src/core/SkGlyphRunPainter.cpp

/*
 * Copyright 2018 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */

#include "src/core/SkGlyphRunPainter.h"
#include "src/core/SkScalerContext.h"

#if SK_SUPPORT_GPU
#include "src/gpu/ganesh/GrColorInfo.h"
#include "src/gpu/ganesh/GrDirectContextPriv.h"
#include "src/gpu/ganesh/v1/SurfaceDrawContext_v1.h"
#include "src/text/gpu/SDFTControl.h"
#include "src/text/gpu/TextBlobRedrawCoordinator.h"
#endif // SK_SUPPORT_GPU

#include "include/core/SkBitmap.h"
#include "include/core/SkColorFilter.h"
#include "include/core/SkColorSpace.h"
#include "include/core/SkMaskFilter.h"
#include "include/core/SkPathEffect.h"
#include "include/private/SkTDArray.h"
#include "src/core/SkDevice.h"
#include "src/core/SkDistanceFieldGen.h"
#include "src/core/SkDraw.h"
#include "src/core/SkEnumerate.h"
#include "src/core/SkFontPriv.h"
#include "src/core/SkGlyphBuffer.h"
#include "src/core/SkRasterClip.h"
#include "src/core/SkScalerCache.h"
#include "src/core/SkStrikeCache.h"
#include "src/core/SkStrikeForGPU.h"
#include "src/core/SkStrikeSpec.h"
#include "src/core/SkTraceEvent.h"
#include "src/text/GlyphRun.h"

#include <cinttypes>
#include <climits>

namespace {
// TODO: unify with code in GrSDFTControl.cpp
SkScalerContextFlags compute_scaler_context_flags(const SkColorSpace* cs) {
    // If we're doing linear blending, then we can disable the gamma hacks.
    // Otherwise, leave them on. In either case, we still want the contrast boost:
    // TODO: Can we be even smarter about mask gamma based on the dest transfer function?
    if (cs && cs->gammaIsLinear()) {
        return SkScalerContextFlags::kBoostContrast;
    } else {
        return SkScalerContextFlags::kFakeGammaAndBoostContrast;
    }
}
}  // namespace

// -- SkGlyphRunListPainterCPU ---------------------------------------------------------------------
SkGlyphRunListPainterCPU::SkGlyphRunListPainterCPU(const SkSurfaceProps& props,
                                                   SkColorType colorType,
                                                   SkColorSpace* cs)
        : fDeviceProps{props}
        , fBitmapFallbackProps{SkSurfaceProps{props.flags(), kUnknown_SkPixelGeometry}}
        , fColorType{colorType}
        , fScalerContextFlags{compute_scaler_context_flags(cs)} {}

void SkGlyphRunListPainterCPU::drawForBitmapDevice(
        SkCanvas* canvas, const BitmapDevicePainter* bitmapDevice,
        const sktext::GlyphRunList& glyphRunList, const SkPaint& paint, const SkMatrix& drawMatrix) {
    auto bufferScope = sktext::SkSubRunBuffers::EnsureBuffers(glyphRunList);
    auto [accepted, rejected] = bufferScope.buffers();

    // The bitmap blitters can only draw lcd text to a N32 bitmap in srcOver. Otherwise,
    // convert the lcd text into A8 text. The props communicates this to the scaler.
    auto& props = (kN32_SkColorType == fColorType && paint.isSrcOver())
                          ? fDeviceProps
                          : fBitmapFallbackProps;

    SkPoint drawOrigin = glyphRunList.origin();
    SkMatrix positionMatrix{drawMatrix};
    positionMatrix.preTranslate(drawOrigin.x(), drawOrigin.y());
    for (auto& glyphRun : glyphRunList) {
        const SkFont& runFont = glyphRun.font();

        rejected->setSource(glyphRun.source());

        if (SkStrikeSpec::ShouldDrawAsPath(paint, runFont, positionMatrix)) {

            auto [strikeSpec, strikeToSourceScale] =
                    SkStrikeSpec::MakePath(runFont, paint, props, fScalerContextFlags);

            auto strike = strikeSpec.findOrCreateStrike();

            accepted->startSource(rejected->source());
            strike->prepareForPathDrawing(accepted, rejected);
            rejected->flipRejectsToSource();

            // The paint we draw paths with must have the same anti-aliasing state as the runFont
            // allowing the paths to have the same edging as the glyph masks.
            SkPaint pathPaint = paint;
            pathPaint.setAntiAlias(runFont.hasSomeAntiAliasing());

            const bool stroking = pathPaint.getStyle() != SkPaint::kFill_Style;
            const bool hairline = pathPaint.getStrokeWidth() == 0;
            const bool needsExactCTM = pathPaint.getShader()     ||
                                       pathPaint.getPathEffect() ||
                                       pathPaint.getMaskFilter() ||
                                       (stroking && !hairline);
            if (!needsExactCTM) {
                for (auto [variant, pos] : accepted->accepted()) {
                    const SkPath* path = variant.glyph()->path();
                    SkMatrix m;
                    SkPoint translate = drawOrigin + pos;
                    m.setScaleTranslate(strikeToSourceScale, strikeToSourceScale,
                                        translate.x(), translate.y());
                    SkAutoCanvasRestore acr(canvas, true);
                    canvas->concat(m);
                    canvas->drawPath(*path, pathPaint);
                }
            } else {
                for (auto [variant, pos] : accepted->accepted()) {
                    const SkPath* path = variant.glyph()->path();
                    SkMatrix m;
                    SkPoint translate = drawOrigin + pos;
                    m.setScaleTranslate(strikeToSourceScale, strikeToSourceScale,
                                        translate.x(), translate.y());

                    SkPath deviceOutline;
                    path->transform(m, &deviceOutline);
                    deviceOutline.setIsVolatile(true);
                    canvas->drawPath(deviceOutline, pathPaint);
                }
            }

            if (!rejected->source().empty()) {
                accepted->startSource(rejected->source());
                strike->prepareForDrawableDrawing(accepted, rejected);
                rejected->flipRejectsToSource();

                for (auto [variant, pos] : accepted->accepted()) {
                    SkDrawable* drawable = variant.glyph()->drawable();
                    SkMatrix m;
                    SkPoint translate = drawOrigin + pos;
                    m.setScaleTranslate(strikeToSourceScale, strikeToSourceScale,
                                        translate.x(), translate.y());
                    SkAutoCanvasRestore acr(canvas, false);
                    SkRect drawableBounds = drawable->getBounds();
                    m.mapRect(&drawableBounds);
                    canvas->saveLayer(&drawableBounds, &paint);
                    drawable->draw(canvas, &m);
                }
            }
        }
        if (!rejected->source().empty() && !positionMatrix.hasPerspective()) {
            SkStrikeSpec strikeSpec = SkStrikeSpec::MakeMask(
                    runFont, paint, props, fScalerContextFlags, positionMatrix);

            auto strike = strikeSpec.findOrCreateStrike();

            accepted->startDevicePositioning(
                    rejected->source(), positionMatrix, strike->roundingSpec());

            strike->prepareForDrawingMasksCPU(accepted);
            rejected->flipRejectsToSource();
            bitmapDevice->paintMasks(accepted, paint);
        }
        if (!rejected->source().empty()) {
            std::vector<SkPoint> sourcePositions;

            // Create a strike is source space to calculate scale information.
            SkStrikeSpec scaleStrikeSpec = SkStrikeSpec::MakeMask(
                    runFont, paint, props, fScalerContextFlags, SkMatrix::I());
            SkBulkGlyphMetrics metrics{scaleStrikeSpec};

            auto glyphIDs = rejected->source().get<0>();
            auto positions = rejected->source().get<1>();
            SkSpan<const SkGlyph*> glyphs = metrics.glyphs(glyphIDs);
            SkScalar maxScale = SK_ScalarMin;

            // Calculate the scale that makes the longest edge 1:1 with its side in the cache.
            for (auto [glyph, pos] : SkMakeZip(glyphs, positions)) {
                SkPoint corners[4];
                SkPoint srcPos = pos + drawOrigin;
                // Store off the positions in device space to position the glyphs during drawing.
                sourcePositions.push_back(srcPos);
                SkRect rect = glyph->rect();
                rect.makeOffset(srcPos);
                positionMatrix.mapRectToQuad(corners, rect);
                // left top -> right top
                SkScalar scale = (corners[1] - corners[0]).length() / rect.width();
                maxScale = std::max(maxScale, scale);
                // right top -> right bottom
                scale = (corners[2] - corners[1]).length() / rect.height();
                maxScale = std::max(maxScale, scale);
                // right bottom -> left bottom
                scale = (corners[3] - corners[2]).length() / rect.width();
                maxScale = std::max(maxScale, scale);
                // left bottom -> left top
                scale = (corners[0] - corners[3]).length() / rect.height();
                maxScale = std::max(maxScale, scale);
            }

            if (maxScale * runFont.getSize() > 256) {
                maxScale = 256.0f / runFont.getSize();
            }

            SkMatrix cacheScale = SkMatrix::Scale(maxScale, maxScale);
            SkStrikeSpec strikeSpec = SkStrikeSpec::MakeMask(
                    runFont, paint, props, fScalerContextFlags, cacheScale);

            auto strike = strikeSpec.findOrCreateStrike();

            // Figure out all the positions and packed glyphIDs based on the device matrix.
            accepted->startDevicePositioning(
                    rejected->source(), positionMatrix, strike->roundingSpec());

            strike->prepareForDrawingMasksCPU(accepted);
            auto variants = accepted->accepted().get<0>();
            for (auto [variant, srcPos] : SkMakeZip(variants, sourcePositions)) {
                const SkGlyph* glyph = variant.glyph();
                SkMask mask = glyph->mask();
                // TODO: is this needed will A8 and BW just work?
                if (mask.fFormat != SkMask::kARGB32_Format) {
                    continue;
                }
                SkBitmap bm;
                bm.installPixels(SkImageInfo::MakeN32Premul(mask.fBounds.size()),
                                 mask.fImage,
                                 mask.fRowBytes);

                // Since the glyph in the cache is scaled by maxScale, its top left vector is too
                // long. Reduce it to find proper positions on the device.
                SkPoint realPos =
                    srcPos + SkPoint::Make(mask.fBounds.left(), mask.fBounds.top())*(1.0f/maxScale);

                // Calculate the preConcat matrix for drawBitmap to get the rectangle from the
                // glyph cache (which is multiplied by maxScale) to land in the right place.
                SkMatrix translate = SkMatrix::Translate(realPos);
                translate.preScale(1.0f/maxScale, 1.0f/maxScale);

                // Draw the bitmap using the rect from the scaled cache, and not the source
                // rectangle for the glyph.
                bitmapDevice->drawBitmap(
                        bm, translate, nullptr, SkSamplingOptions{SkFilterMode::kLinear},
                        paint);
            }
            rejected->flipRejectsToSource();
        }

        // TODO: have the mask stage above reject the glyphs that are too big, and handle the
        //  rejects in a more sophisticated stage.
    }
}