Implement text rendering with NVPR

src/gpu/GrStencilAndCoverTextContext.cpp

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrStencilAndCoverTextContext.h"
+#include "GrDrawTarget.h"
+#include "GrFontScaler.h"
+#include "GrGpu.h"
+#include "GrPath.h"
+#include "GrTextStrike.h"
+#include "GrTextStrike_impl.h"
+#include "SkAutoKern.h"
+#include "SkDraw.h"
+#include "SkGlyphCache.h"
+#include "SkGpuDevice.h"
+#include "SkPath.h"
+
+static const int kBaseSCFontSize = 64;
+static const int kMaxReservedGlyphs = 64;
+
+GrStencilAndCoverTextContext::GrStencilAndCoverTextContext(
+    GrContext* context, const SkDeviceProperties& properties)
+    : GrTextContext(context, properties)
+    , fStroke(SkStrokeRec::kFill_InitStyle) {
+}
+
+GrStencilAndCoverTextContext::~GrStencilAndCoverTextContext() {
+}
+
+void GrStencilAndCoverTextContext::drawText(const GrPaint& paint,
+                                            const SkPaint& skPaint,
+                                            const char text[],
+                                            size_t byteLength,
+                                            SkScalar x, SkScalar y) {
+    SkASSERT(byteLength == 0 || text != NULL);
+
+    // nothing to draw
+    if (text == NULL || byteLength == 0 /*|| fRC->isEmpty()*/) {
+        return;
+    }
+
+    this->init(paint, skPaint, byteLength);
+
+
+    SkDrawCacheProc glyphCacheProc = fSkPaint.getDrawCacheProc();
+    SkAutoGlyphCache autoCache(fSkPaint, &fDeviceProperties, NULL);
+    SkGlyphCache* cache = autoCache.getCache();
+    GrFontScaler* scaler = GetGrFontScaler(cache);
+    GrTextStrike* strike =
+        fContext->getFontCache()->getStrike(scaler, true);
+
+    const char* stop = text + byteLength;
+
+    // Measure first if needed.
+    if (fSkPaint.getTextAlign() != SkPaint::kLeft_Align) {
+        SkFixed    stopX = 0;
+        SkFixed    stopY = 0;
+
+        const char* textPtr = text;
+        while (textPtr < stop) {
+            // don't need x, y here, since all subpixel variants will have the
+            // same advance
+            const SkGlyph& glyph = glyphCacheProc(cache, &textPtr, 0, 0);
+
+            stopX += glyph.fAdvanceX;
+            stopY += glyph.fAdvanceY;
+        }
+        SkASSERT(textPtr == stop);
+
+        SkScalar alignX = SkFixedToScalar(stopX) * fTextRatio;
+        SkScalar alignY = SkFixedToScalar(stopY) * fTextRatio;
+
+        if (fSkPaint.getTextAlign() == SkPaint::kCenter_Align) {
+            alignX = SkScalarHalf(alignX);
+            alignY = SkScalarHalf(alignY);
+        }
+
+        x -= alignX;
+        y -= alignY;
+    }
+
+    SkAutoKern autokern;
+
+    SkFixed fx = SkScalarToFixed(x) + SK_FixedHalf;
+    SkFixed fy = SkScalarToFixed(y) + SK_FixedHalf;
+    SkFixed fixedSizeRatio = SkScalarToFixed(fTextRatio);
+
+    while (text < stop) {
+        const SkGlyph& glyph = glyphCacheProc(cache, &text, fx, fy);

[jvanverth1, 2014/03/24 14:51:05]

I believe fx, fy should always be 0 in this case. Otherwise you'll create
subpixel glyphs when you don't need to.

[Kimmo Kinnunen, 2014/03/25 12:32:48]

Done.

+
+        fx += SkFixedMul_portable(autokern.adjust(glyph), fixedSizeRatio);
+
+        if (glyph.fWidth) {
+            this->appendGlyph(GrGlyph::Pack(glyph.getGlyphID(),
+                                            glyph.getSubXFixed(),
+                                            glyph.getSubYFixed()),
+                              SkPoint::Make(SkFixedToScalar(fx),
+                                            SkFixedToScalar(fy)),
+                              strike,
+                              scaler);
+        }
+
+        fx += SkFixedMul_portable(glyph.fAdvanceX, fixedSizeRatio);
+        fy += SkFixedMul_portable(glyph.fAdvanceY, fixedSizeRatio);
+    }
+
+    this->finish();
+}
+
+void GrStencilAndCoverTextContext::drawPosText(const GrPaint& paint, const SkPaint& skPaint,
+                                               const char text[],
+                                               size_t byteLength,
+                                               const SkScalar pos[],
+                                               SkScalar constY,
+                                               int scalarsPerPosition) {
+    SkASSERT(byteLength == 0 || text != NULL);
+    SkASSERT(1 == scalarsPerPosition || 2 == scalarsPerPosition);
+
+    // nothing to draw
+    if (text == NULL || byteLength == 0/* || fRC->isEmpty()*/) {
+        return;
+    }
+
+    this->init(paint, skPaint, byteLength);
+
+    SkDrawCacheProc glyphCacheProc = fSkPaint.getDrawCacheProc();
+
+    SkAutoGlyphCache autoCache(fSkPaint, &fDeviceProperties, NULL);
+    SkGlyphCache* cache = autoCache.getCache();
+    GrFontScaler* scaler = GetGrFontScaler(cache);
+    GrTextStrike* strike =
+        fContext->getFontCache()->getStrike(scaler, true);
+
+    const char*        stop = text + byteLength;
+
+    SkTDArray<const GrPath*> paths;
+    SkTDArray<SkMatrix> transforms;
+
+    if (SkPaint::kLeft_Align == fSkPaint.getTextAlign()) {
+        while (text < stop) {
+            // the last 2 parameters are ignored
+            const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
+
+            if (glyph.fWidth) {
+                SkScalar x = pos[0];
+                SkScalar y = scalarsPerPosition == 1 ? constY : pos[1];
+                this->appendGlyph(GrGlyph::Pack(glyph.getGlyphID(),
+                                                glyph.getSubXFixed(),
+                                                glyph.getSubYFixed()),
+                                  SkPoint::Make(x, y),
+                                  strike,
+                                  scaler);
+            }
+
+            pos += scalarsPerPosition;
+        }
+    } else {
+        int alignShift = SkPaint::kCenter_Align == fSkPaint.getTextAlign() ? 1 : 0;
+        while (text < stop) {
+            // the last 2 parameters are ignored
+            const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
+
+            if (glyph.fWidth) {
+                SkScalar x = pos[0];
+                SkScalar y = scalarsPerPosition == 1 ? constY : pos[1];
+                x -= SkFixedToScalar((glyph.fAdvanceX >> alignShift));
+                y -= SkFixedToScalar((glyph.fAdvanceY >> alignShift));
+
+                this->appendGlyph(GrGlyph::Pack(glyph.getGlyphID(),
+                                                glyph.getSubXFixed(),
+                                                glyph.getSubYFixed()),
+                                  SkPoint::Make(x, y),
+                                  strike,
+                                  scaler);
+            }
+            pos += scalarsPerPosition;
+        }
+    }
+
+    this->finish();
+}
+
+bool GrStencilAndCoverTextContext::canDraw(const SkPaint& paint) {
+    return !paint.getRasterizer()
+        && !paint.getMaskFilter()
+        && (paint.getStyle() == SkPaint::kFill_Style
+            || paint.getStrokeWidth() > 0);
+
+}
+
+static bool has_thick_frame(const SkPaint& paint) {
+    return paint.getStrokeWidth() > 0 &&
+        paint.getStyle() != SkPaint::kFill_Style;
+}
+
+void GrStencilAndCoverTextContext::init(const GrPaint& paint,
+                                        const SkPaint& skPaint,
+                                        size_t textByteLength) {
+    GrTextContext::init(paint, skPaint);
+    fTextRatio = fSkPaint.getTextSize() / kBaseSCFontSize;
+    fSkPaint.setTextSize(SkIntToScalar(kBaseSCFontSize));
+    fSkPaint.setLCDRenderText(false);
+    fSkPaint.setAutohinted(false);
+    fSkPaint.setSubpixelText(false);

[jvanverth1, 2014/03/24 14:51:05]

You may want to always enable subpixel text so you get the correct positioning.
I had to do this recently in the distance field code.

[Kimmo Kinnunen, 2014/03/25 12:32:48]

Done.

+    if (has_thick_frame(fSkPaint)) {
+        // Compensate the glyphs being scaled up by fTextRatio, by scaling the
+        // stroke down.
+        fSkPaint.setStrokeWidth(fSkPaint.getStrokeWidth() / fTextRatio);
+    }
+    fStroke = SkStrokeRec(fSkPaint);
+
+    // Make glyph cache produce paths geometry for fill. We will stroke them
+    // by passing fStroke to drawPath.
+    fSkPaint.setStyle(SkPaint::kFill_Style);
+
+    fStateRestore.set(fDrawTarget->drawState());
+
+    fDrawTarget->drawState()->setFromPaint(fPaint, fContext->getMatrix(),
+                                           fContext->getRenderTarget());
+
+    GR_STATIC_CONST_SAME_STENCIL(kStencilPass,
+                                 kZero_StencilOp,
+                                 kZero_StencilOp,
+                                 kNotEqual_StencilFunc,
+                                 0xffff,
+                                 0x0000,
+                                 0xffff);
+
+    *fDrawTarget->drawState()->stencil() = kStencilPass;
+
+    size_t reserveAmount;
+    switch (skPaint.getTextEncoding()) {
+    default:

[bsalomon, 2014/03/24 13:53:37]

tiny style nit: we indent the case/defaults (much to my chagrin).

[Kimmo Kinnunen, 2014/03/25 12:32:48]

Done.

+        SkASSERT(false);
+    case SkPaint::kUTF8_TextEncoding:
+        reserveAmount = textByteLength;
+        break;
+    case SkPaint::kUTF16_TextEncoding:
+        reserveAmount = textByteLength / 2;
+        break;
+    case SkPaint::kUTF32_TextEncoding:
+    case SkPaint::kGlyphID_TextEncoding:
+        reserveAmount = textByteLength / 4;
+        break;
+    }
+    fPaths.setReserve(reserveAmount);
+    fTransforms.setReserve(reserveAmount);
+}
+
+inline void GrStencilAndCoverTextContext::appendGlyph(GrGlyph::PackedID glyphID,
+                                                      const SkPoint& pos,
+                                                      GrTextStrike* strike,
+                                                      GrFontScaler* scaler) {
+    GrGlyph* glyph = strike->getGlyph(glyphID, scaler);
+
+    if (scaler->getGlyphPath(glyph->glyphID(), &fTmpPath)) {
+        *fPaths.append() = fContext->createPath(fTmpPath, fStroke);
+        SkMatrix* t = fTransforms.append();
+        t->setTranslate(pos.fX, pos.fY);
+        t->preScale(fTextRatio, fTextRatio);
+    }
+}
+
+void GrStencilAndCoverTextContext::finish() {
+    if (fPaths.count() > 0) {
+        fDrawTarget->drawPaths(static_cast<size_t>(fPaths.count()),
+                               fPaths.begin(), fTransforms.begin(),
+                               SkPath::kWinding_FillType, fStroke.getStyle());
+        for (int i = 0; i < fPaths.count(); ++i) {
+            fPaths[i]->unref();
+        }
+        if (fPaths.count() > kMaxReservedGlyphs) {
+            fPaths.reset();
+            fTransforms.reset();
+        } else {
+            fPaths.rewind();
+            fTransforms.rewind();
+        }
+    }
+    fTmpPath.reset();
+
+    fDrawTarget->drawState()->stencil()->setDisabled();
+    fStateRestore.set(NULL);
+    GrTextContext::finish();
+}
+