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

runtime/embedders/openglui/common/canvas_state.cc

+// 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.
+
+#include "embedders/openglui/common/canvas_state.h"
+
+#include <ctype.h>
+#include <string.h>
+
+#include "embedders/openglui/common/support.h"
+
+// Float parser. Does not handle exponents. This is
+// used to parse font sizes so it doesn't need to be full-blown.
+float ParseFloat(const char* s, int& pos) {
+  int len = strlen(s);
+  float rtn = 0.0;
+  while (pos < len && s[pos] != '.' && !isdigit(s[pos])) {
+    ++pos;
+  }
+  while (pos < len && isdigit(s[pos])) {
+    rtn = rtn * 10.0 + s[pos] - '0';
+    ++pos;
+  }
+  if (pos < len && s[pos] == '.') {
+    pos++;
+    float div = 1.0;
+    while (pos < len && isdigit(s[pos])) {
+      rtn = rtn * 10.0 + s[pos] - '0';
+      ++pos;
+      div *= 10.0;
+    }
+    rtn /= div;
+  }
+  return rtn;
+}
+
+int ParseInt(const char* s, int& pos) {
+  int len = strlen(s);
+  int rtn = 0;
+  while (pos < len && !isdigit(s[pos])) {
+    ++pos;
+  }
+  while (pos < len && isdigit(s[pos])) {
+    rtn = rtn * 10 + s[pos] - '0';
+    ++pos;
+  }
+  return rtn;
+}
+
+void CanvasState::setLineCap(const char* lc) {
+  if (strcmp(lc, "round") == 0) {
+    paint_.setStrokeCap(SkPaint::kRound_Cap);
+  } else if (strcmp(lc, "square") == 0) {
+    paint_.setStrokeCap(SkPaint::kSquare_Cap);
+  } else {
+    paint_.setStrokeCap(SkPaint::kButt_Cap);
+  }
+}
+
+void CanvasState::setLineJoin(const char* lj) {
+  if (strcmp(lj, "round") == 0) {
+    paint_.setStrokeJoin(SkPaint::kRound_Join);
+  } else if (strcmp(lj, "bevel") == 0) {
+    paint_.setStrokeJoin(SkPaint::kBevel_Join);
+  } else {
+    paint_.setStrokeJoin(SkPaint::kMiter_Join);
+  }
+}
+
+const char* CanvasState::setFont(const char*name, float size) {
+  // Font names have the form "<modifier> <size> <family>".
+  // Modifiers are "normal", "italic", "bold".
+  // Sizes have magnitude and units; e.g. "10pt", "20px".
+  const char* rtn = name;
+  if (size < 0) {
+    int pos = 0;
+    // TODO(gram): need to handle these modifiers.
+    if (strncmp(name, "normal", 6) == 0) {
+      pos = 6;
+    } else if (strncmp(name, "italic", 6) == 0) {
+      pos = 6;
+    } else if (strncmp(name, "bold", 4) == 0) {
+      pos = 4;
+    }
+    size = ParseFloat(name, pos);
+    // Font size units: px, etc. For now just px.
+    // TODO(gram): Handle other units.
+    if (strncmp(name + pos, "px", 2) == 0) {
+      pos += 2;
+    }
+    int len = strlen(name);
+    while (pos < len && isspace(name[pos])) {
+      ++pos;
+    }
+    name = name + pos;
+  }
+  SkTypeface *pTypeface = SkTypeface::CreateFromName(name, SkTypeface::kNormal);
+  paint_.setTypeface(pTypeface);
+  paint_.setTextSize(size);
+  pTypeface->unref();
+  // TODO(gram): Must return a normalized font name incorporating size, so
+  // callers can set the Dart canvas font name to an appropriate value.
+  // Actually this may not be necessary in which case we can change this
+  // method to return void.
+  return rtn;
+}
+
+const char* CanvasState::setTextAlign(const char* align) {
+  // TODO(gram): What about "start" and "end"?
+  // I don't see any an analogs in Skia.
+  if (strcmp(align, "left") == 0) {
+    paint_.setTextAlign(SkPaint::kLeft_Align);
+  } else if (strcmp(align, "right") == 0) {
+    paint_.setTextAlign(SkPaint::kRight_Align);
+  } else {
+    paint_.setTextAlign(SkPaint::kCenter_Align);
+  }
+  return align;
+}
+
+const char* CanvasState::setTextBaseline(const char* baseline) {
+  // TODO(gram): Does skia support this? It doesn't seem like
+  // it. Right now we don't use the textBaseline value, but we
+  // may have to implement this ourselves, by adjusting the y
+  // values passed to StrokeText/FillText using the font metrics.
+  if (strcmp(baseline, "top") == 0) {
+  } else if (strcmp(baseline, "middle") == 0) {
+  } else if (strcmp(baseline, "bottom") == 0) {
+  } else if (strcmp(baseline, "hanging") == 0) {
+  } else if (strcmp(baseline, "alphabetic") == 0) {
+  } else if (strcmp(baseline, "ideographic") == 0) {
+  }
+  return baseline;
+}
+
+const char* CanvasState::setTextDirection(const char* direction) {
+    // TODO(gram): Add support for this if Skia does.
+  return direction;
+}
+
+void CanvasState::setGlobalCompositeOperation(const char* op) {
+  SkXfermode::Mode mode;
+  if (strcmp(op, "source-atop") == 0) {
+    mode = SkXfermode::kSrcATop_Mode;
+  } else if (strcmp(op, "source-in") == 0) {
+    mode = SkXfermode::kSrcIn_Mode;
+  } else if (strcmp(op, "source-out") == 0) {
+    mode = SkXfermode::kSrcOut_Mode;
+  } else if (strcmp(op, "source-over") == 0) {
+    mode = SkXfermode::kSrcOver_Mode;  // Default.
+  } else if (strcmp(op, "destination-atop") == 0) {
+    mode = SkXfermode::kDstATop_Mode;
+  } else if (strcmp(op, "destination-in") == 0) {
+    mode = SkXfermode::kDstIn_Mode;
+  } else if (strcmp(op, "destination-out") == 0) {
+    mode = SkXfermode::kDstOut_Mode;
+  } else if (strcmp(op, "destination-over") == 0) {
+    mode = SkXfermode::kDstOver_Mode;
+  } else if (strcmp(op, "lighter") == 0) {
+    mode = SkXfermode::kLighten_Mode;
+  } else if (strcmp(op, "darker") == 0) {
+    mode = SkXfermode::kDarken_Mode;
+  } else if (strcmp(op, "xor") == 0) {
+    mode = SkXfermode::kXor_Mode;
+  } else if (strcmp(op, "copy") == 0) {
+    mode = SkXfermode::kSrc_Mode;
+  }
+  SkXfermode* m = SkXfermode::Create(mode);
+  // It seems we don't need unref() here. Including it causes
+  // a crash. Maybe Skia has a preallocated long-lived set of
+  // instances.
+  paint_.setXfermode(m);
+}
+
+void CanvasState::Arc(float x, float y, float radius,
+                      float startAngle, float endAngle,
+                      bool antiClockwise) {
+  SkRect rect;
+  rect.set(x - radius, y - radius, x + radius, y + radius);
+  bool doCircle = false;
+
+  static float twoPi = 2 * M_PI;
+
+  float sweep = endAngle - startAngle;
+  if (sweep >= twoPi || sweep <= -twoPi) {
+    doCircle = true;
+  }
+
+  if (!antiClockwise && endAngle <= startAngle) {
+    endAngle += 2 * M_PI;
+  } else if (antiClockwise && startAngle <= endAngle) {
+    startAngle += 2 * M_PI;
+  }
+  sweep = endAngle - startAngle;
+
+  startAngle = fmodf(startAngle, twoPi);
+  float sa = Radians2Degrees(startAngle);
+  float ea = Radians2Degrees(sweep);
+  path_->arcTo(rect, sa, ea, false);
+  if (doCircle) {
+    SkPath tmp;
+    tmp.addOval(rect);
+    tmp.addPath(*path_);
+    path_->swap(tmp);
+  }
+}
+
+int hexDigit(char c) {
+  if (c >= '0' && c <= '9') return c - '0';
+  if (c <= 'Z') return c - 'A' + 10;
+  return c - 'a' + 10;
+}
+
+// Color parser.
+// See http://www.w3.org/TR/CSS21/syndata.html#color-units.
+// There is also another format: hsl(240,100%,100%) (and hsla)
+// TODO(gram): We probably eventually want to use a table rather
+// than a big if statement.
+ColorRGBA CanvasState::GetColor(const char* color) {
+  if (color[0] == '#') {
+    int r, g, b;
+    if (strlen(color) == 7) {
+      r = hexDigit(color[1]) * 16 + hexDigit(color[2]);
+      g = hexDigit(color[3]) * 16 + hexDigit(color[4]);
+      b = hexDigit(color[5]) * 16 + hexDigit(color[6]);
+    } else if (strlen(color) == 4) {
+      r = hexDigit(color[1]) * 16 + hexDigit(color[1]);
+      g = hexDigit(color[2]) * 16 + hexDigit(color[2]);
+      b = hexDigit(color[3]) * 16 + hexDigit(color[3]);
+    }
+    return ColorRGBA(r, g, b);
+  } else if (strcmp(color, "maroon") == 0) {
+    return ColorRGBA(0x80, 0x00, 0x00);
+  } else if (strcmp(color, "red") == 0) {
+    return ColorRGBA(0xFF, 0x00, 0x00);
+  } else if (strcmp(color, "orange") == 0) {
+    return ColorRGBA(0xFF, 0xA5, 0x00);
+  } else if (strcmp(color, "yellow") == 0) {
+    return ColorRGBA(0xFF, 0xFF, 0x00);
+  } else if (strcmp(color, "olive") == 0) {
+    return ColorRGBA(0x80, 0x80, 0x00);
+  } else if (strcmp(color, "purple") == 0) {
+    return ColorRGBA(0x80, 0x00, 0x80);
+  } else if (strcmp(color, "fuschia") == 0) {
+    return ColorRGBA(0xFF, 0x00, 0xFF);
+  } else if (strcmp(color, "white") == 0) {
+    return ColorRGBA(0xFF, 0xFF, 0xFF);
+  } else if (strcmp(color, "lime") == 0) {
+    return ColorRGBA(0x00, 0xFF, 0x00);
+  } else if (strcmp(color, "green") == 0) {
+    return ColorRGBA(0x00, 0x80, 0x00);
+  } else if (strcmp(color, "navy") == 0) {
+    return ColorRGBA(0x00, 0x00, 0x80);
+  } else if (strcmp(color, "blue") == 0) {
+    return ColorRGBA(0x00, 0x00, 0xFF);
+  } else if (strcmp(color, "aqua") == 0) {
+    return ColorRGBA(0x00, 0xFF, 0xFF);
+  } else if (strcmp(color, "teal") == 0) {
+    return ColorRGBA(0x00, 0x80, 0x80);
+  } else if (strcmp(color, "silver") == 0) {
+    return ColorRGBA(0xC0, 0xC0, 0xC0);
+  } else if (strcmp(color, "gray") == 0) {
+    return ColorRGBA(0x80, 0x80, 0x80);
+  } else if (strncmp(color, "rgb(", 4) == 0) {
+    int pos = 4;
+    int r = ParseInt(color, pos);
+    ++pos;
+    int g = ParseInt(color, pos);
+    ++pos;
+    int b = ParseInt(color, pos);
+    return ColorRGBA(r, g, b);
+  } else if (strncmp(color, "rgba(", 5) == 0) {
+    int pos = 5;
+    int r = ParseInt(color, pos);
+    ++pos;
+    int g = ParseInt(color, pos);
+    ++pos;
+    int b = ParseInt(color, pos);
+    ++pos;
+    float a = ParseFloat(color, pos);
+    return ColorRGBA(r, g, b, static_cast<int>(a * 255.0));
+  }
+  // Default to black.
+  return ColorRGBA(0x00, 0x00, 0x00);
+}
+
+void CanvasState::DrawImage(const SkBitmap& bm,
+                            int sx, int sy, int sw, int sh,
+                            int dx, int dy, int dw, int dh) {
+  if (sw < 0) sw = bm.width();
+  if (dw < 0) dw = bm.width();
+  if (sh < 0) sh = bm.height();
+  if (dh < 0) dh = bm.height();
+  SkIRect src = SkIRect::MakeXYWH(sx, sy, sw, sh);
+  SkRect dst = SkRect::MakeXYWH(dx, dy, dw, dh);
+  LOGI("DrawImage(_,%d,%d,%d,%d,%d,%d,%d,%d)", sx, sy, sw, sh, dx, dy, dw, dh);
+  canvas_->drawBitmapRect(bm, &src, dst);
+}
+