samplecode/SampleThinAA.cpp - skia - Git at Google

 /*
  * Copyright 2019 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */

 #include "samplecode/Sample.h"

 #include "include/core/SkCanvas.h"
 #include "include/core/SkColorFilter.h"
 #include "include/core/SkFont.h"
 #include "include/core/SkImage.h"
 #include "include/core/SkPath.h"
 #include "include/core/SkSurface.h"
 #include "tools/timer/AnimTimer.h"

 namespace skiagm {

 class ShapeRenderer : public SkRefCntBase {
 public:
     static constexpr SkScalar kTileWidth = 20.f;
     static constexpr SkScalar kTileHeight = 20.f;

     virtual ~ShapeRenderer() {}

     // Draw the shape, limited to kTileWidth x kTileHeight. It must apply the local subpixel (tx,
     // ty) translation and rotation by angle. Prior to these transform adjustments, the SkCanvas
     // will only have pixel aligned translations (these are separated to make super-sampling
     // renderers easier).
     virtual void draw(SkCanvas* canvas, SkPaint* paint,
                       SkScalar tx, SkScalar ty, SkScalar angle) = 0;

     virtual SkString name() = 0;

     virtual sk_sp<ShapeRenderer> toHairline() = 0;

     void applyLocalTransform(SkCanvas* canvas, SkScalar tx, SkScalar ty, SkScalar angle) {
         canvas->translate(tx, ty);
         canvas->rotate(angle, kTileWidth / 2.f, kTileHeight / 2.f);
     }
 };

 class RectRenderer : public ShapeRenderer {
 public:
     static sk_sp<ShapeRenderer> Make() {
         return sk_sp<ShapeRenderer>(new RectRenderer());
     }

     SkString name() override { return SkString("rect"); }

     sk_sp<ShapeRenderer> toHairline() override {
         // Not really available but can't return nullptr
         return Make();
     }

     void draw(SkCanvas* canvas, SkPaint* paint, SkScalar tx, SkScalar ty, SkScalar angle) override {
         SkScalar width = paint->getStrokeWidth();
         paint->setStyle(SkPaint::kFill_Style);

         this->applyLocalTransform(canvas, tx, ty, angle);
         canvas->drawRect(SkRect::MakeLTRB(kTileWidth / 2.f - width / 2.f, 2.f,
                                           kTileWidth / 2.f + width / 2.f, kTileHeight - 2.f),
                          *paint);
     }

 private:
     RectRenderer() {}

     typedef ShapeRenderer INHERITED;
 };

 class PathRenderer : public ShapeRenderer {
 public:
     static sk_sp<ShapeRenderer> MakeLine(bool hairline = false) {
         return MakeCurve(0.f, hairline);
     }

     static sk_sp<ShapeRenderer> MakeLines(SkScalar depth, bool hairline = false) {
         return MakeCurve(-depth, hairline);
     }

     static sk_sp<ShapeRenderer> MakeCurve(SkScalar depth, bool hairline = false) {
         return sk_sp<ShapeRenderer>(new PathRenderer(depth, hairline));
     }

     SkString name() override {
         SkString name;
         if (fHairline) {
             name.append("hairline");
             if (fDepth > 0.f) {
                 name.appendf("-curve-%.2f", fDepth);
             }
         } else if (fDepth > 0.f) {
             name.appendf("curve-%.2f", fDepth);
         } else if (fDepth < 0.f) {
             name.appendf("line-%.2f", -fDepth);
         } else {
             name.append("line");
         }

         return name;
     }

     sk_sp<ShapeRenderer> toHairline() override {
         return sk_sp<ShapeRenderer>(new PathRenderer(fDepth, true));
     }

     void draw(SkCanvas* canvas, SkPaint* paint, SkScalar tx, SkScalar ty, SkScalar angle) override {
         SkPath path;
         path.moveTo(kTileWidth / 2.f, 2.f);

         if (fDepth > 0.f) {
             path.quadTo(kTileWidth / 2.f + fDepth, kTileHeight / 2.f,
                         kTileWidth / 2.f, kTileHeight - 2.f);
         } else {
             if (fDepth < 0.f) {
                 path.lineTo(kTileWidth / 2.f + fDepth, kTileHeight / 2.f);
             }
             path.lineTo(kTileWidth / 2.f, kTileHeight - 2.f);
         }

         if (fHairline) {
             // Fake thinner hairlines by making it transparent, conflating coverage and alpha
             SkColor4f color = paint->getColor4f();
             SkScalar width = paint->getStrokeWidth();
             if (width > 1.f) {
                 // Can't emulate width larger than a pixel
                 return;
             }
             paint->setColor4f({color.fR, color.fG, color.fB, width}, nullptr);
             paint->setStrokeWidth(0.f);
         }

         // Adding round caps forces Ganesh to use the path renderer for lines instead of converting
         // them to rectangles (which are already explicitly tested). However, when not curved, the
         // GrShape will still find a way to turn it into a rrect draw so it doesn't hit the
         // path renderer in that condition.
         paint->setStrokeCap(SkPaint::kRound_Cap);
         paint->setStrokeJoin(SkPaint::kMiter_Join);
         paint->setStyle(SkPaint::kStroke_Style);

         this->applyLocalTransform(canvas, tx, ty, angle);
         canvas->drawPath(path, *paint);
     }

 private:
     SkScalar fDepth; // 0.f to make a line, otherwise outset of curve from end points
     bool fHairline;

     PathRenderer(SkScalar depth, bool hairline)
             : fDepth(depth)
             , fHairline(hairline) {}

     typedef ShapeRenderer INHERITED;
 };

 class OffscreenShapeRenderer : public ShapeRenderer {
 public:
     ~OffscreenShapeRenderer() override = default;

     static sk_sp<OffscreenShapeRenderer> Make(sk_sp<ShapeRenderer> renderer, int supersample,
                                               bool forceRaster = false) {
         SkASSERT(supersample > 0);
         return sk_sp<OffscreenShapeRenderer>(new OffscreenShapeRenderer(std::move(renderer),
                                                                         supersample, forceRaster));
     }

     SkString name() override {
         SkString name = fRenderer->name();
         if (fSupersampleFactor != 1) {
             name.prependf("%dx-", fSupersampleFactor * fSupersampleFactor);
         }
         return name;
     }

     sk_sp<ShapeRenderer> toHairline() override {
         return Make(fRenderer->toHairline(), fSupersampleFactor, fForceRasterBackend);
     }

     void draw(SkCanvas* canvas, SkPaint* paint, SkScalar tx, SkScalar ty, SkScalar angle) override {
         // Subpixel translation+angle are applied in the offscreen buffer
         this->prepareBuffer(canvas, paint, tx, ty, angle);
         this->redraw(canvas);
     }

     // Exposed so that it's easy to fill the offscreen buffer, then draw zooms/filters of it before
     // drawing the original scale back into the canvas.
     void prepareBuffer(SkCanvas* canvas, SkPaint* paint, SkScalar tx, SkScalar ty, SkScalar angle) {
         auto info = SkImageInfo::Make(fSupersampleFactor * kTileWidth,
                                       fSupersampleFactor * kTileHeight,
                                       kRGBA_8888_SkColorType, kPremul_SkAlphaType);
         auto surface = fForceRasterBackend ? SkSurface::MakeRaster(info)
                                            : canvas->makeSurface(info);

         surface->getCanvas()->save();
         // Make fully transparent so it is easy to determine pixels that are touched by partial cov.
         surface->getCanvas()->clear(SK_ColorTRANSPARENT);
         // Set up scaling to fit supersampling amount
         surface->getCanvas()->scale(fSupersampleFactor, fSupersampleFactor);
         fRenderer->draw(surface->getCanvas(), paint, tx, ty, angle);
         surface->getCanvas()->restore();

         // Save image so it can be drawn zoomed in or to visualize touched pixels; only valid until
         // the next call to draw()
         fLastRendered = surface->makeImageSnapshot();
     }

     void redraw(SkCanvas* canvas, SkScalar scale = 1.f, bool debugMode = false) {
         SkASSERT(fLastRendered);
         // Use medium quality filter to get mipmaps when drawing smaller, or use nearest filtering
         // when upscaling
         SkPaint blit;
         blit.setFilterQuality(scale > 1.f ? kNone_SkFilterQuality : kMedium_SkFilterQuality);
         if (debugMode) {
             // Makes anything that's > 1/255 alpha fully opaque and sets color to medium green.
             static constexpr float kFilter[] = {
                 0.f, 0.f, 0.f, 0.f, 16.f/255,
                 0.f, 0.f, 0.f, 0.f, 200.f/255,
                 0.f, 0.f, 0.f, 0.f, 16.f/255,
                 0.f, 0.f, 0.f, 255.f, 0.f
             };

             blit.setColorFilter(SkColorFilters::Matrix(kFilter));
         }

         canvas->scale(scale, scale);
         canvas->drawImageRect(fLastRendered, SkRect::MakeWH(kTileWidth, kTileHeight), &blit);
     }

 private:
     bool                 fForceRasterBackend;
     sk_sp<SkImage>       fLastRendered;
     sk_sp<ShapeRenderer> fRenderer;
     int                  fSupersampleFactor;

     OffscreenShapeRenderer(sk_sp<ShapeRenderer> renderer, int supersample, bool forceRaster)
             : fForceRasterBackend(forceRaster)
             , fLastRendered(nullptr)
             , fRenderer(std::move(renderer))
             , fSupersampleFactor(supersample) { }

     typedef ShapeRenderer INHERITED;
 };

 class ThinAASample : public Sample {
 public:
     ThinAASample() {
         this->setBGColor(0xFFFFFFFF);
     }

 protected:
     void onOnceBeforeDraw() override {
         // Setup all base renderers
         fShapes.push_back(RectRenderer::Make());
         fShapes.push_back(PathRenderer::MakeLine());
         fShapes.push_back(PathRenderer::MakeLines(4.f)); // 2 segments
         fShapes.push_back(PathRenderer::MakeCurve(2.f)); // Shallow curve
         fShapes.push_back(PathRenderer::MakeCurve(8.f)); // Deep curve

         for (int i = 0; i < fShapes.count(); ++i) {
             fNative.push_back(OffscreenShapeRenderer::Make(fShapes[i], 1));
             fRaster.push_back(OffscreenShapeRenderer::Make(fShapes[i], 1, /* raster */ true));
             fSS4.push_back(OffscreenShapeRenderer::Make(fShapes[i], 4)); // 4x4 -> 16 samples
             fSS16.push_back(OffscreenShapeRenderer::Make(fShapes[i], 8)); // 8x8 -> 64 samples

             fHairline.push_back(OffscreenShapeRenderer::Make(fRaster[i]->toHairline(), 1));
         }

         // Start it at something subpixel
         fStrokeWidth = 0.5f;

         fSubpixelX = 0.f;
         fSubpixelY = 0.f;
         fAngle = 0.f;

         fCurrentStage = AnimStage::kMoveLeft;
         fLastFrameTime = -1.f;

         // Don't animate in the beginning
         fAnimTranslate = false;
         fAnimRotate = false;
     }

     void onDrawContent(SkCanvas* canvas) override {
         // Move away from screen edge and add instructions
         SkPaint text;
         SkFont font(nullptr, 12);
         canvas->translate(60.f, 20.f);
         canvas->drawString("Each row features a rendering command under different AA strategies. "
                            "Native refers to the current backend of the viewer, e.g. OpenGL.",
                            0, 0, font, text);

         canvas->drawString(SkStringPrintf("Stroke width: %.2f ('-' to decrease, '=' to increase)",
                 fStrokeWidth), 0, 24, font, text);
         canvas->drawString(SkStringPrintf("Rotation: %.3f ('r' to animate, 'y' sets to 90, 'u' sets"
                 " to 0, 'space' adds 15)", fAngle), 0, 36, font, text);
         canvas->drawString(SkStringPrintf("Translation: %.3f, %.3f ('t' to animate)",
                 fSubpixelX, fSubpixelY), 0, 48, font, text);

         canvas->translate(0.f, 100.f);

         // Draw with surface matching current viewer surface type
         this->drawShapes(canvas, "Native", 0, fNative);

         // Draw with forced raster backend so it's easy to compare side-by-side
         this->drawShapes(canvas, "Raster", 1, fRaster);

         // Draw paths as hairlines + alpha hack
         this->drawShapes(canvas, "Hairline", 2, fHairline);

         // Draw at 4x supersampling in bottom left
         this->drawShapes(canvas, "SSx16", 3, fSS4);

         // And lastly 16x supersampling in bottom right
         this->drawShapes(canvas, "SSx64", 4, fSS16);
     }

     bool onAnimate(const AnimTimer& timer) override {
         SkScalar t = timer.secs();
         SkScalar dt = fLastFrameTime < 0.f ? 0.f : t - fLastFrameTime;
         fLastFrameTime = t;

         if (!fAnimRotate && !fAnimTranslate) {
             // Keep returning true so that the last frame time is tracked
             fLastFrameTime = -1.f;
             return false;
         }

         switch(fCurrentStage) {
             case AnimStage::kMoveLeft:
                 fSubpixelX += 2.f * dt;
                 if (fSubpixelX >= 1.f) {
                     fSubpixelX = 1.f;
                     fCurrentStage = AnimStage::kMoveDown;
                 }
                 break;
             case AnimStage::kMoveDown:
                 fSubpixelY += 2.f * dt;
                 if (fSubpixelY >= 1.f) {
                     fSubpixelY = 1.f;
                     fCurrentStage = AnimStage::kMoveRight;
                 }
                 break;
             case AnimStage::kMoveRight:
                 fSubpixelX -= 2.f * dt;
                 if (fSubpixelX <= -1.f) {
                     fSubpixelX = -1.f;
                     fCurrentStage = AnimStage::kMoveUp;
                 }
                 break;
             case AnimStage::kMoveUp:
                 fSubpixelY -= 2.f * dt;
                 if (fSubpixelY <= -1.f) {
                     fSubpixelY = -1.f;
                     fCurrentStage = fAnimRotate ? AnimStage::kRotate : AnimStage::kMoveLeft;
                 }
                 break;
             case AnimStage::kRotate: {
                 SkScalar newAngle = fAngle + dt * 15.f;
                 bool completed = SkScalarMod(newAngle, 15.f) < SkScalarMod(fAngle, 15.f);
                 fAngle = SkScalarMod(newAngle, 360.f);
                 if (completed) {
                     // Make sure we're on a 15 degree boundary
                     fAngle = 15.f * SkScalarRoundToScalar(fAngle / 15.f);
                     if (fAnimTranslate) {
                         fCurrentStage = this->getTranslationStage();
                     }
                 }
             } break;
         }

         return true;
     }

     bool onQuery(Sample::Event* evt) override {
         if (Sample::TitleQ(*evt)) {
             Sample::TitleR(evt, "Thin-AA");
             return true;
         }

         SkUnichar key;
         if (Sample::CharQ(*evt, &key)) {
             switch(key) {
                 case 't':
                     // Toggle translation animation.
                     fAnimTranslate = !fAnimTranslate;
                     if (!fAnimTranslate && fAnimRotate && fCurrentStage != AnimStage::kRotate) {
                         // Turned off an active translation so go to rotating
                         fCurrentStage = AnimStage::kRotate;
                     } else if (fAnimTranslate && !fAnimRotate &&
                                fCurrentStage == AnimStage::kRotate) {
                         // Turned on translation, rotation had been paused too, so reset the stage
                         fCurrentStage = this->getTranslationStage();
                     }
                     return true;
                 case 'r':
                     // Toggle rotation animation.
                     fAnimRotate = !fAnimRotate;
                     if (!fAnimRotate && fAnimTranslate && fCurrentStage == AnimStage::kRotate) {
                         // Turned off an active rotation so go back to translation
                         fCurrentStage = this->getTranslationStage();
                     } else if (fAnimRotate && !fAnimTranslate &&
                                fCurrentStage != AnimStage::kRotate) {
                         // Turned on rotation, translation had been paused too, so reset to rotate
                         fCurrentStage = AnimStage::kRotate;
                     }
                     return true;
                 case 'u': fAngle = 0.f; return true;
                 case 'y': fAngle = 90.f; return true;
                 case ' ': fAngle = SkScalarMod(fAngle + 15.f, 360.f); return true;
                 case '-': fStrokeWidth = SkMaxScalar(0.1f, fStrokeWidth - 0.05f); return true;
                 case '=': fStrokeWidth = SkMinScalar(1.f, fStrokeWidth + 0.05f); return true;
             }
         }
         return this->INHERITED::onQuery(evt);
     }

 private:
     // Base renderers that get wrapped on the offscreen renderers so that they can be transformed
     // for visualization, or supersampled.
     SkTArray<sk_sp<ShapeRenderer>> fShapes;

     SkTArray<sk_sp<OffscreenShapeRenderer>> fNative;
     SkTArray<sk_sp<OffscreenShapeRenderer>> fRaster;
     SkTArray<sk_sp<OffscreenShapeRenderer>> fHairline;
     SkTArray<sk_sp<OffscreenShapeRenderer>> fSS4;
     SkTArray<sk_sp<OffscreenShapeRenderer>> fSS16;

     SkScalar fStrokeWidth;

     // Animated properties to stress the AA algorithms
     enum class AnimStage {
         kMoveRight, kMoveDown, kMoveLeft, kMoveUp, kRotate
     } fCurrentStage;
     SkScalar fLastFrameTime;
     bool     fAnimRotate;
     bool     fAnimTranslate;

     // Current frame's animation state
     SkScalar fSubpixelX;
     SkScalar fSubpixelY;
     SkScalar fAngle;

     AnimStage getTranslationStage() {
         // For paused translations (i.e. fAnimTranslate toggled while translating), the current
         // stage moves to kRotate, but when restarting the translation animation, we want to
         // go back to where we were without losing any progress.
         if (fSubpixelX > -1.f) {
             if (fSubpixelX >= 1.f) {
                 // Can only be moving down on right edge, given our transition states
                 return AnimStage::kMoveDown;
             } else if (fSubpixelY > 0.f) {
                 // Can only be moving right along top edge
                 return AnimStage::kMoveRight;
             } else {
                 // Must be moving left along bottom edge
                 return AnimStage::kMoveLeft;
             }
         } else {
             // Moving up along the left edge, or is at the very top so start moving left
             return fSubpixelY > -1.f ? AnimStage::kMoveUp : AnimStage::kMoveLeft;
         }
     }

     void drawShapes(SkCanvas* canvas, const char* name, int gridX,
                     SkTArray<sk_sp<OffscreenShapeRenderer>> shapes) {
         SkAutoCanvasRestore autoRestore(canvas, /* save */ true);

         for (int i = 0; i < shapes.count(); ++i) {
             this->drawShape(canvas, name, gridX, shapes[i].get(), i == 0);
             // drawShape positions the canvas properly for the next iteration
         }
     }

     void drawShape(SkCanvas* canvas, const char* name, int gridX,
                    OffscreenShapeRenderer* shape, bool drawNameLabels) {
         static constexpr SkScalar kZoomGridWidth = 8 * ShapeRenderer::kTileWidth + 8.f;
         static constexpr SkRect kTile = SkRect::MakeWH(ShapeRenderer::kTileWidth,
                                                        ShapeRenderer::kTileHeight);
         static constexpr SkRect kZoomTile = SkRect::MakeWH(8 * ShapeRenderer::kTileWidth,
                                                            8 * ShapeRenderer::kTileHeight);

         // Labeling per shape and detailed labeling that isn't per-stroke
         canvas->save();
         SkPaint text;
         SkFont font(nullptr, 12);

         if (gridX == 0) {
             SkString name = shape->name();
             SkScalar centering = name.size() * 4.f; // ad-hoc

             canvas->save();
             canvas->translate(-10.f, 4 * ShapeRenderer::kTileHeight + centering);
             canvas->rotate(-90.f);
             canvas->drawString(shape->name(), 0.f, 0.f, font, text);
             canvas->restore();
         }
         if (drawNameLabels) {
             canvas->drawString(name, gridX * kZoomGridWidth, -10.f, font, text);
         }
         canvas->restore();

         // Paints for outlines and actual shapes
         SkPaint outline;
         outline.setStyle(SkPaint::kStroke_Style);
         SkPaint clear;
         clear.setColor(SK_ColorWHITE);

         SkPaint paint;
         paint.setAntiAlias(true);
         paint.setStrokeWidth(fStrokeWidth);

         // Generate a saved image of the correct stroke width, but don't put it into the canvas
         // yet since we want to draw the "original" size on top of the zoomed in version
         shape->prepareBuffer(canvas, &paint, fSubpixelX, fSubpixelY, fAngle);

         // Draw it at 8X zoom
         SkScalar x = gridX * kZoomGridWidth;

         canvas->save();
         canvas->translate(x, 0.f);
         canvas->drawRect(kZoomTile, outline);
         shape->redraw(canvas, 8.0f);
         canvas->restore();

         // Draw the original
         canvas->save();
         canvas->translate(x + 4.f, 4.f);
         canvas->drawRect(kTile, clear);
         canvas->drawRect(kTile, outline);
         shape->redraw(canvas, 1.f);
         canvas->restore();

         // Now redraw it into the coverage location (just to the right of the original scale)
         canvas->save();
         canvas->translate(x + ShapeRenderer::kTileWidth + 8.f, 4.f);
         canvas->drawRect(kTile, clear);
         canvas->drawRect(kTile, outline);
         shape->redraw(canvas, 1.f, /* debug */ true);
         canvas->restore();

         // Lastly, shift the canvas translation down by 8 * kTH + padding for the next set of shapes
         canvas->translate(0.f, 8.f * ShapeRenderer::kTileHeight + 20.f);
     }

     typedef Sample INHERITED;
 };

 //////////////////////////////////////////////////////////////////////////////

 DEF_SAMPLE( return new ThinAASample; )

 }
	/*
	* Copyright 2019 Google Inc.
	*
	* Use of this source code is governed by a BSD-style license that can be
	* found in the LICENSE file.
	*/

	#include "samplecode/Sample.h"

	#include "include/core/SkCanvas.h"
	#include "include/core/SkColorFilter.h"
	#include "include/core/SkFont.h"
	#include "include/core/SkImage.h"
	#include "include/core/SkPath.h"
	#include "include/core/SkSurface.h"
	#include "tools/timer/AnimTimer.h"

	namespace skiagm {

	class ShapeRenderer : public SkRefCntBase {
	public:
	static constexpr SkScalar kTileWidth = 20.f;
	static constexpr SkScalar kTileHeight = 20.f;

	virtual ~ShapeRenderer() {}

	// Draw the shape, limited to kTileWidth x kTileHeight. It must apply the local subpixel (tx,
	// ty) translation and rotation by angle. Prior to these transform adjustments, the SkCanvas
	// will only have pixel aligned translations (these are separated to make super-sampling
	// renderers easier).
	virtual void draw(SkCanvas* canvas, SkPaint* paint,
	SkScalar tx, SkScalar ty, SkScalar angle) = 0;

	virtual SkString name() = 0;

	virtual sk_sp<ShapeRenderer> toHairline() = 0;

	void applyLocalTransform(SkCanvas* canvas, SkScalar tx, SkScalar ty, SkScalar angle) {
	canvas->translate(tx, ty);
	canvas->rotate(angle, kTileWidth / 2.f, kTileHeight / 2.f);
	}
	};

	class RectRenderer : public ShapeRenderer {
	public:
	static sk_sp<ShapeRenderer> Make() {
	return sk_sp<ShapeRenderer>(new RectRenderer());
	}

	SkString name() override { return SkString("rect"); }

	sk_sp<ShapeRenderer> toHairline() override {
	// Not really available but can't return nullptr
	return Make();
	}

	void draw(SkCanvas* canvas, SkPaint* paint, SkScalar tx, SkScalar ty, SkScalar angle) override {
	SkScalar width = paint->getStrokeWidth();
	paint->setStyle(SkPaint::kFill_Style);

	this->applyLocalTransform(canvas, tx, ty, angle);
	canvas->drawRect(SkRect::MakeLTRB(kTileWidth / 2.f - width / 2.f, 2.f,
	kTileWidth / 2.f + width / 2.f, kTileHeight - 2.f),
	*paint);
	}

	private:
	RectRenderer() {}

	typedef ShapeRenderer INHERITED;
	};

	class PathRenderer : public ShapeRenderer {
	public:
	static sk_sp<ShapeRenderer> MakeLine(bool hairline = false) {
	return MakeCurve(0.f, hairline);
	}

	static sk_sp<ShapeRenderer> MakeLines(SkScalar depth, bool hairline = false) {
	return MakeCurve(-depth, hairline);
	}

	static sk_sp<ShapeRenderer> MakeCurve(SkScalar depth, bool hairline = false) {
	return sk_sp<ShapeRenderer>(new PathRenderer(depth, hairline));
	}

	SkString name() override {
	SkString name;
	if (fHairline) {
	name.append("hairline");
	if (fDepth > 0.f) {
	name.appendf("-curve-%.2f", fDepth);
	}
	} else if (fDepth > 0.f) {
	name.appendf("curve-%.2f", fDepth);
	} else if (fDepth < 0.f) {
	name.appendf("line-%.2f", -fDepth);
	} else {
	name.append("line");
	}

	return name;
	}

	sk_sp<ShapeRenderer> toHairline() override {
	return sk_sp<ShapeRenderer>(new PathRenderer(fDepth, true));
	}

	void draw(SkCanvas* canvas, SkPaint* paint, SkScalar tx, SkScalar ty, SkScalar angle) override {
	SkPath path;
	path.moveTo(kTileWidth / 2.f, 2.f);

	if (fDepth > 0.f) {
	path.quadTo(kTileWidth / 2.f + fDepth, kTileHeight / 2.f,
	kTileWidth / 2.f, kTileHeight - 2.f);
	} else {
	if (fDepth < 0.f) {
	path.lineTo(kTileWidth / 2.f + fDepth, kTileHeight / 2.f);
	}
	path.lineTo(kTileWidth / 2.f, kTileHeight - 2.f);
	}

	if (fHairline) {
	// Fake thinner hairlines by making it transparent, conflating coverage and alpha
	SkColor4f color = paint->getColor4f();
	SkScalar width = paint->getStrokeWidth();
	if (width > 1.f) {
	// Can't emulate width larger than a pixel
	return;
	}
	paint->setColor4f({color.fR, color.fG, color.fB, width}, nullptr);
	paint->setStrokeWidth(0.f);
	}

	// Adding round caps forces Ganesh to use the path renderer for lines instead of converting
	// them to rectangles (which are already explicitly tested). However, when not curved, the
	// GrShape will still find a way to turn it into a rrect draw so it doesn't hit the
	// path renderer in that condition.
	paint->setStrokeCap(SkPaint::kRound_Cap);
	paint->setStrokeJoin(SkPaint::kMiter_Join);
	paint->setStyle(SkPaint::kStroke_Style);

	this->applyLocalTransform(canvas, tx, ty, angle);
	canvas->drawPath(path, *paint);
	}

	private:
	SkScalar fDepth; // 0.f to make a line, otherwise outset of curve from end points
	bool fHairline;

	PathRenderer(SkScalar depth, bool hairline)
	: fDepth(depth)
	, fHairline(hairline) {}

	typedef ShapeRenderer INHERITED;
	};

	class OffscreenShapeRenderer : public ShapeRenderer {
	public:
	~OffscreenShapeRenderer() override = default;

	static sk_sp<OffscreenShapeRenderer> Make(sk_sp<ShapeRenderer> renderer, int supersample,
	bool forceRaster = false) {
	SkASSERT(supersample > 0);
	return sk_sp<OffscreenShapeRenderer>(new OffscreenShapeRenderer(std::move(renderer),
	supersample, forceRaster));
	}

	SkString name() override {
	SkString name = fRenderer->name();
	if (fSupersampleFactor != 1) {
	name.prependf("%dx-", fSupersampleFactor * fSupersampleFactor);
	}
	return name;
	}

	sk_sp<ShapeRenderer> toHairline() override {
	return Make(fRenderer->toHairline(), fSupersampleFactor, fForceRasterBackend);
	}

	void draw(SkCanvas* canvas, SkPaint* paint, SkScalar tx, SkScalar ty, SkScalar angle) override {
	// Subpixel translation+angle are applied in the offscreen buffer
	this->prepareBuffer(canvas, paint, tx, ty, angle);
	this->redraw(canvas);
	}

	// Exposed so that it's easy to fill the offscreen buffer, then draw zooms/filters of it before
	// drawing the original scale back into the canvas.
	void prepareBuffer(SkCanvas* canvas, SkPaint* paint, SkScalar tx, SkScalar ty, SkScalar angle) {
	auto info = SkImageInfo::Make(fSupersampleFactor * kTileWidth,
	fSupersampleFactor * kTileHeight,
	kRGBA_8888_SkColorType, kPremul_SkAlphaType);
	auto surface = fForceRasterBackend ? SkSurface::MakeRaster(info)
	: canvas->makeSurface(info);

	surface->getCanvas()->save();
	// Make fully transparent so it is easy to determine pixels that are touched by partial cov.
	surface->getCanvas()->clear(SK_ColorTRANSPARENT);
	// Set up scaling to fit supersampling amount
	surface->getCanvas()->scale(fSupersampleFactor, fSupersampleFactor);
	fRenderer->draw(surface->getCanvas(), paint, tx, ty, angle);
	surface->getCanvas()->restore();

	// Save image so it can be drawn zoomed in or to visualize touched pixels; only valid until
	// the next call to draw()
	fLastRendered = surface->makeImageSnapshot();
	}

	void redraw(SkCanvas* canvas, SkScalar scale = 1.f, bool debugMode = false) {
	SkASSERT(fLastRendered);
	// Use medium quality filter to get mipmaps when drawing smaller, or use nearest filtering
	// when upscaling
	SkPaint blit;
	blit.setFilterQuality(scale > 1.f ? kNone_SkFilterQuality : kMedium_SkFilterQuality);
	if (debugMode) {
	// Makes anything that's > 1/255 alpha fully opaque and sets color to medium green.
	static constexpr float kFilter[] = {
	0.f, 0.f, 0.f, 0.f, 16.f/255,
	0.f, 0.f, 0.f, 0.f, 200.f/255,
	0.f, 0.f, 0.f, 0.f, 16.f/255,
	0.f, 0.f, 0.f, 255.f, 0.f
	};

	blit.setColorFilter(SkColorFilters::Matrix(kFilter));
	}

	canvas->scale(scale, scale);
	canvas->drawImageRect(fLastRendered, SkRect::MakeWH(kTileWidth, kTileHeight), &blit);
	}

	private:
	bool fForceRasterBackend;
	sk_sp<SkImage> fLastRendered;
	sk_sp<ShapeRenderer> fRenderer;
	int fSupersampleFactor;

	OffscreenShapeRenderer(sk_sp<ShapeRenderer> renderer, int supersample, bool forceRaster)
	: fForceRasterBackend(forceRaster)
	, fLastRendered(nullptr)
	, fRenderer(std::move(renderer))
	, fSupersampleFactor(supersample) { }

	typedef ShapeRenderer INHERITED;
	};

	class ThinAASample : public Sample {
	public:
	ThinAASample() {
	this->setBGColor(0xFFFFFFFF);
	}

	protected:
	void onOnceBeforeDraw() override {
	// Setup all base renderers
	fShapes.push_back(RectRenderer::Make());
	fShapes.push_back(PathRenderer::MakeLine());
	fShapes.push_back(PathRenderer::MakeLines(4.f)); // 2 segments
	fShapes.push_back(PathRenderer::MakeCurve(2.f)); // Shallow curve
	fShapes.push_back(PathRenderer::MakeCurve(8.f)); // Deep curve

	for (int i = 0; i < fShapes.count(); ++i) {
	fNative.push_back(OffscreenShapeRenderer::Make(fShapes[i], 1));
	fRaster.push_back(OffscreenShapeRenderer::Make(fShapes[i], 1, /* raster */ true));
	fSS4.push_back(OffscreenShapeRenderer::Make(fShapes[i], 4)); // 4x4 -> 16 samples
	fSS16.push_back(OffscreenShapeRenderer::Make(fShapes[i], 8)); // 8x8 -> 64 samples

	fHairline.push_back(OffscreenShapeRenderer::Make(fRaster[i]->toHairline(), 1));
	}

	// Start it at something subpixel
	fStrokeWidth = 0.5f;

	fSubpixelX = 0.f;
	fSubpixelY = 0.f;
	fAngle = 0.f;

	fCurrentStage = AnimStage::kMoveLeft;
	fLastFrameTime = -1.f;

	// Don't animate in the beginning
	fAnimTranslate = false;
	fAnimRotate = false;
	}

	void onDrawContent(SkCanvas* canvas) override {
	// Move away from screen edge and add instructions
	SkPaint text;
	SkFont font(nullptr, 12);
	canvas->translate(60.f, 20.f);
	canvas->drawString("Each row features a rendering command under different AA strategies. "
	"Native refers to the current backend of the viewer, e.g. OpenGL.",
	0, 0, font, text);

	canvas->drawString(SkStringPrintf("Stroke width: %.2f ('-' to decrease, '=' to increase)",
	fStrokeWidth), 0, 24, font, text);
	canvas->drawString(SkStringPrintf("Rotation: %.3f ('r' to animate, 'y' sets to 90, 'u' sets"
	" to 0, 'space' adds 15)", fAngle), 0, 36, font, text);
	canvas->drawString(SkStringPrintf("Translation: %.3f, %.3f ('t' to animate)",
	fSubpixelX, fSubpixelY), 0, 48, font, text);

	canvas->translate(0.f, 100.f);

	// Draw with surface matching current viewer surface type
	this->drawShapes(canvas, "Native", 0, fNative);

	// Draw with forced raster backend so it's easy to compare side-by-side
	this->drawShapes(canvas, "Raster", 1, fRaster);

	// Draw paths as hairlines + alpha hack
	this->drawShapes(canvas, "Hairline", 2, fHairline);

	// Draw at 4x supersampling in bottom left
	this->drawShapes(canvas, "SSx16", 3, fSS4);

	// And lastly 16x supersampling in bottom right
	this->drawShapes(canvas, "SSx64", 4, fSS16);
	}

	bool onAnimate(const AnimTimer& timer) override {
	SkScalar t = timer.secs();
	SkScalar dt = fLastFrameTime < 0.f ? 0.f : t - fLastFrameTime;
	fLastFrameTime = t;

	if (!fAnimRotate && !fAnimTranslate) {
	// Keep returning true so that the last frame time is tracked
	fLastFrameTime = -1.f;
	return false;
	}

	switch(fCurrentStage) {
	case AnimStage::kMoveLeft:
	fSubpixelX += 2.f * dt;
	if (fSubpixelX >= 1.f) {
	fSubpixelX = 1.f;
	fCurrentStage = AnimStage::kMoveDown;
	}
	break;
	case AnimStage::kMoveDown:
	fSubpixelY += 2.f * dt;
	if (fSubpixelY >= 1.f) {
	fSubpixelY = 1.f;
	fCurrentStage = AnimStage::kMoveRight;
	}
	break;
	case AnimStage::kMoveRight:
	fSubpixelX -= 2.f * dt;
	if (fSubpixelX <= -1.f) {
	fSubpixelX = -1.f;
	fCurrentStage = AnimStage::kMoveUp;
	}
	break;
	case AnimStage::kMoveUp:
	fSubpixelY -= 2.f * dt;
	if (fSubpixelY <= -1.f) {
	fSubpixelY = -1.f;
	fCurrentStage = fAnimRotate ? AnimStage::kRotate : AnimStage::kMoveLeft;
	}
	break;
	case AnimStage::kRotate: {
	SkScalar newAngle = fAngle + dt * 15.f;
	bool completed = SkScalarMod(newAngle, 15.f) < SkScalarMod(fAngle, 15.f);
	fAngle = SkScalarMod(newAngle, 360.f);
	if (completed) {
	// Make sure we're on a 15 degree boundary
	fAngle = 15.f * SkScalarRoundToScalar(fAngle / 15.f);
	if (fAnimTranslate) {
	fCurrentStage = this->getTranslationStage();
	}
	}
	} break;
	}

	return true;
	}

	bool onQuery(Sample::Event* evt) override {
	if (Sample::TitleQ(*evt)) {
	Sample::TitleR(evt, "Thin-AA");
	return true;
	}

	SkUnichar key;
	if (Sample::CharQ(*evt, &key)) {
	switch(key) {
	case 't':
	// Toggle translation animation.
	fAnimTranslate = !fAnimTranslate;
	if (!fAnimTranslate && fAnimRotate && fCurrentStage != AnimStage::kRotate) {
	// Turned off an active translation so go to rotating
	fCurrentStage = AnimStage::kRotate;
	} else if (fAnimTranslate && !fAnimRotate &&
	fCurrentStage == AnimStage::kRotate) {
	// Turned on translation, rotation had been paused too, so reset the stage
	fCurrentStage = this->getTranslationStage();
	}
	return true;
	case 'r':
	// Toggle rotation animation.
	fAnimRotate = !fAnimRotate;
	if (!fAnimRotate && fAnimTranslate && fCurrentStage == AnimStage::kRotate) {
	// Turned off an active rotation so go back to translation
	fCurrentStage = this->getTranslationStage();
	} else if (fAnimRotate && !fAnimTranslate &&
	fCurrentStage != AnimStage::kRotate) {
	// Turned on rotation, translation had been paused too, so reset to rotate
	fCurrentStage = AnimStage::kRotate;
	}
	return true;
	case 'u': fAngle = 0.f; return true;
	case 'y': fAngle = 90.f; return true;
	case ' ': fAngle = SkScalarMod(fAngle + 15.f, 360.f); return true;
	case '-': fStrokeWidth = SkMaxScalar(0.1f, fStrokeWidth - 0.05f); return true;
	case '=': fStrokeWidth = SkMinScalar(1.f, fStrokeWidth + 0.05f); return true;
	}
	}
	return this->INHERITED::onQuery(evt);
	}

	private:
	// Base renderers that get wrapped on the offscreen renderers so that they can be transformed
	// for visualization, or supersampled.
	SkTArray<sk_sp<ShapeRenderer>> fShapes;

	SkTArray<sk_sp<OffscreenShapeRenderer>> fNative;
	SkTArray<sk_sp<OffscreenShapeRenderer>> fRaster;
	SkTArray<sk_sp<OffscreenShapeRenderer>> fHairline;
	SkTArray<sk_sp<OffscreenShapeRenderer>> fSS4;
	SkTArray<sk_sp<OffscreenShapeRenderer>> fSS16;

	SkScalar fStrokeWidth;

	// Animated properties to stress the AA algorithms
	enum class AnimStage {
	kMoveRight, kMoveDown, kMoveLeft, kMoveUp, kRotate
	} fCurrentStage;
	SkScalar fLastFrameTime;
	bool fAnimRotate;
	bool fAnimTranslate;

	// Current frame's animation state
	SkScalar fSubpixelX;
	SkScalar fSubpixelY;
	SkScalar fAngle;

	AnimStage getTranslationStage() {
	// For paused translations (i.e. fAnimTranslate toggled while translating), the current
	// stage moves to kRotate, but when restarting the translation animation, we want to
	// go back to where we were without losing any progress.
	if (fSubpixelX > -1.f) {
	if (fSubpixelX >= 1.f) {
	// Can only be moving down on right edge, given our transition states
	return AnimStage::kMoveDown;
	} else if (fSubpixelY > 0.f) {
	// Can only be moving right along top edge
	return AnimStage::kMoveRight;
	} else {
	// Must be moving left along bottom edge
	return AnimStage::kMoveLeft;
	}
	} else {
	// Moving up along the left edge, or is at the very top so start moving left
	return fSubpixelY > -1.f ? AnimStage::kMoveUp : AnimStage::kMoveLeft;
	}
	}

	void drawShapes(SkCanvas* canvas, const char* name, int gridX,
	SkTArray<sk_sp<OffscreenShapeRenderer>> shapes) {
	SkAutoCanvasRestore autoRestore(canvas, /* save */ true);

	for (int i = 0; i < shapes.count(); ++i) {
	this->drawShape(canvas, name, gridX, shapes[i].get(), i == 0);
	// drawShape positions the canvas properly for the next iteration
	}
	}

	void drawShape(SkCanvas* canvas, const char* name, int gridX,
	OffscreenShapeRenderer* shape, bool drawNameLabels) {
	static constexpr SkScalar kZoomGridWidth = 8 * ShapeRenderer::kTileWidth + 8.f;
	static constexpr SkRect kTile = SkRect::MakeWH(ShapeRenderer::kTileWidth,
	ShapeRenderer::kTileHeight);
	static constexpr SkRect kZoomTile = SkRect::MakeWH(8 * ShapeRenderer::kTileWidth,
	8 * ShapeRenderer::kTileHeight);

	// Labeling per shape and detailed labeling that isn't per-stroke
	canvas->save();
	SkPaint text;
	SkFont font(nullptr, 12);

	if (gridX == 0) {
	SkString name = shape->name();
	SkScalar centering = name.size() * 4.f; // ad-hoc

	canvas->save();
	canvas->translate(-10.f, 4 * ShapeRenderer::kTileHeight + centering);
	canvas->rotate(-90.f);
	canvas->drawString(shape->name(), 0.f, 0.f, font, text);
	canvas->restore();
	}
	if (drawNameLabels) {
	canvas->drawString(name, gridX * kZoomGridWidth, -10.f, font, text);
	}
	canvas->restore();

	// Paints for outlines and actual shapes
	SkPaint outline;
	outline.setStyle(SkPaint::kStroke_Style);
	SkPaint clear;
	clear.setColor(SK_ColorWHITE);

	SkPaint paint;
	paint.setAntiAlias(true);
	paint.setStrokeWidth(fStrokeWidth);

	// Generate a saved image of the correct stroke width, but don't put it into the canvas
	// yet since we want to draw the "original" size on top of the zoomed in version
	shape->prepareBuffer(canvas, &paint, fSubpixelX, fSubpixelY, fAngle);

	// Draw it at 8X zoom
	SkScalar x = gridX * kZoomGridWidth;

	canvas->save();
	canvas->translate(x, 0.f);
	canvas->drawRect(kZoomTile, outline);
	shape->redraw(canvas, 8.0f);
	canvas->restore();

	// Draw the original
	canvas->save();
	canvas->translate(x + 4.f, 4.f);
	canvas->drawRect(kTile, clear);
	canvas->drawRect(kTile, outline);
	shape->redraw(canvas, 1.f);
	canvas->restore();

	// Now redraw it into the coverage location (just to the right of the original scale)
	canvas->save();
	canvas->translate(x + ShapeRenderer::kTileWidth + 8.f, 4.f);
	canvas->drawRect(kTile, clear);
	canvas->drawRect(kTile, outline);
	shape->redraw(canvas, 1.f, /* debug */ true);
	canvas->restore();

	// Lastly, shift the canvas translation down by 8 * kTH + padding for the next set of shapes
	canvas->translate(0.f, 8.f * ShapeRenderer::kTileHeight + 20.f);
	}

	typedef Sample INHERITED;
	};

	//////////////////////////////////////////////////////////////////////////////

	DEF_SAMPLE( return new ThinAASample; )

	}