	dx = dy = 0;
+	
+	if (event->y < viewport.y)
+	{
+	    dy = event->y - viewport.y;
+	    dy = MIN (dy + 2, 0);
+	}
+	else if (event->y >= viewport.y + viewport.height)
+	{
+#if 0
+	    g_print ("event->y: %d, y + h: %d\n",
+		     event->y, viewport.y + viewport.height);
+#endif
+	    
+	    dy = event->y - (viewport.y + viewport.height - 1);
+	    dy = MAX (dy - 2, 0);
+	}
+	
+	if (event->x < viewport.x)
+	{
+	    dx = event->x - viewport.x;
+	    dx = MIN (dx + 2, 0);
+	}
+	else if (event->x >= viewport.x + viewport.width)
+	{
+	    dx = event->x - (viewport.x + viewport.width - 1);
+	    dx = MAX (dx - 2, 0);
+	}
+
+#if 0
+	g_print ("dx, dy: %d %d\n", dx, dy);
+#endif
+	
+	ensure_scrolling (scroll_area, dx, dy);
+    }
+}
+
+void
+foo_scroll_area_begin_auto_scroll (FooScrollArea *scroll_area)
+{
+    /* noop  for now */
+}
+
+void
+foo_scroll_area_end_auto_scroll (FooScrollArea *scroll_area)
+{
+    stop_scrolling (scroll_area);
+}
diff --git a/scrollarea.h b/scrollarea.h
new file mode 100644
index 0000000..1c95c9a
--- /dev/null
+++ b/scrollarea.h
@@ -0,0 +1,107 @@
+#include <cairo/cairo.h>
+#include <gtk/gtk.h>
+
+#define FOO_TYPE_SCROLL_AREA            (foo_scroll_area_get_type ())
+#define FOO_SCROLL_AREA(obj)            (G_TYPE_CHECK_INSTANCE_CAST ((obj), FOO_TYPE_SCROLL_AREA, FooScrollArea))
+#define FOO_SCROLL_AREA_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST ((klass),  FOO_TYPE_SCROLL_AREA, FooScrollAreaClass))
+#define FOO_IS_SCROLL_AREA(obj)         (G_TYPE_CHECK_INSTANCE_TYPE ((obj), FOO_TYPE_SCROLL_AREA))
+#define FOO_IS_SCROLL_AREA_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE ((klass),  FOO_TYPE_SCROLL_AREA))
+#define FOO_SCROLL_AREA_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS ((obj),  FOO_TYPE_SCROLL_AREA, FooScrollAreaClass))
+
+typedef struct FooScrollArea FooScrollArea;
+typedef struct FooScrollAreaClass FooScrollAreaClass;
+typedef struct FooScrollAreaPrivate FooScrollAreaPrivate;
+typedef struct FooScrollAreaEvent FooScrollAreaEvent;
+
+typedef enum
+{
+    FOO_BUTTON_PRESS,
+    FOO_BUTTON_RELEASE,
+    FOO_MOTION
+} FooScrollAreaEventType;
+
+struct FooScrollAreaEvent
+{
+    FooScrollAreaEventType	type;
+    int				x;
+    int				y;
+    int				button;
+};
+
+typedef void (* FooScrollAreaEventFunc) (FooScrollArea      *area,
+					 FooScrollAreaEvent *event,
+					 gpointer            data);
+
+struct FooScrollArea
+{
+    GtkContainer parent_instance;
+
+    FooScrollAreaPrivate *priv;
+};
+
+struct FooScrollAreaClass
+{
+    GtkContainerClass parent_class;
+
+    void (*set_scroll_adjustments) (FooScrollArea *scroll_area,
+				    GtkAdjustment *hadjustment,
+				    GtkAdjustment *vadjustment);
+
+    void (*viewport_changed) (FooScrollArea *scroll_area,
+			      GdkRectangle  *viewport);
+
+    void (*paint) (FooScrollArea *scroll_area,
+		   cairo_t       *cr,
+		   GdkRectangle  *extents,
+		   GdkRegion     *region);
+};
+
+GType foo_scroll_area_get_type (void);
+
+FooScrollArea *foo_scroll_area_new (void);
+
+/* Set the requisition for the widget. */
+void	      foo_scroll_area_set_min_size (FooScrollArea *scroll_area,
+					    int		   min_width,
+					    int            min_height);
+
+/* Set how much of the canvas can be scrolled into view */
+void	      foo_scroll_area_set_size (FooScrollArea	       *scroll_area,
+					int			width,
+					int			height);
+void	      foo_scroll_area_set_size_fixed_y (FooScrollArea  *scroll_area,
+						int		width,
+						int		height,
+						int		old_y,
+						int		new_y);
+void	      foo_scroll_area_set_viewport_pos (FooScrollArea  *scroll_area,
+						int		x,
+						int		y);
+void	      foo_scroll_area_get_viewport (FooScrollArea *scroll_area,
+					    GdkRectangle  *viewport);
+void          foo_scroll_area_add_input_from_stroke (FooScrollArea           *scroll_area,
+						     cairo_t	                *cr,
+						     FooScrollAreaEventFunc   func,
+						     gpointer                 data);
+void          foo_scroll_area_add_input_from_fill (FooScrollArea *scroll_area,
+						      cairo_t	      *cr,
+						      FooScrollAreaEventFunc func,
+						      gpointer       data);
+void          foo_scroll_area_invalidate_region (FooScrollArea *area,
+						 GdkRegion     *region);
+void	      foo_scroll_area_invalidate (FooScrollArea *scroll_area);
+void	      foo_scroll_area_invalidate_rect (FooScrollArea *scroll_area,
+					       int	      x,
+					       int	      y,
+					       int	      width,
+					       int	      height);
+void foo_scroll_area_begin_grab (FooScrollArea *scroll_area,
+				 FooScrollAreaEventFunc func,
+				 gpointer       input_data);
+void foo_scroll_area_end_grab (FooScrollArea *scroll_area);
+gboolean foo_scroll_area_is_grabbed (FooScrollArea *scroll_area);
+
+void foo_scroll_area_begin_auto_scroll (FooScrollArea *scroll_area);
+void foo_scroll_area_auto_scroll (FooScrollArea *scroll_area,
+				  FooScrollAreaEvent *event);
+void foo_scroll_area_end_auto_scroll (FooScrollArea *scroll_area);