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 "src/gpu/text/GrTextContext.h"
9
10 #include "include/core/SkGraphics.h"
11 #include "include/gpu/GrContext.h"
12 #include "include/private/SkTo.h"
13 #include "src/core/SkDistanceFieldGen.h"
14 #include "src/core/SkDraw.h"
15 #include "src/core/SkDrawProcs.h"
16 #include "src/core/SkGlyphRun.h"
17 #include "src/core/SkMakeUnique.h"
18 #include "src/core/SkMaskFilterBase.h"
19 #include "src/core/SkPaintPriv.h"
20 #include "src/gpu/GrCaps.h"
21 #include "src/gpu/GrRecordingContextPriv.h"
22 #include "src/gpu/SkGr.h"
23 #include "src/gpu/ops/GrMeshDrawOp.h"
24 #include "src/gpu/text/GrSDFMaskFilter.h"
25 #include "src/gpu/text/GrTextBlobCache.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
scaled_text_size(const SkScalar textSize,const SkMatrix & viewMatrix)132 SkScalar scaled_text_size(const SkScalar textSize, const SkMatrix& viewMatrix) {
133 SkScalar scaledTextSize = textSize;
134
135 if (viewMatrix.hasPerspective()) {
136 // for perspective, we simply force to the medium size
137 // TODO: compute a size based on approximate screen area
138 scaledTextSize = kMediumDFFontLimit;
139 } else {
140 SkScalar maxScale = viewMatrix.getMaxScale();
141 // if we have non-unity scale, we need to choose our base text size
142 // based on the SkPaint's text size multiplied by the max scale factor
143 // TODO: do we need to do this if we're scaling down (i.e. maxScale < 1)?
144 if (maxScale > 0 && !SkScalarNearlyEqual(maxScale, SK_Scalar1)) {
145 scaledTextSize *= maxScale;
146 }
147 }
148
149 return scaledTextSize;
150 }
151
InitDistanceFieldFont(const SkFont & font,const SkMatrix & viewMatrix,const Options & options,SkScalar * textRatio)152 SkFont GrTextContext::InitDistanceFieldFont(const SkFont& font,
153 const SkMatrix& viewMatrix,
154 const Options& options,
155 SkScalar* textRatio) {
156 SkScalar textSize = font.getSize();
157 SkScalar scaledTextSize = scaled_text_size(textSize, viewMatrix);
158
159 SkFont dfFont{font};
160
161 if (scaledTextSize <= kSmallDFFontLimit) {
162 *textRatio = textSize / kSmallDFFontSize;
163 dfFont.setSize(SkIntToScalar(kSmallDFFontSize));
164 } else if (scaledTextSize <= kMediumDFFontLimit) {
165 *textRatio = textSize / kMediumDFFontSize;
166 dfFont.setSize(SkIntToScalar(kMediumDFFontSize));
167 } else {
168 *textRatio = textSize / kLargeDFFontSize;
169 dfFont.setSize(SkIntToScalar(kLargeDFFontSize));
170 }
171
172 dfFont.setEdging(SkFont::Edging::kAntiAlias);
173 dfFont.setForceAutoHinting(false);
174 dfFont.setHinting(SkFontHinting::kNormal);
175
176 // The sub-pixel position will always happen when transforming to the screen.
177 dfFont.setSubpixel(false);
178 return dfFont;
179 }
180
InitDistanceFieldMinMaxScale(SkScalar textSize,const SkMatrix & viewMatrix,const GrTextContext::Options & options)181 std::pair<SkScalar, SkScalar> GrTextContext::InitDistanceFieldMinMaxScale(
182 SkScalar textSize,
183 const SkMatrix& viewMatrix,
184 const GrTextContext::Options& options) {
185
186 SkScalar scaledTextSize = scaled_text_size(textSize, viewMatrix);
187
188 // We have three sizes of distance field text, and within each size 'bucket' there is a floor
189 // and ceiling. A scale outside of this range would require regenerating the distance fields
190 SkScalar dfMaskScaleFloor;
191 SkScalar dfMaskScaleCeil;
192 if (scaledTextSize <= kSmallDFFontLimit) {
193 dfMaskScaleFloor = options.fMinDistanceFieldFontSize;
194 dfMaskScaleCeil = kSmallDFFontLimit;
195 } else if (scaledTextSize <= kMediumDFFontLimit) {
196 dfMaskScaleFloor = kSmallDFFontLimit;
197 dfMaskScaleCeil = kMediumDFFontLimit;
198 } else {
199 dfMaskScaleFloor = kMediumDFFontLimit;
200 dfMaskScaleCeil = options.fMaxDistanceFieldFontSize;
201 }
202
203 // Because there can be multiple runs in the blob, we want the overall maxMinScale, and
204 // minMaxScale to make regeneration decisions. Specifically, we want the maximum minimum scale
205 // we can tolerate before we'd drop to a lower mip size, and the minimum maximum scale we can
206 // tolerate before we'd have to move to a large mip size. When we actually test these values
207 // we look at the delta in scale between the new viewmatrix and the old viewmatrix, and test
208 // against these values to decide if we can reuse or not(ie, will a given scale change our mip
209 // level)
210 SkASSERT(dfMaskScaleFloor <= scaledTextSize && scaledTextSize <= dfMaskScaleCeil);
211
212 return std::make_pair(dfMaskScaleFloor / scaledTextSize, dfMaskScaleCeil / scaledTextSize);
213 }
214
InitDistanceFieldPaint(const SkPaint & paint)215 SkPaint GrTextContext::InitDistanceFieldPaint(const SkPaint& paint) {
216 SkPaint dfPaint{paint};
217 dfPaint.setMaskFilter(GrSDFMaskFilter::Make());
218 return dfPaint;
219 }
220
221 ///////////////////////////////////////////////////////////////////////////////////////////////////
222
223 #if GR_TEST_UTILS
224
225 #include "src/gpu/GrRenderTargetContext.h"
226
GR_DRAW_OP_TEST_DEFINE(GrAtlasTextOp)227 GR_DRAW_OP_TEST_DEFINE(GrAtlasTextOp) {
228 static uint32_t gContextID = SK_InvalidGenID;
229 static std::unique_ptr<GrTextContext> gTextContext;
230 static SkSurfaceProps gSurfaceProps(SkSurfaceProps::kLegacyFontHost_InitType);
231
232 if (context->priv().contextID() != gContextID) {
233 gContextID = context->priv().contextID();
234 gTextContext = GrTextContext::Make(GrTextContext::Options());
235 }
236
237 // Setup dummy SkPaint / GrPaint / GrRenderTargetContext
238 sk_sp<GrRenderTargetContext> rtc(context->priv().makeDeferredRenderTargetContext(
239 SkBackingFit::kApprox, 1024, 1024, GrColorType::kRGBA_8888, nullptr));
240
241 SkMatrix viewMatrix = GrTest::TestMatrixInvertible(random);
242
243 SkPaint skPaint;
244 skPaint.setColor(random->nextU());
245
246 SkFont font;
247 if (random->nextBool()) {
248 font.setEdging(SkFont::Edging::kSubpixelAntiAlias);
249 } else {
250 font.setEdging(random->nextBool() ? SkFont::Edging::kAntiAlias : SkFont::Edging::kAlias);
251 }
252 font.setSubpixel(random->nextBool());
253
254 const char* text = "The quick brown fox jumps over the lazy dog.";
255
256 // create some random x/y offsets, including negative offsets
257 static const int kMaxTrans = 1024;
258 int xPos = (random->nextU() % 2) * 2 - 1;
259 int yPos = (random->nextU() % 2) * 2 - 1;
260 int xInt = (random->nextU() % kMaxTrans) * xPos;
261 int yInt = (random->nextU() % kMaxTrans) * yPos;
262
263 return gTextContext->createOp_TestingOnly(context, gTextContext.get(), rtc.get(),
264 skPaint, font, viewMatrix, text, xInt, yInt);
265 }
266
267 #endif
268