Changeset 137368 in webkit

Timestamp:

Dec 11, 2012 3:22:05 PM (11 years ago)

Author:

wangxianzhu@chromium.org

Message:

Incorrect position of layers for fixed position elements when page is scaled smaller than viewport
​https://bugs.webkit.org/show_bug.cgi?id=104294

Reviewed by James Robinson.

Source/WebCore:

Fixed issue in scrollOffsetForFixedPosition when contentRect is smaller than visibleContentRect.
This happens when a page originally bigger than viewport is scaled down to smaller than the viewport.

Test: compositing/geometry/fixed-position-composited-page-scale-smaller-than-viewport.html

• page/scrolling/ScrollingCoordinator.cpp:

(WebCore::fixedPositionScrollOffset): Moved common code in scrollOffsetForFixedPosition here. Fixed issue when contentsSize < visibleContentSize.
(WebCore::scrollOffsetForFixedPosition):

LayoutTests:

Test the case that a page containing a composited fixed position element originally bigger than the viewport
is scaled down to be smaller than the viewport.

• compositing/geometry/fixed-position-composited-page-scale-smaller-than-viewport.html: Added.
• compositing/geometry/fixed-position-composited-page-scale-smaller-than-viewport-expected.html: Added.

Location:

trunk

Files:

• LayoutTests/ChangeLog (modified) (1 diff)
• LayoutTests/compositing/geometry/fixed-position-composited-page-scale-smaller-than-viewport-expected.html (added)
• LayoutTests/compositing/geometry/fixed-position-composited-page-scale-smaller-than-viewport.html (added)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/page/scrolling/ScrollingCoordinator.cpp (modified) (1 diff)

trunk/LayoutTests/ChangeLog

@@ +1 @@
+2012-12-11  Xianzhu Wang  <wangxianzhu@chromium.org>
+
+        Incorrect position of layers for fixed position elements when page is scaled smaller than viewport
+        https://bugs.webkit.org/show_bug.cgi?id=104294
+
+        Reviewed by James Robinson.
+
+        Test the case that a page containing a composited fixed position element originally bigger than the viewport
+        is scaled down to be smaller than the viewport.
+
+        * compositing/geometry/fixed-position-composited-page-scale-smaller-than-viewport.html: Added.
+        * compositing/geometry/fixed-position-composited-page-scale-smaller-than-viewport-expected.html: Added.
+
 2012-12-11  Adam Klein  <adamk@chromium.org>
 

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2012-12-11  Xianzhu Wang  <wangxianzhu@chromium.org>
+
+        Incorrect position of layers for fixed position elements when page is scaled smaller than viewport
+        https://bugs.webkit.org/show_bug.cgi?id=104294
+
+        Reviewed by James Robinson.
+
+        Fixed issue in scrollOffsetForFixedPosition when contentRect is smaller than visibleContentRect.
+        This happens when a page originally bigger than viewport is scaled down to smaller than the viewport.
+
+        Test: compositing/geometry/fixed-position-composited-page-scale-smaller-than-viewport.html
+
+        * page/scrolling/ScrollingCoordinator.cpp:
+        (WebCore::fixedPositionScrollOffset): Moved common code in scrollOffsetForFixedPosition here. Fixed issue when contentsSize < visibleContentSize.
+        (WebCore::scrollOffsetForFixedPosition):
+
 2012-12-11  Beth Dakin  <bdakin@apple.com>
 

trunk/Source/WebCore/page/scrolling/ScrollingCoordinator.cpp

@@ -66 +66 @@
 }
 
-static int fixedPositionScrollOffset(int scrollPosition, int maxValue, int scrollOrigin, float dragFactor)
-{
-    if (!maxValue)
+static int fixedPositionScrollOffset(int visibleContentSize, int contentsSize, int scrollPosition, int scrollOrigin, float frameScaleFactor, bool fixedElementsLayoutRelativeToFrame)
+{
+    int maxValue = contentsSize - visibleContentSize;
+    if (maxValue <= 0)
         return 0;
 
     if (!scrollOrigin) {
-        if (scrollPosition < 0)
-            scrollPosition = 0;
-        else if (scrollPosition > maxValue)
+        if (scrollPosition <= 0)
+            return 0;
+        if (scrollPosition > maxValue)
             scrollPosition = maxValue;
     } else {
-        if (scrollPosition > 0)
-            scrollPosition = 0;
-        else if (scrollPosition < -maxValue)
+        if (scrollPosition >= 0)
+            return 0;
+        if (scrollPosition < -maxValue)
             scrollPosition = -maxValue;
     }
-    
-    return scrollPosition * dragFactor;
+
+    float dragFactor = fixedElementsLayoutRelativeToFrame ? 1 : (contentsSize - visibleContentSize * frameScaleFactor) / maxValue;
+    return scrollPosition * dragFactor / frameScaleFactor;
 }
 
 IntSize scrollOffsetForFixedPosition(const IntRect& visibleContentRect, const IntSize& contentsSize, const IntPoint& scrollPosition, const IntPoint& scrollOrigin, float frameScaleFactor, bool fixedElementsLayoutRelativeToFrame)
 {
-    IntSize maxOffset(contentsSize.width() - visibleContentRect.width(), contentsSize.height() - visibleContentRect.height());
-    
-    FloatSize dragFactor = fixedElementsLayoutRelativeToFrame ? FloatSize(1, 1) : FloatSize(
-        (contentsSize.width() - visibleContentRect.width() * frameScaleFactor) / maxOffset.width(),
-        (contentsSize.height() - visibleContentRect.height() * frameScaleFactor) / maxOffset.height());
-
-    int x = fixedPositionScrollOffset(scrollPosition.x(), maxOffset.width(), scrollOrigin.x(), dragFactor.width() / frameScaleFactor);
-    int y = fixedPositionScrollOffset(scrollPosition.y(), maxOffset.height(), scrollOrigin.y(), dragFactor.height() / frameScaleFactor);
-
+    int x = fixedPositionScrollOffset(visibleContentRect.width(), contentsSize.width(), scrollPosition.x(), scrollOrigin.x(), frameScaleFactor, fixedElementsLayoutRelativeToFrame);
+    int y = fixedPositionScrollOffset(visibleContentRect.height(), contentsSize.height(), scrollPosition.y(), scrollOrigin.y(), frameScaleFactor, fixedElementsLayoutRelativeToFrame);
     return IntSize(x, y);
 }