1 files changed, 73 insertions, 0 deletions

diff --git a/WebKit/mac/WebView/WebDynamicScrollBarsView.mm b/WebKit/mac/WebView/WebDynamicScrollBarsView.mm
index 74439dd..1c6980f 100644
--- a/WebKit/mac/WebView/WebDynamicScrollBarsView.mm
+++ b/WebKit/mac/WebView/WebDynamicScrollBarsView.mm
@@ -62,6 +62,17 @@ struct WebDynamicScrollBarsViewPrivate {
     bool alwaysHideVerticalScroller;
     bool horizontalScrollingAllowedButScrollerHidden;
     bool verticalScrollingAllowedButScrollerHidden;
+
+    // scrollOrigin is set for various combinations of writing mode and direction.
+    // See the comment next to the corresponding member in ScrollView.h.
+    NSPoint scrollOrigin;
+
+    // Flag to indicate that the scrollbar thumb's initial position needs to
+    // be manually set.
+    bool scrollOriginChanged;
+    NSPoint scrollPositionExcludingOrigin;
+
+    bool inProgrammaticScroll;
 };
 
 @implementation WebDynamicScrollBarsView
@@ -149,6 +160,11 @@ struct WebDynamicScrollBarsViewPrivate {
     return _private->verticalScrollingAllowedButScrollerHidden || [self hasVerticalScroller];
 }
 
+- (BOOL)inProgramaticScroll
+{
+    return _private->inProgrammaticScroll;
+}
+
 @end
 
 @implementation WebDynamicScrollBarsView (WebInternal)
@@ -201,6 +217,24 @@ struct WebDynamicScrollBarsViewPrivate {
 #endif
 }
 
+- (void)adjustForScrollOriginChange
+{
+    if (!_private->scrollOriginChanged)
+        return;
+
+    _private->scrollOriginChanged = false;
+
+    NSView *documentView = [self documentView];
+    NSRect documentRect = [documentView bounds];
+
+    // The call to [NSView scrollPoint:] fires off notification the handler for which needs to know that
+    // we're setting the initial scroll position so it doesn't interpret this as a user action and
+    // fire off a JS event.
+    _private->inProgrammaticScroll = true;
+    [documentView scrollPoint:NSMakePoint(_private->scrollPositionExcludingOrigin.x + documentRect.origin.x, _private->scrollPositionExcludingOrigin.y + documentRect.origin.y)];
+    _private->inProgrammaticScroll = false;
+}
+
 static const unsigned cMaxUpdateScrollbarsPass = 2;
 
 - (void)updateScrollers
@@ -304,6 +338,10 @@ static const unsigned cMaxUpdateScrollbarsPass = 2;
         [self setHasHorizontalScroller:newHasHorizontalScroller];
         _private->inUpdateScrollers = NO;
         needsLayout = YES;
+        NSView *documentView = [self documentView];
+        NSRect documentRect = [documentView bounds];
+        if (documentRect.origin.y < 0 && !newHasHorizontalScroller)
+            [documentView setBoundsOrigin:NSMakePoint(documentRect.origin.x, documentRect.origin.y + 15)];
     }
 
     if (hasVerticalScroller != newHasVerticalScroller) {
@@ -311,6 +349,10 @@ static const unsigned cMaxUpdateScrollbarsPass = 2;
         [self setHasVerticalScroller:newHasVerticalScroller];
         _private->inUpdateScrollers = NO;
         needsLayout = YES;
+        NSView *documentView = [self documentView];
+        NSRect documentRect = [documentView bounds];
+        if (documentRect.origin.x < 0 && !newHasVerticalScroller)
+            [documentView setBoundsOrigin:NSMakePoint(documentRect.origin.x + 15, documentRect.origin.y)];
     }
 
     if (needsLayout && _private->inUpdateScrollersLayoutPass < cMaxUpdateScrollbarsPass &&
@@ -364,6 +406,11 @@ static const unsigned cMaxUpdateScrollbarsPass = 2;
     }
 #endif
 
+    // The call to [NSView reflectScrolledClipView] sets the scrollbar thumb
+    // position to 0 (the left) when the view is initially displayed.
+    // This call updates the initial position correctly.
+    [self adjustForScrollOriginChange];
+
 #if USE(ACCELERATED_COMPOSITING) && defined(BUILDING_ON_LEOPARD)
     NSView *documentView = [self documentView];
     if ([documentView isKindOfClass:[WebHTMLView class]]) {
@@ -525,4 +572,30 @@ static const unsigned cMaxUpdateScrollbarsPass = 2;
     return [super accessibilityIsIgnored];
 }
 
+- (void)setScrollOrigin:(NSPoint)scrollOrigin updatePosition:(BOOL)updatePosition
+{
+    // The cross-platform ScrollView call already checked to see if the old/new scroll origins were the same or not
+    // so we don't have to check for equivalence here.
+    _private->scrollOrigin = scrollOrigin;
+    id docView = [self documentView];
+    NSPoint docOrigin = [docView bounds].origin;
+
+    NSRect visibleRect = [self documentVisibleRect];
+
+    [docView setBoundsOrigin:NSMakePoint(-scrollOrigin.x, -scrollOrigin.y)];
+
+    _private->scrollOriginChanged = true;
+
+    // Maintain our original position in the presence of the new scroll origin.
+    _private->scrollPositionExcludingOrigin = NSMakePoint(visibleRect.origin.x + scrollOrigin.x, visibleRect.origin.y + scrollOrigin.y);
+
+    if (updatePosition) // Otherwise we'll just let the snap happen when we update for the resize.
+        [self adjustForScrollOriginChange];
+}
+
+- (NSPoint)scrollOrigin
+{
+    return _private->scrollOrigin;
+}
+
 @end