src/core/SkGlyphRun.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/SkGlyphRun.h"

#include "include/core/SkFont.h"
#include "include/core/SkPaint.h"
#include "include/core/SkRSXform.h"
#include "include/core/SkTextBlob.h"
#include "include/private/SkTo.h"
#include "src/core/SkDevice.h"
#include "src/core/SkFontPriv.h"
#include "src/core/SkScalerCache.h"
#include "src/core/SkStrikeCache.h"
#include "src/core/SkStrikeSpec.h"
#include "src/core/SkTextBlobPriv.h"
#include "src/core/SkUtils.h"

// -- SkGlyphRun -----------------------------------------------------------------------------------
SkGlyphRun::SkGlyphRun(const SkFont& font,
                       SkSpan<const SkPoint> positions,
                       SkSpan<const SkGlyphID> glyphIDs,
                       SkSpan<const char> text,
                       SkSpan<const uint32_t> clusters,
                       SkSpan<const SkVector> scaledRotations)
        : fSource{SkMakeZip(glyphIDs, positions)}
        , fText{text}
        , fClusters{clusters}
        , fScaledRotations{scaledRotations}
        , fFont{font} {}

SkGlyphRun::SkGlyphRun(const SkGlyphRun& that, const SkFont& font)
    : fSource{that.fSource}
    , fText{that.fText}
    , fClusters{that.fClusters}
    , fFont{font} {}

// -- SkGlyphRunList -------------------------------------------------------------------------------
SkGlyphRunList::SkGlyphRunList() = default;
SkGlyphRunList::SkGlyphRunList(
        const SkTextBlob* blob,
        SkPoint origin,
        SkSpan<const SkGlyphRun> glyphRunList)
        : fGlyphRuns{glyphRunList}
        , fOriginalTextBlob{blob}
        , fOrigin{origin} { }

SkGlyphRunList::SkGlyphRunList(const SkGlyphRun& glyphRun)
        : fGlyphRuns{SkSpan<const SkGlyphRun>{&glyphRun, 1}}
        , fOriginalTextBlob{nullptr}
        , fOrigin{SkPoint::Make(0, 0)} {}

uint64_t SkGlyphRunList::uniqueID() const {
    return fOriginalTextBlob != nullptr ? fOriginalTextBlob->uniqueID()
                                        : SK_InvalidUniqueID;
}

bool SkGlyphRunList::anyRunsLCD() const {
    for (const auto& r : fGlyphRuns) {
        if (r.font().getEdging() == SkFont::Edging::kSubpixelAntiAlias) {
            return true;
        }
    }
    return false;
}

void SkGlyphRunList::temporaryShuntBlobNotifyAddedToCache(uint32_t cacheID) const {
    SkASSERT(fOriginalTextBlob != nullptr);
    fOriginalTextBlob->notifyAddedToCache(cacheID);
}

// -- SkGlyphRunBuilder ----------------------------------------------------------------------------
static SkSpan<const SkPoint> draw_text_positions(
        const SkFont& font, SkSpan<const SkGlyphID> glyphIDs, SkPoint origin, SkPoint* buffer) {
    SkStrikeSpec strikeSpec = SkStrikeSpec::MakeWithNoDevice(font);
    SkBulkGlyphMetrics storage{strikeSpec};
    auto glyphs = storage.glyphs(glyphIDs);

    SkPoint* positionCursor = buffer;
    SkPoint endOfLastGlyph = origin;
    for (auto glyph : glyphs) {
        *positionCursor++ = endOfLastGlyph;
        endOfLastGlyph += glyph->advanceVector();
    }
    return SkSpan(buffer, glyphIDs.size());
}

const SkGlyphRunList& SkGlyphRunBuilder::textToGlyphRunList(
        const SkFont& font, const void* bytes, size_t byteLength, SkPoint origin,
        SkTextEncoding encoding) {
    auto glyphIDs = textToGlyphIDs(font, bytes, byteLength, encoding);
    if (!glyphIDs.empty()) {
        this->initialize(glyphIDs.size());
        SkSpan<const SkPoint> positions = draw_text_positions(font, glyphIDs, {0, 0}, fPositions);
        this->makeGlyphRun(font,
                           glyphIDs,
                           positions,
                           SkSpan<const char>{},
                           SkSpan<const uint32_t>{},
                           SkSpan<const SkVector>{});
    }

    return this->makeGlyphRunList(nullptr, origin);
}

const SkGlyphRunList& SkGlyphRunBuilder::blobToGlyphRunList(
        const SkTextBlob& blob, SkPoint origin) {
    // Pre-size all the buffers so they don't move during processing.
    this->initialize(blob);

    SkPoint* positionCursor = fPositions;
    SkVector* scaledRotationsCursor = fScaledRotations;
    for (SkTextBlobRunIterator it(&blob); !it.done(); it.next()) {
        size_t runSize = it.glyphCount();
        if (runSize == 0 || !SkFontPriv::IsFinite(it.font())) {
            // If no glyphs or the font is not finite, don't add the run.
            continue;
        }

        const SkFont& font = it.font();
        auto glyphIDs = SkSpan<const SkGlyphID>{it.glyphs(), runSize};

        SkSpan<const SkPoint> positions;
        SkSpan<const SkVector> scaledRotations;
        switch (it.positioning()) {
            case SkTextBlobRunIterator::kDefault_Positioning: {
                positions = draw_text_positions(font, glyphIDs, it.offset(), positionCursor);
                positionCursor += positions.size();
                break;
            }
            case SkTextBlobRunIterator::kHorizontal_Positioning: {
                positions = SkSpan(positionCursor, runSize);
                for (auto x : SkSpan<const SkScalar>{it.pos(), glyphIDs.size()}) {
                    *positionCursor++ = SkPoint::Make(x, it.offset().y());
                }
                break;
            }
            case SkTextBlobRunIterator::kFull_Positioning: {
                positions = SkSpan(it.points(), runSize);
                break;
            }
            case SkTextBlobRunIterator::kRSXform_Positioning: {
                positions = SkSpan(positionCursor, runSize);
                scaledRotations = SkSpan(scaledRotationsCursor, runSize);
                for (const SkRSXform& xform : SkSpan(it.xforms(), runSize)) {
                    *positionCursor++ = {xform.fTx, xform.fTy};
                    *scaledRotationsCursor++ = {xform.fSCos, xform.fSSin};
                }
                break;
            }
        }

        this->makeGlyphRun(
                font,
                glyphIDs,
                positions,
                SkSpan<const char>(it.text(), it.textSize()),
                SkSpan<const uint32_t>(it.clusters(), runSize),
                scaledRotations);
    }

    return this->makeGlyphRunList(&blob, origin);
}

void SkGlyphRunBuilder::initialize(int totalRunSize) {

    if (totalRunSize > fMaxTotalRunSize) {
        fMaxTotalRunSize = totalRunSize;
        fPositions.reset(fMaxTotalRunSize);
    }

    fGlyphRunListStorage.clear();
}

void SkGlyphRunBuilder::initialize(const SkTextBlob& blob) {
    int positionCount = 0;
    int rsxFormCount = 0;
    for (SkTextBlobRunIterator it(&blob); !it.done(); it.next()) {
        if (it.positioning() != SkTextBlobRunIterator::kFull_Positioning) {
            positionCount += it.glyphCount();
        }
        if (it.positioning() == SkTextBlobRunIterator::kRSXform_Positioning) {
            rsxFormCount += it.glyphCount();
        }
    }

    if (positionCount > fMaxTotalRunSize) {
        fMaxTotalRunSize = positionCount;
        fPositions.reset(fMaxTotalRunSize);
    }

    if (rsxFormCount > fMaxScaledRotations) {
        fMaxScaledRotations = rsxFormCount;
        fScaledRotations.reset(rsxFormCount);
    }

    fGlyphRunListStorage.clear();
}

SkSpan<const SkGlyphID> SkGlyphRunBuilder::textToGlyphIDs(
        const SkFont& font, const void* bytes, size_t byteLength, SkTextEncoding encoding) {
    if (encoding != SkTextEncoding::kGlyphID) {
        int count = font.countText(bytes, byteLength, encoding);
        if (count > 0) {
            fScratchGlyphIDs.resize(count);
            font.textToGlyphs(bytes, byteLength, encoding, fScratchGlyphIDs.data(), count);
            return SkSpan(fScratchGlyphIDs);
        } else {
            return SkSpan<const SkGlyphID>();
        }
    } else {
        return SkSpan<const SkGlyphID>((const SkGlyphID*)bytes, byteLength / 2);
    }
}

void SkGlyphRunBuilder::makeGlyphRun(
        const SkFont& font,
        SkSpan<const SkGlyphID> glyphIDs,
        SkSpan<const SkPoint> positions,
        SkSpan<const char> text,
        SkSpan<const uint32_t> clusters,
        SkSpan<const SkVector> scaledRotations) {

    // Ignore empty runs.
    if (!glyphIDs.empty()) {
        fGlyphRunListStorage.emplace_back(
                font,
                positions,
                glyphIDs,
                text,
                clusters,
                scaledRotations);
    }
}

const SkGlyphRunList& SkGlyphRunBuilder::makeGlyphRunList(const SkTextBlob* blob, SkPoint origin) {

    fGlyphRunList.~SkGlyphRunList();
    return *new (&fGlyphRunList) SkGlyphRunList{blob, origin, SkSpan(fGlyphRunListStorage)};
}