1 /*
2 * Copyright 2015 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8 #include "GrTextContext.h"
9
10 #include "GrCaps.h"
11 #include "GrContext.h"
12 #include "GrRecordingContextPriv.h"
13 #include "GrSDFMaskFilter.h"
14 #include "GrTextBlobCache.h"
15 #include "SkDistanceFieldGen.h"
16 #include "SkDraw.h"
17 #include "SkDrawProcs.h"
18 #include "SkGlyphRun.h"
19 #include "SkGr.h"
20 #include "SkGraphics.h"
21 #include "SkMakeUnique.h"
22 #include "SkMaskFilterBase.h"
23 #include "SkPaintPriv.h"
24 #include "SkTo.h"
25 #include "ops/GrMeshDrawOp.h"
26
27 // DF sizes and thresholds for usage of the small and medium sizes. For example, above
28 // kSmallDFFontLimit we will use the medium size. The large size is used up until the size at
29 // which we switch over to drawing as paths as controlled by Options.
30 static const int kSmallDFFontSize = 32;
31 static const int kSmallDFFontLimit = 32;
32 static const int kMediumDFFontSize = 72;
33 static const int kMediumDFFontLimit = 72;
34 static const int kLargeDFFontSize = 162;
35
36 static const int kDefaultMinDistanceFieldFontSize = 18;
37 #ifdef SK_BUILD_FOR_ANDROID
38 static const int kDefaultMaxDistanceFieldFontSize = 384;
39 #else
40 static const int kDefaultMaxDistanceFieldFontSize = 2 * kLargeDFFontSize;
41 #endif
42
GrTextContext(const Options & options)43 GrTextContext::GrTextContext(const Options& options)
44 : fDistanceAdjustTable(new GrDistanceFieldAdjustTable), fOptions(options) {
45 SanitizeOptions(&fOptions);
46 }
47
Make(const Options & options)48 std::unique_ptr<GrTextContext> GrTextContext::Make(const Options& options) {
49 return std::unique_ptr<GrTextContext>(new GrTextContext(options));
50 }
51
ComputeCanonicalColor(const SkPaint & paint,bool lcd)52 SkColor GrTextContext::ComputeCanonicalColor(const SkPaint& paint, bool lcd) {
53 SkColor canonicalColor = SkPaintPriv::ComputeLuminanceColor(paint);
54 if (lcd) {
55 // This is the correct computation, but there are tons of cases where LCD can be overridden.
56 // For now we just regenerate if any run in a textblob has LCD.
57 // TODO figure out where all of these overrides are and see if we can incorporate that logic
58 // at a higher level *OR* use sRGB
59 SkASSERT(false);
60 //canonicalColor = SkMaskGamma::CanonicalColor(canonicalColor);
61 } else {
62 // A8, though can have mixed BMP text but it shouldn't matter because BMP text won't have
63 // gamma corrected masks anyways, nor color
64 U8CPU lum = SkComputeLuminance(SkColorGetR(canonicalColor),
65 SkColorGetG(canonicalColor),
66 SkColorGetB(canonicalColor));
67 // reduce to our finite number of bits
68 canonicalColor = SkMaskGamma::CanonicalColor(SkColorSetRGB(lum, lum, lum));
69 }
70 return canonicalColor;
71 }
72
ComputeScalerContextFlags(const GrColorSpaceInfo & colorSpaceInfo)73 SkScalerContextFlags GrTextContext::ComputeScalerContextFlags(
74 const GrColorSpaceInfo& colorSpaceInfo) {
75 // If we're doing linear blending, then we can disable the gamma hacks.
76 // Otherwise, leave them on. In either case, we still want the contrast boost:
77 // TODO: Can we be even smarter about mask gamma based on the dest transfer function?
78 if (colorSpaceInfo.isLinearlyBlended()) {
79 return SkScalerContextFlags::kBoostContrast;
80 } else {
81 return SkScalerContextFlags::kFakeGammaAndBoostContrast;
82 }
83 }
84
SanitizeOptions(Options * options)85 void GrTextContext::SanitizeOptions(Options* options) {
86 if (options->fMaxDistanceFieldFontSize < 0.f) {
87 options->fMaxDistanceFieldFontSize = kDefaultMaxDistanceFieldFontSize;
88 }
89 if (options->fMinDistanceFieldFontSize < 0.f) {
90 options->fMinDistanceFieldFontSize = kDefaultMinDistanceFieldFontSize;
91 }
92 }
93
CanDrawAsDistanceFields(const SkPaint & paint,const SkFont & font,const SkMatrix & viewMatrix,const SkSurfaceProps & props,bool contextSupportsDistanceFieldText,const Options & options)94 bool GrTextContext::CanDrawAsDistanceFields(const SkPaint& paint, const SkFont& font,
95 const SkMatrix& viewMatrix,
96 const SkSurfaceProps& props,
97 bool contextSupportsDistanceFieldText,
98 const Options& options) {
99 if (!viewMatrix.hasPerspective()) {
100 SkScalar maxScale = viewMatrix.getMaxScale();
101 SkScalar scaledTextSize = maxScale * font.getSize();
102 // Hinted text looks far better at small resolutions
103 // Scaling up beyond 2x yields undesireable artifacts
104 if (scaledTextSize < options.fMinDistanceFieldFontSize ||
105 scaledTextSize > options.fMaxDistanceFieldFontSize) {
106 return false;
107 }
108
109 bool useDFT = props.isUseDeviceIndependentFonts();
110 #if SK_FORCE_DISTANCE_FIELD_TEXT
111 useDFT = true;
112 #endif
113
114 if (!useDFT && scaledTextSize < kLargeDFFontSize) {
115 return false;
116 }
117 }
118
119 // mask filters modify alpha, which doesn't translate well to distance
120 if (paint.getMaskFilter() || !contextSupportsDistanceFieldText) {
121 return false;
122 }
123
124 // TODO: add some stroking support
125 if (paint.getStyle() != SkPaint::kFill_Style) {
126 return false;
127 }
128
129 return true;
130 }
131
InitDistanceFieldPaint(const SkScalar textSize,const SkMatrix & viewMatrix,const Options & options,GrTextBlob * blob,SkPaint * skPaint,SkFont * skFont,SkScalar * textRatio,SkScalerContextFlags * flags)132 void GrTextContext::InitDistanceFieldPaint(const SkScalar textSize,
133 const SkMatrix& viewMatrix,
134 const Options& options,
135 GrTextBlob* blob,
136 SkPaint* skPaint,
137 SkFont* skFont,
138 SkScalar* textRatio,
139 SkScalerContextFlags* flags) {
140 SkScalar scaledTextSize = textSize;
141
142 if (viewMatrix.hasPerspective()) {
143 // for perspective, we simply force to the medium size
144 // TODO: compute a size based on approximate screen area
145 scaledTextSize = kMediumDFFontLimit;
146 } else {
147 SkScalar maxScale = viewMatrix.getMaxScale();
148 // if we have non-unity scale, we need to choose our base text size
149 // based on the SkPaint's text size multiplied by the max scale factor
150 // TODO: do we need to do this if we're scaling down (i.e. maxScale < 1)?
151 if (maxScale > 0 && !SkScalarNearlyEqual(maxScale, SK_Scalar1)) {
152 scaledTextSize *= maxScale;
153 }
154 }
155
156 // We have three sizes of distance field text, and within each size 'bucket' there is a floor
157 // and ceiling. A scale outside of this range would require regenerating the distance fields
158 SkScalar dfMaskScaleFloor;
159 SkScalar dfMaskScaleCeil;
160 if (scaledTextSize <= kSmallDFFontLimit) {
161 dfMaskScaleFloor = options.fMinDistanceFieldFontSize;
162 dfMaskScaleCeil = kSmallDFFontLimit;
163 *textRatio = textSize / kSmallDFFontSize;
164 skFont->setSize(SkIntToScalar(kSmallDFFontSize));
165 } else if (scaledTextSize <= kMediumDFFontLimit) {
166 dfMaskScaleFloor = kSmallDFFontLimit;
167 dfMaskScaleCeil = kMediumDFFontLimit;
168 *textRatio = textSize / kMediumDFFontSize;
169 skFont->setSize(SkIntToScalar(kMediumDFFontSize));
170 } else {
171 dfMaskScaleFloor = kMediumDFFontLimit;
172 dfMaskScaleCeil = options.fMaxDistanceFieldFontSize;
173 *textRatio = textSize / kLargeDFFontSize;
174 skFont->setSize(SkIntToScalar(kLargeDFFontSize));
175 }
176
177 // Because there can be multiple runs in the blob, we want the overall maxMinScale, and
178 // minMaxScale to make regeneration decisions. Specifically, we want the maximum minimum scale
179 // we can tolerate before we'd drop to a lower mip size, and the minimum maximum scale we can
180 // tolerate before we'd have to move to a large mip size. When we actually test these values
181 // we look at the delta in scale between the new viewmatrix and the old viewmatrix, and test
182 // against these values to decide if we can reuse or not(ie, will a given scale change our mip
183 // level)
184 SkASSERT(dfMaskScaleFloor <= scaledTextSize && scaledTextSize <= dfMaskScaleCeil);
185 if (blob) {
186 blob->setMinAndMaxScale(dfMaskScaleFloor / scaledTextSize,
187 dfMaskScaleCeil / scaledTextSize);
188 }
189
190 skFont->setEdging(SkFont::Edging::kAntiAlias);
191 skFont->setForceAutoHinting(false);
192 skFont->setHinting(kNormal_SkFontHinting);
193 skFont->setSubpixel(true);
194
195 skPaint->setMaskFilter(GrSDFMaskFilter::Make());
196
197 // We apply the fake-gamma by altering the distance in the shader, so we ignore the
198 // passed-in scaler context flags. (It's only used when we fall-back to bitmap text).
199 *flags = SkScalerContextFlags::kNone;
200 }
201
202 ///////////////////////////////////////////////////////////////////////////////////////////////////
203
204 #if GR_TEST_UTILS
205
206 #include "GrRenderTargetContext.h"
207
GR_DRAW_OP_TEST_DEFINE(GrAtlasTextOp)208 GR_DRAW_OP_TEST_DEFINE(GrAtlasTextOp) {
209 static uint32_t gContextID = SK_InvalidGenID;
210 static std::unique_ptr<GrTextContext> gTextContext;
211 static SkSurfaceProps gSurfaceProps(SkSurfaceProps::kLegacyFontHost_InitType);
212
213 if (context->priv().contextID() != gContextID) {
214 gContextID = context->priv().contextID();
215 gTextContext = GrTextContext::Make(GrTextContext::Options());
216 }
217
218 const GrBackendFormat format =
219 context->contextPriv().caps()->getBackendFormatFromColorType(kRGBA_8888_SkColorType);
220
221 // Setup dummy SkPaint / GrPaint / GrRenderTargetContext
222 sk_sp<GrRenderTargetContext> rtc(context->contextPriv().makeDeferredRenderTargetContext(
223 format, SkBackingFit::kApprox, 1024, 1024, kRGBA_8888_GrPixelConfig, nullptr));
224
225 SkMatrix viewMatrix = GrTest::TestMatrixInvertible(random);
226
227 SkPaint skPaint;
228 skPaint.setColor(random->nextU());
229
230 SkFont font;
231 if (random->nextBool()) {
232 font.setEdging(SkFont::Edging::kSubpixelAntiAlias);
233 } else {
234 font.setEdging(random->nextBool() ? SkFont::Edging::kAntiAlias : SkFont::Edging::kAlias);
235 }
236 font.setSubpixel(random->nextBool());
237
238 const char* text = "The quick brown fox jumps over the lazy dog.";
239
240 // create some random x/y offsets, including negative offsets
241 static const int kMaxTrans = 1024;
242 int xPos = (random->nextU() % 2) * 2 - 1;
243 int yPos = (random->nextU() % 2) * 2 - 1;
244 int xInt = (random->nextU() % kMaxTrans) * xPos;
245 int yInt = (random->nextU() % kMaxTrans) * yPos;
246
247 return gTextContext->createOp_TestingOnly(context, gTextContext.get(), rtc.get(),
248 skPaint, font, viewMatrix, text, xInt, yInt);
249 }
250
251 #endif
252