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

runtime/embedders/openglui/common/canvas_state.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_STATE_H_
+#define 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 CanvasState {
+  SkPaint paint_;
+  float globalAlpha_;
+  float miterLimit_;
+  ColorRGBA fillColor_;
+  ColorRGBA strokeColor_;
+  ColorRGBA shadowColor_;
+  float shadowBlur_;
+  float shadowOffsetX_;
+  float shadowOffsetY_;
+  float* lineDash_;
+  int lineDashCount_;
+  int lineDashOffset_;
+
+  SkPath* path_;
+  SkCanvas* canvas_;
+  CanvasState* next_;  // For stack.
+
+  CanvasState(SkCanvas* canvas)
+    : paint_(),
+      globalAlpha_(1.0),
+      miterLimit_(10),
+      fillColor_(ColorRGBA(255, 0, 0, 255)),
+      strokeColor_(fillColor_),
+      shadowColor_(ColorRGBA(0, 0, 0, 0)),
+      shadowBlur_(0.0),
+      shadowOffsetX_(0.0),
+      shadowOffsetY_(0.0),
+      lineDash_(NULL),
+      lineDashCount_(0),
+      lineDashOffset_(0),
+      path_(new SkPath()),
+      canvas_(canvas),
+      next_(NULL) {
+    paint_.setStrokeCap(SkPaint::kButt_Cap);
+    paint_.setStrokeJoin(SkPaint::kMiter_Join);
+    paint_.setStrokeWidth(1);
+    paint_.setTextAlign(SkPaint::kLeft_Align);
+    paint_.setAntiAlias(true);
+    paint_.setStyle(SkPaint::kStroke_Style);
+    setFont("Helvetica", 10);
+  }
+
+  CanvasState(const CanvasState& state)
+    : paint_(state.paint_),
+      globalAlpha_(state.globalAlpha_),
+      miterLimit_(state.miterLimit_),
+      fillColor_(state.fillColor_),
+      strokeColor_(state.strokeColor_),
+      shadowColor_(state.shadowColor_),
+      shadowBlur_(state.shadowBlur_),
+      shadowOffsetX_(state.shadowOffsetX_),
+      shadowOffsetY_(state.shadowOffsetY_),
+      lineDash_(NULL),
+      lineDashCount_(state.lineDashCount_),
+      lineDashOffset_(state.lineDashOffset_),
+      path_(new SkPath()),
+      canvas_(state.canvas_),
+      next_(NULL) {
+    setLineDash(state.lineDash_, lineDashCount_);
+  }
+
+  ~CanvasState() {
+    delete path_;
+    delete[] lineDash_;
+  }
+
+  static ColorRGBA GetColor(const char* color);
+
+  inline CanvasState* Save() {
+    canvas_->save();  // For clip and transform.
+    CanvasState *new_state = new CanvasState(*this);
+    new_state->next_ = this;
+    // If the old state has a non-empty path, use its
+    // last point as the new states first point.
+    int np = path_->countPoints();
+    if (np > 0) {
+      new_state->path_->moveTo(path_->getPoint(np-1));
+    }
+    return new_state;
+  }
+
+  inline CanvasState* Restore() {
+    if (next_ != NULL) {
+      // If the state we are popping has a non-empty path,
+      // apply the state's transform to the path, then
+      // add the path to the previous state's path.
+      if (path_->countPoints() > 0) {
+        path_->transform(canvas_->getTotalMatrix());
+        next_->path_->addPath(*path_);
+      }
+      canvas_->restore();
+      return next_;
+    }
+    canvas_->restore();
+    return next_;  // TODO(gram): Should we assert/throw?
+  }
+
+  inline float Radians2Degrees(float angle) {
+    return 180.0 * angle / M_PI;
+  }
+
+  inline void setGlobalAlpha(float alpha) {
+    globalAlpha_ = alpha;
+  }
+
+  inline void setFillColor(const char* color) {
+    fillColor_ = GetColor(color);
+  }
+
+  inline void setStrokeColor(const char* color) {
+    strokeColor_ = GetColor(color);
+  }
+
+  const char* setFont(const char*name, float size = -1);
+  void setLineCap(const char* lc);
+  void setLineJoin(const char* lj);
+
+  inline void setMiterLimit(float limit) {
+    miterLimit_ = limit;
+  }
+
+  const char* setTextAlign(const char* align);
+  const char* setTextBaseline(const char* baseline);
+  const char* setTextDirection(const char* direction);
+
+  inline void FillText(const char* text, float x, float y, float maxWidth) {
+    setFillMode();
+    canvas_->drawText(text, strlen(text), x, y, paint_);
+  }
+
+  inline void StrokeText(const char* text, float x, float y, float maxWidth) {
+    setStrokeMode();
+    canvas_->drawText(text, strlen(text), x, y, paint_);
+  }
+
+  inline float MeasureText(const char *text) {
+    // TODO(gram): make sure this is not supposed to be affected
+    // by the canvas transform.
+    return paint_.measureText(text, strlen(text));
+  }
+
+  inline void setLineWidth(float w) {
+    paint_.setStrokeWidth(w);
+  }
+
+  inline void setMode(SkPaint::Style style, ColorRGBA color) {
+    paint_.setStyle(style);
+    paint_.setColor(color.v);
+    uint8_t alpha = static_cast<uint8_t>(
+        globalAlpha_ * static_cast<float>(color.alpha()));
+    paint_.setAlpha(alpha);
+    bool drawShadow = (shadowOffsetX_ != 0 ||
+                       shadowOffsetY_ != 0 ||
+                       shadowBlur_ != 0) &&
+                       shadowColor_.alpha() > 0;
+    if (drawShadow) {
+      // TODO(gram): should we mult shadowColor by globalAlpha?
+      paint_.setLooper(new SkBlurDrawLooper(SkFloatToScalar(shadowBlur_),
+                                            SkFloatToScalar(shadowOffsetX_),
+                                            SkFloatToScalar(shadowOffsetY_),
+                                            shadowColor_.v))->unref();
+    } else {
+      paint_.setLooper(NULL);
+    }
+  }
+
+  inline void setLineDashEffect() {
+    if (lineDashCount_ > 0) {
+      SkDashPathEffect* dashPathEffect =
+        new SkDashPathEffect(lineDash_, lineDashCount_, lineDashOffset_);
+        paint_.setPathEffect(dashPathEffect)->unref();
+    } else {
+      paint_.setPathEffect(NULL);
+    }
+  }
+
+  inline void setLineDash(float* dashes, int len) {
+    if (len == 0) {
+      lineDashCount_ = 0;
+      delete[] lineDash_;
+      lineDash_ = NULL;
+    } else {
+      lineDash_ = new float[lineDashCount_ = len];
+      for (int i = 0; i < len; i++) {
+        lineDash_[i] = dashes[i];
+      }
+    }
+    setLineDashEffect();
+  }
+
+  inline void setLineDashOffset(int offset) {
+    if (offset != lineDashOffset_) {
+      lineDashOffset_ = offset;
+      setLineDashEffect();
+    }
+  }
+
+  inline void setShadowColor(const char* color) {
+    shadowColor_ = GetColor(color);
+  }
+
+  inline void setShadowBlur(float blur) {
+    shadowBlur_ = blur;
+  }
+
+  inline void setShadowOffsetX(float ox) {
+    shadowOffsetX_ = ox;
+  }
+
+  inline void setShadowOffsetY(float oy) {
+    shadowOffsetY_ = oy;
+  }
+
+  inline void setFillMode() {
+    setMode(SkPaint::kFill_Style, fillColor_);
+  }
+
+  inline void setStrokeMode() {
+    setMode(SkPaint::kStroke_Style, strokeColor_);
+  }
+
+  inline void FillRect(float left, float top,
+                       float width, float height) {
+    // Does not affect the path.
+    setFillMode();
+    canvas_->drawRectCoords(left, top, left + width, top + height, paint_);
+  }
+
+  inline void StrokeRect(float left, float top,
+                         float width, float height) {
+    // Does not affect the path.
+    setStrokeMode();
+    canvas_->drawRectCoords(left, top, left + width, top + height, paint_);
+  }
+
+  inline void BeginPath() {
+    path_->rewind();
+  }
+
+  inline void Fill() {
+    setFillMode();
+    canvas_->drawPath(*path_, paint_);
+  }
+
+  inline void Stroke() {
+    setStrokeMode();
+    canvas_->drawPath(*path_, paint_);
+  }
+
+  inline void ClosePath() {
+    path_->close();
+  }
+
+  inline void MoveTo(float x, float y) {
+    path_->moveTo(x, y);
+  }
+
+  inline void LineTo(float x, float y) {
+    path_->lineTo(x, y);
+  }
+
+  void Arc(float x, float y, float radius, float startAngle, float endAngle,
+           bool antiClockwise);
+
+  inline void QuadraticCurveTo(float cpx, float cpy, float x, float y) {
+    path_->quadTo(cpx, cpy, x, y);
+  }
+
+  inline void BezierCurveTo(float cp1x, float cp1y, float cp2x, float cp2y,
+                     float x, float y) {
+    path_->cubicTo(cp1x, cp1y, cp2x, cp2y, x, y);
+  }
+
+  inline void ArcTo(float x1, float y1, float x2, float y2, float radius) {
+    path_->arcTo(x1, y1, x2, y2, radius);
+  }
+
+  inline void Rect(float x, float y, float w, float h) {
+    // TODO(gram): Should we draw this directly? If so, what happens with the
+    // path?
+    path_->addRect(x, y, x + w, y + h);
+  }
+
+  void setGlobalCompositeOperation(const char* op);
+
+  void DrawImage(const SkBitmap& bm,
+                 int sx, int sy, int sw, int sh,
+                 int dx, int dy, int dw, int dh);
+
+  inline void Clip() {
+    canvas_->clipPath(*path_);
+  }
+} CanvasState;
+
+#endif  // EMBEDDERS_OPENGLUI_COMMON_CANVAS_STATE_H_
+