Move distance field text positioning into GrTextUtils

src/gpu/text/GrTextUtils.cpp

Index: src/gpu/text/GrTextUtils.cpp
diff --git a/src/gpu/text/GrTextUtils.cpp b/src/gpu/text/GrTextUtils.cpp
index 969be421c332f9fab147055aee8fb2f8765361dd..2f2c1f116a973a705da558f2c52f1944b926c344 100644
--- a/src/gpu/text/GrTextUtils.cpp
+++ b/src/gpu/text/GrTextUtils.cpp
@@ -10,9 +10,12 @@
 #include "GrAtlasTextBlob.h"
 #include "GrBatchFontCache.h"
 #include "GrBlurUtils.h"
+#include "GrCaps.h"
 #include "GrContext.h"
 #include "GrDrawContext.h"
 #include "GrTextContext.h"
+
+#include "SkDistanceFieldGen.h"
 #include "SkDrawProcs.h"
 #include "SkFindAndPlaceGlyph.h"
 #include "SkGlyphCache.h"
@@ -21,6 +24,20 @@
 #include "SkTextMapStateProc.h"
 #include "SkTextToPathIter.h"
 
+namespace {
+static const int kMinDFFontSize = 18;
+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;
+#ifdef SK_BUILD_FOR_ANDROID
+static const int kLargeDFFontLimit = 384;
+#else
+static const int kLargeDFFontLimit = 2 * kLargeDFFontSize;
+#endif
+};
+
 void GrTextUtils::DrawBmpText(GrAtlasTextBlob* blob, int runIndex,
                               GrBatchFontCache* fontCache,
                               const SkSurfaceProps& props, const SkPaint& skPaint,
@@ -135,6 +152,316 @@ void GrTextUtils::BmpAppendGlyph(GrAtlasTextBlob* blob, int runIndex,
                       SkIntToScalar(vx), SkIntToScalar(vy), 1.0f, false);
 }
 
+bool GrTextUtils::CanDrawAsDistanceFields(const SkPaint& skPaint, const SkMatrix& viewMatrix,
+                                          const SkSurfaceProps& props, const GrShaderCaps& caps) {
+    // TODO: support perspective (need getMaxScale replacement)
+    if (viewMatrix.hasPerspective()) {
+        return false;
+    }
+
+    SkScalar maxScale = viewMatrix.getMaxScale();
+    SkScalar scaledTextSize = maxScale*skPaint.getTextSize();
+    // Hinted text looks far better at small resolutions
+    // Scaling up beyond 2x yields undesireable artifacts
+    if (scaledTextSize < kMinDFFontSize ||
+        scaledTextSize > kLargeDFFontLimit) {
+        return false;
+    }
+
+    bool useDFT = props.isUseDeviceIndependentFonts();
+#if SK_FORCE_DISTANCE_FIELD_TEXT
+    useDFT = true;
+#endif
+
+    if (!useDFT && scaledTextSize < kLargeDFFontSize) {
+        return false;
+    }
+
+    // rasterizers and mask filters modify alpha, which doesn't
+    // translate well to distance
+    if (skPaint.getRasterizer() || skPaint.getMaskFilter() || !caps.shaderDerivativeSupport()) {
+        return false;
+    }
+
+    // TODO: add some stroking support
+    if (skPaint.getStyle() != SkPaint::kFill_Style) {
+        return false;
+    }
+
+    return true;
+}
+
+void GrTextUtils::InitDistanceFieldPaint(GrAtlasTextBlob* blob,
+                                         SkPaint* skPaint,
+                                         SkScalar* textRatio,
+                                         const SkMatrix& viewMatrix) {
+    // getMaxScale doesn't support perspective, so neither do we at the moment
+    SkASSERT(!viewMatrix.hasPerspective());
+    SkScalar maxScale = viewMatrix.getMaxScale();
+    SkScalar textSize = skPaint->getTextSize();
+    SkScalar scaledTextSize = textSize;
+    // 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 = kMinDFFontSize;
+        dfMaskScaleCeil = kSmallDFFontLimit;
+        *textRatio = textSize / kSmallDFFontSize;
+        skPaint->setTextSize(SkIntToScalar(kSmallDFFontSize));
+    } else if (scaledTextSize <= kMediumDFFontLimit) {
+        dfMaskScaleFloor = kSmallDFFontLimit;
+        dfMaskScaleCeil = kMediumDFFontLimit;
+        *textRatio = textSize / kMediumDFFontSize;
+        skPaint->setTextSize(SkIntToScalar(kMediumDFFontSize));
+    } else {
+        dfMaskScaleFloor = kMediumDFFontLimit;
+        dfMaskScaleCeil = kLargeDFFontLimit;
+        *textRatio = textSize / kLargeDFFontSize;
+        skPaint->setTextSize(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);
+    blob->fMaxMinScale = SkMaxScalar(dfMaskScaleFloor / scaledTextSize, blob->fMaxMinScale);
+    blob->fMinMaxScale = SkMinScalar(dfMaskScaleCeil / scaledTextSize, blob->fMinMaxScale);
+
+    skPaint->setLCDRenderText(false);
+    skPaint->setAutohinted(false);
+    skPaint->setHinting(SkPaint::kNormal_Hinting);
+    skPaint->setSubpixelText(true);
+}
+
+void GrTextUtils::DrawDFText(GrAtlasTextBlob* blob, int runIndex,
+                             GrBatchFontCache* fontCache, const SkSurfaceProps& props,
+                             const SkPaint& skPaint, GrColor color,
+                             const SkMatrix& viewMatrix,
+                             const char text[], size_t byteLength,
+                             SkScalar x, SkScalar y) {
+    SkASSERT(byteLength == 0 || text != nullptr);
+
+    // nothing to draw
+    if (text == nullptr || byteLength == 0) {
+        return;
+    }
+
+    SkDrawCacheProc glyphCacheProc = skPaint.getDrawCacheProc();
+    SkAutoDescriptor desc;
+    skPaint.getScalerContextDescriptor(&desc, props, nullptr, true);
+    SkGlyphCache* origPaintCache = SkGlyphCache::DetachCache(skPaint.getTypeface(),
+                                                             desc.getDesc());
+
+    SkTArray<SkScalar> positions;
+
+    const char* textPtr = text;
+    SkFixed stopX = 0;
+    SkFixed stopY = 0;
+    SkFixed origin = 0;
+    switch (skPaint.getTextAlign()) {
+        case SkPaint::kRight_Align: origin = SK_Fixed1; break;
+        case SkPaint::kCenter_Align: origin = SK_FixedHalf; break;
+        case SkPaint::kLeft_Align: origin = 0; break;
+    }
+
+    SkAutoKern autokern;
+    const char* stop = text + byteLength;
+    while (textPtr < stop) {
+        // don't need x, y here, since all subpixel variants will have the
+        // same advance
+        const SkGlyph& glyph = glyphCacheProc(origPaintCache, &textPtr, 0, 0);
+
+        SkFixed width = glyph.fAdvanceX + autokern.adjust(glyph);
+        positions.push_back(SkFixedToScalar(stopX + SkFixedMul(origin, width)));
+
+        SkFixed height = glyph.fAdvanceY;
+        positions.push_back(SkFixedToScalar(stopY + SkFixedMul(origin, height)));
+
+        stopX += width;
+        stopY += height;
+    }
+    SkASSERT(textPtr == stop);
+
+    SkGlyphCache::AttachCache(origPaintCache);
+
+    // now adjust starting point depending on alignment
+    SkScalar alignX = SkFixedToScalar(stopX);
+    SkScalar alignY = SkFixedToScalar(stopY);
+    if (skPaint.getTextAlign() == SkPaint::kCenter_Align) {
+        alignX = SkScalarHalf(alignX);
+        alignY = SkScalarHalf(alignY);
+    } else if (skPaint.getTextAlign() == SkPaint::kLeft_Align) {
+        alignX = 0;
+        alignY = 0;
+    }
+    x -= alignX;
+    y -= alignY;
+    SkPoint offset = SkPoint::Make(x, y);
+
+    DrawDFPosText(blob, runIndex, fontCache, props, skPaint, color, viewMatrix, text, byteLength,
+                  positions.begin(), 2, offset);
+}
+
+void GrTextUtils::DrawDFPosText(GrAtlasTextBlob* blob, int runIndex,
+                                GrBatchFontCache* fontCache, const SkSurfaceProps& props,
+                                const SkPaint& origPaint,
+                                GrColor color, const SkMatrix& viewMatrix,
+                                const char text[], size_t byteLength,
+                                const SkScalar pos[], int scalarsPerPosition,
+                                const SkPoint& offset) {
+    SkASSERT(byteLength == 0 || text != nullptr);
+    SkASSERT(1 == scalarsPerPosition || 2 == scalarsPerPosition);
+
+    // nothing to draw
+    if (text == nullptr || byteLength == 0) {
+        return;
+    }
+
+    SkTDArray<char> fallbackTxt;
+    SkTDArray<SkScalar> fallbackPos;
+
+    // Setup distance field paint and text ratio
+    SkScalar textRatio;
+    SkPaint dfPaint(origPaint);
+    GrTextUtils::InitDistanceFieldPaint(blob, &dfPaint, &textRatio, viewMatrix);
+    blob->setHasDistanceField();
+    blob->setSubRunHasDistanceFields(runIndex, origPaint.isLCDRenderText());
+
+    GrBatchTextStrike* currStrike = nullptr;
+
+    SkGlyphCache* cache = blob->setupCache(runIndex, props, dfPaint, nullptr, true);
+    SkDrawCacheProc glyphCacheProc = dfPaint.getDrawCacheProc();
+    GrFontScaler* fontScaler = GrTextContext::GetGrFontScaler(cache);
+
+    const char* stop = text + byteLength;
+
+    if (SkPaint::kLeft_Align == dfPaint.getTextAlign()) {
+        while (text < stop) {
+            const char* lastText = text;
+            // the last 2 parameters are ignored
+            const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
+
+            if (glyph.fWidth) {
+                SkScalar x = offset.x() + pos[0];
+                SkScalar y = offset.y() + (2 == scalarsPerPosition ? pos[1] : 0);
+
+                if (!DfAppendGlyph(blob,
+                                   runIndex,
+                                   fontCache,
+                                   &currStrike,
+                                   glyph,
+                                   x, y, color, fontScaler,
+                                   textRatio, viewMatrix)) {
+                    // couldn't append, send to fallback
+                    fallbackTxt.append(SkToInt(text-lastText), lastText);
+                    *fallbackPos.append() = pos[0];
+                    if (2 == scalarsPerPosition) {
+                        *fallbackPos.append() = pos[1];
+                    }
+                }
+            }
+            pos += scalarsPerPosition;
+        }
+    } else {
+        SkScalar alignMul = SkPaint::kCenter_Align == dfPaint.getTextAlign() ? SK_ScalarHalf
+                                                                             : SK_Scalar1;
+        while (text < stop) {
+            const char* lastText = text;
+            // the last 2 parameters are ignored
+            const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
+
+            if (glyph.fWidth) {
+                SkScalar x = offset.x() + pos[0];
+                SkScalar y = offset.y() + (2 == scalarsPerPosition ? pos[1] : 0);
+
+                SkScalar advanceX = SkFixedToScalar(glyph.fAdvanceX) * alignMul * textRatio;
+                SkScalar advanceY = SkFixedToScalar(glyph.fAdvanceY) * alignMul * textRatio;
+
+                if (!DfAppendGlyph(blob,
+                                   runIndex,
+                                   fontCache,
+                                   &currStrike,
+                                   glyph,
+                                   x - advanceX, y - advanceY, color,
+                                   fontScaler,
+                                   textRatio,
+                                   viewMatrix)) {
+                    // couldn't append, send to fallback
+                    fallbackTxt.append(SkToInt(text-lastText), lastText);
+                    *fallbackPos.append() = pos[0];
+                    if (2 == scalarsPerPosition) {
+                        *fallbackPos.append() = pos[1];
+                    }
+                }
+            }
+            pos += scalarsPerPosition;
+        }
+    }
+
+    SkGlyphCache::AttachCache(cache);
+    if (fallbackTxt.count()) {
+        blob->initOverride(runIndex);
+        GrTextUtils::DrawBmpPosText(blob, runIndex, fontCache, props,
+                                    origPaint, origPaint.getColor(), viewMatrix,
+                                    fallbackTxt.begin(), fallbackTxt.count(),
+                                    fallbackPos.begin(), scalarsPerPosition, offset);
+    }
+}
+
+bool GrTextUtils::DfAppendGlyph(GrAtlasTextBlob* blob, int runIndex, GrBatchFontCache* cache,
+                                GrBatchTextStrike** strike, const SkGlyph& skGlyph,
+                                SkScalar sx, SkScalar sy, GrColor color,
+                                GrFontScaler* scaler,
+                                SkScalar textRatio, const SkMatrix& viewMatrix) {
+    if (!*strike) {
+        *strike = cache->getStrike(scaler);
+    }
+
+    GrGlyph::PackedID id = GrGlyph::Pack(skGlyph.getGlyphID(),
+                                         skGlyph.getSubXFixed(),
+                                         skGlyph.getSubYFixed(),
+                                         GrGlyph::kDistance_MaskStyle);
+    GrGlyph* glyph = (*strike)->getGlyph(skGlyph, id, scaler);
+    if (!glyph) {
+        return true;
+    }
+
+    // fallback to color glyph support
+    if (kA8_GrMaskFormat != glyph->fMaskFormat) {
+        return false;
+    }
+
+    SkScalar dx = SkIntToScalar(glyph->fBounds.fLeft + SK_DistanceFieldInset);
+    SkScalar dy = SkIntToScalar(glyph->fBounds.fTop + SK_DistanceFieldInset);
+    SkScalar width = SkIntToScalar(glyph->fBounds.width() - 2 * SK_DistanceFieldInset);
+    SkScalar height = SkIntToScalar(glyph->fBounds.height() - 2 * SK_DistanceFieldInset);
+
+    SkScalar scale = textRatio;
+    dx *= scale;
+    dy *= scale;
+    width *= scale;
+    height *= scale;
+    sx += dx;
+    sy += dy;
+    SkRect glyphRect = SkRect::MakeXYWH(sx, sy, width, height);
+
+    blob->appendGlyph(runIndex, glyphRect, color, *strike, glyph, scaler, skGlyph,
+                      sx - dx, sy - dy, scale, true);
+    return true;
+}
+
 void GrTextUtils::DrawTextAsPath(GrContext* context, GrDrawContext* dc,
                                  const GrClip& clip,
                                  const SkPaint& skPaint, const SkMatrix& viewMatrix,