Bug 655005 - [RTL] left scrollbar is mispositioned when the control sidebar is visible [r=mfinkle]

mobile/chrome/content/browser.js

@@ -1394,13 +1394,12 @@ Browser.MainDragger.prototype = {
       // the 'solution' for now is to reposition it if needed
       let x = 0;
       if (Browser.floatedWhileDragging) {
+        let [tabsVis, controlsVis, tabsW, controlsW] = Browser.computeSidebarVisibility();
+        let [tabsSidebar, controlsSidebar] = [Elements.tabs.getBoundingClientRect(), Elements.controls.getBoundingClientRect()];
+
         // Check if the sidebars are inverted (rtl)
-        let [leftVis, rightVis, leftW, rightW] = Browser.computeSidebarVisibility();
-        let [leftSidebar, rightSidebar] = [Elements.tabs.getBoundingClientRect(), Elements.controls.getBoundingClientRect()];
-        if (leftSidebar.left > rightSidebar.left)
-          x = Math.round(Math.max(0, rightW * rightVis));
-        else
-          x = Math.round(Math.max(0, leftW * leftVis)) * -1.0;
+        let direction = (tabsSidebar.left > controlsSidebar.left) ? 1 : -1;
+        x = Math.round(tabsW * tabsVis) * direction
       }
 
       this._verticalScrollbar.style.MozTransform = "translate(" + x + "px," + y + "px)";

mobile/chrome/tests/browser_scrollbar.js

@@ -56,6 +56,21 @@ function checkScrollbars(aHorizontalVisible, aVerticalVisible, aHorizontalPositi
   EventUtils.synthesizeMouse(browser, width / 2, height * 3 / 4, { type: "mouseup" });
 }
 
+function checkScrollbarsPosition(aX) {
+  let browser = getBrowser();
+  let width = browser.getBoundingClientRect().width;
+  let height = browser.getBoundingClientRect().height;
+  EventUtils.synthesizeMouse(browser, width / 2, height / 4, { type: "mousedown" });
+  EventUtils.synthesizeMouse(browser, width / 2, height * 3 / 4, { type: "mousemove" });
+
+  let verticalRect = verticalScrollbar.getBoundingClientRect();
+  let margin = parseInt(verticalScrollbar.getAttribute("end"));
+  let expectedPosition = window.innerWidth - aX - margin;
+  is(verticalRect.right, expectedPosition, "The vertical scrollbar should be position to " + expectedPosition + " (got " + verticalRect.right + ")");
+
+  EventUtils.synthesizeMouse(browser, width / 2, height * 3 / 4, { type: "mouseup" });
+}
+
 gTests.push({
   desc: "Testing visibility of scrollbars",
 
@@ -101,6 +116,41 @@ gTests.push({
   }
 });
 
+gTests.push({
+  desc: "Testing position of scrollbars",
+
+  run: function() {
+    waitForPageShow(testURL_01 + "vertical", gCurrentTest.checkScrollbarsPosition);
+    gOpenedTabs.push(Browser.addTab(testURL_01 + "vertical", true));
+  },
+
+  checkScrollbarsPosition: function() {
+    let [,, tabsWidth, controlsWidth] = Browser.computeSidebarVisibility();
+
+    checkScrollbarsPosition(0);
+
+    // Show the left sidebar and ensure scrollbar is visible
+    Browser.controlsScrollboxScroller.scrollTo(0, 0);
+    checkScrollbarsPosition(-tabsWidth);
+
+    // Show the right sidebar and ensure scrollbar is visible
+    Browser.controlsScrollboxScroller.scrollTo(tabsWidth + controlsWidth, 0);
+    checkScrollbarsPosition(controlsWidth);
+
+    gCurrentTest.finish();
+  },
+
+  finish: function() {
+    Elements.browsers.addEventListener("PanFinished", function(aEvent) {
+      Elements.browsers.removeEventListener("PanFinished", arguments.callee, false);
+      setTimeout(function() {
+        Browser.hideSidebars();
+      }, 0);
+      runNextTest();
+    }, false);
+  }
+});
+
 
 gTests.push({
   desc: "Check scrollbar visibility when the touch sequence is cancelled",