Canvas API. There are still a number of things to do:

runtime/embedders/openglui/common/canvas_context.h

+// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+#ifndef EMBEDDERS_OPENGLUI_COMMON_CANVAS_CONTEXT_H_
+#define EMBEDDERS_OPENGLUI_COMMON_CANVAS_CONTEXT_H_
+
+#include "embedders/openglui/common/canvas_state.h"
+#include "embedders/openglui/common/graphics_handler.h"
+#include "embedders/openglui/common/log.h"
+#include "embedders/openglui/common/opengl.h"
+#include "embedders/openglui/common/support.h"
+
+typedef struct ImageData {
+  int width;
+  int height;
+  GLubyte* pixels;
+
+  ImageData(int wp, int hp, GLubyte* pp)
+    : width(wp), height(hp), pixels(pp) {
+  }
+  ImageData() {}

[vsm, 2013/02/04 18:18:41]

Initialize 0/NULL on empty constructor?

[gram, 2013/02/04 22:02:28]

Done.

+} ImageData;
+
+class CanvasContext {
+ protected:
+  SkCanvas* canvas_;
+
+  int16_t width_, height_;
+
+  bool imageSmoothingEnabled_;
+
+  CanvasState* state_;
+
+  inline float Radians2Degrees(float angle) {

[vsm, 2013/02/04 18:18:41]

Can make static to avoid implicit this argument.

[gram, 2013/02/04 22:02:28]

Done.

+    return 180.0 * angle / M_PI;
+  }
+
+  inline void NotImplemented(const char* method) {
+    LOGE("Method CanvasContext::%s is not yet implemented", method);
+  }
+
+ public:
+  CanvasContext(int16_t width, int16_t height);
+  virtual ~CanvasContext();
+
+  inline void setGlobalAlpha(float alpha) {
+    state_->setGlobalAlpha(alpha);
+  }
+
+  inline void setFillColor(const char* color) {
+    state_->setFillColor(color);
+  }
+
+  inline void setStrokeColor(const char* color) {
+    state_->setStrokeColor(color);
+  }
+
+  inline void setShadowBlur(float blur) {
+    state_->setShadowBlur(blur);
+  }
+
+  inline void setShadowColor(const char* color) {
+    state_->setShadowColor(color);
+  }
+
+  inline void setShadowOffsetX(float offset) {
+    state_->setShadowOffsetX(offset);
+  }
+
+  inline void setShadowOffsetY(float offset) {
+    state_->setShadowOffsetY(offset);
+  }
+
+  // For now, we don't allow resizing.
+  // TODO(gram): fix this or remove these.
+  inline int setWidth(int widthp) {
+    return width_;
+  }
+
+  inline int setHeight(int heightp) {
+    return height_;
+  }
+
+  inline bool imageSmoothingEnabled() {
+    return imageSmoothingEnabled_;
+  }
+
+  inline void setImageSmoothingEnabled(bool enabled) {
+    // TODO(gram): We're not actually doing anything with this yet.
+    imageSmoothingEnabled_ = enabled;
+  }
+
+  inline void setGlobalCompositeOperation(const char* op) {
+    state_->setGlobalCompositeOperation(op);
+  }
+
+  inline void Save() {
+    state_ = state_->Save();
+  }
+
+  inline void Restore() {
+    CanvasState* popped_state = state_;
+    state_ = state_->Restore();
+    if (state_ != popped_state) {

[vsm, 2013/02/04 18:18:41]

Not sure I understand the model here.  Is it possible for the last two states to
be same?  Is it possible for states to repeat interleaving?  Is the delete save,
if so?

[gram, 2013/02/04 22:02:28]

I'm not sure on the exact semantics of Canvas if you pop more than you restore.
In my case, I wanted a pop when there is no saved state to be a no-op. In this
case we simply return the current state and hence no delete. I'll add a comment.

+      delete popped_state;
+    }
+  }
+
+  inline void Rotate(float angle) {
+    canvas_->rotate(Radians2Degrees(angle));
+  }
+
+  inline void Translate(float x, float y) {
+    canvas_->translate(x, y);
+  }
+
+  inline void Scale(float x, float y) {
+    canvas_->scale(x, y);
+  }
+
+  inline void Transform(float a, float b,
+                        float c, float d,
+                        float e, float f) {
+    SkMatrix t;
+    // Our params are for a 3 x 2 matrix in column order:
+    //
+    // a c e
+    // b d f
+    //
+    // We need to turn this into a 3x3 matrix:
+    //
+    // a c e
+    // b d f
+    // 0 0 1
+    //
+    // and pass the params in row order:
+    t.setAll(a, c, e, b, d, f, 0, 0, 1);
+    canvas_->concat(t);
+  }
+
+  inline void setTransform(float a, float b,
+                           float c, float d,
+                           float e, float f) {
+    SkMatrix t;
+    t.setAll(a, c, e, b, d, f, 0, 0, 1);
+    canvas_->setMatrix(t);
+  }
+
+  ImageData* GetImageData(float sx, float sy, float sw, float sh) {
+    NotImplemented("GetImageData");
+    return NULL;
+  }
+
+  void PutImageData(ImageData* imageData, float  dx, float dy) {
+    NotImplemented("PutImageData");
+  }
+
+  void DrawImage(const char* src_url,
+                 int sx, int sy, bool has_src_dimensions, int sw, int sh,
+                 int dx, int dy, bool has_dst_dimensions, int dw, int dh);
+
+  inline void Clear() {
+    canvas_->drawColor(0xFFFFFFFF);
+  }
+
+  void ClearRect(float left, float top, float width, float height);
+
+  inline void FillRect(float left, float top, float width, float height) {
+    // Does not affect the path.
+    state_->FillRect(left, top, width, height);
+  }
+
+  inline void StrokeRect(float left, float top, float width, float height) {
+    // Does not affect the path.
+    state_->StrokeRect(left, top, width, height);
+  }
+
+  inline void BeginPath() {
+    state_->BeginPath();
+  }
+
+  inline void Fill() {
+    state_->Fill();
+  }
+
+  inline void Stroke() {
+    state_->Stroke();
+  }
+
+  inline void ClosePath() {
+    state_->ClosePath();
+  }
+
+  inline void MoveTo(float x, float y) {
+    state_->MoveTo(x, y);
+  }
+
+  inline void LineTo(float x, float y) {
+    state_->LineTo(x, y);
+  }
+
+  inline void QuadraticCurveTo(float cpx, float cpy, float x, float y) {
+    state_->QuadraticCurveTo(cpx, cpy, x, y);
+  }
+
+  inline void BezierCurveTo(float cp1x, float cp1y, float cp2x, float cp2y,
+                     float x, float y) {
+    state_->BezierCurveTo(cp1x, cp1y, cp2x, cp2y, x, y);
+  }
+
+  inline void ArcTo(float x1, float y1, float x2, float y2, float radius) {
+    state_->ArcTo(x1, y1, x2, y2, radius);
+  }
+
+  inline void Rect(float x, float y, float w, float h) {
+    state_->Rect(x, y, w, h);
+  }
+
+  inline void Arc(float x, float y, float radius,
+                  float startAngle, float endAngle,
+                  bool antiClockwise) {
+    state_->Arc(x, y, radius, startAngle, endAngle, antiClockwise);
+  }
+
+  inline void setLineWidth(double w) {
+    state_->setLineWidth(w);
+  }
+
+  inline void setLineCap(const char* lc) {
+    state_->setLineCap(lc);
+  }
+
+  inline void setLineDash(float* dashes, int len) {
+    state_->setLineDash(dashes, len);
+  }
+
+  inline void setLineDashOffset(float offset) {
+    state_->setLineDashOffset(offset);
+  }
+
+  inline void setLineJoin(const char* lj) {
+    state_->setLineJoin(lj);
+  }
+
+  inline void setMiterLimit(float limit) {
+    state_->setMiterLimit(limit);
+  }
+
+  inline const char* setFont(const char* font) {
+    return state_->setFont(font);
+  }
+
+  inline const char* setTextAlign(const char* align) {
+    return state_->setTextAlign(align);
+  }
+
+  const char* setTextBaseline(const char* baseline) {
+    return state_->setTextBaseline(baseline);
+  }
+
+  inline const char* setDirection(const char* direction) {
+    return state_->setTextDirection(direction);
+  }
+
+  inline void FillText(const char* text, float x, float y,
+                       float maxWidth = -1) {
+    state_->FillText(text, x, y, maxWidth);
+  }
+
+  inline void StrokeText(const char* text, float x, float y,
+                         float maxWidth = -1) {
+    state_->StrokeText(text, x, y, maxWidth);
+  }
+
+  inline float MeasureText(const char *text) {
+    return state_->MeasureText(text);
+  }
+
+  inline void Clip() {
+    state_->Clip();
+  }
+
+  inline void ResetClip() {
+    // TODO(gram): Check this. Is it affected by the transform?
+    canvas_->clipRect(SkRect::MakeLTRB(0, 0, width_, height_),
+                      SkRegion::kReplace_Op);
+  }
+
+  virtual void Flush() {
+    canvas_->flush();
+    graphics->Flush();
+  }
+
+  void Create();
+};
+
+#endif  // EMBEDDERS_OPENGLUI_COMMON_CANVAS_CONTEXT_H_
+