1 // Copyright 2014 The Chromium Authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #include "config.h"
6 #include "core/paint/BoxDecorationData.h"
7
8 #include "core/rendering/style/BorderEdge.h"
9 #include "core/rendering/style/RenderStyle.h"
10 #include "platform/graphics/GraphicsContext.h"
11
12 namespace blink {
13
BoxDecorationData(const RenderStyle & style,bool canRenderBorderImage,bool backgroundHasOpaqueTopLayer,GraphicsContext * context)14 BoxDecorationData::BoxDecorationData(const RenderStyle& style, bool canRenderBorderImage, bool backgroundHasOpaqueTopLayer, GraphicsContext* context)
15 {
16 backgroundColor = style.visitedDependentColor(CSSPropertyBackgroundColor);
17 hasBackground = backgroundColor.alpha() || style.hasBackgroundImage();
18 ASSERT(hasBackground == style.hasBackground());
19 hasBorder = style.hasBorder();
20 hasAppearance = style.hasAppearance();
21
22 m_bleedAvoidance = determineBackgroundBleedAvoidance(style, canRenderBorderImage, backgroundHasOpaqueTopLayer, context);
23 }
24
determineBackgroundBleedAvoidance(const RenderStyle & style,bool canRenderBorderImage,bool backgroundHasOpaqueTopLayer,GraphicsContext * context)25 BackgroundBleedAvoidance BoxDecorationData::determineBackgroundBleedAvoidance(const RenderStyle& style, bool canRenderBorderImage, bool backgroundHasOpaqueTopLayer, GraphicsContext* context)
26 {
27 if (!hasBackground || !hasBorder || !style.hasBorderRadius() || canRenderBorderImage)
28 return BackgroundBleedNone;
29
30 // FIXME: See crbug.com/382491. getCTM does not accurately reflect the scale at the time content is
31 // rasterized, and should not be relied on to make decisions about bleeding.
32 AffineTransform ctm = context->getCTM();
33 FloatSize contextScaling(static_cast<float>(ctm.xScale()), static_cast<float>(ctm.yScale()));
34
35 // Because RoundedRect uses IntRect internally the inset applied by the
36 // BackgroundBleedShrinkBackground strategy cannot be less than one integer
37 // layout coordinate, even with subpixel layout enabled. To take that into
38 // account, we clamp the contextScaling to 1.0 for the following test so
39 // that borderObscuresBackgroundEdge can only return true if the border
40 // widths are greater than 2 in both layout coordinates and screen
41 // coordinates.
42 // This precaution will become obsolete if RoundedRect is ever promoted to
43 // a sub-pixel representation.
44 if (contextScaling.width() > 1)
45 contextScaling.setWidth(1);
46 if (contextScaling.height() > 1)
47 contextScaling.setHeight(1);
48
49 if (borderObscuresBackgroundEdge(style, contextScaling))
50 return BackgroundBleedShrinkBackground;
51 if (!hasAppearance && style.borderObscuresBackground() && backgroundHasOpaqueTopLayer)
52 return BackgroundBleedBackgroundOverBorder;
53
54 return BackgroundBleedClipBackground;
55 }
56
borderObscuresBackgroundEdge(const RenderStyle & style,const FloatSize & contextScale) const57 bool BoxDecorationData::borderObscuresBackgroundEdge(const RenderStyle& style, const FloatSize& contextScale) const
58 {
59 BorderEdge edges[4];
60 style.getBorderEdgeInfo(edges);
61
62 for (int i = BSTop; i <= BSLeft; ++i) {
63 const BorderEdge& currEdge = edges[i];
64 // FIXME: for vertical text
65 float axisScale = (i == BSTop || i == BSBottom) ? contextScale.height() : contextScale.width();
66 if (!currEdge.obscuresBackgroundEdge(axisScale))
67 return false;
68 }
69
70 return true;
71 }
72
73 } // namespace blink
74