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// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "config.h"
#include "core/paint/BoxDecorationData.h"
#include "core/rendering/RenderBox.h"
#include "core/rendering/style/BorderEdge.h"
#include "core/rendering/style/RenderStyle.h"
#include "platform/RuntimeEnabledFeatures.h"
#include "platform/graphics/GraphicsContext.h"
namespace blink {
BoxDecorationData::BoxDecorationData(const RenderBox& renderBox, GraphicsContext* context)
{
backgroundColor = renderBox.style()->visitedDependentColor(CSSPropertyBackgroundColor);
hasBackground = backgroundColor.alpha() || renderBox.style()->hasBackgroundImage();
ASSERT(hasBackground == renderBox.style()->hasBackground());
hasBorder = renderBox.style()->hasBorder();
hasAppearance = renderBox.style()->hasAppearance();
m_bleedAvoidance = determineBackgroundBleedAvoidance(renderBox, context);
}
BackgroundBleedAvoidance BoxDecorationData::determineBackgroundBleedAvoidance(const RenderBox& renderBox, GraphicsContext* context)
{
if (renderBox.isDocumentElement())
return BackgroundBleedNone;
if (!hasBackground)
return BackgroundBleedNone;
if (!hasBorder || !renderBox.style()->hasBorderRadius() || renderBox.canRenderBorderImage()) {
if (renderBox.backgroundShouldAlwaysBeClipped())
return BackgroundBleedClipBackground;
return BackgroundBleedNone;
}
// If display lists are enabled (via Slimming Paint), then simply clip the background and do not
// perform advanced bleed-avoidance heuristics. These heuristics are not correct in the presence
// of impl-side rasterization or layerization, since the actual pixel-relative scaling and rotation
// of the content is not known to Blink.
if (RuntimeEnabledFeatures::slimmingPaintEnabled())
return BackgroundBleedClipBackground;
// FIXME: See crbug.com/382491. getCTM does not accurately reflect the scale at the time content is
// rasterized, and should not be relied on to make decisions about bleeding.
AffineTransform ctm = context->getCTM();
FloatSize contextScaling(static_cast<float>(ctm.xScale()), static_cast<float>(ctm.yScale()));
// Because RoundedRect uses IntRect internally the inset applied by the
// BackgroundBleedShrinkBackground strategy cannot be less than one integer
// layout coordinate, even with subpixel layout enabled. To take that into
// account, we clamp the contextScaling to 1.0 for the following test so
// that borderObscuresBackgroundEdge can only return true if the border
// widths are greater than 2 in both layout coordinates and screen
// coordinates.
// This precaution will become obsolete if RoundedRect is ever promoted to
// a sub-pixel representation.
if (contextScaling.width() > 1)
contextScaling.setWidth(1);
if (contextScaling.height() > 1)
contextScaling.setHeight(1);
if (borderObscuresBackgroundEdge(*renderBox.style(), contextScaling))
return BackgroundBleedShrinkBackground;
if (!hasAppearance && renderBox.style()->borderObscuresBackground() && renderBox.backgroundHasOpaqueTopLayer())
return BackgroundBleedBackgroundOverBorder;
return BackgroundBleedClipBackground;
}
bool BoxDecorationData::borderObscuresBackgroundEdge(const RenderStyle& style, const FloatSize& contextScale) const
{
BorderEdge edges[4];
style.getBorderEdgeInfo(edges);
for (int i = BSTop; i <= BSLeft; ++i) {
const BorderEdge& currEdge = edges[i];
// FIXME: for vertical text
float axisScale = (i == BSTop || i == BSBottom) ? contextScale.height() : contextScale.width();
if (!currEdge.obscuresBackgroundEdge(axisScale))
return false;
}
return true;
}
} // namespace blink
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