path: root/gtk/gtkpixelcache.c

/* GTK - The GIMP Toolkit
 * Copyright (C) 2013 Red Hat, Inc.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library. If not, see <http://www.gnu.org/licenses/>.
 */

#include "config.h"

#include "gtkdebug.h"
#include "gtkpixelcacheprivate.h"

/* The extra size of the offscreen surface we allocate
   to make scrolling more efficient */
#define EXTRA_SIZE 64

/* When resizing viewport to smaller we allow this extra
   size to avoid constantly reallocating when resizing */
#define ALLOW_LARGER_SIZE 32

struct _GtkPixelCache {
  cairo_surface_t *surface;

  /* Valid if surface != NULL */
  int surface_x;
  int surface_y;
  int surface_w;
  int surface_h;

  /* may be null if not dirty */
  cairo_region_t *surface_dirty;
};

GtkPixelCache *
_gtk_pixel_cache_new ()
{
  GtkPixelCache *cache;

  cache = g_new0 (GtkPixelCache, 1);

  return cache;
}

void
_gtk_pixel_cache_free (GtkPixelCache *cache)
{
  if (cache == NULL)
    return;

  if (cache->surface != NULL)
    cairo_surface_destroy (cache->surface);

  if (cache->surface_dirty != NULL)
    cairo_region_destroy (cache->surface_dirty);

  g_free (cache);
}

/* Region is in canvas coordinates */
void
_gtk_pixel_cache_invalidate (GtkPixelCache *cache,
			     cairo_region_t *region)
{
  cairo_rectangle_int_t r;
  cairo_region_t *free_region = NULL;

  if (cache->surface == NULL ||
      (region != NULL && cairo_region_is_empty (region)))
    return;

  if (region == NULL)
    {
      r.x = cache->surface_x;
      r.y = cache->surface_y;
      r.width = cache->surface_w;
      r.height = cache->surface_h;

      free_region = region =
	cairo_region_create_rectangle (&r);
    }

  if (cache->surface_dirty == NULL)
    {
      cache->surface_dirty = cairo_region_copy (region);
      cairo_region_translate (cache->surface_dirty,
			      -cache->surface_x,
			      -cache->surface_y);
    }
  else
    {
      cairo_region_translate (region,
			      -cache->surface_x,
			      -cache->surface_y);
      cairo_region_union (cache->surface_dirty, region);
      cairo_region_translate (region,
			      cache->surface_x,
			      cache->surface_y);
    }

  if (free_region)
    cairo_region_destroy (free_region);

  r.x = 0;
  r.y = 0;
  r.width = cache->surface_w;
  r.height = cache->surface_h;

  cairo_region_intersect_rectangle (cache->surface_dirty, &r);
}

static void
_gtk_pixel_cache_create_surface_if_needed (GtkPixelCache         *cache,
					   GdkWindow             *window,
					   cairo_rectangle_int_t *view_rect,
					   cairo_rectangle_int_t *canvas_rect)
{
  cairo_rectangle_int_t rect;
  int surface_w, surface_h;
  cairo_content_t content;
  cairo_pattern_t *bg;
  double red, green, blue, alpha;

  content = CAIRO_CONTENT_COLOR_ALPHA;
  bg = gdk_window_get_background_pattern (window);
  if (bg != NULL &&
      cairo_pattern_get_type (bg) == CAIRO_PATTERN_TYPE_SOLID &&
      cairo_pattern_get_rgba (bg, &red, &green, &blue, &alpha) == CAIRO_STATUS_SUCCESS &&
      alpha == 1.0)
    content = CAIRO_CONTENT_COLOR;

  surface_w = view_rect->width;
  if (canvas_rect->width > surface_w)
    surface_w = MIN (surface_w + EXTRA_SIZE, canvas_rect->width);

  surface_h = view_rect->height;
  if (canvas_rect->height > surface_h)
    surface_h = MIN (surface_h + EXTRA_SIZE, canvas_rect->height);

  /* If current surface can't fit view_rect or is too large, kill it */
  if (cache->surface != NULL &&
      (cairo_surface_get_content (cache->surface) != content ||
       cache->surface_w < view_rect->width ||
       cache->surface_w > surface_w + ALLOW_LARGER_SIZE ||
       cache->surface_h < view_rect->height ||
       cache->surface_h > surface_h + ALLOW_LARGER_SIZE))
    {
      cairo_surface_destroy (cache->surface);
      cache->surface = NULL;
      if (cache->surface_dirty)
	cairo_region_destroy (cache->surface_dirty);
      cache->surface_dirty = NULL;
    }

  /* Don't allocate a surface if view >= canvas, as we won't
     be scrolling then anyway */
  if (cache->surface == NULL &&
      (view_rect->width < canvas_rect->width ||
       view_rect->height < canvas_rect->height))
    {
      cache->surface_x = -canvas_rect->x;
      cache->surface_y = -canvas_rect->y;
      cache->surface_w = surface_w;
      cache->surface_h = surface_h;

      cache->surface =
	gdk_window_create_similar_surface (window, content,
					   surface_w, surface_h);
      rect.x = 0;
      rect.y = 0;
      rect.width = surface_w;
      rect.height = surface_h;
      cache->surface_dirty =
	cairo_region_create_rectangle (&rect);
    }
}

void
_gtk_pixel_cache_set_position (GtkPixelCache         *cache,
			       cairo_rectangle_int_t *view_rect,
			       cairo_rectangle_int_t *canvas_rect)
{
  cairo_rectangle_int_t r, view_pos;
  cairo_region_t *copy_region;
  int new_surf_x, new_surf_y;
  cairo_t *backing_cr;

  if (cache->surface == NULL)
    return;

  /* Position of view inside canvas */
  view_pos.x = -canvas_rect->x;
  view_pos.y = -canvas_rect->y;
  view_pos.width = view_rect->width;
  view_pos.height = view_rect->height;

  /* Reposition so all is visible */
  if (view_pos.x < cache->surface_x ||
      view_pos.x + view_pos.width >
      cache->surface_x + cache->surface_w ||
      view_pos.y < cache->surface_y ||
      view_pos.y + view_pos.height >
      cache->surface_y + cache->surface_h)
    {
      new_surf_x = cache->surface_x;
      if (view_pos.x < cache->surface_x)
	new_surf_x = MAX (view_pos.x + view_pos.width - cache->surface_w, 0);
      else if (view_pos.x + view_pos.width >
	       cache->surface_x + cache->surface_w)
	new_surf_x = MIN (view_pos.x, canvas_rect->width - cache->surface_w);

      new_surf_y = cache->surface_y;
      if (view_pos.y < cache->surface_y)
	new_surf_y = MAX (view_pos.y + view_pos.height - cache->surface_h, 0);
      else if (view_pos.y + view_pos.height >
	       cache->surface_y + cache->surface_h)
	new_surf_y = MIN (view_pos.y, canvas_rect->height - cache->surface_h);

      r.x = 0;
      r.y = 0;
      r.width = cache->surface_w;
      r.height = cache->surface_h;
      copy_region = cairo_region_create_rectangle (&r);

      if (cache->surface_dirty)
	{
	  cairo_region_subtract (copy_region, cache->surface_dirty);
	  cairo_region_destroy (cache->surface_dirty);
	  cache->surface_dirty = NULL;
	}

      cairo_region_translate (copy_region,
			      cache->surface_x - new_surf_x,
			      cache->surface_y - new_surf_y);
      cairo_region_intersect_rectangle (copy_region, &r);

      backing_cr = cairo_create (cache->surface);
      gdk_cairo_region (backing_cr, copy_region);
      cairo_set_operator (backing_cr, CAIRO_OPERATOR_SOURCE);
      cairo_clip (backing_cr);
      cairo_push_group (backing_cr);
      cairo_set_source_surface (backing_cr, cache->surface,
				cache->surface_x - new_surf_x,
				cache->surface_y - new_surf_y);
      cairo_paint (backing_cr);
      cairo_pop_group_to_source (backing_cr);
      cairo_paint (backing_cr);
      cairo_destroy (backing_cr);

      cache->surface_x = new_surf_x;
      cache->surface_y = new_surf_y;

      cairo_region_xor_rectangle (copy_region, &r);
      cache->surface_dirty = copy_region;
    }
}

void
_gtk_pixel_cache_repaint (GtkPixelCache *cache,
			  GtkPixelCacheDrawFunc draw,
			  cairo_rectangle_int_t *view_rect,
			  cairo_rectangle_int_t *canvas_rect,
			  gpointer user_data)
{
  cairo_t *backing_cr;

  if (cache->surface &&
      cache->surface_dirty &&
      !cairo_region_is_empty (cache->surface_dirty))
    {
      backing_cr = cairo_create (cache->surface);
      gdk_cairo_region (backing_cr, cache->surface_dirty);
      cairo_clip (backing_cr);
      cairo_translate (backing_cr,
		       -cache->surface_x - canvas_rect->x - view_rect->x,
		       -cache->surface_y - canvas_rect->y - view_rect->y);
      cairo_set_source_rgba (backing_cr,
			     0.0, 0, 0, 0.0);
      cairo_set_operator (backing_cr, CAIRO_OPERATOR_SOURCE);
      cairo_paint (backing_cr);

      cairo_set_operator (backing_cr, CAIRO_OPERATOR_OVER);

      cairo_save (backing_cr);
      draw (backing_cr, user_data);
      cairo_restore (backing_cr);

#ifdef G_ENABLE_DEBUG
      if (gtk_get_debug_flags () & GTK_DEBUG_PIXEL_CACHE)
	{
	  GdkRGBA colors[] = {
	    { 1, 0, 0, 0.08},
	    { 0, 1, 0, 0.08},
	    { 0, 0, 1, 0.08},
	    { 1, 0, 1, 0.08},
	    { 1, 1, 0, 0.08},
	    { 0, 1, 1, 0.08},
	  };
	  static int current_color = 0;

	  gdk_cairo_set_source_rgba (backing_cr, &colors[(current_color++) % G_N_ELEMENTS (colors)]);
	  cairo_paint (backing_cr);
	}
#endif

      cairo_destroy (backing_cr);
    }

  if (cache->surface_dirty)
    {
      cairo_region_destroy (cache->surface_dirty);
      cache->surface_dirty = NULL;
    }
}

void
_gtk_pixel_cache_draw (GtkPixelCache *cache,
		       cairo_t *cr,
		       GdkWindow *window,
		       /* View position in widget coords */
		       cairo_rectangle_int_t *view_rect,
		       /* Size and position of canvas in view coords */
		       cairo_rectangle_int_t *canvas_rect,
		       GtkPixelCacheDrawFunc draw,
		       gpointer user_data)
{
  _gtk_pixel_cache_create_surface_if_needed (cache, window,
					     view_rect, canvas_rect);
  _gtk_pixel_cache_set_position (cache, view_rect, canvas_rect);
  _gtk_pixel_cache_repaint (cache, draw, view_rect, canvas_rect, user_data);

  if (cache->surface &&
      /* Don't use backing surface if rendering elsewhere */
      cairo_surface_get_type (cache->surface) == cairo_surface_get_type (cairo_get_target (cr)))
    {
      cairo_save (cr);
      cairo_set_source_surface (cr, cache->surface,
				cache->surface_x + view_rect->x + canvas_rect->x,
				cache->surface_y + view_rect->y + canvas_rect->y);
      cairo_rectangle (cr, view_rect->x, view_rect->y,
		       view_rect->width, view_rect->height);
      cairo_fill (cr);
      cairo_restore (cr);
    }
  else
    {
      cairo_rectangle (cr,
		       view_rect->x, view_rect->y,
		       view_rect->width, view_rect->height);
      cairo_clip (cr);
      draw (cr, user_data);
    }
}