[gtk+] Fix damage report for lines drawn on offscreen windows

[Alexander Larsson <alexl src gnome org>]

commit 98a9c5c69a796b48d3797a35a301dabe1dcb2430
Author: Alexander Larsson <alexl redhat com>
Date:   Mon Dec 7 10:47:05 2009 +0100

    Fix damage report for lines drawn on offscreen windows
    
    All kinds of lines (lines, segments, arcs, etc) need to take into
    account the line properties (width, miter limit, joins, caps, etc)
    to get proper damage extents.
    
    This is not really possible to do, but we can make it likely to work
    with some ad-hoc estimates.
    
    Fixes bug 603904.

 gdk/gdkoffscreenwindow.c |   48 +++++++++++++++++++++++++++++++++------------
 1 files changed, 35 insertions(+), 13 deletions(-)
---
diff --git a/gdk/gdkoffscreenwindow.c b/gdk/gdkoffscreenwindow.c
index 2622235..76d9015 100644
--- a/gdk/gdkoffscreenwindow.c
+++ b/gdk/gdkoffscreenwindow.c
@@ -257,7 +257,8 @@ gdk_offscreen_window_get_visual (GdkDrawable    *drawable)
 static void
 add_damage (GdkOffscreenWindow *offscreen,
 	    int x, int y,
-	    int w, int h)
+	    int w, int h,
+	    gboolean is_line)
 {
   GdkRectangle rect;
   GdkRegion *damage;
@@ -267,6 +268,26 @@ add_damage (GdkOffscreenWindow *offscreen,
   rect.width = w;
   rect.height = h;
 
+  if (is_line)
+    {
+      /* This should really take into account line width, line
+       * joins (and miter) and line caps. But these are hard
+       * to compute, rarely used and generally a pain. And in
+       * the end a snug damage rectangle is not that important
+       * as multiple damages are generally created anyway.
+       *
+       * So, we just add some padding around the rect.
+       * We use a padding of 3 pixels, plus an extra row
+       * below and on the right for the normal line size. I.E.
+       * line from (0,0) to (2,0) gets h=0 but is really
+       * at least one pixel tall.
+       */
+      rect.x -= 3;
+      rect.y -= 3;
+      rect.width += 7;
+      rect.height += 7;
+    }
+
   damage = gdk_region_rectangle (&rect);
   _gdk_window_add_damage (offscreen->wrapper, damage);
   gdk_region_destroy (damage);
@@ -300,7 +321,7 @@ gdk_offscreen_window_draw_drawable (GdkDrawable *drawable,
 		     xdest, ydest,
 		     width, height);
 
-  add_damage (offscreen, xdest, ydest, width, height);
+  add_damage (offscreen, xdest, ydest, width, height, FALSE);
 }
 
 static void
@@ -318,7 +339,7 @@ gdk_offscreen_window_draw_rectangle (GdkDrawable  *drawable,
   gdk_draw_rectangle (real_drawable,
 		      gc, filled, x, y, width, height);
 
-  add_damage (offscreen, x, y, width, height);
+  add_damage (offscreen, x, y, width, height, !filled);
 
 }
 
@@ -345,7 +366,7 @@ gdk_offscreen_window_draw_arc (GdkDrawable  *drawable,
 		height,
 		angle1,
 		angle2);
-  add_damage (offscreen, x, y, width, height);
+  add_damage (offscreen, x, y, width, height, !filled);
 }
 
 static void
@@ -381,7 +402,7 @@ gdk_offscreen_window_draw_polygon (GdkDrawable  *drawable,
 
 	add_damage (offscreen, min_x, min_y,
 		    max_x - min_x,
-		    max_y - min_y);
+		    max_y - min_y, !filled);
     }
 }
 
@@ -407,7 +428,7 @@ gdk_offscreen_window_draw_text (GdkDrawable  *drawable,
 		 text_length);
 
   /* Hard to compute the minimal size, not that often used anyway. */
-  add_damage (offscreen, 0, 0, private->width, private->height);
+  add_damage (offscreen, 0, 0, private->width, private->height, FALSE);
 }
 
 static void
@@ -432,7 +453,7 @@ gdk_offscreen_window_draw_text_wc (GdkDrawable	 *drawable,
 		    text_length);
 
   /* Hard to compute the minimal size, not that often used anyway. */
-  add_damage (offscreen, 0, 0, private->width, private->height);
+  add_damage (offscreen, 0, 0, private->width, private->height, FALSE);
 }
 
 static void
@@ -466,8 +487,9 @@ gdk_offscreen_window_draw_points (GdkDrawable  *drawable,
 	  }
 
 	add_damage (offscreen, min_x, min_y,
-		    max_x - min_x,
-		    max_y - min_y);
+		    max_x - min_x + 1,
+		    max_y - min_y + 1,
+		    FALSE);
     }
 }
 
@@ -506,7 +528,7 @@ gdk_offscreen_window_draw_segments (GdkDrawable  *drawable,
 
 	add_damage (offscreen, min_x, min_y,
 		    max_x - min_x,
-		    max_y - min_y);
+		    max_y - min_y, TRUE);
     }
 
 }
@@ -529,7 +551,7 @@ gdk_offscreen_window_draw_lines (GdkDrawable  *drawable,
   /* Hard to compute the minimal size, as we don't know the line
      width, and since joins are hard to calculate.
      Its not that often used anyway, damage it all */
-  add_damage (offscreen, 0, 0, private->width, private->height);
+  add_damage (offscreen, 0, 0, private->width, private->height, TRUE);
 }
 
 static void
@@ -556,7 +578,7 @@ gdk_offscreen_window_draw_image (GdkDrawable *drawable,
 		  width,
 		  height);
 
-  add_damage (offscreen, xdest, ydest, width, height);
+  add_damage (offscreen, xdest, ydest, width, height, FALSE);
 }
 
 
@@ -590,7 +612,7 @@ gdk_offscreen_window_draw_pixbuf (GdkDrawable *drawable,
 		   x_dither,
 		   y_dither);
 
-  add_damage (offscreen, dest_x, dest_y, width, height);
+  add_damage (offscreen, dest_x, dest_y, width, height, FALSE);
 
 }