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grd-damage-utils.c

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+/*
+ * Copyright (C) 2020 Pascal Nowack
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of the
+ * License, or (at your option) any later version.
+ *
+ * This program 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
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
+ * 02111-1307, USA.
+ */
+
+#include "config.h"
+
+#include "grd-damage-utils.h"
+
+#include <string.h>
+
+bool
+grd_is_tile_dirty (cairo_rectangle_int_t *tile,
+                   uint8_t               *current_data,
+                   uint8_t               *prev_data,
+                   uint32_t               stride,
+                   uint32_t               bytes_per_pixel)
+{
+  uint32_t y;
+
+  for (y = tile->y; y < tile->y + tile->height; ++y)
+    {
+      if (memcmp (prev_data + y * stride + tile->x * bytes_per_pixel,
+                  current_data + y * stride + tile->x * bytes_per_pixel,
+                  tile->width * bytes_per_pixel))
+        return true;
+    }
+
+  return false;
+}
+
+cairo_region_t *
+grd_get_damage_region (uint8_t  *current_data,
+                       uint8_t  *prev_data,
+                       uint32_t  surface_width,
+                       uint32_t  surface_height,
+                       uint32_t  tile_width,
+                       uint32_t  tile_height,
+                       uint32_t  stride,
+                       uint32_t  bytes_per_pixel)
+{
+  cairo_region_t *damage_region;
+  cairo_rectangle_int_t tile;
+  uint32_t cols, rows;
+  uint32_t x, y;
+
+  damage_region = cairo_region_create ();
+  if (current_data == NULL || prev_data == NULL)
+    {
+      tile.x = tile.y = 0;
+      tile.width = surface_width;
+      tile.height = surface_height;
+      cairo_region_union_rectangle (damage_region, &tile);
+
+      return damage_region;
+    }
+
+  cols = surface_width / tile_width + (surface_width % tile_width ? 1 : 0);
+  rows = surface_height / tile_height + (surface_height % tile_height ? 1 : 0);
+
+  for (y = 0; y < rows; ++y)
+    {
+      for (x = 0; x < cols; ++x)
+        {
+          tile.x = x * tile_width;
+          tile.y = y * tile_height;
+          tile.width = surface_width - tile.x < tile_width ? surface_width - tile.x
+                                                           : tile_width;
+          tile.height = surface_height - tile.y < tile_height ? surface_height - tile.y
+                                                              : tile_height;
+
+          if (grd_is_tile_dirty (&tile, current_data, prev_data, stride, bytes_per_pixel))
+            cairo_region_union_rectangle (damage_region, &tile);
+        }
+    }
+
+  return damage_region;
+}