src/gpu/text/GrTextContext.cpp - skia - Git at Google

 /*
  * 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 "GrTextContext.h"

 #include "GrCaps.h"
 #include "GrContext.h"
 #include "GrRecordingContextPriv.h"
 #include "GrSDFMaskFilter.h"
 #include "GrTextBlobCache.h"
 #include "SkDistanceFieldGen.h"
 #include "SkDraw.h"
 #include "SkDrawProcs.h"
 #include "SkGlyphRun.h"
 #include "SkGr.h"
 #include "SkGraphics.h"
 #include "SkMakeUnique.h"
 #include "SkMaskFilterBase.h"
 #include "SkPaintPriv.h"
 #include "SkTo.h"
 #include "ops/GrMeshDrawOp.h"

 // DF sizes and thresholds for usage of the small and medium sizes. For example, above
 // kSmallDFFontLimit we will use the medium size. The large size is used up until the size at
 // which we switch over to drawing as paths as controlled by Options.
 static const int kSmallDFFontSize = 32;
 static const int kSmallDFFontLimit = 32;
 static const int kMediumDFFontSize = 72;
 static const int kMediumDFFontLimit = 72;
 static const int kLargeDFFontSize = 162;

 static const int kDefaultMinDistanceFieldFontSize = 18;
 #ifdef SK_BUILD_FOR_ANDROID
 static const int kDefaultMaxDistanceFieldFontSize = 384;
 #else
 static const int kDefaultMaxDistanceFieldFontSize = 2 * kLargeDFFontSize;
 #endif

 GrTextContext::GrTextContext(const Options& options)
         : fDistanceAdjustTable(new GrDistanceFieldAdjustTable), fOptions(options) {
     SanitizeOptions(&fOptions);
 }

 std::unique_ptr<GrTextContext> GrTextContext::Make(const Options& options) {
     return std::unique_ptr<GrTextContext>(new GrTextContext(options));
 }

 SkColor GrTextContext::ComputeCanonicalColor(const SkPaint& paint, bool lcd) {
     SkColor canonicalColor = SkPaintPriv::ComputeLuminanceColor(paint);
     if (lcd) {
         // This is the correct computation, but there are tons of cases where LCD can be overridden.
         // For now we just regenerate if any run in a textblob has LCD.
         // TODO figure out where all of these overrides are and see if we can incorporate that logic
         // at a higher level *OR* use sRGB
         SkASSERT(false);
         //canonicalColor = SkMaskGamma::CanonicalColor(canonicalColor);
     } else {
         // A8, though can have mixed BMP text but it shouldn't matter because BMP text won't have
         // gamma corrected masks anyways, nor color
         U8CPU lum = SkComputeLuminance(SkColorGetR(canonicalColor),
                                        SkColorGetG(canonicalColor),
                                        SkColorGetB(canonicalColor));
         // reduce to our finite number of bits
         canonicalColor = SkMaskGamma::CanonicalColor(SkColorSetRGB(lum, lum, lum));
     }
     return canonicalColor;
 }

 SkScalerContextFlags GrTextContext::ComputeScalerContextFlags(
         const GrColorSpaceInfo& colorSpaceInfo) {
     // If we're doing linear blending, then we can disable the gamma hacks.
     // Otherwise, leave them on. In either case, we still want the contrast boost:
     // TODO: Can we be even smarter about mask gamma based on the dest transfer function?
     if (colorSpaceInfo.isLinearlyBlended()) {
         return SkScalerContextFlags::kBoostContrast;
     } else {
         return SkScalerContextFlags::kFakeGammaAndBoostContrast;
     }
 }

 void GrTextContext::SanitizeOptions(Options* options) {
     if (options->fMaxDistanceFieldFontSize < 0.f) {
         options->fMaxDistanceFieldFontSize = kDefaultMaxDistanceFieldFontSize;
     }
     if (options->fMinDistanceFieldFontSize < 0.f) {
         options->fMinDistanceFieldFontSize = kDefaultMinDistanceFieldFontSize;
     }
 }

 bool GrTextContext::CanDrawAsDistanceFields(const SkPaint& paint, const SkFont& font,
                                             const SkMatrix& viewMatrix,
                                             const SkSurfaceProps& props,
                                             bool contextSupportsDistanceFieldText,
                                             const Options& options) {
     if (!viewMatrix.hasPerspective()) {
         SkScalar maxScale = viewMatrix.getMaxScale();
         SkScalar scaledTextSize = maxScale * font.getSize();
         // Hinted text looks far better at small resolutions
         // Scaling up beyond 2x yields undesireable artifacts
         if (scaledTextSize < options.fMinDistanceFieldFontSize ||
             scaledTextSize > options.fMaxDistanceFieldFontSize) {
             return false;
         }

         bool useDFT = props.isUseDeviceIndependentFonts();
 #if SK_FORCE_DISTANCE_FIELD_TEXT
         useDFT = true;
 #endif

         if (!useDFT && scaledTextSize < kLargeDFFontSize) {
             return false;
         }
     }

     // mask filters modify alpha, which doesn't translate well to distance
     if (paint.getMaskFilter() || !contextSupportsDistanceFieldText) {
         return false;
     }

     // TODO: add some stroking support
     if (paint.getStyle() != SkPaint::kFill_Style) {
         return false;
     }

     return true;
 }

 void GrTextContext::InitDistanceFieldPaint(const SkScalar textSize,
                                            const SkMatrix& viewMatrix,
                                            const Options& options,
                                            GrTextBlob* blob,
                                            SkPaint* skPaint,
                                            SkFont* skFont,
                                            SkScalar* textRatio,
                                            SkScalerContextFlags* flags) {
     SkScalar scaledTextSize = textSize;

     if (viewMatrix.hasPerspective()) {
         // for perspective, we simply force to the medium size
         // TODO: compute a size based on approximate screen area
         scaledTextSize = kMediumDFFontLimit;
     } else {
         SkScalar maxScale = viewMatrix.getMaxScale();
         // if we have non-unity scale, we need to choose our base text size
         // based on the SkPaint's text size multiplied by the max scale factor
         // TODO: do we need to do this if we're scaling down (i.e. maxScale < 1)?
         if (maxScale > 0 && !SkScalarNearlyEqual(maxScale, SK_Scalar1)) {
             scaledTextSize *= maxScale;
         }
     }

     // We have three sizes of distance field text, and within each size 'bucket' there is a floor
     // and ceiling.  A scale outside of this range would require regenerating the distance fields
     SkScalar dfMaskScaleFloor;
     SkScalar dfMaskScaleCeil;
     if (scaledTextSize <= kSmallDFFontLimit) {
         dfMaskScaleFloor = options.fMinDistanceFieldFontSize;
         dfMaskScaleCeil = kSmallDFFontLimit;
         *textRatio = textSize / kSmallDFFontSize;
         skFont->setSize(SkIntToScalar(kSmallDFFontSize));
     } else if (scaledTextSize <= kMediumDFFontLimit) {
         dfMaskScaleFloor = kSmallDFFontLimit;
         dfMaskScaleCeil = kMediumDFFontLimit;
         *textRatio = textSize / kMediumDFFontSize;
         skFont->setSize(SkIntToScalar(kMediumDFFontSize));
     } else {
         dfMaskScaleFloor = kMediumDFFontLimit;
         dfMaskScaleCeil = options.fMaxDistanceFieldFontSize;
         *textRatio = textSize / kLargeDFFontSize;
         skFont->setSize(SkIntToScalar(kLargeDFFontSize));
     }

     // Because there can be multiple runs in the blob, we want the overall maxMinScale, and
     // minMaxScale to make regeneration decisions.  Specifically, we want the maximum minimum scale
     // we can tolerate before we'd drop to a lower mip size, and the minimum maximum scale we can
     // tolerate before we'd have to move to a large mip size.  When we actually test these values
     // we look at the delta in scale between the new viewmatrix and the old viewmatrix, and test
     // against these values to decide if we can reuse or not(ie, will a given scale change our mip
     // level)
     SkASSERT(dfMaskScaleFloor <= scaledTextSize && scaledTextSize <= dfMaskScaleCeil);
     if (blob) {
         blob->setMinAndMaxScale(dfMaskScaleFloor / scaledTextSize,
                                 dfMaskScaleCeil / scaledTextSize);
     }

     skFont->setEdging(SkFont::Edging::kAntiAlias);
     skFont->setForceAutoHinting(false);
     skFont->setHinting(kNormal_SkFontHinting);
     skFont->setSubpixel(true);

     skPaint->setMaskFilter(GrSDFMaskFilter::Make());

     // We apply the fake-gamma by altering the distance in the shader, so we ignore the
     // passed-in scaler context flags. (It's only used when we fall-back to bitmap text).
     *flags = SkScalerContextFlags::kNone;
 }

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

 #if GR_TEST_UTILS

 #include "GrRenderTargetContext.h"

 GR_DRAW_OP_TEST_DEFINE(GrAtlasTextOp) {
     static uint32_t gContextID = SK_InvalidGenID;
     static std::unique_ptr<GrTextContext> gTextContext;
     static SkSurfaceProps gSurfaceProps(SkSurfaceProps::kLegacyFontHost_InitType);

     if (context->priv().contextID() != gContextID) {
         gContextID = context->priv().contextID();
         gTextContext = GrTextContext::Make(GrTextContext::Options());
     }

     const GrBackendFormat format =
             context->priv().caps()->getBackendFormatFromColorType(kRGBA_8888_SkColorType);

     // Setup dummy SkPaint / GrPaint / GrRenderTargetContext
     sk_sp<GrRenderTargetContext> rtc(context->priv().makeDeferredRenderTargetContext(
         format, SkBackingFit::kApprox, 1024, 1024, kRGBA_8888_GrPixelConfig, nullptr));

     SkMatrix viewMatrix = GrTest::TestMatrixInvertible(random);

     SkPaint skPaint;
     skPaint.setColor(random->nextU());

     SkFont font;
     if (random->nextBool()) {
         font.setEdging(SkFont::Edging::kSubpixelAntiAlias);
     } else {
         font.setEdging(random->nextBool() ? SkFont::Edging::kAntiAlias : SkFont::Edging::kAlias);
     }
     font.setSubpixel(random->nextBool());

     const char* text = "The quick brown fox jumps over the lazy dog.";

     // create some random x/y offsets, including negative offsets
     static const int kMaxTrans = 1024;
     int xPos = (random->nextU() % 2) * 2 - 1;
     int yPos = (random->nextU() % 2) * 2 - 1;
     int xInt = (random->nextU() % kMaxTrans) * xPos;
     int yInt = (random->nextU() % kMaxTrans) * yPos;

     return gTextContext->createOp_TestingOnly(context, gTextContext.get(), rtc.get(),
                                               skPaint, font, viewMatrix, text, xInt, yInt);
 }

 #endif
	/*
	* 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 "GrTextContext.h"

	#include "GrCaps.h"
	#include "GrContext.h"
	#include "GrRecordingContextPriv.h"
	#include "GrSDFMaskFilter.h"
	#include "GrTextBlobCache.h"
	#include "SkDistanceFieldGen.h"
	#include "SkDraw.h"
	#include "SkDrawProcs.h"
	#include "SkGlyphRun.h"
	#include "SkGr.h"
	#include "SkGraphics.h"
	#include "SkMakeUnique.h"
	#include "SkMaskFilterBase.h"
	#include "SkPaintPriv.h"
	#include "SkTo.h"
	#include "ops/GrMeshDrawOp.h"

	// DF sizes and thresholds for usage of the small and medium sizes. For example, above
	// kSmallDFFontLimit we will use the medium size. The large size is used up until the size at
	// which we switch over to drawing as paths as controlled by Options.
	static const int kSmallDFFontSize = 32;
	static const int kSmallDFFontLimit = 32;
	static const int kMediumDFFontSize = 72;
	static const int kMediumDFFontLimit = 72;
	static const int kLargeDFFontSize = 162;

	static const int kDefaultMinDistanceFieldFontSize = 18;
	#ifdef SK_BUILD_FOR_ANDROID
	static const int kDefaultMaxDistanceFieldFontSize = 384;
	#else
	static const int kDefaultMaxDistanceFieldFontSize = 2 * kLargeDFFontSize;
	#endif

	GrTextContext::GrTextContext(const Options& options)
	: fDistanceAdjustTable(new GrDistanceFieldAdjustTable), fOptions(options) {
	SanitizeOptions(&fOptions);
	}

	std::unique_ptr<GrTextContext> GrTextContext::Make(const Options& options) {
	return std::unique_ptr<GrTextContext>(new GrTextContext(options));
	}

	SkColor GrTextContext::ComputeCanonicalColor(const SkPaint& paint, bool lcd) {
	SkColor canonicalColor = SkPaintPriv::ComputeLuminanceColor(paint);
	if (lcd) {
	// This is the correct computation, but there are tons of cases where LCD can be overridden.
	// For now we just regenerate if any run in a textblob has LCD.
	// TODO figure out where all of these overrides are and see if we can incorporate that logic
	// at a higher level OR use sRGB
	SkASSERT(false);
	//canonicalColor = SkMaskGamma::CanonicalColor(canonicalColor);
	} else {
	// A8, though can have mixed BMP text but it shouldn't matter because BMP text won't have
	// gamma corrected masks anyways, nor color
	U8CPU lum = SkComputeLuminance(SkColorGetR(canonicalColor),
	SkColorGetG(canonicalColor),
	SkColorGetB(canonicalColor));
	// reduce to our finite number of bits
	canonicalColor = SkMaskGamma::CanonicalColor(SkColorSetRGB(lum, lum, lum));
	}
	return canonicalColor;
	}

	SkScalerContextFlags GrTextContext::ComputeScalerContextFlags(
	const GrColorSpaceInfo& colorSpaceInfo) {
	// If we're doing linear blending, then we can disable the gamma hacks.
	// Otherwise, leave them on. In either case, we still want the contrast boost:
	// TODO: Can we be even smarter about mask gamma based on the dest transfer function?
	if (colorSpaceInfo.isLinearlyBlended()) {
	return SkScalerContextFlags::kBoostContrast;
	} else {
	return SkScalerContextFlags::kFakeGammaAndBoostContrast;
	}
	}

	void GrTextContext::SanitizeOptions(Options* options) {
	if (options->fMaxDistanceFieldFontSize < 0.f) {
	options->fMaxDistanceFieldFontSize = kDefaultMaxDistanceFieldFontSize;
	}
	if (options->fMinDistanceFieldFontSize < 0.f) {
	options->fMinDistanceFieldFontSize = kDefaultMinDistanceFieldFontSize;
	}
	}

	bool GrTextContext::CanDrawAsDistanceFields(const SkPaint& paint, const SkFont& font,
	const SkMatrix& viewMatrix,
	const SkSurfaceProps& props,
	bool contextSupportsDistanceFieldText,
	const Options& options) {
	if (!viewMatrix.hasPerspective()) {
	SkScalar maxScale = viewMatrix.getMaxScale();
	SkScalar scaledTextSize = maxScale * font.getSize();
	// Hinted text looks far better at small resolutions
	// Scaling up beyond 2x yields undesireable artifacts
	if (scaledTextSize < options.fMinDistanceFieldFontSize \|\|
	scaledTextSize > options.fMaxDistanceFieldFontSize) {
	return false;
	}

	bool useDFT = props.isUseDeviceIndependentFonts();
	#if SK_FORCE_DISTANCE_FIELD_TEXT
	useDFT = true;
	#endif

	if (!useDFT && scaledTextSize < kLargeDFFontSize) {
	return false;
	}
	}

	// mask filters modify alpha, which doesn't translate well to distance
	if (paint.getMaskFilter() \|\| !contextSupportsDistanceFieldText) {
	return false;
	}

	// TODO: add some stroking support
	if (paint.getStyle() != SkPaint::kFill_Style) {
	return false;
	}

	return true;
	}

	void GrTextContext::InitDistanceFieldPaint(const SkScalar textSize,
	const SkMatrix& viewMatrix,
	const Options& options,
	GrTextBlob* blob,
	SkPaint* skPaint,
	SkFont* skFont,
	SkScalar* textRatio,
	SkScalerContextFlags* flags) {
	SkScalar scaledTextSize = textSize;

	if (viewMatrix.hasPerspective()) {
	// for perspective, we simply force to the medium size
	// TODO: compute a size based on approximate screen area
	scaledTextSize = kMediumDFFontLimit;
	} else {
	SkScalar maxScale = viewMatrix.getMaxScale();
	// if we have non-unity scale, we need to choose our base text size
	// based on the SkPaint's text size multiplied by the max scale factor
	// TODO: do we need to do this if we're scaling down (i.e. maxScale < 1)?
	if (maxScale > 0 && !SkScalarNearlyEqual(maxScale, SK_Scalar1)) {
	scaledTextSize *= maxScale;
	}
	}

	// We have three sizes of distance field text, and within each size 'bucket' there is a floor
	// and ceiling. A scale outside of this range would require regenerating the distance fields
	SkScalar dfMaskScaleFloor;
	SkScalar dfMaskScaleCeil;
	if (scaledTextSize <= kSmallDFFontLimit) {
	dfMaskScaleFloor = options.fMinDistanceFieldFontSize;
	dfMaskScaleCeil = kSmallDFFontLimit;
	*textRatio = textSize / kSmallDFFontSize;
	skFont->setSize(SkIntToScalar(kSmallDFFontSize));
	} else if (scaledTextSize <= kMediumDFFontLimit) {
	dfMaskScaleFloor = kSmallDFFontLimit;
	dfMaskScaleCeil = kMediumDFFontLimit;
	*textRatio = textSize / kMediumDFFontSize;
	skFont->setSize(SkIntToScalar(kMediumDFFontSize));
	} else {
	dfMaskScaleFloor = kMediumDFFontLimit;
	dfMaskScaleCeil = options.fMaxDistanceFieldFontSize;
	*textRatio = textSize / kLargeDFFontSize;
	skFont->setSize(SkIntToScalar(kLargeDFFontSize));
	}

	// Because there can be multiple runs in the blob, we want the overall maxMinScale, and
	// minMaxScale to make regeneration decisions. Specifically, we want the maximum minimum scale
	// we can tolerate before we'd drop to a lower mip size, and the minimum maximum scale we can
	// tolerate before we'd have to move to a large mip size. When we actually test these values
	// we look at the delta in scale between the new viewmatrix and the old viewmatrix, and test
	// against these values to decide if we can reuse or not(ie, will a given scale change our mip
	// level)
	SkASSERT(dfMaskScaleFloor <= scaledTextSize && scaledTextSize <= dfMaskScaleCeil);
	if (blob) {
	blob->setMinAndMaxScale(dfMaskScaleFloor / scaledTextSize,
	dfMaskScaleCeil / scaledTextSize);
	}

	skFont->setEdging(SkFont::Edging::kAntiAlias);
	skFont->setForceAutoHinting(false);
	skFont->setHinting(kNormal_SkFontHinting);
	skFont->setSubpixel(true);

	skPaint->setMaskFilter(GrSDFMaskFilter::Make());

	// We apply the fake-gamma by altering the distance in the shader, so we ignore the
	// passed-in scaler context flags. (It's only used when we fall-back to bitmap text).
	*flags = SkScalerContextFlags::kNone;
	}

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

	#if GR_TEST_UTILS

	#include "GrRenderTargetContext.h"

	GR_DRAW_OP_TEST_DEFINE(GrAtlasTextOp) {
	static uint32_t gContextID = SK_InvalidGenID;
	static std::unique_ptr<GrTextContext> gTextContext;
	static SkSurfaceProps gSurfaceProps(SkSurfaceProps::kLegacyFontHost_InitType);

	if (context->priv().contextID() != gContextID) {
	gContextID = context->priv().contextID();
	gTextContext = GrTextContext::Make(GrTextContext::Options());
	}

	const GrBackendFormat format =
	context->priv().caps()->getBackendFormatFromColorType(kRGBA_8888_SkColorType);

	// Setup dummy SkPaint / GrPaint / GrRenderTargetContext
	sk_sp<GrRenderTargetContext> rtc(context->priv().makeDeferredRenderTargetContext(
	format, SkBackingFit::kApprox, 1024, 1024, kRGBA_8888_GrPixelConfig, nullptr));

	SkMatrix viewMatrix = GrTest::TestMatrixInvertible(random);

	SkPaint skPaint;
	skPaint.setColor(random->nextU());

	SkFont font;
	if (random->nextBool()) {
	font.setEdging(SkFont::Edging::kSubpixelAntiAlias);
	} else {
	font.setEdging(random->nextBool() ? SkFont::Edging::kAntiAlias : SkFont::Edging::kAlias);
	}
	font.setSubpixel(random->nextBool());

	const char* text = "The quick brown fox jumps over the lazy dog.";

	// create some random x/y offsets, including negative offsets
	static const int kMaxTrans = 1024;
	int xPos = (random->nextU() % 2) * 2 - 1;
	int yPos = (random->nextU() % 2) * 2 - 1;
	int xInt = (random->nextU() % kMaxTrans) * xPos;
	int yInt = (random->nextU() % kMaxTrans) * yPos;

	return gTextContext->createOp_TestingOnly(context, gTextContext.get(), rtc.get(),
	skPaint, font, viewMatrix, text, xInt, yInt);
	}

	#endif