Improvement: Change clear_shadow implementation

- Implement clear_shadow with painting region limitation instead of
  calculation in shadow image, to make it work correctly on windows with
  rounded corners, requested by funeral1988. This might cause more load
  on CPU, but could mean less load for GPU. The original implementation
  is kept but commented out.

- Code cleanup.

compton.c

@@ -463,7 +463,7 @@ presum_gaussian(conv *map) {
 
 static XImage *
 make_shadow(Display *dpy, double opacity,
-            int width, int height) {
+            int width, int height, Bool clear_shadow) {
   XImage *ximage;
   unsigned char *data;
   int ylimit, xlimit;
@@ -500,8 +500,8 @@ make_shadow(Display *dpy, double opacity,
   // later will be filled) could entirely cover the area of the shadow
   // that will be displayed, do not bother filling other pixels. If it
   // can't, we must fill the other pixels here.
-  if (!(opts.clear_shadow && opts.shadow_offset_x <= 0 && opts.shadow_offset_x >= -cgsize
-        && opts.shadow_offset_y <= 0 && opts.shadow_offset_y >= -cgsize)) {
+  /* if (!(clear_shadow && opts.shadow_offset_x <= 0 && opts.shadow_offset_x >= -cgsize
+        && opts.shadow_offset_y <= 0 && opts.shadow_offset_y >= -cgsize)) { */
     if (cgsize > 0) {
       d = shadow_top[opacity_int * (cgsize + 1) + cgsize];
     } else {
@@ -509,7 +509,7 @@ make_shadow(Display *dpy, double opacity,
         opacity, center, center, width, height);
     }
     memset(data, d, sheight * swidth);
-  }
+  // }
 
   /*
    * corners
@@ -572,7 +572,9 @@ make_shadow(Display *dpy, double opacity,
     }
   }
 
-  if (opts.clear_shadow) {
+  assert(!clear_shadow);
+  /*
+  if (clear_shadow) {
     // Clear the region in the shadow that the window would cover based
     // on shadow_offset_{x,y} user provides
     int xstart = normalize_i_range(- (int) opts.shadow_offset_x, 0, swidth);
@@ -587,18 +589,20 @@ make_shadow(Display *dpy, double opacity,
       memset(&data[y * swidth + xstart], 0, xrange);
     }
   }
+  */
 
   return ximage;
 }
 
 static Picture
-shadow_picture(Display *dpy, double opacity, int width, int height) {
+shadow_picture(Display *dpy, double opacity, int width, int height,
+    Bool clear_shadow) {
   XImage *shadow_image = NULL;
   Pixmap shadow_pixmap = None, shadow_pixmap_argb = None;
   Picture shadow_picture = None, shadow_picture_argb = None;
   GC gc = None;
 
-  shadow_image = make_shadow(dpy, opacity, width, height);
+  shadow_image = make_shadow(dpy, opacity, width, height, clear_shadow);
   if (!shadow_image)
     return None;
 
@@ -1466,7 +1470,7 @@ paint_preprocess(Display *dpy, win *list) {
 
     if (w->shadow && !w->shadow_pict) {
       w->shadow_pict = shadow_picture(dpy, 1,
-          w->widthb, w->heightb);
+          w->widthb, w->heightb, False);
     }
 
     w->shadow_alpha_pict = get_alpha_pict_d(w->shadow_opacity);
@@ -1672,8 +1676,13 @@ paint_all(Display *dpy, XserverRegion region, win *t) {
         XFixesIntersectRegion(dpy, reg_paint, reg_paint, w->extents);
       }
       else {
-        reg_paint = region;
+        reg_paint = reg_tmp;
+        XFixesIntersectRegion(dpy, reg_paint, region, w->extents);
       }
+      // Clear the shadow here instead of in make_shadow() for saving GPU
+      // power and handling shaped windows
+      if (opts.clear_shadow)
+        XFixesSubtractRegion(dpy, reg_paint, reg_paint, w->border_size);
 
       // Detect if the region is empty before painting
       if (region == reg_paint || !is_region_empty(dpy, reg_paint)) {
@@ -1885,11 +1894,7 @@ map_win(Display *dpy, Window id,
 #endif
 
   // Detect if the window is shaped or has rounded corners
-  if (opts.shadow_ignore_shaped) {
-    w->bounding_shaped = wid_bounding_shaped(dpy, w->id);
-    if (w->bounding_shaped && opts.detect_rounded_corners)
-      win_rounded_corners(dpy, w);
-  }
+  win_update_shape(dpy, w);
 
   // Get window name and class if we are tracking them
   if (opts.track_wdata) {
@@ -2144,6 +2149,30 @@ determine_fade(Display *dpy, win *w) {
   w->fade = opts.wintype_fade[w->window_type];
 }
 
+/**
+ * Update window-shape related information.
+ */
+static void
+win_update_shape(Display *dpy, win *w) {
+  if (shape_exists && (opts.shadow_ignore_shaped /* || opts.clear_shadow */)) {
+    // Bool bounding_shaped_old = w->bounding_shaped;
+
+    w->bounding_shaped = wid_bounding_shaped(dpy, w->id);
+    if (w->bounding_shaped && opts.detect_rounded_corners)
+      win_rounded_corners(dpy, w);
+
+    // Shadow state could be changed
+    determine_shadow(dpy, w);
+
+    /*
+    // If clear_shadow state on the window possibly changed, destroy the old
+    // shadow_pict
+    if (opts.clear_shadow && w->bounding_shaped != bounding_shaped_old)
+      free_picture(dpy, &w->shadow_pict);
+    */
+  }
+}
+
 /**
  * Determine if a window should have shadow, and update things depending
  * on shadow state.
@@ -3130,14 +3159,7 @@ ev_shape_notify(XShapeEvent *ev) {
   }
 
   // Redo bounding shape detection and rounded corner detection
-  if (opts.shadow_ignore_shaped) {
-    w->bounding_shaped = wid_bounding_shaped(dpy, w->id);
-    if (w->bounding_shaped && opts.detect_rounded_corners)
-      win_rounded_corners(dpy, w);
-
-    // Shadow state could be changed
-    determine_shadow(dpy, w);
-  }
+  win_update_shape(dpy, w);
 }
 
 /**

compton.h

@@ -740,10 +740,11 @@ presum_gaussian(conv *map);
 
 static XImage *
 make_shadow(Display *dpy, double opacity,
-            int width, int height);
+            int width, int height, Bool clear_shadow);
 
 static Picture
-shadow_picture(Display *dpy, double opacity, int width, int height);
+shadow_picture(Display *dpy, double opacity, int width, int height,
+    Bool clear_shadow);
 
 static Picture
 solid_picture(Display *dpy, Bool argb, double a,
@@ -922,6 +923,9 @@ set_focused(Display *dpy, win *w, Bool focused) {
 static void
 determine_fade(Display *dpy, win *w);
 
+static void
+win_update_shape(Display *dpy, win *w);
+
 static void
 determine_shadow(Display *dpy, win *w);