Bug 531871 - Clipping problem with some flash [r=mfinkle]

mobile/chrome/content/browser.js

@@ -3045,8 +3045,7 @@ PluginObserver.prototype = {
     }
   },
 
-  /** More accurate version of finding the current visible region. */
-  // XXX should visible rect call take some of these things into account?
+  /** More accurate version of finding the current visible region. Returns client coords. */
   getCriticalRect: function getCriticalRect() {
     let bv = this._bv;
     if (!bv.isRendering())
@@ -3057,23 +3056,30 @@ PluginObserver.prototype = {
     let vs = bv._browserViewportState;
     let vr = bv.getVisibleRect();
     let crit = BrowserView.Util.visibleRectToCriticalRect(vr, vs);
+    crit = Browser.browserViewToClientRect(crit);
 
     if (BrowserUI.isToolbarLocked()) {
-      let urlbar = document.getElementById("toolbar-moveable-container");
-      let height = urlbar.getBoundingClientRect().height;
-      crit.top += height;
+      let urlbar = document.getElementById("toolbar-container");
+      let urlbarRect = urlbar.getBoundingClientRect();
+      // Subtract urlbar area from critical rect area.  In general subtracting a rect from another
+      // results in a region that can be described by a union of rects.  Luckily in this case,
+      // we can cheat because the resulting area is still just one rect.
+      crit.top = Math.max(urlbarRect.height, crit.top);
     }
     return crit;
   },
 
-  /** Tell embedded objects where to absolutely render, using crit for clipping. */
+  /**
+   * Tell embedded objects where to absolutely render, using crit for clipping.
+   * @param crit Specified in client coordinates
+   */
   updateEmbedRegions: function updateEmbedRegions(objects, crit) {
     let bv = this._bv;
     let oprivate, r, dest, clip;
     for (let i = objects.length - 1; i >= 0; i--) {
       r = bv.browserToViewportRect(Browser.getBoundingContentRect(objects[i]));
       dest = Browser.browserViewToClientRect(r);
-      clip = Browser.browserViewToClientRect(r.intersect(crit)).translate(-dest.left, -dest.top);
+      clip = dest.intersect(crit).translate(-dest.left, -dest.top);
       oprivate = objects[i].QueryInterface(nsIObjectLoadingContent);
       oprivate.setAbsoluteScreenPosition(Browser.contentScrollbox, dest, clip);
     }