Bug 334765. Don't include scroll offsets in DOM element offset calculations. r+sr=bzbarsky

git-svn-id: svn://10.0.0.236/trunk@199159 18797224-902f-48f8-a5cc-f745e15eee43

mozilla/content/html/content/src/nsGenericHTMLElement.cpp

@@ -142,6 +142,7 @@
 #include "nsIEditor.h"
 #include "nsIEditorIMESupport.h"
 #include "nsEventDispatcher.h"
+#include "nsLayoutUtils.h"
 
 // XXX todo: add in missing out-of-memory checks
 
@@ -625,20 +626,7 @@ nsGenericHTMLElement::GetOffsetRect(nsRect& aRect, nsIContent** aOffsetParent)
   }
 
   // Get the union of all rectangles in this and continuation frames
-  nsRect rcFrame;
-  nsIFrame* next = frame;
-
-  do {
-    rcFrame.UnionRect(rcFrame, next->GetRect());
-    next = next->GetNextContinuation();
-  } while (next);
-
-  if (rcFrame.IsEmpty()) {
-    // It could happen that all the rects are empty (eg zero-width or
-    // zero-height).  In that case, use the first rect for the frame.
-    rcFrame = frame->GetRect();
-  }
-
+  nsRect rcFrame = nsLayoutUtils::GetUnionOfAllRects(frame);
   nsIContent *docElement = document->GetRootContent();
 
   // Find the frame parent whose content's tagName either matches
@@ -662,7 +650,7 @@ nsGenericHTMLElement::GetOffsetRect(nsRect& aRect, nsIContent** aOffsetParent)
     PRBool is_absolutely_positioned = PR_FALSE;
     PRBool is_positioned = PR_FALSE;
 
-    origin = frame->GetPosition();
+    origin = nsLayoutUtils::GetPositionIgnoringScrolling(frame);
 
     const nsStyleDisplay* display = frame->GetStyleDisplay();
 
@@ -698,7 +686,7 @@ nsGenericHTMLElement::GetOffsetRect(nsRect& aRect, nsIContent** aOffsetParent)
       // right coordinate system
 
       if (!is_absolutely_positioned) {
-        origin += parent->GetPosition();
+        origin += nsLayoutUtils::GetPositionIgnoringScrolling(parent);
       }
 
       content = parent->GetContent();

mozilla/layout/base/nsLayoutUtils.cpp

@@ -473,6 +473,47 @@ nsLayoutUtils::GetNearestScrollingView(nsIView* aView, Direction aDirection)
   return scrollableView;
 }
 
+nsPoint
+nsLayoutUtils::GetPositionIgnoringScrolling(nsIFrame* aFrame)
+{
+  nsIFrame* parent = aFrame->GetParent();
+  if (!parent)
+    return aFrame->GetPosition();
+  nsIScrollableFrame* scrollable;
+  CallQueryInterface(parent, &scrollable);
+  if (!scrollable)
+    return aFrame->GetPosition();
+  // Compensate for the scroll position ... this might not result in (0,0)
+  // if there is a scrollbar above or to the left of the content. Note that
+  // scrolling moves the frame's position by the negative of GetScrollPosition.
+  return aFrame->GetPosition() + scrollable->GetScrollPosition();
+}
+
+nsRect
+nsLayoutUtils::GetUnionOfAllRects(nsIFrame* aFrame)
+{
+  nsRect rcFrame;
+  nsIFrame* next = aFrame;
+  nsIFrame* frameParent = aFrame->GetParent();
+  if (!frameParent)
+    return aFrame->GetRect();
+
+  do {
+    nsRect r = next->GetRect() + next->GetParent()->GetOffsetTo(frameParent);
+    rcFrame.UnionRect(rcFrame, r);
+    next = next->GetNextContinuation();
+  } while (next);
+
+  if (rcFrame.IsEmpty()) {
+    // It could happen that all the rects are empty (eg zero-width or
+    // zero-height).  In that case, use the first rect for the frame, so the
+    // x and y coordinates are usable.
+    rcFrame = aFrame->GetRect();
+  }
+
+  return rcFrame;
+}
+
 nsPoint
 nsLayoutUtils::GetDOMEventCoordinatesRelativeTo(nsIDOMEvent* aDOMEvent, nsIFrame* aFrame)
 {

mozilla/layout/base/nsLayoutUtils.h

@@ -261,6 +261,19 @@ public:
    * its pres-shell
    */
   static PRBool IsInitialContainingBlock(nsIFrame* aFrame);
+  
+  /**
+   * @return the offset of aFrame from its parent, as if it were scrolled to
+   * the top.
+   */
+  static nsPoint GetPositionIgnoringScrolling(nsIFrame* aFrame);
+
+  /**
+   * @return a rectangle relative to aFrame's parent that is the union of
+   * aFrame->GetRect() plus the GetRect()s of all aFrame's continuations. If
+   * all the rects are empty we just return aFrame->GetRect().
+   */
+  static nsRect GetUnionOfAllRects(nsIFrame* aFrame);
 
   /**
    * Get the coordinates of a given DOM mouse event, relative to a given

mozilla/layout/xul/base/src/nsBoxObject.cpp

@@ -56,6 +56,7 @@
 #include "nsIWidget.h"
 #include "nsIDOMXULElement.h"
 #include "nsIFrame.h"
+#include "nsLayoutUtils.h"
 
 // Static IIDs/CIDs. Try to minimize these.
 static NS_DEFINE_CID(kLookAndFeelCID, NS_LOOKANDFEEL_CID);
@@ -195,15 +196,10 @@ nsBoxObject::GetOffsetRect(nsRect& aRect)
   nsIFrame* frame = GetFrame(PR_TRUE);
   if (frame) {
     // Get its origin
-    nsPoint origin = frame->GetPosition();
+    nsPoint origin = nsLayoutUtils::GetPositionIgnoringScrolling(frame);
 
     // Get the union of all rectangles in this and continuation frames
-    nsRect rcFrame;
-    nsIFrame* next = frame;
-    do {
-      rcFrame.UnionRect(rcFrame, next->GetRect());
-      next = next->GetNextContinuation();
-    } while (nsnull != next);
+    nsRect rcFrame = nsLayoutUtils::GetUnionOfAllRects(frame);
         
     // Find the frame parent whose content is the document element.
     nsIContent *docElement = mContent->GetCurrentDoc()->GetRootContent();
@@ -216,7 +212,7 @@ nsBoxObject::GetOffsetRect(nsRect& aRect)
 
       // Add the parent's origin to our own to get to the
       // right coordinate system
-      origin += parent->GetPosition();
+      origin += nsLayoutUtils::GetPositionIgnoringScrolling(parent);
 
       parent = parent->GetParent();
     }