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/*
* Copyright 2015 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkFindAndPositionGlyph_DEFINED
#define SkFindAndPositionGlyph_DEFINED
#include "SkArenaAlloc.h"
#include "SkAutoKern.h"
#include "SkGlyph.h"
#include "SkGlyphCache.h"
#include "SkPaint.h"
#include "SkTemplates.h"
#include "SkUtils.h"
#include <utility>
class SkFindAndPlaceGlyph {
public:
template<typename ProcessOneGlyph>
static void ProcessText(
SkPaint::TextEncoding, const char text[], size_t byteLength,
SkPoint offset, const SkMatrix& matrix, SkPaint::Align textAlignment,
SkGlyphCache* cache, ProcessOneGlyph&& processOneGlyph);
// ProcessPosText handles all cases for finding and positioning glyphs. It has a very large
// multiplicity. It figures out the glyph, position and rounding and pass those parameters to
// processOneGlyph.
//
// The routine processOneGlyph passed in by the client has the following signature:
// void f(const SkGlyph& glyph, SkPoint position, SkPoint rounding);
//
// * Sub-pixel positioning (2) - use sub-pixel positioning.
// * Text alignment (3) - text alignment with respect to the glyph's width.
// * Matrix type (3) - special cases for translation and X-coordinate scaling.
// * Components per position (2) - the positions vector can have a common Y with different
// Xs, or XY-pairs.
// * Axis Alignment (for sub-pixel positioning) (3) - when using sub-pixel positioning, round
// to a whole coordinate instead of using sub-pixel positioning.
// The number of variations is 108 for sub-pixel and 36 for full-pixel.
// This routine handles all of them using inline polymorphic variable (no heap allocation).
template<typename ProcessOneGlyph>
static void ProcessPosText(
SkPaint::TextEncoding, const char text[], size_t byteLength,
SkPoint offset, const SkMatrix& matrix, const SkScalar pos[], int scalarsPerPosition,
SkPaint::Align textAlignment,
SkGlyphCache* cache, ProcessOneGlyph&& processOneGlyph);
private:
// GlyphFinderInterface is the polymorphic base for classes that parse a stream of chars into
// the right UniChar (or GlyphID) and lookup up the glyph on the cache. The concrete
// implementations are: Utf8GlyphFinder, Utf16GlyphFinder, Utf32GlyphFinder,
// and GlyphIdGlyphFinder.
class GlyphFinderInterface {
public:
virtual ~GlyphFinderInterface() {}
virtual const SkGlyph& lookupGlyph(const char** text) = 0;
virtual const SkGlyph& lookupGlyphXY(const char** text, SkFixed x, SkFixed y) = 0;
};
class UtfNGlyphFinder : public GlyphFinderInterface {
public:
explicit UtfNGlyphFinder(SkGlyphCache* cache)
: fCache(cache) {
SkASSERT(cache != nullptr);
}
const SkGlyph& lookupGlyph(const char** text) override {
SkASSERT(text != nullptr);
return fCache->getUnicharMetrics(nextUnichar(text));
}
const SkGlyph& lookupGlyphXY(const char** text, SkFixed x, SkFixed y) override {
SkASSERT(text != nullptr);
return fCache->getUnicharMetrics(nextUnichar(text), x, y);
}
private:
virtual SkUnichar nextUnichar(const char** text) = 0;
SkGlyphCache* fCache;
};
class Utf8GlyphFinder final : public UtfNGlyphFinder {
public:
explicit Utf8GlyphFinder(SkGlyphCache* cache) : UtfNGlyphFinder(cache) { }
private:
SkUnichar nextUnichar(const char** text) override { return SkUTF8_NextUnichar(text); }
};
class Utf16GlyphFinder final : public UtfNGlyphFinder {
public:
explicit Utf16GlyphFinder(SkGlyphCache* cache) : UtfNGlyphFinder(cache) { }
private:
SkUnichar nextUnichar(const char** text) override {
return SkUTF16_NextUnichar((const uint16_t**)text);
}
};
class Utf32GlyphFinder final : public UtfNGlyphFinder {
public:
explicit Utf32GlyphFinder(SkGlyphCache* cache) : UtfNGlyphFinder(cache) { }
private:
SkUnichar nextUnichar(const char** text) override {
const int32_t* ptr = *(const int32_t**)text;
SkUnichar uni = *ptr++;
*text = (const char*)ptr;
return uni;
}
};
class GlyphIdGlyphFinder final : public GlyphFinderInterface {
public:
explicit GlyphIdGlyphFinder(SkGlyphCache* cache)
: fCache(cache) {
SkASSERT(cache != nullptr);
}
const SkGlyph& lookupGlyph(const char** text) override {
return fCache->getGlyphIDMetrics(nextGlyphId(text));
}
const SkGlyph& lookupGlyphXY(const char** text, SkFixed x, SkFixed y) override {
return fCache->getGlyphIDMetrics(nextGlyphId(text), x, y);
}
private:
uint16_t nextGlyphId(const char** text) {
SkASSERT(text != nullptr);
const uint16_t* ptr = *(const uint16_t**)text;
uint16_t glyphID = *ptr;
ptr += 1;
*text = (const char*)ptr;
return glyphID;
}
SkGlyphCache* fCache;
};
static GlyphFinderInterface* getGlyphFinder(
SkArenaAlloc* arena, SkPaint::TextEncoding encoding, SkGlyphCache* cache) {
switch(encoding) {
case SkPaint::kUTF8_TextEncoding:
return arena->make<Utf8GlyphFinder>(cache);
case SkPaint::kUTF16_TextEncoding:
return arena->make<Utf16GlyphFinder>(cache);
case SkPaint::kUTF32_TextEncoding:
return arena->make<Utf32GlyphFinder>(cache);
case SkPaint::kGlyphID_TextEncoding:
return arena->make<GlyphIdGlyphFinder>(cache);
}
SK_ABORT("Should not get here.");
return nullptr;
}
// PositionReaderInterface reads a point from the pos vector.
// * HorizontalPositions - assumes a common Y for many X values.
// * ArbitraryPositions - a list of (X,Y) pairs.
class PositionReaderInterface {
public:
virtual ~PositionReaderInterface() { }
virtual SkPoint nextPoint() = 0;
};
class HorizontalPositions final : public PositionReaderInterface {
public:
explicit HorizontalPositions(const SkScalar* positions)
: fPositions(positions) { }
SkPoint nextPoint() override {
SkScalar x = *fPositions++;
return {x, 0};
}
private:
const SkScalar* fPositions;
};
class ArbitraryPositions final : public PositionReaderInterface {
public:
explicit ArbitraryPositions(const SkScalar* positions)
: fPositions(positions) { }
SkPoint nextPoint() override {
SkPoint to_return{fPositions[0], fPositions[1]};
fPositions += 2;
return to_return;
}
private:
const SkScalar* fPositions;
};
// MapperInterface given a point map it through the matrix. There are several shortcut
// variants.
// * TranslationMapper - assumes a translation only matrix.
// * XScaleMapper - assumes an X scaling and a translation.
// * GeneralMapper - Does all other matricies.
class MapperInterface {
public:
virtual ~MapperInterface() { }
virtual SkPoint map(SkPoint position) const = 0;
};
class TranslationMapper final : public MapperInterface {
public:
TranslationMapper(const SkMatrix& matrix, const SkPoint origin)
: fTranslate(matrix.mapXY(origin.fX, origin.fY)) { }
SkPoint map(SkPoint position) const override {
return position + fTranslate;
}
private:
const SkPoint fTranslate;
};
class XScaleMapper final : public MapperInterface {
public:
XScaleMapper(const SkMatrix& matrix, const SkPoint origin)
: fTranslate(matrix.mapXY(origin.fX, origin.fY)), fXScale(matrix.getScaleX()) { }
SkPoint map(SkPoint position) const override {
return {fXScale * position.fX + fTranslate.fX, fTranslate.fY};
}
private:
const SkPoint fTranslate;
const SkScalar fXScale;
};
// The caller must keep matrix alive while this class is used.
class GeneralMapper final : public MapperInterface {
public:
GeneralMapper(const SkMatrix& matrix, const SkPoint origin)
: fOrigin(origin), fMatrix(matrix), fMapProc(matrix.getMapXYProc()) { }
SkPoint map(SkPoint position) const override {
SkPoint result;
fMapProc(fMatrix, position.fX + fOrigin.fX, position.fY + fOrigin.fY, &result);
return result;
}
private:
const SkPoint fOrigin;
const SkMatrix& fMatrix;
const SkMatrix::MapXYProc fMapProc;
};
// TextAlignmentAdjustment handles shifting the glyph based on its width.
static SkPoint TextAlignmentAdjustment(SkPaint::Align textAlignment, const SkGlyph& glyph) {
switch (textAlignment) {
case SkPaint::kLeft_Align:
return {0.0f, 0.0f};
case SkPaint::kCenter_Align:
return {SkFloatToScalar(glyph.fAdvanceX) / 2,
SkFloatToScalar(glyph.fAdvanceY) / 2};
case SkPaint::kRight_Align:
return {SkFloatToScalar(glyph.fAdvanceX),
SkFloatToScalar(glyph.fAdvanceY)};
}
// Even though the entire enum is covered above, MVSC doesn't think so. Make it happy.
SK_ABORT("Should never get here.");
return {0.0f, 0.0f};
}
// The "call" to SkFixedToScalar is actually a macro. It's macros all the way down.
// Needs to be a macro because you can't have a const float unless you make it constexpr.
#define kSubpixelRounding (SkFixedToScalar(SkGlyph::kSubpixelRound))
// The SubpixelPositionRounding function returns a point suitable for rounding a sub-pixel
// positioned glyph.
static SkPoint SubpixelPositionRounding(SkAxisAlignment axisAlignment) {
switch (axisAlignment) {
case kX_SkAxisAlignment:
return {kSubpixelRounding, SK_ScalarHalf};
case kY_SkAxisAlignment:
return {SK_ScalarHalf, kSubpixelRounding};
case kNone_SkAxisAlignment:
return {kSubpixelRounding, kSubpixelRounding};
}
SK_ABORT("Should not get here.");
return {0.0f, 0.0f};
}
// The SubpixelAlignment function produces a suitable position for the glyph cache to
// produce the correct sub-pixel alignment. If a position is aligned with an axis a shortcut
// of 0 is used for the sub-pixel position.
static SkIPoint SubpixelAlignment(SkAxisAlignment axisAlignment, SkPoint position) {
// Only the fractional part of position.fX and position.fY matter, because the result of
// this function will just be passed to FixedToSub.
switch (axisAlignment) {
case kX_SkAxisAlignment:
return {SkScalarToFixed(SkScalarFraction(position.fX) + kSubpixelRounding), 0};
case kY_SkAxisAlignment:
return {0, SkScalarToFixed(SkScalarFraction(position.fY) + kSubpixelRounding)};
case kNone_SkAxisAlignment:
return {SkScalarToFixed(SkScalarFraction(position.fX) + kSubpixelRounding),
SkScalarToFixed(SkScalarFraction(position.fY) + kSubpixelRounding)};
}
SK_ABORT("Should not get here.");
return {0, 0};
}
#undef kSubpixelRounding
// GlyphFindAndPlaceInterface given the text and position finds the correct glyph and does
// glyph specific position adjustment. The findAndPositionGlyph method takes text and
// position and calls processOneGlyph with the correct glyph, final position and rounding
// terms. The final position is not rounded yet and is the responsibility of processOneGlyph.
template<typename ProcessOneGlyph>
class GlyphFindAndPlaceInterface : SkNoncopyable {
public:
virtual ~GlyphFindAndPlaceInterface() { }
// findAndPositionGlyph calculates the position of the glyph, finds the glyph, and
// returns the position of where the next glyph will be using the glyph's advance and
// possibly kerning. The returned position is used by drawText, but ignored by drawPosText.
// The compiler should prune all this calculation if the return value is not used.
//
// This should be a pure virtual, but some versions of GCC <= 4.8 have a bug that causes a
// compile error.
// See GCC bug: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60277
virtual SkPoint findAndPositionGlyph(
const char** text, SkPoint position, ProcessOneGlyph&& processOneGlyph) {
SK_ABORT("Should never get here.");
return {0.0f, 0.0f};
}
};
// GlyphFindAndPlaceSubpixel handles finding and placing glyphs when sub-pixel positioning is
// requested. After it has found and placed the glyph it calls the templated function
// ProcessOneGlyph in order to actually perform an action.
template<typename ProcessOneGlyph, SkPaint::Align kTextAlignment,
SkAxisAlignment kAxisAlignment>
class GlyphFindAndPlaceSubpixel final : public GlyphFindAndPlaceInterface<ProcessOneGlyph> {
public:
explicit GlyphFindAndPlaceSubpixel(GlyphFinderInterface* glyphFinder)
: fGlyphFinder(glyphFinder) { }
SkPoint findAndPositionGlyph(
const char** text, SkPoint position, ProcessOneGlyph&& processOneGlyph) override {
if (kTextAlignment != SkPaint::kLeft_Align) {
// Get the width of an un-sub-pixel positioned glyph for calculating the
// alignment. This is not needed for kLeftAlign because its adjustment is
// always {0, 0}.
const char* tempText = *text;
const SkGlyph &metricGlyph = fGlyphFinder->lookupGlyph(&tempText);
if (metricGlyph.fWidth <= 0) {
// Exiting early, be sure to update text pointer.
*text = tempText;
return position + SkPoint{SkFloatToScalar(metricGlyph.fAdvanceX),
SkFloatToScalar(metricGlyph.fAdvanceY)};
}
// Adjust the final position by the alignment adjustment.
position -= TextAlignmentAdjustment(kTextAlignment, metricGlyph);
}
// Find the glyph.
SkIPoint lookupPosition = SkScalarsAreFinite(position.fX, position.fY)
? SubpixelAlignment(kAxisAlignment, position)
: SkIPoint{0, 0};
const SkGlyph& renderGlyph =
fGlyphFinder->lookupGlyphXY(text, lookupPosition.fX, lookupPosition.fY);
// If the glyph has no width (no pixels) then don't bother processing it.
if (renderGlyph.fWidth > 0) {
processOneGlyph(renderGlyph, position,
SubpixelPositionRounding(kAxisAlignment));
}
return position + SkPoint{SkFloatToScalar(renderGlyph.fAdvanceX),
SkFloatToScalar(renderGlyph.fAdvanceY)};
}
private:
GlyphFinderInterface* fGlyphFinder;
};
enum SelectKerning {
kNoKerning = false,
kUseKerning = true
};
// GlyphFindAndPlaceFullPixel handles finding and placing glyphs when no sub-pixel
// positioning is requested. The kUseKerning argument should be true for drawText, and false
// for drawPosText.
template<typename ProcessOneGlyph, SkPaint::Align kTextAlignment, SelectKerning kUseKerning>
class GlyphFindAndPlaceFullPixel final : public GlyphFindAndPlaceInterface<ProcessOneGlyph> {
public:
explicit GlyphFindAndPlaceFullPixel(GlyphFinderInterface* glyphFinder)
: fGlyphFinder(glyphFinder) {
// Kerning can only be used with SkPaint::kLeft_Align
static_assert(!kUseKerning || SkPaint::kLeft_Align == kTextAlignment,
"Kerning can only be used with left aligned text.");
}
SkPoint findAndPositionGlyph(
const char** text, SkPoint position, ProcessOneGlyph&& processOneGlyph) override {
SkPoint finalPosition = position;
const SkGlyph& glyph = fGlyphFinder->lookupGlyph(text);
if (kUseKerning) {
finalPosition += {fAutoKern.adjust(glyph), 0.0f};
}
if (glyph.fWidth > 0) {
finalPosition -= TextAlignmentAdjustment(kTextAlignment, glyph);
processOneGlyph(glyph, finalPosition, {SK_ScalarHalf, SK_ScalarHalf});
}
return finalPosition + SkPoint{SkFloatToScalar(glyph.fAdvanceX),
SkFloatToScalar(glyph.fAdvanceY)};
}
private:
GlyphFinderInterface* fGlyphFinder;
SkAutoKern fAutoKern;
};
template <typename ProcessOneGlyph, SkPaint::Align kTextAlignment>
static GlyphFindAndPlaceInterface<ProcessOneGlyph>* getSubpixel(
SkArenaAlloc* arena, SkAxisAlignment axisAlignment, GlyphFinderInterface* glyphFinder)
{
switch (axisAlignment) {
case kX_SkAxisAlignment:
return arena->make<GlyphFindAndPlaceSubpixel<
ProcessOneGlyph, kTextAlignment, kX_SkAxisAlignment>>(glyphFinder);
case kNone_SkAxisAlignment:
return arena->make<GlyphFindAndPlaceSubpixel<
ProcessOneGlyph, kTextAlignment, kNone_SkAxisAlignment>>(glyphFinder);
case kY_SkAxisAlignment:
return arena->make<GlyphFindAndPlaceSubpixel<
ProcessOneGlyph, kTextAlignment, kY_SkAxisAlignment>>(glyphFinder);
}
SK_ABORT("Should never get here.");
return nullptr;
}
static SkPoint MeasureText(
GlyphFinderInterface* glyphFinder, const char text[], size_t byteLength) {
SkScalar x = 0, y = 0;
const char* stop = text + byteLength;
SkAutoKern autokern;
while (text < stop) {
// don't need x, y here, since all subpixel variants will have the
// same advance
const SkGlyph& glyph = glyphFinder->lookupGlyph(&text);
x += autokern.adjust(glyph) + SkFloatToScalar(glyph.fAdvanceX);
y += SkFloatToScalar(glyph.fAdvanceY);
}
SkASSERT(text == stop);
return {x, y};
}
};
template<typename ProcessOneGlyph>
inline void SkFindAndPlaceGlyph::ProcessPosText(
SkPaint::TextEncoding textEncoding, const char text[], size_t byteLength,
SkPoint offset, const SkMatrix& matrix, const SkScalar pos[], int scalarsPerPosition,
SkPaint::Align textAlignment,
SkGlyphCache* cache, ProcessOneGlyph&& processOneGlyph) {
SkAxisAlignment axisAlignment = cache->getScalerContext()->computeAxisAlignmentForHText();
uint32_t mtype = matrix.getType();
// Specialized code for handling the most common case for blink.
if (textEncoding == SkPaint::kGlyphID_TextEncoding
&& textAlignment == SkPaint::kLeft_Align
&& axisAlignment == kX_SkAxisAlignment
&& cache->isSubpixel()
&& mtype <= SkMatrix::kTranslate_Mask)
{
GlyphIdGlyphFinder glyphFinder(cache);
using Positioner =
GlyphFindAndPlaceSubpixel <
ProcessOneGlyph, SkPaint::kLeft_Align, kX_SkAxisAlignment>;
HorizontalPositions hPositions{pos};
ArbitraryPositions aPositions{pos};
PositionReaderInterface* positions = nullptr;
if (scalarsPerPosition == 2) {
positions = &aPositions;
} else {
positions = &hPositions;
}
TranslationMapper mapper{matrix, offset};
Positioner positioner(&glyphFinder);
const char* cursor = text;
const char* stop = text + byteLength;
while (cursor < stop) {
SkPoint mappedPoint = mapper.TranslationMapper::map(positions->nextPoint());
positioner.Positioner::findAndPositionGlyph(
&cursor, mappedPoint, std::forward<ProcessOneGlyph>(processOneGlyph));
}
return;
}
SkSTArenaAlloc<120> arena;
GlyphFinderInterface* glyphFinder = getGlyphFinder(&arena, textEncoding, cache);
PositionReaderInterface* positionReader = nullptr;
if (2 == scalarsPerPosition) {
positionReader = arena.make<ArbitraryPositions>(pos);
} else {
positionReader = arena.make<HorizontalPositions>(pos);
}
MapperInterface* mapper = nullptr;
if (mtype & (SkMatrix::kAffine_Mask | SkMatrix::kPerspective_Mask)
|| scalarsPerPosition == 2) {
mapper = arena.make<GeneralMapper>(matrix, offset);
} else if (mtype & SkMatrix::kScale_Mask) {
mapper = arena.make<XScaleMapper>(matrix, offset);
} else {
mapper = arena.make<TranslationMapper>(matrix, offset);
}
GlyphFindAndPlaceInterface<ProcessOneGlyph>* findAndPosition = nullptr;
if (cache->isSubpixel()) {
switch (textAlignment) {
case SkPaint::kLeft_Align:
findAndPosition = getSubpixel<ProcessOneGlyph, SkPaint::kLeft_Align>(
&arena, axisAlignment, glyphFinder);
break;
case SkPaint::kCenter_Align:
findAndPosition = getSubpixel<ProcessOneGlyph, SkPaint::kCenter_Align>(
&arena, axisAlignment, glyphFinder);
break;
case SkPaint::kRight_Align:
findAndPosition = getSubpixel<ProcessOneGlyph, SkPaint::kRight_Align>(
&arena, axisAlignment, glyphFinder);
break;
}
} else {
switch (textAlignment) {
case SkPaint::kLeft_Align:
findAndPosition = arena.make<
GlyphFindAndPlaceFullPixel<ProcessOneGlyph,
SkPaint::kLeft_Align, kNoKerning>>(glyphFinder);
break;
case SkPaint::kCenter_Align:
findAndPosition = arena.make<
GlyphFindAndPlaceFullPixel<ProcessOneGlyph,
SkPaint::kCenter_Align, kNoKerning>>(glyphFinder);
break;
case SkPaint::kRight_Align:
findAndPosition = arena.make<
GlyphFindAndPlaceFullPixel<ProcessOneGlyph,
SkPaint::kRight_Align, kNoKerning>>(glyphFinder);
break;
}
}
const char* stop = text + byteLength;
while (text < stop) {
SkPoint mappedPoint = mapper->map(positionReader->nextPoint());
findAndPosition->findAndPositionGlyph(
&text, mappedPoint, std::forward<ProcessOneGlyph>(processOneGlyph));
}
}
template<typename ProcessOneGlyph>
inline void SkFindAndPlaceGlyph::ProcessText(
SkPaint::TextEncoding textEncoding, const char text[], size_t byteLength,
SkPoint offset, const SkMatrix& matrix, SkPaint::Align textAlignment,
SkGlyphCache* cache, ProcessOneGlyph&& processOneGlyph) {
SkSTArenaAlloc<64> arena;
// transform the starting point
matrix.mapPoints(&offset, 1);
GlyphFinderInterface* glyphFinder = getGlyphFinder(&arena, textEncoding, cache);
// need to measure first
if (textAlignment != SkPaint::kLeft_Align) {
SkVector stop = MeasureText(glyphFinder, text, byteLength);
if (textAlignment == SkPaint::kCenter_Align) {
stop *= SK_ScalarHalf;
}
offset -= stop;
}
GlyphFindAndPlaceInterface<ProcessOneGlyph>* findAndPosition = nullptr;
if (cache->isSubpixel()) {
SkAxisAlignment axisAlignment = cache->getScalerContext()->computeAxisAlignmentForHText();
findAndPosition = getSubpixel<ProcessOneGlyph, SkPaint::kLeft_Align>(
&arena, axisAlignment, glyphFinder);
} else {
using FullPixel =
GlyphFindAndPlaceFullPixel<ProcessOneGlyph, SkPaint::kLeft_Align, kUseKerning>;
findAndPosition = arena.make<FullPixel>(glyphFinder);
}
const char* stop = text + byteLength;
SkPoint current = offset;
while (text < stop) {
current =
findAndPosition->findAndPositionGlyph(
&text, current, std::forward<ProcessOneGlyph>(processOneGlyph));
}
}
#endif // SkFindAndPositionGlyph_DEFINED
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