diff --git a/src/common.h b/src/common.h
index 7778c74..1414ceb 100644
--- a/src/common.h
+++ b/src/common.h
@@ -1028,6 +1028,16 @@ typedef struct session {
 #endif
 } session_t;
 
+/**
+ * About coordinate systems
+ *
+ * In general, X is the horizontal axis, Y is the vertical axis.
+ * X goes from left to right, Y goes downwards.
+ *
+ * Global: the origin is the top left corner of the Xorg screen.
+ * Local: the origin is the top left corner of the window, including border.
+ */
+
 /// Structure representing a top-level window compton manages.
 struct win {
   /// Pointer to the next lower window in window stack.
@@ -1061,7 +1071,8 @@ struct win {
   xcb_damage_damage_t damage;
   /// Paint info of the window.
   paint_t paint;
-  /// Bounding shape of the window.
+  /// Bounding shape of the window. In local coordinates.
+  /// See above about coordinate systems.
   region_t bounding_shape;
   /// Window flags. Definitions above.
   int_fast16_t flags;
diff --git a/src/compton.c b/src/compton.c
index ab8fbdd..b2b991c 100644
--- a/src/compton.c
+++ b/src/compton.c
@@ -654,6 +654,7 @@ static bool
 win_build_shadow(session_t *ps, win *w, double opacity) {
   const int width = w->widthb;
   const int height = w->heightb;
+  //printf_errf("(): building shadow for %s %d %d", w->name, width, height);
 
   xcb_image_t *shadow_image = NULL;
   xcb_pixmap_t shadow_pixmap = None, shadow_pixmap_argb = None;
@@ -1113,6 +1114,7 @@ paint_preprocess(session_t *ps, win *list) {
         || get_alpha_pict_o(ps, w->opacity) == ps->alpha_picts[0]
         || w->paint_excluded)
       to_paint = false;
+    //printf_errf("(): %s %d %d %d", w->name, to_paint, w->opacity, w->paint_excluded);
 
     // Add window to damaged area if its painting status changes
     // or opacity changes
@@ -1125,11 +1127,6 @@ paint_preprocess(session_t *ps, win *list) {
     if (!to_paint)
       goto skip_window;
 
-    // XXX shouldn't need these
-    // Fetch bounding region
-    if (!pixman_region32_not_empty(&w->bounding_shape))
-      win_update_bounding_shape(ps, w);
-
     // Fetch window extents
     region_t extents;
     pixman_region32_init(&extents);
@@ -1148,10 +1145,11 @@ paint_preprocess(session_t *ps, win *list) {
     if (w->mode == WMODE_SOLID && !ps->o.force_win_blend) {
       region_t *tmp = rc_region_new();
       if (w->frame_opacity == 1)
-        copy_region(tmp, &w->bounding_shape);
+        *tmp = win_get_bounding_shape_global_by_val(w);
       else {
-        win_get_region_noframe(ps, w, true, tmp);
+        win_get_region_noframe_local(ps, w, tmp);
         pixman_region32_intersect(tmp, tmp, &w->bounding_shape);
+        pixman_region32_translate(tmp, w->g.x, w->g.y);
       }
 
       pixman_region32_union(tmp, tmp, last_reg_ignore);
@@ -1389,13 +1387,12 @@ win_blur_background(session_t *ps, win *w, xcb_render_picture_t tgt_buffer,
 
         // Minimize the region we try to blur, if the window itself is not
         // opaque, only the frame is.
-        region_t reg_blur;
-        pixman_region32_init(&reg_blur);
-        pixman_region32_copy(&reg_blur, &w->bounding_shape);
+        region_t reg_blur = win_get_bounding_shape_global_by_val(w);
         if (win_is_solid(ps, w)) {
           region_t reg_noframe;
           pixman_region32_init(&reg_noframe);
-          win_get_region_noframe(ps, w, true, &reg_noframe);
+          win_get_region_noframe_local(ps, w, &reg_noframe);
+          pixman_region32_translate(&reg_noframe, w->g.x, w->g.y);
           pixman_region32_subtract(&reg_blur, &reg_blur, &reg_noframe);
           pixman_region32_fini(&reg_noframe);
         }
@@ -1754,6 +1751,7 @@ paint_all(session_t *ps, region_t *region, const region_t *region_real, win * co
   //
   // Whether this is beneficial is to be determined XXX
   for (win *w = t; w; w = w->prev_trans) {
+    region_t bshape = win_get_bounding_shape_global_by_val(w);
     // Painting shadow
     if (w->shadow) {
       // Lazy shadow building
@@ -1777,7 +1775,7 @@ paint_all(session_t *ps, region_t *region, const region_t *region_real, win * co
       // Mask out the body of the window from the shadow
       // Doing it here instead of in make_shadow() for saving GPU
       // power and handling shaped windows (XXX unconfirmed)
-      pixman_region32_subtract(&reg_tmp, &reg_tmp, &w->bounding_shape);
+      pixman_region32_subtract(&reg_tmp, &reg_tmp, &bshape);
 
 #ifdef CONFIG_XINERAMA
       if (ps->o.xinerama_shadow_crop && w->xinerama_scr >= 0)
@@ -1796,7 +1794,8 @@ paint_all(session_t *ps, region_t *region, const region_t *region_real, win * co
     // window and the bounding region
     // XXX XXX
     pixman_region32_subtract(&reg_tmp, region, w->reg_ignore);
-    pixman_region32_intersect(&reg_tmp, &reg_tmp, &w->bounding_shape);
+    pixman_region32_intersect(&reg_tmp, &reg_tmp, &bshape);
+    pixman_region32_fini(&bshape);
 
     if (pixman_region32_not_empty(&reg_tmp)) {
         set_tgt_clip(ps, &reg_tmp);
@@ -2280,18 +2279,12 @@ configure_win(session_t *ps, xcb_configure_notify_event_t *ce) {
     // If window geometry change, free old extents
     if (w->g.x != ce->x || w->g.y != ce->y
         || w->g.width != ce->width || w->g.height != ce->height
-        || w->g.border_width != ce->border_width) {
+        || w->g.border_width != ce->border_width)
       factor_change = true;
-      pixman_region32_clear(&w->bounding_shape);
-    }
 
     w->g.x = ce->x;
     w->g.y = ce->y;
 
-    if (w->g.width != ce->width || w->g.height != ce->height
-        || w->g.border_width != ce->border_width)
-      free_wpaint(ps, w);
-
     if (w->g.width != ce->width || w->g.height != ce->height
         || w->g.border_width != ce->border_width) {
       w->g.width = ce->width;
@@ -2310,7 +2303,6 @@ configure_win(session_t *ps, xcb_configure_notify_event_t *ce) {
     if (factor_change) {
       add_damage(ps, &damage);
       cxinerama_win_upd_scr(ps, w);
-      win_on_factor_change(ps, w);
     }
   }
 
@@ -2981,10 +2973,17 @@ ev_shape_notify(session_t *ps, xcb_shape_notify_event_t *ev) {
    * if we attempt to rebuild border_size
    */
   // Mark the old border_size as damaged
-  add_damage(ps, &w->bounding_shape);
+  region_t tmp = win_get_bounding_shape_global_by_val(w);
+  add_damage(ps, &tmp);
+  pixman_region32_fini(&tmp);
+
   win_update_bounding_shape(ps, w);
+
   // Mark the new border_size as damaged
-  add_damage(ps, &w->bounding_shape);
+  tmp = win_get_bounding_shape_global_by_val(w);
+  add_damage(ps, &tmp);
+  pixman_region32_fini(&tmp);
+
   w->reg_ignore_valid = false;
 }
 
diff --git a/src/win.c b/src/win.c
index 73d4e2d..ab205f2 100644
--- a/src/win.c
+++ b/src/win.c
@@ -16,6 +16,16 @@
 
 #include "win.h"
 
+/// Generate a "return by value" function, from a function that returns the
+/// region via a region_t pointer argument.
+/// Function signature has to be (win *, region_t *)
+#define gen_by_val(fun) void region_t fun##_by_val(win *w) { \
+  region_t ret; \
+  pixman_region32_init(&ret); \
+  fun(w, &ret); \
+  return ret; \
+}
+
 /**
  * Clear leader cache of all windows.
  */
@@ -78,23 +88,20 @@ group_is_focused(session_t *ps, Window leader) {
 /**
  * Get a rectangular region a window occupies, excluding shadow.
  */
-void win_get_region(session_t *ps, win *w, bool global, region_t *res) {
+static void win_get_region_local(session_t *ps, win *w, region_t *res) {
   pixman_region32_fini(res);
-  pixman_region32_init_rect(res,
-      global ? w->g.x : 0,
-      global ? w->g.y : 0,
-      w->widthb, w->heightb);
+  pixman_region32_init_rect(res, 0, 0, w->widthb, w->heightb);
 }
 
 
 /**
  * Get a rectangular region a window occupies, excluding frame and shadow.
  */
-void win_get_region_noframe(session_t *ps, win *w, bool global, region_t *res) {
+void win_get_region_noframe_local(session_t *ps, win *w, region_t *res) {
   const margin_t extents = win_calc_frame_extents(ps, w);
 
-  int x = (global ? w->g.x: 0) + extents.left;
-  int y = (global ? w->g.y: 0) + extents.top;
+  int x = extents.left;
+  int y = extents.top;
   int width = max_i(w->g.width - extents.left - extents.right, 0);
   int height = max_i(w->g.height - extents.top - extents.bottom, 0);
 
@@ -880,6 +887,7 @@ bool add_win(session_t *ps, Window id, Window prev) {
 
   new->next = *p;
   *p = new;
+  win_update_bounding_shape(ps, new);
 
 #ifdef CONFIG_DBUS
   // Send D-Bus signal
@@ -1144,10 +1152,11 @@ void win_update_bounding_shape(session_t *ps, win *w) {
 
   pixman_region32_clear(&w->bounding_shape);
   // Start with the window rectangular region
-  win_get_region(ps, w, true, &w->bounding_shape);
+  win_get_region_local(ps, w, &w->bounding_shape);
 
   // Only request for a bounding region if the window is shaped
-  if (w->bounding_shaped) {
+  // (while loop is used to avoid goto, not an actual loop)
+  while (w->bounding_shaped) {
     /*
      * if window doesn't exist anymore,  this will generate an error
      * as well as not generate a region.
@@ -1157,7 +1166,7 @@ void win_update_bounding_shape(session_t *ps, win *w) {
         xcb_shape_get_rectangles(ps->c, w->id, XCB_SHAPE_SK_BOUNDING), NULL);
 
     if (!r)
-      return;
+      break;
 
     xcb_rectangle_t *xrects = xcb_shape_get_rectangles_rectangles(r);
     int nrects = xcb_shape_get_rectangles_rectangles_length(r);
@@ -1171,22 +1180,24 @@ void win_update_bounding_shape(session_t *ps, win *w) {
     // Add border width because we are using a different origin.
     // X thinks the top left of the inner window is the origin,
     // We think the top left of the border is the origin
-    pixman_region32_translate(&br, w->g.x + w->g.border_width,
-      w->g.y + w->g.border_width);
+    pixman_region32_translate(&br, w->g.border_width, w->g.border_width);
 
     // Intersect the bounding region we got with the window rectangle, to
     // make sure the bounding region is not bigger than the window
     // rectangle
     pixman_region32_intersect(&w->bounding_shape, &w->bounding_shape, &br);
     pixman_region32_fini(&br);
+    break;
   }
 
   if (w->bounding_shaped && ps->o.detect_rounded_corners)
     win_rounded_corners(ps, w);
 
-  // XXX Window shape changed, and if we didn't fill in the pixels
-  // behind the window (not implemented yet), we should rebuild
-  // the shadow_pict
+  // Window shape changed, we should free old wpaint and shadow pict
+  free_wpaint(ps, w);
+  free_paint(ps, &w->shadow_paint);
+  //printf_errf("(): free out dated pict");
+
   win_on_factor_change(ps, w);
 }
 
diff --git a/src/win.h b/src/win.h
index 9374283..42b0cc0 100644
--- a/src/win.h
+++ b/src/win.h
@@ -70,16 +70,12 @@ void win_extents(win *w, region_t *res);
  * @param w struct _win element representing the window
  */
 void add_damage_from_win(session_t *ps, win *w);
-/**
- * Get a rectangular region a window occupies, excluding shadow.
- *
- * global = use global coordinates
- */
-void win_get_region(session_t *ps, win *w, bool global, region_t *);
 /**
  * Get a rectangular region a window occupies, excluding frame and shadow.
+ *
+ * Return region in global coordinates.
  */
-void win_get_region_noframe(session_t *ps, win *w, bool global, region_t *);
+void win_get_region_noframe_local(session_t *ps, win *w, region_t *);
 /**
  * Retrieve frame extents from a window.
  */
@@ -102,3 +98,12 @@ bool win_has_alpha(win *w);
 
 /// check if reg_ignore_valid is true for all windows above us
 bool win_is_region_ignore_valid(session_t *ps, win *w);
+
+static inline region_t
+win_get_bounding_shape_global_by_val(win *w) {
+  region_t ret;
+  pixman_region32_init(&ret);
+  pixman_region32_copy(&ret, &w->bounding_shape);
+  pixman_region32_translate(&ret, w->g.x, w->g.y);
+  return ret;
+}