[SVGDom] Initial <pattern> support

https://www.w3.org/TR/SVG/pservers.html#Patterns

Change-Id: I80455c4ae04cf03526f8e8797f40b0b2d24e043f
Reviewed-on: https://skia-review.googlesource.com/58461
Commit-Queue: Florin Malita <fmalita@chromium.org>
Reviewed-by: Robert Phillips <robertphillips@google.com>

8 files changed, 242 insertions, 0 deletions

diff --git a/BUILD.gn b/BUILD.gn
index 66ea0d82c8..0d99236781 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1177,6 +1177,7 @@ if (skia_enable_tools) {
       "experimental/svg/model/SkSVGLinearGradient.cpp",
       "experimental/svg/model/SkSVGNode.cpp",
       "experimental/svg/model/SkSVGPath.cpp",
+      "experimental/svg/model/SkSVGPattern.cpp",
       "experimental/svg/model/SkSVGPoly.cpp",
       "experimental/svg/model/SkSVGRadialGradient.cpp",
       "experimental/svg/model/SkSVGRect.cpp",
diff --git a/experimental/svg/model/SkSVGAttribute.h b/experimental/svg/model/SkSVGAttribute.h
index 9ba38f944c..71eeb916b0 100644
--- a/experimental/svg/model/SkSVGAttribute.h
+++ b/experimental/svg/model/SkSVGAttribute.h
@@ -29,6 +29,7 @@ enum class SkSVGAttribute {
     kHref,
     kOffset,
     kOpacity,
+    kPatternTransform,
     kPoints,
     kR,  // <circle>, <radialGradient>: radius
     kRx, // <ellipse>,<rect>: horizontal (corner) radius
diff --git a/experimental/svg/model/SkSVGDOM.cpp b/experimental/svg/model/SkSVGDOM.cpp
index 7d6b0b75cd..7bb524b48c 100644
--- a/experimental/svg/model/SkSVGDOM.cpp
+++ b/experimental/svg/model/SkSVGDOM.cpp
@@ -20,6 +20,7 @@
 #include "SkSVGLinearGradient.h"
 #include "SkSVGNode.h"
 #include "SkSVGPath.h"
+#include "SkSVGPattern.h"
 #include "SkSVGPoly.h"
 #include "SkSVGRadialGradient.h"
 #include "SkSVGRect.h"
@@ -294,6 +295,7 @@ SortedDictionaryEntry<AttrParseInfo> gAttributeParseInfo[] = {
     { "height"           , { SkSVGAttribute::kHeight           , SetLengthAttribute       }},
     { "offset"           , { SkSVGAttribute::kOffset           , SetLengthAttribute       }},
     { "opacity"          , { SkSVGAttribute::kOpacity          , SetNumberAttribute       }},
+    { "patternTransform" , { SkSVGAttribute::kPatternTransform , SetTransformAttribute    }},
     { "points"           , { SkSVGAttribute::kPoints           , SetPointsAttribute       }},
     { "r"                , { SkSVGAttribute::kR                , SetLengthAttribute       }},
     { "rx"               , { SkSVGAttribute::kRx               , SetLengthAttribute       }},
@@ -330,6 +332,7 @@ SortedDictionaryEntry<sk_sp<SkSVGNode>(*)()> gTagFactories[] = {
     { "line"          , []() -> sk_sp<SkSVGNode> { return SkSVGLine::Make();           }},
     { "linearGradient", []() -> sk_sp<SkSVGNode> { return SkSVGLinearGradient::Make(); }},
     { "path"          , []() -> sk_sp<SkSVGNode> { return SkSVGPath::Make();           }},
+    { "pattern"       , []() -> sk_sp<SkSVGNode> { return SkSVGPattern::Make();        }},
     { "polygon"       , []() -> sk_sp<SkSVGNode> { return SkSVGPoly::MakePolygon();    }},
     { "polyline"      , []() -> sk_sp<SkSVGNode> { return SkSVGPoly::MakePolyline();   }},
     { "radialGradient", []() -> sk_sp<SkSVGNode> { return SkSVGRadialGradient::Make(); }},
diff --git a/experimental/svg/model/SkSVGNode.h b/experimental/svg/model/SkSVGNode.h
index c0190c4b0c..c9955d1638 100644
--- a/experimental/svg/model/SkSVGNode.h
+++ b/experimental/svg/model/SkSVGNode.h
@@ -27,6 +27,7 @@ enum class SkSVGTag {
     kLine,
     kLinearGradient,
     kPath,
+    kPattern,
     kPolygon,
     kPolyline,
     kRadialGradient,
diff --git a/experimental/svg/model/SkSVGPattern.cpp b/experimental/svg/model/SkSVGPattern.cpp
new file mode 100644
index 0000000000..ef334d7cb0
--- /dev/null
+++ b/experimental/svg/model/SkSVGPattern.cpp
@@ -0,0 +1,170 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkSVGPattern.h"
+
+#include "SkPictureRecorder.h"
+#include "SkShader.h"
+#include "SkSVGRenderContext.h"
+#include "SkSVGValue.h"
+
+SkSVGPattern::SkSVGPattern() : INHERITED(SkSVGTag::kPattern) {}
+
+void SkSVGPattern::setX(const SkSVGLength& x) {
+    fAttributes.fX.set(x);
+}
+
+void SkSVGPattern::setY(const SkSVGLength& y) {
+    fAttributes.fY.set(y);
+}
+
+void SkSVGPattern::setWidth(const SkSVGLength& w) {
+    fAttributes.fWidth.set(w);
+}
+
+void SkSVGPattern::setHeight(const SkSVGLength& h) {
+    fAttributes.fHeight.set(h);
+}
+
+void SkSVGPattern::setHref(const SkSVGStringType& href) {
+    fHref = std::move(href);
+}
+
+void SkSVGPattern::setPatternTransform(const SkSVGTransformType& patternTransform) {
+    fAttributes.fPatternTransform.set(patternTransform);
+}
+
+void SkSVGPattern::onSetAttribute(SkSVGAttribute attr, const SkSVGValue& v) {
+    switch (attr) {
+    case SkSVGAttribute::kX:
+        if (const auto* x = v.as<SkSVGLengthValue>()) {
+            this->setX(*x);
+        }
+        break;
+    case SkSVGAttribute::kY:
+        if (const auto* y = v.as<SkSVGLengthValue>()) {
+            this->setY(*y);
+        }
+        break;
+    case SkSVGAttribute::kWidth:
+        if (const auto* w = v.as<SkSVGLengthValue>()) {
+            this->setWidth(*w);
+        }
+        break;
+    case SkSVGAttribute::kHeight:
+        if (const auto* h = v.as<SkSVGLengthValue>()) {
+            this->setHeight(*h);
+        }
+        break;
+    case SkSVGAttribute::kHref:
+        if (const auto* href = v.as<SkSVGStringValue>()) {
+            this->setHref(*href);
+        }
+        break;
+    case SkSVGAttribute::kPatternTransform:
+        if (const auto* t = v.as<SkSVGTransformValue>()) {
+            this->setPatternTransform(*t);
+        }
+        break;
+    default:
+        this->INHERITED::onSetAttribute(attr, v);
+    }
+}
+
+const SkSVGPattern* SkSVGPattern::hrefTarget(const SkSVGRenderContext& ctx) const {
+    if (fHref.value().isEmpty()) {
+        return nullptr;
+    }
+
+    const auto* href = ctx.findNodeById(fHref);
+    if (!href || href->tag() != SkSVGTag::kPattern) {
+        return nullptr;
+    }
+
+    return static_cast<const SkSVGPattern*>(href);
+}
+
+template <typename T>
+bool inherit_if_needed(const SkTLazy<T>& src, SkTLazy<T>& dst) {
+    if (!dst.isValid()) {
+        dst = src;
+        return true;
+    }
+
+    return false;
+}
+
+/* https://www.w3.org/TR/SVG/pservers.html#PatternElementHrefAttribute
+ *
+ * Any attributes which are defined on the referenced element which are not defined on this element
+ * are inherited by this element. If this element has no children, and the referenced element does
+ * (possibly due to its own ‘xlink:href’ attribute), then this element inherits the children from
+ * the referenced element. Inheritance can be indirect to an arbitrary level; thus, if the
+ * referenced element inherits attributes or children due to its own ‘xlink:href’ attribute, then
+ * the current element can inherit those attributes or children.
+ */
+const SkSVGPattern* SkSVGPattern::resolveHref(const SkSVGRenderContext& ctx,
+                                              PatternAttributes* attrs) const {
+    const SkSVGPattern *currentNode = this,
+                       *contentNode = this;
+    do {
+        // Bitwise OR to avoid short-circuiting.
+        const bool didInherit =
+            inherit_if_needed(currentNode->fAttributes.fX               , attrs->fX)      |
+            inherit_if_needed(currentNode->fAttributes.fY               , attrs->fY)      |
+            inherit_if_needed(currentNode->fAttributes.fWidth           , attrs->fWidth)  |
+            inherit_if_needed(currentNode->fAttributes.fHeight          , attrs->fHeight) |
+            inherit_if_needed(currentNode->fAttributes.fPatternTransform, attrs->fPatternTransform);
+
+        if (!contentNode->hasChildren()) {
+            contentNode = currentNode;
+        }
+
+        if (contentNode->hasChildren() && !didInherit) {
+            // All attributes have been resolved, and a valid content node has been found.
+            // We can terminate the href chain early.
+            break;
+        }
+
+        // TODO: reference loop mitigation.
+        currentNode = currentNode->hrefTarget(ctx);
+    } while (currentNode);
+
+    return contentNode;
+}
+
+bool SkSVGPattern::onAsPaint(const SkSVGRenderContext& ctx, SkPaint* paint) const {
+    PatternAttributes attrs;
+    const auto* contentNode = this->resolveHref(ctx, &attrs);
+
+    const auto tile = ctx.lengthContext().resolveRect(
+            attrs.fX.isValid()      ? *attrs.fX.get()      : SkSVGLength(0),
+            attrs.fY.isValid()      ? *attrs.fY.get()      : SkSVGLength(0),
+            attrs.fWidth.isValid()  ? *attrs.fWidth.get()  : SkSVGLength(0),
+            attrs.fHeight.isValid() ? *attrs.fHeight.get() : SkSVGLength(0));
+
+    if (tile.isEmpty()) {
+        return false;
+    }
+
+    const SkMatrix* patternTransform = attrs.fPatternTransform.isValid()
+            ? &attrs.fPatternTransform.get()->value()
+            : nullptr;
+
+    SkPictureRecorder recorder;
+    SkSVGRenderContext recordingContext(ctx, recorder.beginRecording(tile));
+
+    // Cannot call into INHERITED:: because SkSVGHiddenContainer skips rendering.
+    contentNode->SkSVGContainer::onRender(recordingContext);
+
+    paint->setShader(SkShader::MakePictureShader(recorder.finishRecordingAsPicture(),
+                                                 SkShader::kRepeat_TileMode,
+                                                 SkShader::kRepeat_TileMode,
+                                                 patternTransform,
+                                                 &tile));
+    return true;
+}
diff --git a/experimental/svg/model/SkSVGPattern.h b/experimental/svg/model/SkSVGPattern.h
new file mode 100644
index 0000000000..6ae0fee039
--- /dev/null
+++ b/experimental/svg/model/SkSVGPattern.h
@@ -0,0 +1,59 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkSVGPattern_DEFINED
+#define SkSVGPattern_DEFINED
+
+#include "SkSVGHiddenContainer.h"
+#include "SkSVGTypes.h"
+
+class SkSVGRenderContext;
+
+class SkSVGPattern final : public SkSVGHiddenContainer {
+public:
+    ~SkSVGPattern() override = default;
+
+    static sk_sp<SkSVGPattern> Make() {
+        return sk_sp<SkSVGPattern>(new SkSVGPattern());
+    }
+
+    void setX(const SkSVGLength&);
+    void setY(const SkSVGLength&);
+    void setWidth(const SkSVGLength&);
+    void setHeight(const SkSVGLength&);
+    void setHref(const SkSVGStringType&);
+    void setPatternTransform(const SkSVGTransformType&);
+
+protected:
+    SkSVGPattern();
+
+    void onSetAttribute(SkSVGAttribute, const SkSVGValue&) override;
+
+    bool onAsPaint(const SkSVGRenderContext&, SkPaint*) const override;
+
+private:
+    struct PatternAttributes {
+        SkTLazy<SkSVGLength>        fX,
+                                    fY,
+                                    fWidth,
+                                    fHeight;
+        SkTLazy<SkSVGTransformType> fPatternTransform;
+    } fAttributes;
+
+    SkSVGStringType    fHref;
+
+    const SkSVGPattern* resolveHref(const SkSVGRenderContext&, PatternAttributes*) const;
+    const SkSVGPattern* hrefTarget(const SkSVGRenderContext&) const;
+
+    // TODO:
+    //   - patternUnits
+    //   - patternContentUnits
+
+    typedef SkSVGHiddenContainer INHERITED;
+};
+
+#endif // SkSVGPattern_DEFINED
diff --git a/experimental/svg/model/SkSVGRenderContext.cpp b/experimental/svg/model/SkSVGRenderContext.cpp
index 7fa61d48a3..a3e37cb965 100644
--- a/experimental/svg/model/SkSVGRenderContext.cpp
+++ b/experimental/svg/model/SkSVGRenderContext.cpp
@@ -253,6 +253,12 @@ SkSVGRenderContext::SkSVGRenderContext(const SkSVGRenderContext& other)
                          *other.fLengthContext,
                          *other.fPresentationContext) {}
 
+SkSVGRenderContext::SkSVGRenderContext(const SkSVGRenderContext& other, SkCanvas* canvas)
+    : SkSVGRenderContext(canvas,
+                         other.fIDMapper,
+                         *other.fLengthContext,
+                         *other.fPresentationContext) {}
+
 SkSVGRenderContext::~SkSVGRenderContext() {
     fCanvas->restoreToCount(fCanvasSaveCount);
 }
diff --git a/experimental/svg/model/SkSVGRenderContext.h b/experimental/svg/model/SkSVGRenderContext.h
index b5d8720ab3..69bf9f278f 100644
--- a/experimental/svg/model/SkSVGRenderContext.h
+++ b/experimental/svg/model/SkSVGRenderContext.h
@@ -61,6 +61,7 @@ public:
     SkSVGRenderContext(SkCanvas*, const SkSVGIDMapper&, const SkSVGLengthContext&,
                        const SkSVGPresentationContext&);
     SkSVGRenderContext(const SkSVGRenderContext&);
+    SkSVGRenderContext(const SkSVGRenderContext&, SkCanvas*);
     ~SkSVGRenderContext();
 
     const SkSVGLengthContext& lengthContext() const { return *fLengthContext; }