[SVGDom] Add <svg> viewBox support

experimental/svg/model/SkSVGRenderContext.cpp

 /*
  * Copyright 2016 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
+#include "SkCanvas.h"
 #include "SkSVGRenderContext.h"
 #include "SkSVGTypes.h"
 
 namespace {
 
 SkScalar length_size_for_type(const SkSize& viewport, SkSVGLengthContext::LengthType t) {
     switch (t) {
     case SkSVGLengthContext::LengthType::kHorizontal:
         return viewport.width();
     case SkSVGLengthContext::LengthType::kVertical:
@@ skipping 17 matching lines @@
         return l.value() * length_size_for_type(fViewport, t) / 100;
         break;
     default:
         SkDebugf("unsupported unit type: <%d>\n", l.unit());
         break;
     }
 
     return 0;
 }
 
-SkSVGRenderContext::SkSVGRenderContext(const SkSize& initialViewport)
-    : fLengthContext(initialViewport) {}
+SkRect SkSVGLengthContext::resolveRect(const SkSVGLength& x, const SkSVGLength& y,
+                                       const SkSVGLength& w, const SkSVGLength& h) const {
+    return SkRect::MakeXYWH(
+        this->resolve(x, SkSVGLengthContext::LengthType::kHorizontal),
+        this->resolve(y, SkSVGLengthContext::LengthType::kVertical),
+        this->resolve(w, SkSVGLengthContext::LengthType::kHorizontal),
+        this->resolve(h, SkSVGLengthContext::LengthType::kVertical));
+}
 
-SkSVGRenderContext& SkSVGRenderContext::operator=(const SkSVGRenderContext& other) {
+SkSVGPresentationContext::SkSVGPresentationContext() {}
+
+SkSVGPresentationContext::SkSVGPresentationContext(const SkSVGPresentationContext& o) {
+    this->initFrom(o);
+}
+
+SkSVGPresentationContext& SkSVGPresentationContext::operator=(const SkSVGPresentationContext& o) {
+    this->initFrom(o);
+    return *this;
+}
+
+void SkSVGPresentationContext::initFrom(const SkSVGPresentationContext& other) {
     if (other.fFill.isValid()) {
         fFill.set(*other.fFill.get());
     } else {
         fFill.reset();
     }
 
     if (other.fStroke.isValid()) {
         fStroke.set(*other.fStroke.get());
     } else {
         fStroke.reset();
     }
-
-    return *this;
 }
 
-SkPaint& SkSVGRenderContext::ensureFill() {
+SkPaint& SkSVGPresentationContext::ensureFill() {
     if (!fFill.isValid()) {
         fFill.init();
         fFill.get()->setStyle(SkPaint::kFill_Style);
         fFill.get()->setAntiAlias(true);
     }
     return *fFill.get();
 }
 
-SkPaint& SkSVGRenderContext::ensureStroke() {
+SkPaint& SkSVGPresentationContext::ensureStroke() {
     if (!fStroke.isValid()) {
         fStroke.init();
         fStroke.get()->setStyle(SkPaint::kStroke_Style);
         fStroke.get()->setAntiAlias(true);
     }
     return *fStroke.get();
 }
 
-void SkSVGRenderContext::setFillColor(SkColor color) {
+void SkSVGPresentationContext::setFillColor(SkColor color) {
     this->ensureFill().setColor(color);
 }
 
-void SkSVGRenderContext::setStrokeColor(SkColor color) {
+void SkSVGPresentationContext::setStrokeColor(SkColor color) {
     this->ensureStroke().setColor(color);
 }
+
+SkSVGRenderContext::SkSVGRenderContext(SkCanvas* canvas,
+                                       const SkSVGLengthContext& lctx,
+                                       const SkSVGPresentationContext& pctx)
+    : fLengthContext(lctx)
+    , fPresentationContext(pctx)
+    , fCanvas(canvas)
+    , fCanvasSaveCount(canvas->getSaveCount()) {}
+

[robertphillips, 2016/08/08 17:56:10]

Depending on what semantics you expect, the new SkSVGRenderContext could have a
different fCanvasSaveCount from the original.

[f(malita), 2016/08/08 18:12:03]

Indeed, that's intentional: the original save count reflects the state for
parent node rendering, we need to save the state upon entering the current node.

It would be clearer to keep the canvas/save count external, and just use a local
AutoCanvasRestore where needed.  but since we can e.g. apply transforms at
multiple levels (SkSVGSVG viewbox, SkSVGTransformable transform), the current
approach avoids some redundant save/restores.  Possibly not worth the complexity
in the long run.

+SkSVGRenderContext::SkSVGRenderContext(const SkSVGRenderContext& other)
+    : SkSVGRenderContext(other.canvas(),
+                         other.lengthContext(),
+                         other.presentationContext()) {}
+
+SkSVGRenderContext::~SkSVGRenderContext() {
+    fCanvas->restoreToCount(fCanvasSaveCount);
+}