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Bug 1158933 - Prevent scrollbars from jumping while zoomed in the B2G browser. r=botond

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This commit is contained in:
Kartikaya Gupta
2015-04-29 07:22:27 -04:00
parent 2e9e2574b1
commit 6661eab85d
3 changed files with 16 additions and 7 deletions
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13
gfx/layers/composite/AsyncCompositionManager.cpp
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@@ -726,8 +726,12 @@ ApplyAsyncTransformToScrollbarForContent(Layer* aScrollbar,
const CSSCoord compositedHeight = (metrics.mCompositionBounds / effectiveZoom).height;
const CSSCoord scrollableHeight = metrics.GetScrollableRect().height;
// The scrollbar thumb ratio is in AppUnits.
const float ratio = aScrollbar->GetScrollbarThumbRatio();
const LayoutDeviceToParentLayerScale nonLayoutScale = effectiveZoom /
metrics.GetDevPixelsPerCSSPixel();
// Here we convert the scrollbar thumb ratio into a true unitless ratio by
// dividing out the conversion factor from the scrollframe's parent's space
// to the scrollframe's space.
const float ratio = aScrollbar->GetScrollbarThumbRatio() / nonLayoutScale.scale;
ParentLayerCoord yTranslation = -asyncScrollY * ratio;
// The scroll thumb additionally needs to be translated to compensate for
@@ -773,8 +777,9 @@ ApplyAsyncTransformToScrollbarForContent(Layer* aScrollbar,
const CSSCoord compositedWidth = (metrics.mCompositionBounds / effectiveZoom).width;
const CSSCoord scrollableWidth = metrics.GetScrollableRect().width;
// The scrollbar thumb ratio is in AppUnits.
const float ratio = aScrollbar->GetScrollbarThumbRatio();
const LayoutDeviceToParentLayerScale nonLayoutScale = effectiveZoom /
metrics.GetDevPixelsPerCSSPixel();
const float ratio = aScrollbar->GetScrollbarThumbRatio() / nonLayoutScale.scale;
ParentLayerCoord xTranslation = -asyncScrollX * ratio;
const CSSCoord thumbOrigin = (metrics.GetScrollOffset().x / scrollableWidth) * compositedWidth;