1 files changed, 60 insertions, 7 deletions

diff --git a/multitouch.c b/multitouch.c
index ec95eac..654719c 100644
--- a/multitouch.c
+++ b/multitouch.c
@@ -22,6 +22,8 @@ struct multitouch {
     Screen* screen;
     Window root;
     Window win;
+    GC gc;
+    Visual *visual;
     int xi_opcode;
 
     Pixmap pixmap;
@@ -30,8 +32,13 @@ struct multitouch {
     int height;
 
     cairo_t *cr;
+    cairo_t *cr_win;
+    cairo_surface_t *surface;
+    cairo_surface_t *surface_win;
 };
 
+static void expose(struct multitouch *mt, int x1, int y1, int x2, int y2);
+
 static int error(const char *fmt, ...)
 {
     va_list args;
@@ -98,6 +105,15 @@ static Pixmap init_pixmap(struct multitouch *mt)
     return p;
 }
 
+static GC init_gc(struct multitouch *mt)
+{
+    GC gc;
+
+    gc = XCreateGC(mt->dpy, mt->win, 0, NULL);
+
+    return gc;
+}
+
 static int init_x11(struct multitouch *mt, int width, int height)
 {
     Display *dpy;
@@ -119,15 +135,18 @@ static int init_x11(struct multitouch *mt, int width, int height)
     mt->screen_no = DefaultScreen(dpy);
     mt->screen    = DefaultScreenOfDisplay(dpy);
     mt->root      = DefaultRootWindow(dpy);
+    mt->visual    = DefaultVisual(dpy, mt->screen_no);
     mt->xi_opcode = xi_opcode;
     mt->width     = width;
     mt->height    = height;
 
     mt->win = init_window(mt);
     mt->pixmap = init_pixmap(mt);
+    mt->gc = init_gc(mt);
     if (!mt->win)
         return error("Failed to create window.\n");
 
+    XFlush(mt->dpy);
     return EXIT_SUCCESS;
 }
 
@@ -157,25 +176,54 @@ static int init_cairo(struct multitouch *mt)
     cairo_surface_t *surface;
     cairo_t *cr;
 
-    surface = cairo_xlib_surface_create_for_bitmap(mt->dpy, mt->pixmap,
-                                                   mt->screen, mt->width, mt->height);
+    /* frontbuffer */
+    surface = cairo_xlib_surface_create(mt->dpy, mt->win,
+                                        mt->visual, mt->width, mt->height);
     if (!surface)
         return error("Failed to create cairo surface\n");
 
+    mt->surface_win = surface;
+
+    cr = cairo_create(surface);
+    if (!cr)
+        return error("Failed to create cairo context\n");
+
+    mt->cr_win = cr;
+
+    /* backbuffer */
+    surface = cairo_surface_create_similar(surface,
+                                           CAIRO_CONTENT_COLOR_ALPHA,
+                                           mt->width, mt->height);
+    if (!surface)
+        return error("Failed to create cairo surface\n");
+
+    mt->surface = surface;
+
     cr = cairo_create(surface);
     if (!cr)
         return error("Failed to create cairo context\n");
 
     cairo_set_line_width(cr, 1);
-    cairo_set_source_rgb(cr, 0, 0, 0);
-    cairo_rectangle(cr, 0, 0, 1, 1);
+    cairo_set_source_rgb(cr, 1, 1, 1);
+    cairo_rectangle(cr, 0, 0, mt->width, mt->height);
     cairo_fill(cr);
+    cairo_move_to(cr, 10, 10);
+    cairo_line_to(cr, 100, 100);
+    cairo_stroke(cr);
 
     mt->cr = cr;
 
+    expose(mt, 0, 0, mt->width, mt->height);
+
     return EXIT_SUCCESS;
 }
 
+static void expose(struct multitouch *mt, int x1, int y1, int x2, int y2)
+{
+    cairo_set_source_surface(mt->cr_win, mt->surface, 0, 0);
+    cairo_paint(mt->cr_win);
+}
+
 static int main_loop(struct multitouch *mt)
 {
     struct pollfd fd;
@@ -194,9 +242,14 @@ static int main_loop(struct multitouch *mt)
             XGenericEventCookie *cookie = &ev.xcookie;
 
             XNextEvent(mt->dpy, &ev);
-            if (XGetEventData(mt->dpy, cookie) &&
-                    cookie->type == GenericEvent &&
-                    cookie->extension == mt->xi_opcode)
+            if (ev.type == Expose) {
+                expose(mt, ev.xexpose.x, ev.xexpose.y,
+                           ev.xexpose.x + ev.xexpose.width,
+                           ev.xexpose.y + ev.xexpose.height);
+            } else if (ev.type == GenericEvent &&
+                XGetEventData(mt->dpy, cookie) &&
+                cookie->type == GenericEvent &&
+                cookie->extension == mt->xi_opcode)
             {
                 print_event(mt, cookie->data);
             }