38// These values come from the WhatWG spec.
39const int CanvasSurface::DefaultWidth = 300;
40const int CanvasSurface::DefaultHeight = 150;
41
42// Firefox limits width/height to 32767 pixels, but slows down dramatically before it
43// reaches that limit. We limit by area instead, giving us larger maximum dimensions,
44// in exchange for a smaller maximum canvas size.
45const float CanvasSurface::MaxCanvasArea = 32768 * 8192; // Maximum canvas area in CSS pixels
46
47CanvasSurface::CanvasSurface(float pageScaleFactor)
48 : m_size(DefaultWidth, DefaultHeight)
49 , m_pageScaleFactor(pageScaleFactor)
50 , m_originClean(true)
51 , m_hasCreatedImageBuffer(false)
52{
53}
54
55CanvasSurface::~CanvasSurface()
56{
57}
58
59void CanvasSurface::setSurfaceSize(const IntSize& size)
60{
61 m_size = size;
62 m_hasCreatedImageBuffer = false;
63 m_imageBuffer.clear();
64}
65
66String CanvasSurface::toDataURL(const String& mimeType, ExceptionCode& ec)
67{
68 if (!m_originClean) {
69 ec = SECURITY_ERR;
70 return String();
71 }
72
73 if (m_size.isEmpty() || !buffer())
74 return String("data:,");
75
76 // FIXME: Make isSupportedImageMIMETypeForEncoding threadsafe (to allow this method to be used on a worker thread).
77 if (mimeType.isNull() || !MIMETypeRegistry::isSupportedImageMIMETypeForEncoding(mimeType))
78 return buffer()->toDataURL("image/png");
79
80 return buffer()->toDataURL(mimeType);
81}
82
83void CanvasSurface::willDraw(const FloatRect&)
84{
85 if (m_imageBuffer)
86 m_imageBuffer->clearImage();
87}
88
89IntRect CanvasSurface::convertLogicalToDevice(const FloatRect& logicalRect) const
90{
91 return IntRect(convertLogicalToDevice(logicalRect.location()), convertLogicalToDevice(logicalRect.size()));
92}
93
94IntSize CanvasSurface::convertLogicalToDevice(const FloatSize& logicalSize) const
95{
96 float wf = ceilf(logicalSize.width() * m_pageScaleFactor);
97 float hf = ceilf(logicalSize.height() * m_pageScaleFactor);
98
99 if (!(wf >= 1 && hf >= 1 && wf * hf <= MaxCanvasArea))
100 return IntSize();
101
102 return IntSize(static_cast<unsigned>(wf), static_cast<unsigned>(hf));
103}
104
105IntPoint CanvasSurface::convertLogicalToDevice(const FloatPoint& logicalPos) const
106{
107 float xf = logicalPos.x() * m_pageScaleFactor;
108 float yf = logicalPos.y() * m_pageScaleFactor;
109
110 return IntPoint(static_cast<unsigned>(xf), static_cast<unsigned>(yf));
111}
112
113void CanvasSurface::createImageBuffer() const
114{
115 ASSERT(!m_imageBuffer);
116
117 m_hasCreatedImageBuffer = true;
118
119 FloatSize unscaledSize(width(), height());
120 IntSize size = convertLogicalToDevice(unscaledSize);
121 if (!size.width() || !size.height())
122 return;
123
124 m_imageBuffer = ImageBuffer::create(size);
125 // The convertLogicalToDevice MaxCanvasArea check should prevent common cases
126 // where ImageBuffer::create() returns 0, however we could still be low on memory.
127 if (!m_imageBuffer)
128 return;
129 m_imageBuffer->context()->scale(FloatSize(size.width() / unscaledSize.width(), size.height() / unscaledSize.height()));
130 m_imageBuffer->context()->setShadowsIgnoreTransforms(true);
131}
132
133GraphicsContext* CanvasSurface::drawingContext() const
134{
135 return buffer() ? m_imageBuffer->context() : 0;
136}
137
138ImageBuffer* CanvasSurface::buffer() const
139{
140 if (!m_hasCreatedImageBuffer)
141 createImageBuffer();
142 return m_imageBuffer.get();
143}
144
145AffineTransform CanvasSurface::baseTransform() const
146{
147 ASSERT(m_hasCreatedImageBuffer);
148 FloatSize unscaledSize(width(), height());
149 IntSize size = convertLogicalToDevice(unscaledSize);
150 AffineTransform transform;
151 if (size.width() && size.height())
152 transform.scaleNonUniform(size.width() / unscaledSize.width(), size.height() / unscaledSize.height());
153 transform.multiply(m_imageBuffer->baseTransform());
154 return transform;
155}
156