[SkSVGDevice] Initial shader/gradient support

experimental/svg/SkSVGDevice.cpp

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkSVGDevice.h"
 
 #include "SkBitmap.h"
 #include "SkDraw.h"
 #include "SkPaint.h"
 #include "SkParsePath.h"
+#include "SkShader.h"
 #include "SkStream.h"
 #include "SkXMLWriter.h"
 
 namespace {
 
-class AutoElement {
+static SkString svg_color(SkColor color) {
+    SkString colorStr;
+    colorStr.printf("rgb(%u,%u,%u)",
+                     SkColorGetR(color),
+                     SkColorGetG(color),
+                     SkColorGetB(color));
+    return colorStr;
+}
+
+static SkScalar svg_opacity(SkColor color) {
+    return SkIntToScalar(SkColorGetA(color)) / SK_AlphaOPAQUE;
+}
+
+struct Resources {

[mtklein, 2015/02/02 22:30:10]

FWIW, I am a big fan of data passed by value until proven slow.  +1 here.

[f(malita), 2015/02/02 23:32:29]

Ack.

+    Resources(const SkPaint& paint)
+        : fPaint(svg_color(paint.getColor())) {}
+
+    SkString fPaint;

[mtklein, 2015/02/02 22:30:10]

fPaintColor?

[f(malita), 2015/02/02 23:32:29]

The thing is it's not necessarily a color: it can be a gradient/pattern
reference. In SVG land they're called paint servers, so maybe we should use the
same. Updated.

+};
+
+}
+
+class SkSVGDevice::AutoElement : ::SkNoncopyable {
 public:
     AutoElement(const char name[], SkXMLWriter* writer)
         : fWriter(writer) {
         fWriter->startElement(name);
     }
 
+    AutoElement(const char name[], SkXMLWriter* writer, const SkDraw& draw, const SkPaint& paint)
+        : fWriter(writer) {
+
+        Resources res = this->addResources(paint);
+
+        fWriter->startElement(name);
+
+        this->addPaint(paint, res);
+        this->addTransform(*draw.fMatrix);
+    }
+
     ~AutoElement() {
         fWriter->endElement();
     }
 
+    void addAttribute(const char name[], const char val[]) {
+        fWriter->addAttribute(name, val);
+    }
+
+    void addAttribute(const char name[], const SkString& val) {
+        fWriter->addAttribute(name, val.c_str());
+    }
+
+    void addAttribute(const char name[], int32_t val) {
+        fWriter->addS32Attribute(name, val);
+    }
+
+    void addAttribute(const char name[], SkScalar val) {
+        fWriter->addScalarAttribute(name, val);
+    }
+
 private:
+    Resources addResources(const SkPaint& paint);
+    void addPaint(const SkPaint& paint, const Resources& resources);
+    void addTransform(const SkMatrix& transform, const char name[] = "transform");
+
+    SkString addLinearGradientDef(const SkShader::GradientInfo& info, const SkShader* shader);
+
     SkXMLWriter* fWriter;
 };
 
+void SkSVGDevice::AutoElement::addPaint(const SkPaint& paint, const Resources& resources) {
+    SkPaint::Style style = paint.getStyle();
+    if (style == SkPaint::kFill_Style || style == SkPaint::kStrokeAndFill_Style) {
+        fWriter->addAttribute("fill", resources.fPaint.c_str());

[mtklein, 2015/02/02 22:30:10]

Might be more readable here if you dogfood your own methods, e.g. 
this->addAttribute("fill", resources.fPaint); ?

[f(malita), 2015/02/02 23:32:30]

Done.

+    } else {
+        fWriter->addAttribute("fill", "none");
+    }
+
+    if (style == SkPaint::kStroke_Style || style == SkPaint::kStrokeAndFill_Style) {
+        fWriter->addAttribute("stroke", resources.fPaint.c_str());
+        fWriter->addScalarAttribute("stroke-width", paint.getStrokeWidth());
+    } else {
+        fWriter->addAttribute("stroke", "none");
+    }
+
+    if (SK_AlphaOPAQUE != SkColorGetA(paint.getColor())) {
+        fWriter->addScalarAttribute("opacity", svg_opacity(paint.getColor()));
+    }
+}
+
+void SkSVGDevice::AutoElement::addTransform(const SkMatrix& t, const char name[]) {
+    if (t.isIdentity()) {
+        return;
+    }
+
+    SkString tstr;
+    switch (t.getType()) {
+    case SkMatrix::kPerspective_Mask:
+        SkDebugf("Can't handle perspective matrices.");
+        break;
+    case SkMatrix::kTranslate_Mask:
+        tstr.printf("translate(%g %g)",
+                     SkScalarToFloat(t.getTranslateX()),
+                     SkScalarToFloat(t.getTranslateY()));
+        break;
+    case SkMatrix::kScale_Mask:
+        tstr.printf("scale(%g %g)",
+                     SkScalarToFloat(t.getScaleX()),
+                     SkScalarToFloat(t.getScaleY()));
+        break;
+    default:
+        tstr.printf("matrix(%g %g %g %g %g %g)",
+                     SkScalarToFloat(t.getScaleX()), SkScalarToFloat(t.getSkewY()),
+                     SkScalarToFloat(t.getSkewX()), SkScalarToFloat(t.getScaleY()),
+                     SkScalarToFloat(t.getTranslateX()), SkScalarToFloat(t.getTranslateY()));
+        break;
+    }
+
+    fWriter->addAttribute(name, tstr.c_str());
+}
+
+Resources SkSVGDevice::AutoElement::addResources(const SkPaint& paint) {
+    Resources resources(paint);

[mtklein, 2015/02/02 22:30:10]

Given the number of times you need to "return resources", you might consider
factoring that out:

Resources addResources(const SkPaint& paint) {
   Resources resources(paint);
   this->addResourceDefs(resources, paint);
   return resources;
}

void addResourceDefs(const Resources&, const SkPaint&) {
  const SkShader* shader = paint.getShader();
  if (!shader) {
    return;
  } 
  ...etc...
}

[f(malita), 2015/02/02 23:32:29]

Done.

+
+    const SkShader* shader = paint.getShader();
+    if (!SkToBool(shader)) {
+        // TODO: clip support
+        return resources;
+    }
+
+    SkShader::GradientInfo grInfo;
+    grInfo.fColorCount = 0;
+    if (SkShader::kLinear_GradientType != shader->asAGradient(&grInfo)) {
+        // TODO: non-linear gradient support
+        SkDebugf("unsupported shader type\n");
+        return resources;
+    }
+
+    {
+        AutoElement defs("defs", fWriter);
+
+        SkAutoSTArray<16, SkColor>  grColors(grInfo.fColorCount);
+        SkAutoSTArray<16, SkScalar> grOffsets(grInfo.fColorCount);
+        grInfo.fColors = grColors.get();
+        grInfo.fColorOffsets = grOffsets.get();
+
+        // One more call to get the actual colors/offsets.
+        shader->asAGradient(&grInfo);
+        SkASSERT(grInfo.fColorCount <= grColors.count());
+        SkASSERT(grInfo.fColorCount <= grOffsets.count());
+
+        resources.fPaint.printf("url(#%s)", addLinearGradientDef(grInfo, shader).c_str());
+    }
+
+    return resources;
+}
+
+SkString SkSVGDevice::AutoElement::addLinearGradientDef(const SkShader::GradientInfo& info,
+                                                        const SkShader* shader) {
+    static uint32_t linear_gradient_counter = 0;

[mtklein, 2015/02/02 22:30:10]

ಠ_ಠ

Not incremented atomically.  Not initialized to zero in a threadsafe way in
Chrome.  Yet another thread-hostile Skia backend... lame.

(I'd go with static int32_t linear_gradient_counter = 0 outside the function and
sk_atomic_inc() it for now, or even better scope the counter to your device.)

[f(malita), 2015/02/02 23:32:30]

What?! You're telling me this is not single-threaded Blink?!

One of these days I'll turn full-schizo from all this context switching. In the
meantime, you can find me in the shame cube.

+
+    SkString id("linear_gradient_");
+    id.appendU32(linear_gradient_counter++);
+
+    {
+        AutoElement gradient("linearGradient", fWriter);
+
+        gradient.addAttribute("id", id);
+        gradient.addAttribute("gradientUnits", "userSpaceOnUse");
+        gradient.addAttribute("x1", info.fPoint[0].x());
+        gradient.addAttribute("y1", info.fPoint[0].y());
+        gradient.addAttribute("x2", info.fPoint[1].x());
+        gradient.addAttribute("y2", info.fPoint[1].y());
+        gradient.addTransform(shader->getLocalMatrix(), "gradientTransform");
+
+        SkASSERT(info.fColorCount >= 2);
+        for (int i = 0; i < info.fColorCount; ++i) {
+            SkColor color = info.fColors[i];
+            SkString colorStr(svg_color(color));
+
+            {
+                AutoElement stop("stop", fWriter);
+                stop.addAttribute("offset", info.fColorOffsets[i]);
+                stop.addAttribute("stop-color", colorStr.c_str());
+
+                if (SK_AlphaOPAQUE != SkColorGetA(color)) {
+                    stop.addAttribute("stop-opacity", svg_opacity(color));
+                }
+            }
+        }
+
+        return id;
+    }
 }
 
 SkBaseDevice* SkSVGDevice::Create(const SkISize& size, SkWStream* wstream) {
     if (!SkToBool(wstream)) {
         return NULL;
     }
 
     return SkNEW_ARGS(SkSVGDevice, (size, wstream));
 }
 
 SkSVGDevice::SkSVGDevice(const SkISize& size, SkWStream* wstream)
     : fWriter(SkNEW_ARGS(SkXMLStreamWriter, (wstream))) {
 
     fLegacyBitmap.setInfo(SkImageInfo::MakeUnknown(size.width(), size.height()));
 
     fWriter->writeHeader();
-    fWriter->startElement("svg");
-    fWriter->addAttribute("xmlns", "http://www.w3.org/2000/svg");
-    fWriter->addAttribute("xmlns:xlink", "http://www.w3.org/1999/xlink");
-    fWriter->addS32Attribute("width", size.width());
-    fWriter->addS32Attribute("height", size.height());
+
+    // The root <svg> tag gets closed by the destructor.
+    fRootElement.reset(SkNEW_ARGS(AutoElement, ("svg", fWriter)));
+
+    fRootElement->addAttribute("xmlns", "http://www.w3.org/2000/svg");
+    fRootElement->addAttribute("xmlns:xlink", "http://www.w3.org/1999/xlink");
+    fRootElement->addAttribute("width", size.width());
+    fRootElement->addAttribute("height", size.height());
 }
 
 SkSVGDevice::~SkSVGDevice() {
-    fWriter->endElement();
-    fWriter->flush();
-    SkDELETE(fWriter);
 }
 
 SkImageInfo SkSVGDevice::imageInfo() const {
     return fLegacyBitmap.info();
 }
 
 const SkBitmap& SkSVGDevice::onAccessBitmap() {
     return fLegacyBitmap;
 }
 
-void SkSVGDevice::addPaint(const SkPaint& paint) {
-    SkColor color = paint.getColor();
-    SkString colorStr;
-    colorStr.appendf("rgb(%u,%u,%u)", SkColorGetR(color), SkColorGetG(color), SkColorGetB(color));
-
-    SkPaint::Style style = paint.getStyle();
-    if (style == SkPaint::kFill_Style || style == SkPaint::kStrokeAndFill_Style) {
-        fWriter->addAttribute("fill", colorStr.c_str());
-    } else {
-        fWriter->addAttribute("fill", "none");
-    }
-
-    if (style == SkPaint::kStroke_Style || style == SkPaint::kStrokeAndFill_Style) {
-        fWriter->addAttribute("stroke", colorStr.c_str());
-        fWriter->addScalarAttribute("stroke-width", paint.getStrokeWidth());
-    } else {
-        fWriter->addAttribute("stroke", "none");
-    }
-}
-
-void SkSVGDevice::addTransform(const SkMatrix &t) {
-    if (t.isIdentity()) {
-        return;
-    }
-
-    SkString tstr;
-    tstr.appendf("matrix(%g %g %g %g %g %g)",
-                 SkScalarToFloat(t.getScaleX()), SkScalarToFloat(t.getSkewY()),
-                 SkScalarToFloat(t.getSkewX()), SkScalarToFloat(t.getScaleY()),
-                 SkScalarToFloat(t.getTranslateX()), SkScalarToFloat(t.getTranslateY()));
-    fWriter->addAttribute("transform", tstr.c_str());
-}
-
-void SkSVGDevice::drawPaint(const SkDraw&, const SkPaint& paint) {
-    // todo
+void SkSVGDevice::drawPaint(const SkDraw& draw, const SkPaint& paint) {
+    AutoElement rect("rect", fWriter, draw, paint);
+    rect.addAttribute("x", 0);
+    rect.addAttribute("y", 0);
+    rect.addAttribute("width", this->width());
+    rect.addAttribute("height", this->height());
 }
 
 void SkSVGDevice::drawPoints(const SkDraw&, SkCanvas::PointMode mode, size_t count,
                              const SkPoint[], const SkPaint& paint) {
     // todo
+    SkDebugf("unsupported operation: drawPoints()");
 }
 
 void SkSVGDevice::drawRect(const SkDraw& draw, const SkRect& r, const SkPaint& paint) {
-    AutoElement elem("rect", fWriter);
-
-    fWriter->addScalarAttribute("x", r.fLeft);
-    fWriter->addScalarAttribute("y", r.fTop);
-    fWriter->addScalarAttribute("width", r.width());
-    fWriter->addScalarAttribute("height", r.height());
-
-    this->addPaint(paint);
-    this->addTransform(*draw.fMatrix);
+    AutoElement rect("rect", fWriter, draw, paint);
+    rect.addAttribute("x", r.fLeft);
+    rect.addAttribute("y", r.fTop);
+    rect.addAttribute("width", r.width());
+    rect.addAttribute("height", r.height());
 }
 
-void SkSVGDevice::drawOval(const SkDraw&, const SkRect& oval, const SkPaint& paint) {
-    // todo
+void SkSVGDevice::drawOval(const SkDraw& draw, const SkRect& oval, const SkPaint& paint) {
+    AutoElement ellipse("ellipse", fWriter, draw, paint);
+    ellipse.addAttribute("cx", oval.centerX());
+    ellipse.addAttribute("cy", oval.centerY());
+    ellipse.addAttribute("rx", oval.width() / 2);
+    ellipse.addAttribute("ry", oval.height() / 2);
 }
 
 void SkSVGDevice::drawRRect(const SkDraw&, const SkRRect& rr, const SkPaint& paint) {
     // todo
+    SkDebugf("unsupported operation: drawRRect()");
 }
 
 void SkSVGDevice::drawPath(const SkDraw& draw, const SkPath& path, const SkPaint& paint,
                            const SkMatrix* prePathMatrix, bool pathIsMutable) {
-    AutoElement elem("path", fWriter);
+    AutoElement elem("path", fWriter, draw, paint);
 
     SkString pathStr;
     SkParsePath::ToSVGString(path, &pathStr);
-    fWriter->addAttribute("d", pathStr.c_str());
-
-    this->addPaint(paint);
-    this->addTransform(*draw.fMatrix);
+    elem.addAttribute("d", pathStr.c_str());
 }
 
 void SkSVGDevice::drawBitmap(const SkDraw&, const SkBitmap& bitmap,
                              const SkMatrix& matrix, const SkPaint& paint) {
     // todo
+    SkDebugf("unsupported operation: drawBitmap()");
 }
 
 void SkSVGDevice::drawSprite(const SkDraw&, const SkBitmap& bitmap,
                              int x, int y, const SkPaint& paint) {
     // todo
+    SkDebugf("unsupported operation: drawSprite()");
 }
 
 void SkSVGDevice::drawBitmapRect(const SkDraw&, const SkBitmap&, const SkRect* srcOrNull,
                                  const SkRect& dst, const SkPaint& paint,
                                  SkCanvas::DrawBitmapRectFlags flags) {
     // todo
+    SkDebugf("unsupported operation: drawBitmapRect()");
 }
 
 void SkSVGDevice::drawText(const SkDraw&, const void* text, size_t len,
                            SkScalar x, SkScalar y, const SkPaint& paint) {
     // todo
+    SkDebugf("unsupported operation: drawText()");
 }
 
 void SkSVGDevice::drawPosText(const SkDraw&, const void* text, size_t len,const SkScalar pos[],
                               int scalarsPerPos, const SkPoint& offset, const SkPaint& paint) {
     // todo
+    SkDebugf("unsupported operation: drawPosText()");
 }
 
 void SkSVGDevice::drawTextOnPath(const SkDraw&, const void* text, size_t len, const SkPath& path,
                                  const SkMatrix* matrix, const SkPaint& paint) {
     // todo
+    SkDebugf("unsupported operation: drawTextOnPath()");
 }
 
 void SkSVGDevice::drawVertices(const SkDraw&, SkCanvas::VertexMode, int vertexCount,
                                const SkPoint verts[], const SkPoint texs[],
                                const SkColor colors[], SkXfermode* xmode,
                                const uint16_t indices[], int indexCount,
                                const SkPaint& paint) {
     // todo
+    SkDebugf("unsupported operation: drawVertices()");
 }
 
 void SkSVGDevice::drawDevice(const SkDraw&, SkBaseDevice*, int x, int y,
                              const SkPaint&) {
     // todo
+    SkDebugf("unsupported operation: drawDevice()");
 }