[metacity] compositor: don't draw shadow under decorations

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 215dd8e9de7c416cdd5053eb638a163d49e603e8
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Tue Jan 20 16:32:39 2015 +0200

    compositor: don't draw shadow under decorations

 src/compositor/compositor-xrender.c |   91 +++++++++++++++++------------------
 1 files changed, 45 insertions(+), 46 deletions(-)
---
diff --git a/src/compositor/compositor-xrender.c b/src/compositor/compositor-xrender.c
index 2d2588f..0f92e19 100644
--- a/src/compositor/compositor-xrender.c
+++ b/src/compositor/compositor-xrender.c
@@ -629,51 +629,54 @@ cairo_region_to_xserver_region (Display        *xdisplay,
 }
 
 static void
-shadow_clip (Display          *xdisplay,
-             Picture           shadow_picture,
-             XImage           *shadow_image,
-             MetaShadowType    shadow_type,
-             MetaFrameBorders  borders,
-             int               width,
-             int               height)
-{
-  int shadow_dx = -1 * shadow_offsets_x [shadow_type];
-  int shadow_dy = -1 * shadow_offsets_y [shadow_type];
-  XRectangle clip[4];
-
-  /* Top */
-  clip[0].x      = 0;
-  clip[0].y      = 0;
-  clip[0].width  = shadow_image->width;
-  clip[0].height = shadow_dy + borders.visible.top;
-
-  /* Bottom */
-  clip[1].x      = 0;
-  clip[1].y      = shadow_dy + (height - borders.visible.bottom);
-  clip[1].width  = shadow_image->width;
-  clip[1].height = shadow_image->height - (shadow_dy + (height - borders.visible.bottom));
-
-  /* Left */
-  clip[2].x      = 0;
-  clip[2].y      = shadow_dy + borders.visible.top;
-  clip[2].width  = shadow_dx + borders.visible.left;
-  clip[2].height = height - borders.visible.top - borders.visible.bottom;
-
-  /* Right */
-  clip[3].x      = width + shadow_dx;
-  clip[3].y      = shadow_dy + borders.visible.top;
-  clip[3].width  = shadow_image->width - (width + shadow_dx);
-  clip[3].height = height - borders.visible.top - borders.visible.bottom;
-
-  XRenderSetPictureClipRectangles (xdisplay, shadow_picture, 0, 0, clip, 4);
+shadow_picture_clip (Display          *xdisplay,
+                     Picture           shadow_picture,
+                     MetaCompWindow   *cw,
+                     MetaFrameBorders  borders,
+                     int               width,
+                     int               height)
+{
+  int shadow_dx;
+  int shadow_dy;
+  cairo_region_t *visible_region;
+  XRectangle rect;
+  XserverRegion region1;
+  XserverRegion region2;
+
+  if (!cw->window)
+    return;
+
+  visible_region = meta_window_get_frame_bounds (cw->window);
+
+  if (!visible_region)
+    return;
+
+  shadow_dx = -1 * shadow_offsets_x [cw->shadow_type];
+  shadow_dy = -1 * shadow_offsets_y [cw->shadow_type];
+
+  rect.x = 0;
+  rect.y = 0;
+  rect.width = width;
+  rect.height = height;
+
+  region1 = XFixesCreateRegion (xdisplay, &rect, 1);
+  region2 = cairo_region_to_xserver_region (xdisplay, visible_region);
+
+  XFixesTranslateRegion (xdisplay, region2,
+                         shadow_dx, shadow_dy);
+
+  XFixesSubtractRegion (xdisplay, region1, region1, region2);
+  XFixesSetPictureClipRegion (xdisplay, shadow_picture, 0, 0, region1);
+
+  XFixesDestroyRegion (xdisplay, region1);
+  XFixesDestroyRegion (xdisplay, region2);
 }
 
 static Picture
 shadow_picture (MetaDisplay      *display,
                 MetaScreen       *screen,
-                MetaShadowType    shadow_type,
+                MetaCompWindow   *cw,
                 double            opacity,
-                Picture           alpha_pict,
                 MetaFrameBorders  borders,
                 int               width,
                 int               height,
@@ -687,7 +690,7 @@ shadow_picture (MetaDisplay      *display,
   Window xroot = meta_screen_get_xroot (screen);
   GC gc;
 
-  shadow_image = make_shadow (display, screen, shadow_type,
+  shadow_image = make_shadow (display, screen, cw->shadow_type,
                               opacity, width, height);
   if (!shadow_image)
     return None;
@@ -710,10 +713,8 @@ shadow_picture (MetaDisplay      *display,
       return None;
     }
 
-  shadow_clip (xdisplay,
-               shadow_picture, shadow_image, shadow_type,
-               borders,
-               width, height);
+  shadow_picture_clip (xdisplay, shadow_picture, cw, borders,
+                       shadow_image->width, shadow_image->height);
 
   gc = XCreateGC (xdisplay, shadow_pixmap, 0, 0);
   if (!gc)
@@ -1069,9 +1070,7 @@ win_extents (MetaCompWindow *cw)
           if (cw->opacity != (guint) OPAQUE)
             opacity = opacity * ((double) cw->opacity) / ((double) OPAQUE);
 
-          cw->shadow = shadow_picture (display, screen, cw->shadow_type,
-                                       opacity, cw->alpha_pict,
-                                       borders,
+          cw->shadow = shadow_picture (display, screen, cw, opacity, borders,
                                        cw->attrs.width + cw->attrs.border_width * 2,
                                        cw->attrs.height + cw->attrs.border_width * 2,
                                        &cw->shadow_width, &cw->shadow_height);