#include <gdk/gdkx.h>
#include <X11/Xlib.h>
#include "backingstore.h"

typedef struct InputPath InputPath;
typedef struct InputRegion InputRegion;

struct BackingStore
{
    GdkPixmap *			pixmap;
    GdkRegion *			update_region;
    int				width;
    int				height;

    /* Input */
    InputRegion *		current_input;
    GPtrArray *			input_regions;
    int				current_x;
    int				current_y;
    BackingStoreEventFunc	last_func;
    gpointer			last_data;
    int				last_x;
    int				last_y;
    gboolean			last_was_motion;
    gboolean			implicit_grab;
    gboolean			grabbed;
    BackingStoreEventFunc	grab_func;
    gpointer			grab_data;

    guint32			motion_notify_time;
    gboolean			need_fake_motion;
    gboolean			in_process_updates;
};

struct InputPath
{
    cairo_fill_rule_t		fill_rule;
    double			line_width;
    cairo_path_t	       *path;		
    gboolean			is_stroke;
    
    BackingStoreEventFunc	func;
    gpointer			data;
};

/* InputRegions are mutually disjoint */
struct InputRegion
{
    GdkRegion *region;
    GArray *paths;
};

void
backing_store_free (BackingStore *store)
{
    g_object_unref (store->pixmap);
    gdk_region_destroy (store->update_region);
    g_free (store);
}

void
backing_store_move_area (BackingStore *store,
                         int           x,
                         int           y,
                         int           width,
                         int           height,
                         int           dx,
                         int           dy)
{
    GdkRegion *moving_invalid;
    GdkRegion *region;
    GdkRectangle rect;
    GdkGC *gc;
    
    gc = gdk_gc_new (store->pixmap);
    gdk_draw_drawable (store->pixmap, gc, store->pixmap,
                       x, y, x + dx, y + dy,
                       width, height);
    g_object_unref (gc);

    rect.x = x;
    rect.y = y;
    rect.width = width;
    rect.height = height;

    region = gdk_region_rectangle (&rect);

    /* Compute the invalid part of the region that moves */
    moving_invalid = gdk_region_copy (region);
    gdk_region_intersect (moving_invalid, store->update_region);

    /* Invalidate the source rectangle */
    gdk_region_union (store->update_region, region);

    /* Uninvalidate the destination rectangle */
    gdk_region_offset (region, dx, dy);
    gdk_region_subtract (store->update_region, region);

    /* Invalidate the invalid parts that moved */
    gdk_region_union (store->update_region, moving_invalid);

    gdk_region_destroy (moving_invalid);
    gdk_region_destroy (region);

    /* Intersect invalid area with store extents */
    rect.x = 0;
    rect.y = 0;
    rect.width = store->width;
    rect.height = store->height;

    region = gdk_region_rectangle (&rect);
    gdk_region_intersect (store->update_region, region);
    gdk_region_destroy (region);

    /* FIXME: move the input areas instead */
    backing_store_invalidate_all (store);

    if (!gdk_region_empty (store->update_region))
	store->need_fake_motion = TRUE;
}

static void
process_event (BackingStore	       *store,
	       BackingStoreEventType    input_type,
	       int			x,
	       int			y,
	       int			button);


void
backing_store_scroll (BackingStore *store,
		      int           dx,
		      int           dy)
{
    backing_store_move_area (store, 0, 0, store->width, store->height, dx, dy);
}

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);
}

static void
begin_grab_internal (BackingStore           *store,
		     gboolean		     implicit,
		     BackingStoreEventFunc   func,
		     gpointer                data)
{
#if 0
    g_print ("begin%s grab\n", implicit? " implicit" : "");
#endif
    
    /* FIXME: we should probably take a server grab */
    /* Also, there should be support for setting the grab cursor */

    /* Grabs can be overridden if desired - FIXME: make sure this right */
    /* We may need a grab counter here if there are both implicit and
     * explicit grabs in play at the same time
     */
    store->implicit_grab = implicit;
    store->grabbed = TRUE;
    store->grab_func = func;
    store->grab_data = data;
}

static void
end_grab_internal (BackingStore *store,
		   gboolean	 only_implicit)
{
    if (only_implicit && !store->implicit_grab)
	return;

#if 0
    g_print ("end grab\n");
#endif
    
    store->implicit_grab = FALSE;
    store->grabbed = FALSE;
    store->grab_func = NULL;
    store->grab_data = NULL;
}

static void
emit_input (BackingStore           *store,
	    BackingStoreEventType   type,
	    int			    x,
	    int			    y,
	    int			    button,
	    BackingStoreEventFunc   func,
	    gpointer		    data)
{
    BackingStoreEvent event;
    gboolean finished_grab = FALSE;

    event.x = x;
    event.y = y;
    event.button = button;

#if 0
    if (store->grabbed)
	g_print ("grabbed\n");
#endif
    
    /* Handle crossing events */
    if (store->last_func != func || store->last_data != data)
    {
	if (!store->grabbed	||
	    (store->last_func == store->grab_func &&
	     store->last_data == store->grab_data))
	{
	    event.type = BACKING_STORE_LEAVE;

	    if (store->last_func)
	    {
#if 0
		g_print ("leave: %d\n", ec);
		g_print ("leave %p -> %p\n", store->last_func, func);
#endif
		
		store->last_func (store, &event, store->last_data);
	    }
	}

	if (!store->grabbed ||
	    (func == store->grab_func	&&
	     data == store->grab_data))
	{
	    event.type = BACKING_STORE_ENTER;
	    
	    if (func)
	    {
#if 0
		g_print ("enter %d\n", ec);
#endif
		func (store, &event, data);
	    }
	}
    }
    
    event.type = type;

    if (event.type != BACKING_STORE_NONE)
    {
	BackingStoreEventFunc emit_func;
	gpointer emit_data;

	if (store->grabbed)
	{
	    emit_func = store->grab_func;
	    emit_data = store->grab_data;
	}
	else
	{
	    emit_func = func;
	    emit_data = data;
	}

	if (emit_func)
	{
	    if (event.type == BACKING_STORE_BUTTON_PRESS)
		begin_grab_internal (store, TRUE, emit_func, emit_data);

#if 0
	    g_print ("other %d\n", ec);
#endif
	    
	    emit_func (store, &event, emit_data);
	    
	    if (event.type == BACKING_STORE_BUTTON_RELEASE)
	    {
		end_grab_internal (store, TRUE);
		
		finished_grab = TRUE;
	    }
	}
    }
    
    store->last_func = func;
    store->last_data = data;
    store->last_x = x;
    store->last_y = y;
    store->last_was_motion = (event.type == BACKING_STORE_MOTION);

    if (finished_grab)
    {
	/* When a grab has finished, fake a motion to where
	 * the last grabbed event happened.
	 */
	process_event (store, BACKING_STORE_MOTION, x, y, 0);
    }
}

static void
process_event (BackingStore	       *store,
	       BackingStoreEventType	input_type,
	       int			x,
	       int			y,
	       int			button)
{
    int i;

    for (i = 0; i < store->input_regions->len; ++i)
    {
	InputRegion *region = store->input_regions->pdata[i];

	if (gdk_region_point_in (region->region, x, y))
	{
	    int j;

	    /* Iterate backwards since the topmost paths are at
	     * the back.
	     */
	    for (j = region->paths->len - 1; j >= 0; --j)
	    {
		InputPath *path = &g_array_index (region->paths, InputPath, j);
		cairo_t *cr;
		gboolean inside;

		if (store->grabbed &&
		    (path->func != store->grab_func ||
		     path->data != store->grab_data))
		{
		    /* When there is a grab in place we only care
		     * about input regions for the purposes of
		     * generating enter events for the grab
		     * function. 
		     */
		    continue;
		}

		cr = gdk_cairo_create (store->pixmap);
		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 (store, input_type,
				x, y, button,
				path->func,
				path->data);

		    return;
		}
	    }

	    /* 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.
	     */
	    break;
	}
    }
    
    /* If we got here, no event was emitted, so we emit
     * an event with a NULL event function. This will cause some
     * internal bookkeeping to be updated, and an event to be
     * emitted if a grab happens to be active.
     */
    emit_input (store, input_type, x, y, button, NULL, NULL);
}

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;
	}
    }
}

/* Input */
void
backing_store_process_event (BackingStore *store,
			     GdkEvent     *event)
{
    BackingStoreEventType input_type = BACKING_STORE_NONE;
    int button = 0;
    int x, y;

    if (event->type == GDK_BUTTON_PRESS)
    {
	input_type = BACKING_STORE_BUTTON_PRESS;
	button = event->button.button;
	x = event->button.x;
	y = event->button.y;
    }
    else if (event->type == GDK_BUTTON_RELEASE)
    {
	input_type = BACKING_STORE_BUTTON_RELEASE;
	button = event->button.button;
	x = event->button.x;
	y = event->button.y;
    }
    else if (event->type == GDK_MOTION_NOTIFY	||
	     event->type == GDK_LEAVE_NOTIFY	||
	     event->type == GDK_ENTER_NOTIFY)
    {
	GdkWindow *window;
	guint32 time;
	
	input_type = BACKING_STORE_MOTION;
	button = 0;

	if (event->type == GDK_MOTION_NOTIFY)
	{
	    x = event->motion.x;
	    y = event->motion.y;
	    window = event->motion.window;
	    time = event->motion.time;
	}
	else
	{
	    x = event->crossing.x;
	    y = event->crossing.y;
	    window = event->crossing.window;
	    time = event->crossing.time;
	}

	if (!use_this_motion_notify (window, time, &store->motion_notify_time))
	    return;
    }
    else
    {
	return;
    }

    process_event (store, input_type, x, y, button);

    store->current_x = x;
    store->current_y = y;
}

static void
user_to_device (double *x, double *y,
		gpointer data)
{
    cairo_surface_t *surface = cairo_get_target (data);
    double dev_x;
    double dev_y;
    
    cairo_surface_get_device_offset (surface, &dev_x, &dev_y);

    cairo_user_to_device (data, x, y);
    *x += dev_x;
    *y += dev_y;

    
}

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;
	}
    }
}

void
backing_store_add_input (BackingStore    *store,
			 cairo_t         *cr,
			 gboolean	  is_stroke,
			 BackingStoreEventFunc func,
			 gpointer         data)
{
    InputPath path;

    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;

    g_array_append_val (store->current_input->paths, path);
}

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;

    store->current_input = NULL;
    store->input_regions = g_ptr_array_new ();
    
    return store;
}

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);
}

void
backing_store_resize (BackingStore    *store,
		      int              width,
		      int              height)
{
    GdkPixmap *pixmap;
    GdkRegion *old, *invalid;
    GdkRectangle r;
    GdkGC *gc;
    
    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.
     */
    gc = gdk_gc_new (pixmap);
    gdk_draw_drawable (pixmap, gc, store->pixmap, 0, 0, 0, 0, -1, -1);
    g_object_unref (gc);
    
    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);
}

void
backing_store_draw (BackingStore *store, 
		    GdkDrawable  *dest,
		    GdkRegion    *clip,
		    int           dest_x,
		    int           dest_y)
{
    GdkGC *gc;

    if (store->in_process_updates)
    {
	g_critical ("backing_store_draw() cannot be called when "
		    "backing_store_process_updates() is running\n");

	return;
    }
    
    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);
}

static GdkRegion *
make_store_region (BackingStore *store)
{
    GdkRectangle store_rect;

    store_rect.x = 0;
    store_rect.y = 0;
    store_rect.width = store->width;
    store_rect.height = store->height;

    return gdk_region_rectangle (&store_rect);
}

static void
input_region_free (InputRegion *region)
{
    int i;

    for (i = 0; i < region->paths->len; ++i)
    {
	InputPath *path = &g_array_index (region->paths, InputPath, i);

	cairo_path_destroy (path->path);
    }

    g_array_free (region->paths, TRUE);

    gdk_region_destroy (region->region);
    
    g_free (region);
}

static void
clear_exposed_input_region (BackingStore *store,
			    GdkRegion    *region)
{
    int i;
    GdkRegion *store_reg = make_store_region (store);
    
    gdk_region_subtract (store_reg, region);
    
    for (i = 0; i < store->input_regions->len; ++i)
    {
	InputRegion *region = store->input_regions->pdata[i];

	gdk_region_intersect (region->region, store_reg);

	if (gdk_region_empty (region->region))
	{
	    input_region_free (region);

	    g_ptr_array_remove_index_fast (store->input_regions, i--);
	}
    }

    gdk_region_destroy (store_reg);
}

static void
clip_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_process_updates (BackingStore       *store,
			       BackingPaintFunc    func,
			       gpointer            data)
{
    store->in_process_updates = TRUE;
    
    /* FIXME:
     *
     * The expose process itself can generate invalidations,
     * so we need to continue to process updates until
     * the update region is empty
     *
     * Yes, this can lead to infinite loops. Something should be
     * done about that, but it's not completely clear what exactly.
     *
     * Consider the case where hovering an object causes the object to
     * move out of the way, which causes non-hovering, which causes
     * the object to move back - and so on. If the application is
     * actually in this situation, then an infnitely loop is
     * in some sense the logical result.
     *
     * A possibility is to only loop, say, five times, and just let
     * applications sort it out by itself. (If they don't do anything,
     * they will get flickering back and forth, which is probably the
     * correct default behavior).
     */
    while (!gdk_region_empty (store->update_region))
    {
	cairo_t *cr = gdk_cairo_create (store->pixmap);
	GdkRegion *region = store->update_region;
	GdkRegion *store_reg = make_store_region (store);
	
	gdk_region_intersect (region, store_reg);
	
	gdk_region_destroy (store_reg);
	
	store->update_region = gdk_region_new ();
	
	clip_to_region (cr, region);
	
	{
	    /* To make sure all of the clip region is painted */
	    cairo_set_source_rgb (cr, g_random_double(), 0, 0);
	    cairo_paint (cr);
	}
	
	clear_exposed_input_region (store, region);
	
	store->current_input = g_new0 (InputRegion, 1);
	store->current_input->region = region;
	store->current_input->paths = g_array_new (
	    FALSE, FALSE, sizeof (InputPath));
	
	func (cr, region, data);
	
	g_ptr_array_add (store->input_regions, store->current_input);
	
	store->current_input = NULL;
	
	cairo_destroy (cr);

	if (store->need_fake_motion)
	{
	    /* The backing store was scrolled, so generate a fake
	     * motion event so that scrolling while dragging produces
	     * the correct result.
	     */
	    process_event (store, BACKING_STORE_MOTION,
			   store->current_x, store->current_y, 0);	

	    store->need_fake_motion = FALSE;
	}
	else
	{
	    /* Make sure any crossing events generated during the
	     * expose process are emitted here
	     */

	    process_event (store, BACKING_STORE_NONE,
			   store->current_x, store->current_y, 0);
	}
    }

    store->in_process_updates = FALSE;
}