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 "SkDrawProcs.h"
+#include "SkGlyphCache.h"
+#include "SkGpuDevice.h"
+#include "SkPath.h"
+#include "SkTextMapState.h"
+
+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);
+
+    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) {
+            // We 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 fixedSizeRatio = SkScalarToFixed(fTextRatio);
+    SkFixed halfSampleX, halfSampleY;
+    if (cache->isSubpixel()) {
+        halfSampleX = halfSampleY = (SK_FixedHalf >> SkGlyph::kSubBits);
+        SkAxisAlignment baseline = SkComputeAxisAlignmentForHText(fContext->getMatrix());
+        if (kX_SkAxisAlignment == baseline) {
+            halfSampleY = SK_FixedHalf;
+        } else if (kY_SkAxisAlignment == baseline) {
+            halfSampleX = SK_FixedHalf;
+        }
+    } else {
+        halfSampleX = halfSampleY = SK_FixedHalf;
+    }
+
+    SkFixed fx = SkScalarToFixed(x) + halfSampleX;

[jvanverth1, 2014/06/09 13:48:07]

Doesn't this lead to glyphs being off by half a pixel? I had to remove it in the
distance field code.

[bungeman-skia, 2014/06/09 15:00:07]

Yeah, this was done in SkDraw because of SkDraw1Glyph::Proc and SkGlyph::MakeID.
See the documentation there, but the basic reason was to speed up rounding. By
adding half the sampling frequency on the outside means that below it truncation
is rounding. Since you're not calling into SkDraw1Glyph::Proc or SkDrawCacheProc
here, perhaps this is unnecessary. On the other hand GrGlyph::Pack appears to be
depending on this for its truncated x,y rounding? I'm not familiar enough with
the Gr code to say what's really going on through the pipeline, but perhaps this
is enough information to understand the motivation for the half sampling
frequency addition up front. Note that if you get it wrong, subpixel text tends
to just look subtly kerned incorrectly, but it is noticeable.

[Kimmo Kinnunen, 2014/06/11 12:33:24]

Done.

+    SkFixed fy = SkScalarToFixed(y) + halfSampleY;
+    while (text < stop) {
+        const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
+        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);
+
+    SkMatrix ctm = fContext->getMatrix();
+
+    const char* stop = text + byteLength;
+    SkTextAlignProcScalar alignProc(fSkPaint.getTextAlign());
+    SkTextMapState tms(SkMatrix::I(), constY);
+    SkTextMapState::Proc tmsProc = tms.pickProc(scalarsPerPosition);
+
+    SkTDArray<const GrPath*> paths;
+    SkTDArray<SkMatrix> transforms;
+    SkScalar halfSampleX = 0, halfSampleY = 0;
+
+    if (cache->isSubpixel()) {
+        // maybe we should skip the rounding if linearText is set
+        SkAxisAlignment baseline = SkComputeAxisAlignmentForHText(ctm);
+
+#ifndef SK_IGNORE_SUBPIXEL_AXIS_ALIGN_FIX
+        if (kX_SkAxisAlignment == baseline) {
+            halfSampleY = SK_ScalarHalf;
+        } else if (kY_SkAxisAlignment == baseline) {
+            halfSampleX = SK_ScalarHalf;
+        }
+#endif
+
+        if (SkPaint::kLeft_Align == fSkPaint.getTextAlign()) {
+            while (text < stop) {
+                tmsProc(tms, pos);
+                const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
+                if (glyph.fWidth) {
+                    SkScalar x = tms.fLoc.fX + halfSampleX;

[jvanverth1, 2014/06/09 13:48:07]

Same issue with half-pixel alignment as above?  (and others, below)

[Kimmo Kinnunen, 2014/06/11 12:33:24]

Done.

+                    SkScalar y = tms.fLoc.fY + halfSampleY;
+
+                    this->appendGlyph(GrGlyph::Pack(glyph.getGlyphID(),
+                                                    glyph.getSubXFixed(),
+                                                    glyph.getSubYFixed()),
+                                      SkPoint::Make(x, y),
+                                      strike,
+                                      scaler);
+                }
+                pos += scalarsPerPosition;
+            }
+        } else {
+            while (text < stop) {
+                const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
+
+                if (glyph.fWidth) {
+                    tmsProc(tms, pos);
+                    SkPoint loc;
+                    alignProc(tms.fLoc, glyph, &loc);
+
+                    loc.fX += halfSampleX;
+                    loc.fY += halfSampleY;
+
+                    this->appendGlyph(GrGlyph::Pack(glyph.getGlyphID(),
+                                                    glyph.getSubXFixed(),
+                                                    glyph.getSubYFixed()),
+                                      loc,
+                                      strike,
+                                      scaler);
+
+                }
+                pos += scalarsPerPosition;
+            }
+        }
+    } else {    // Codepath for "not subpixel" case.
+        if (SkPaint::kLeft_Align == fSkPaint.getTextAlign()) {

[jvanverth1, 2014/06/09 13:48:07]

Do we need to support non-subpixel layout when drawing with path rendering?

[Kimmo Kinnunen, 2014/06/11 12:33:24]

Done.

[Kimmo Kinnunen, 2014/06/11 12:39:21]

Actually, I mean to say that I couldn't get the glyph positions match the 8888
or gpu rendering in all cases without this case.

+            while (text < stop) {
+                const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
+
+                if (glyph.fWidth) {
+                    tmsProc(tms, pos);
+
+                    SkScalar x = tms.fLoc.fX + SK_ScalarHalf; //halfSampleX;
+                    SkScalar y = tms.fLoc.fY + SK_ScalarHalf; //halfSampleY;
+                    this->appendGlyph(GrGlyph::Pack(glyph.getGlyphID(),
+                                                    glyph.getSubXFixed(),
+                                                    glyph.getSubYFixed()),
+                                      SkPoint::Make(x, y),
+                                      strike,
+                                      scaler);
+                }
+                pos += scalarsPerPosition;
+            }
+        } else {
+            while (text < stop) {
+                const SkGlyph& glyph = glyphCacheProc(cache, &text, 0, 0);
+
+                if (glyph.fWidth) {
+                    tmsProc(tms, pos);
+
+                    SkPoint loc;
+                    alignProc(tms.fLoc, glyph, &loc);
+
+                    loc.fX += SK_ScalarHalf; //halfSampleX;
+                    loc.fY += SK_ScalarHalf; //halfSampleY;
+                    this->appendGlyph(GrGlyph::Pack(glyph.getGlyphID(),
+                                                   glyph.getSubXFixed(),
+                                                   glyph.getSubYFixed()),
+                                      loc,
+                                      strike,
+                                      scaler);
+                }
+                pos += scalarsPerPosition;
+            }
+        }
+    }
+
+    this->finish();
+}
+
+bool GrStencilAndCoverTextContext::canDraw(const SkPaint& paint) {
+    if (paint.getRasterizer()) {
+        return false;
+    }
+    if (paint.getMaskFilter()) {
+        return false;
+    }
+    if (paint.getPathEffect()) {
+        return false;
+    }
+
+    // No hairlines unless we can map the 1 px width to the object space.
+    if (paint.getStyle() != SkPaint::kFill_Style
+        && paint.getStrokeWidth() == 0
+        && (fContext->getMatrix().hasPerspective()
+            || !fContext->getMatrix().invert(NULL))) {
+        return false;
+    }
+
+    // No color bitmap fonts.
+    SkScalerContext::Rec    rec;
+    SkScalerContext::MakeRec(paint, &fDeviceProperties, NULL, &rec);
+    return rec.getFormat() != SkMask::kARGB32_Format;
+}
+
+void GrStencilAndCoverTextContext::init(const GrPaint& paint,
+                                        const SkPaint& skPaint,
+                                        size_t textByteLength) {
+    GrTextContext::init(paint, skPaint);
+
+    if (SkDraw::ShouldDrawTextAsPaths(skPaint, fContext->getMatrix())) {
+        // This is to reproduce SkDraw::drawText_asPaths glyph positions.
+        fSkPaint.setLinearText(true);
+        fTextRatio = fSkPaint.getTextSize() / SkPaint::kCanonicalTextSizeForPaths;
+        fSkPaint.setTextSize(SkIntToScalar(SkPaint::kCanonicalTextSizeForPaths));
+    } else {
+        fTextRatio = 1.0f;
+    }
+    // Note: if Chrome ever draws text in very different text sizes in real
+    // time, then glyphs need to be looked up untransformed and scaled, but
+    // still based on the requested text size. This will let the path cache
+    // work. This will probably not be needed until 1) text size is animating,
+    // 2) layout change animations are fast enough 3) pictures are rasterized
+    // directly to framebuffer.
+
+    if (fSkPaint.getStyle() != SkPaint::kFill_Style) {
+        SkScalar strokeWidth = fSkPaint.getStrokeWidth();
+        if (0 == strokeWidth) {
+            SkMatrix inv;
+            if (fContext->getMatrix().invert(&inv)) {

[jvanverth1, 2014/06/09 13:48:07]

This won't work for non-uniform scale. And if you're assuming uniform scale, you
don't have to invert the whole matrix, just take 1/length of SkVector(kScaleX,
kSkewY).

[Kimmo Kinnunen, 2014/06/11 12:33:24]

Right.. 
I changed to what you suggested. 

I added a test to test transformed hairline text drawing. Since it doesn't seem
to be that stellar with the default implementations, I'm hoping the buggy
non-uniform case suffices for now for NVPR initial implementation. 

+                strokeWidth = SK_Scalar1 * inv.getScaleX();
+            } else {
+                // Avoid unused return value warning.
+                SkASSERT(false);
+                strokeWidth = SK_Scalar1;
+            }
+        }
+        // Compensate the glyphs being scaled up by fTextRatio by scaling the
+        // stroke down.
+        fSkPaint.setStrokeWidth(strokeWidth / 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:
+            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 (NULL == glyph || glyph->fBounds.isEmpty()) {
+        return;
+    }
+
+    if (scaler->getGlyphPath(glyph->glyphID(), &fTmpPath)) {
+        if (!fTmpPath.isEmpty()) {
+            *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();
+}
+