Changeset 118569 in webkit

Timestamp:

May 25, 2012 2:48:51 PM (12 years ago)

Author:

jknotten@chromium.org

Message:

Body scrollWidth() and scrollHeight() should be page scale-invariant
​https://bugs.webkit.org/show_bug.cgi?id=87494

RenderView::documentRect() is calculating the "scaled" document rect by applying
the current transformation matrix to the unscaledDocumentRect() and then
returning the rounded-out IntRect result.

This rounding out is incorrect because it allows the scaled rectangle to
represent an area that is not actually covered by the document.

We fix this by applying the current transform to the document rect
as a FloatRect and then explicitly converting to IntRect, which
takes the floor of the resulting rectangle coordinates instead of
rounding them out.

This is evidenced by the document.body.scrollWidth() and
document.body.scrollHeight() changing under page scale factor when
they are expected to remain invariant.

Reviewed by James Robinson.

Source/WebCore:

Test: fast/dom/window-scroll-scaling.html

• rendering/RenderView.cpp:

(WebCore::RenderView::documentRect):

LayoutTests:

• fast/dom/window-scroll-scaling-expected.txt: Added.
• fast/dom/window-scroll-scaling.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/fast/dom/window-scroll-scaling-expected.txt (added)
• LayoutTests/fast/dom/window-scroll-scaling.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/rendering/RenderView.cpp (modified) (1 diff)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2012-05-25  John Knottenbelt  <jknotten@chromium.org>
+
+        Body scrollWidth() and scrollHeight() should be page scale-invariant
+        https://bugs.webkit.org/show_bug.cgi?id=87494
+
+        RenderView::documentRect() is calculating the "scaled" document rect by applying
+        the current transformation matrix to the unscaledDocumentRect() and then
+        returning the rounded-out IntRect result.
+
+        This rounding out is incorrect because it allows the scaled rectangle to
+        represent an area that is not actually covered by the document.
+
+        We fix this by applying the current transform to the document rect
+        as a FloatRect and then explicitly converting to IntRect, which
+        takes the floor of the resulting rectangle coordinates instead of
+        rounding them out.
+
+        This is evidenced by the document.body.scrollWidth() and
+        document.body.scrollHeight() changing under page scale factor when
+        they are expected to remain invariant.
+
+        Reviewed by James Robinson.
+
+        * fast/dom/window-scroll-scaling-expected.txt: Added.
+        * fast/dom/window-scroll-scaling.html: Added.
+
 2012-05-25  Simon Fraser  <simon.fraser@apple.com>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2012-05-25  John Knottenbelt  <jknotten@chromium.org>
+
+        Body scrollWidth() and scrollHeight() should be page scale-invariant
+        https://bugs.webkit.org/show_bug.cgi?id=87494
+
+        RenderView::documentRect() is calculating the "scaled" document rect by applying
+        the current transformation matrix to the unscaledDocumentRect() and then
+        returning the rounded-out IntRect result.
+
+        This rounding out is incorrect because it allows the scaled rectangle to
+        represent an area that is not actually covered by the document.
+
+        We fix this by applying the current transform to the document rect
+        as a FloatRect and then explicitly converting to IntRect, which
+        takes the floor of the resulting rectangle coordinates instead of
+        rounding them out.
+
+        This is evidenced by the document.body.scrollWidth() and
+        document.body.scrollHeight() changing under page scale factor when
+        they are expected to remain invariant.
+
+        Reviewed by James Robinson.
+
+        Test: fast/dom/window-scroll-scaling.html
+
+        * rendering/RenderView.cpp:
+        (WebCore::RenderView::documentRect):
+
 2012-05-25  Dan Bernstein  <mitz@apple.com>
 

trunk/Source/WebCore/rendering/RenderView.cpp

@@ -756 +756 @@
 IntRect RenderView::documentRect() const
 {
-    IntRect overflowRect(unscaledDocumentRect());
+    FloatRect overflowRect(unscaledDocumentRect());
     if (hasTransform())
         overflowRect = layer()->currentTransform().mapRect(overflowRect);
-    return overflowRect;
+    return IntRect(overflowRect);
 }