Rotate emoji with FreeType.

src/ports/SkFontHost_FreeType.cpp

 /*
  * Copyright 2006 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 "SkAdvancedTypefaceMetrics.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
@@ skipping 179 matching lines @@
     unsigned generateGlyphCount() override;
     uint16_t generateCharToGlyph(SkUnichar uni) override;
     void generateAdvance(SkGlyph* glyph) override;
     void generateMetrics(SkGlyph* glyph) override;
     void generateImage(const SkGlyph& glyph) override;
     void generatePath(const SkGlyph& glyph, SkPath* path) override;
     void generateFontMetrics(SkPaint::FontMetrics*) override;
     SkUnichar generateGlyphToChar(uint16_t glyph) override;
 
 private:
-    FT_Face     fFace;              // reference to shared face in gFaceRecHead
-    FT_Size     fFTSize;            // our own copy
-    FT_Int      fStrikeIndex;
-    FT_F26Dot6  fScaleX, fScaleY;
-    FT_Matrix   fMatrix22;
-    uint32_t    fLoadGlyphFlags;
-    bool        fDoLinearMetrics;
-    bool        fLCDIsVert;
+    FT_Face   fFace;  // Shared face from gFaceRecHead.
+    FT_Size   fFTSize;  // The size on the fFace for this scaler.
+    FT_Int    fStrikeIndex;
 
-    // Need scalar versions for generateFontMetrics
-    SkVector    fScale;
-    SkMatrix    fMatrix22Scalar;
+    /** The rest of the matrix after FreeType handles the size.
+     *  With outline font rasterization this is handled by FreeType with FT_Set_Transform.
+     *  With bitmap only fonts this matrix must be applied to scale the bitmap.
+     */
+    SkMatrix  fMatrix22Scalar;
+    /** Same as fMatrix22Scalar, but in FreeType units and space. */
+    FT_Matrix fMatrix22;
+    /** The actual size requested. */
+    SkVector  fScale;
+
+    uint32_t  fLoadGlyphFlags;
+    bool      fDoLinearMetrics;
+    bool      fLCDIsVert;
 
     FT_Error setupSize();
     void getBBoxForCurrentGlyph(SkGlyph* glyph, FT_BBox* bbox,
                                 bool snapToPixelBoundary = false);
     bool getCBoxForLetter(char letter, FT_BBox* bbox);
     // Caller must lock gFTMutex before calling this function.
     void updateGlyphIfLCD(SkGlyph* glyph);
     // Caller must lock gFTMutex before calling this function.
     // update FreeType2 glyph slot with glyph emboldened
     void emboldenIfNeeded(FT_Face face, FT_GlyphSlot glyph);
@@ skipping 518 matching lines @@
         FT_Error err = FT_Get_Kerning(face, glyphs[i], glyphs[i+1],
                                       FT_KERNING_UNSCALED, &delta);
         if (err) {
             return false;
         }
         adjustments[i] = delta.x;
     }
     return true;
 }
 
+/** Returns the bitmap strike equal to or just larger than the requested size. */
 static FT_Int chooseBitmapStrike(FT_Face face, FT_F26Dot6 scaleY) {
-    // early out if face is bad
     if (face == nullptr) {
-        SkDEBUGF(("chooseBitmapStrike aborted due to nullptr face\n"));
+        SkDEBUGF(("chooseBitmapStrike aborted due to nullptr face.\n"));
         return -1;
     }
-    // determine target ppem
-    FT_Pos targetPPEM = scaleY;
-    // find a bitmap strike equal to or just larger than the requested size
+
+    FT_Pos requestedPPEM = scaleY;  // FT_Bitmap_Size::y_ppem is in 26.6 format.
     FT_Int chosenStrikeIndex = -1;
     FT_Pos chosenPPEM = 0;
     for (FT_Int strikeIndex = 0; strikeIndex < face->num_fixed_sizes; ++strikeIndex) {
-        FT_Pos thisPPEM = face->available_sizes[strikeIndex].y_ppem;
-        if (thisPPEM == targetPPEM) {
+        FT_Pos strikePPEM = face->available_sizes[strikeIndex].y_ppem;
+        if (strikePPEM == requestedPPEM) {
             // exact match - our search stops here
-            chosenPPEM = thisPPEM;
-            chosenStrikeIndex = strikeIndex;
-            break;
-        } else if (chosenPPEM < targetPPEM) {
+            return strikeIndex;
+        } else if (chosenPPEM < requestedPPEM) {
             // attempt to increase chosenPPEM
-            if (thisPPEM > chosenPPEM) {
-                chosenPPEM = thisPPEM;
+            if (chosenPPEM < strikePPEM) {
+                chosenPPEM = strikePPEM;
                 chosenStrikeIndex = strikeIndex;
             }
         } else {
-            // attempt to decrease chosenPPEM, but not below targetPPEM
-            if (thisPPEM < chosenPPEM && thisPPEM > targetPPEM) {
-                chosenPPEM = thisPPEM;
+            // attempt to decrease chosenPPEM, but not below requestedPPEM
+            if (requestedPPEM < strikePPEM && strikePPEM < chosenPPEM) {
+                chosenPPEM = strikePPEM;
                 chosenStrikeIndex = strikeIndex;
             }
         }
     }
-    if (chosenStrikeIndex != -1) {
-        // use the chosen strike
-        FT_Error err = FT_Select_Size(face, chosenStrikeIndex);
-        if (err != 0) {
-            SkDEBUGF(("FT_Select_Size(%s, %d) returned 0x%x\n", face->family_name,
-                      chosenStrikeIndex, err));
-            chosenStrikeIndex = -1;
-        }
-    }
     return chosenStrikeIndex;
 }
 
 SkScalerContext_FreeType::SkScalerContext_FreeType(SkTypeface* typeface,
                                                    const SkScalerContextEffects& effects,
                                                    const SkDescriptor* desc)
     : SkScalerContext_FreeType_Base(typeface, effects, desc)
     , fFace(nullptr)
     , fFTSize(nullptr)
     , fStrikeIndex(-1)
 {
     SkAutoMutexAcquire  ac(gFTMutex);
 
     if (!ref_ft_library()) {
         sk_throw();
     }
 
     // load the font file
     using UnrefFTFace = SkFunctionWrapper<void, skstd::remove_pointer_t<FT_Face>, unref_ft_face>;
     std::unique_ptr<skstd::remove_pointer_t<FT_Face>, UnrefFTFace> ftFace(ref_ft_face(typeface));
     if (nullptr == ftFace) {
         SkDEBUGF(("Could not create FT_Face.\n"));
         return;
     }
 
     fRec.computeMatrices(SkScalerContextRec::kFull_PreMatrixScale, &fScale, &fMatrix22Scalar);
-    fMatrix22Scalar.setSkewX(-fMatrix22Scalar.getSkewX());
-    fMatrix22Scalar.setSkewY(-fMatrix22Scalar.getSkewY());
 
-    fScaleX = SkScalarToFDot6(fScale.fX);
-    fScaleY = SkScalarToFDot6(fScale.fY);
+    FT_F26Dot6 scaleX = SkScalarToFDot6(fScale.fX);
+    FT_F26Dot6 scaleY = SkScalarToFDot6(fScale.fY);
     fMatrix22.xx = SkScalarToFixed(fMatrix22Scalar.getScaleX());
-    fMatrix22.xy = SkScalarToFixed(fMatrix22Scalar.getSkewX());
-    fMatrix22.yx = SkScalarToFixed(fMatrix22Scalar.getSkewY());
+    fMatrix22.xy = SkScalarToFixed(-fMatrix22Scalar.getSkewX());
+    fMatrix22.yx = SkScalarToFixed(-fMatrix22Scalar.getSkewY());
     fMatrix22.yy = SkScalarToFixed(fMatrix22Scalar.getScaleY());
 
     fLCDIsVert = SkToBool(fRec.fFlags & SkScalerContext::kLCD_Vertical_Flag);
 
     // compute the flags we send to Load_Glyph
     bool linearMetrics = SkToBool(fRec.fFlags & SkScalerContext::kSubpixelPositioning_Flag);
     {
         FT_Int32 loadFlags = FT_LOAD_DEFAULT;
 
         if (SkMask::kBW_Format == fRec.fMaskFormat) {
@@ skipping 58 matching lines @@
         loadFlags |= FT_LOAD_COLOR;
 
         fLoadGlyphFlags = loadFlags;
     }
 
     using DoneFTSize = SkFunctionWrapper<FT_Error, skstd::remove_pointer_t<FT_Size>, FT_Done_Size>;
     std::unique_ptr<skstd::remove_pointer_t<FT_Size>, DoneFTSize> ftSize([&ftFace]() -> FT_Size {
         FT_Size size;
         FT_Error err = FT_New_Size(ftFace.get(), &size);
         if (err != 0) {
-            SkDEBUGF(("FT_New_Size returned %x for face %s\n", err, ftFace->family_name));
+            SkDEBUGF(("FT_New_Size(%s) returned 0x%x.\n", ftFace->family_name, err));
             return nullptr;
         }
         return size;
     }());
     if (nullptr == ftSize) {
         SkDEBUGF(("Could not create FT_Size.\n"));
         return;
     }
 
     FT_Error err = FT_Activate_Size(ftSize.get());
     if (err != 0) {
-        SkDEBUGF(("FT_Activate_Size(%08x, 0x%x, 0x%x) returned 0x%x\n",
-                         ftFace.get(), fScaleX,   fScaleY,       err));
+        SkDEBUGF(("FT_Activate_Size(%s) returned 0x%x.\n", ftFace->family_name, err));
         return;
     }
 
     if (FT_IS_SCALABLE(ftFace)) {
-        err = FT_Set_Char_Size(ftFace.get(), fScaleX, fScaleY, 72, 72);
+        err = FT_Set_Char_Size(ftFace.get(), scaleX, scaleY, 72, 72);
         if (err != 0) {
-            SkDEBUGF(("FT_Set_CharSize(%08x, 0x%x, 0x%x) returned 0x%x\n",
-                               ftFace.get(), fScaleX, fScaleY,      err));
+            SkDEBUGF(("FT_Set_CharSize(%s, %f, %f) returned 0x%x.\n",
+                      ftFace->family_name, fScale.fX, fScale.fY, err));
             return;
         }
-        FT_Set_Transform(ftFace.get(), &fMatrix22, nullptr);
     } else if (FT_HAS_FIXED_SIZES(ftFace)) {
-        fStrikeIndex = chooseBitmapStrike(ftFace.get(), fScaleY);
+        fStrikeIndex = chooseBitmapStrike(ftFace.get(), scaleY);
         if (fStrikeIndex == -1) {
-            SkDEBUGF(("no glyphs for font \"%s\" size %f?\n",
-                            ftFace->family_name,      SkFDot6ToScalar(fScaleY)));
-        } else {
-            // FreeType does no provide linear metrics for bitmap fonts.
-            linearMetrics = false;
+            SkDEBUGF(("No glyphs for font \"%s\" size %f.\n", ftFace->family_name, fScale.fY));
+            return;
+        }
 
-            // FreeType documentation says:
-            // FT_LOAD_NO_BITMAP -- Ignore bitmap strikes when loading.
-            // Bitmap-only fonts ignore this flag.
-            //
-            // However, in FreeType 2.5.1 color bitmap only fonts do not ignore this flag.
-            // Force this flag off for bitmap only fonts.
-            fLoadGlyphFlags &= ~FT_LOAD_NO_BITMAP;
+        err = FT_Select_Size(ftFace.get(), fStrikeIndex);
+        if (err != 0) {
+            SkDEBUGF(("FT_Select_Size(%s, %d) returned 0x%x.\n",
+                      ftFace->family_name, fStrikeIndex, err));
+            fStrikeIndex = -1;
+            return;
         }
+
+        // A non-ideal size was picked, so recompute the matrix.
+        // This adjusts for the difference between FT_Set_Char_Size and FT_Select_Size.
+        fMatrix22Scalar.preScale(fScale.x() / ftFace->size->metrics.x_ppem,
+                                 fScale.y() / ftFace->size->metrics.y_ppem);
+        fMatrix22.xx = SkScalarToFixed(fMatrix22Scalar.getScaleX());
+        fMatrix22.xy = SkScalarToFixed(-fMatrix22Scalar.getSkewX());
+        fMatrix22.yx = SkScalarToFixed(-fMatrix22Scalar.getSkewY());
+        fMatrix22.yy = SkScalarToFixed(fMatrix22Scalar.getScaleY());
+
+        // FreeType does not provide linear metrics for bitmap fonts.
+        linearMetrics = false;
+
+        // FreeType documentation says:
+        // FT_LOAD_NO_BITMAP -- Ignore bitmap strikes when loading.
+        // Bitmap-only fonts ignore this flag.
+        //
+        // However, in FreeType 2.5.1 color bitmap only fonts do not ignore this flag.
+        // Force this flag off for bitmap only fonts.
+        fLoadGlyphFlags &= ~FT_LOAD_NO_BITMAP;
     } else {
-        SkDEBUGF(("unknown kind of font \"%s\" size %f?\n",
-                            fFace->family_name,     SkFDot6ToScalar(fScaleY)));
+        SkDEBUGF(("Unknown kind of font \"%s\" size %f.\n", fFace->family_name, fScale.fY));
+        return;
     }
 
     fFTSize = ftSize.release();
     fFace = ftFace.release();
     fDoLinearMetrics = linearMetrics;
 }
 
 SkScalerContext_FreeType::~SkScalerContext_FreeType() {
     SkAutoMutexAcquire  ac(gFTMutex);
 
     if (fFTSize != nullptr) {
         FT_Done_Size(fFTSize);
     }
 
     if (fFace != nullptr) {
         unref_ft_face(fFace);
     }
 
     unref_ft_library();
 }
 
 /*  We call this before each use of the fFace, since we may be sharing
     this face with other context (at different sizes).
 */
 FT_Error SkScalerContext_FreeType::setupSize() {
     gFTMutex.assertHeld();
     FT_Error err = FT_Activate_Size(fFTSize);
     if (err != 0) {
-        SkDEBUGF(("SkScalerContext_FreeType::FT_Activate_Size(%s %s, 0x%x, 0x%x) returned 0x%x\n",
-                  fFace->family_name, fFace->style_name, fScaleX, fScaleY, err));
-        fFTSize = nullptr;
         return err;
     }
-
-    // seems we need to reset this every time (not sure why, but without it
-    // I get random italics from some other fFTSize)
     FT_Set_Transform(fFace, &fMatrix22, nullptr);
     return 0;
 }
 
 unsigned SkScalerContext_FreeType::generateGlyphCount() {
     return fFace->num_glyphs;
 }
 
 uint16_t SkScalerContext_FreeType::generateCharToGlyph(SkUnichar uni) {
     SkAutoMutexAcquire  ac(gFTMutex);
@@ skipping 36 matching lines @@
         FT_Fixed    advance;
 
         error = FT_Get_Advance( fFace, glyph->getGlyphID(),
                                 fLoadGlyphFlags | FT_ADVANCE_FLAG_FAST_ONLY,
                                 &advance );
         if (0 == error) {
             glyph->fRsbDelta = 0;
             glyph->fLsbDelta = 0;
             const SkScalar advanceScalar = SkFT_FixedToScalar(advance);
             glyph->fAdvanceX = SkScalarToFloat(fMatrix22Scalar.getScaleX() * advanceScalar);
-            glyph->fAdvanceY = -SkScalarToFloat(fMatrix22Scalar.getSkewY() * advanceScalar);
+            glyph->fAdvanceY = SkScalarToFloat(fMatrix22Scalar.getSkewY() * advanceScalar);
             return;
         }
     }
 
     /* otherwise, we need to load/hint the glyph, which is slower */
     this->generateMetrics(glyph);
     return;
 }
 
 void SkScalerContext_FreeType::getBBoxForCurrentGlyph(SkGlyph* glyph,
@@ skipping 53 matching lines @@
         if (fLCDIsVert) {
             glyph->fHeight += gFTLibrary->lcdExtra();
             glyph->fTop -= gFTLibrary->lcdExtra() >> 1;
         } else {
             glyph->fWidth += gFTLibrary->lcdExtra();
             glyph->fLeft -= gFTLibrary->lcdExtra() >> 1;
         }
     }
 }
 
-inline void scaleGlyphMetrics(SkGlyph& glyph, SkScalar scale) {
-    glyph.fWidth *= scale;
-    glyph.fHeight *= scale;
-    glyph.fTop *= scale;
-    glyph.fLeft *= scale;
-
-    float floatScale = SkScalarToFloat(scale);
-    glyph.fAdvanceX *= floatScale;
-    glyph.fAdvanceY *= floatScale;
-}
-
 void SkScalerContext_FreeType::generateMetrics(SkGlyph* glyph) {
     SkAutoMutexAcquire  ac(gFTMutex);
 
     glyph->fRsbDelta = 0;
     glyph->fLsbDelta = 0;
 
     FT_Error    err;
 
     if (this->setupSize()) {
         glyph->zeroMetrics();
@@ skipping 34 matching lines @@
             vector.y = -fFace->glyph->metrics.vertBearingY - fFace->glyph->metrics.horiBearingY;
             FT_Vector_Transform(&vector, &fMatrix22);
             fFace->glyph->bitmap_left += SkFDot6Floor(vector.x);
             fFace->glyph->bitmap_top  += SkFDot6Floor(vector.y);
         }
 
         if (fFace->glyph->bitmap.pixel_mode == FT_PIXEL_MODE_BGRA) {
             glyph->fMaskFormat = SkMask::kARGB32_Format;
         }
 
-        glyph->fWidth   = SkToU16(fFace->glyph->bitmap.width);
-        glyph->fHeight  = SkToU16(fFace->glyph->bitmap.rows);
-        glyph->fTop     = -SkToS16(fFace->glyph->bitmap_top);
-        glyph->fLeft    = SkToS16(fFace->glyph->bitmap_left);
+        {
+            SkRect rect = SkRect::MakeXYWH(SkIntToScalar(fFace->glyph->bitmap_left),
+                                          -SkIntToScalar(fFace->glyph->bitmap_top),
+                                           SkIntToScalar(fFace->glyph->bitmap.width),
+                                           SkIntToScalar(fFace->glyph->bitmap.rows));
+            fMatrix22Scalar.mapRect(&rect);
+            SkIRect irect = rect.roundOut();
+            glyph->fWidth   = SkToU16(irect.width());
+            glyph->fHeight  = SkToU16(irect.height());
+            glyph->fTop     = SkToS16(irect.top());
+            glyph->fLeft    = SkToS16(irect.left());
+        }
         break;
 
       default:
         SkDEBUGFAIL("unknown glyph format");
         glyph->zeroMetrics();
         return;
     }
 
     if (fRec.fFlags & SkScalerContext::kVertical_Flag) {
         if (fDoLinearMetrics) {
             const SkScalar advanceScalar = SkFT_FixedToScalar(fFace->glyph->linearVertAdvance);
-            glyph->fAdvanceX = -SkScalarToFloat(fMatrix22Scalar.getSkewX() * advanceScalar);
+            glyph->fAdvanceX = SkScalarToFloat(fMatrix22Scalar.getSkewX() * advanceScalar);
             glyph->fAdvanceY = SkScalarToFloat(fMatrix22Scalar.getScaleY() * advanceScalar);
         } else {
             glyph->fAdvanceX = -SkFDot6ToFloat(fFace->glyph->advance.x);
             glyph->fAdvanceY = SkFDot6ToFloat(fFace->glyph->advance.y);
         }
     } else {
         if (fDoLinearMetrics) {
             const SkScalar advanceScalar = SkFT_FixedToScalar(fFace->glyph->linearHoriAdvance);
             glyph->fAdvanceX = SkScalarToFloat(fMatrix22Scalar.getScaleX() * advanceScalar);
-            glyph->fAdvanceY = -SkScalarToFloat(fMatrix22Scalar.getSkewY() * advanceScalar);
+            glyph->fAdvanceY = SkScalarToFloat(fMatrix22Scalar.getSkewY() * advanceScalar);
         } else {
             glyph->fAdvanceX = SkFDot6ToFloat(fFace->glyph->advance.x);
             glyph->fAdvanceY = -SkFDot6ToFloat(fFace->glyph->advance.y);
 
             if (fRec.fFlags & kDevKernText_Flag) {
                 glyph->fRsbDelta = SkToS8(fFace->glyph->rsb_delta);
                 glyph->fLsbDelta = SkToS8(fFace->glyph->lsb_delta);
             }
         }
     }
 
-    // If the font isn't scalable, scale the metrics from the non-scalable strike.
-    // This means do not try to scale embedded bitmaps; only scale bitmaps in bitmap only fonts.
-    if (!FT_IS_SCALABLE(fFace) && !SkScalarNearlyZero(fScale.fY) && fFace->size->metrics.y_ppem) {
-        // NOTE: both dimensions are scaled by y_ppem. this is WAI.
-        scaleGlyphMetrics(*glyph, fScale.fY / fFace->size->metrics.y_ppem);
-    }
-
 #ifdef ENABLE_GLYPH_SPEW
-    SkDEBUGF(("FT_Set_Char_Size(this:%p sx:%x sy:%x ", this, fScaleX, fScaleY));
     SkDEBUGF(("Metrics(glyph:%d flags:0x%x) w:%d\n", glyph->getGlyphID(), fLoadGlyphFlags, glyph->fWidth));
 #endif
 }
 
 static void clear_glyph_image(const SkGlyph& glyph) {
     sk_bzero(glyph.fImage, glyph.rowBytes() * glyph.fHeight);
 }
 
 void SkScalerContext_FreeType::generateImage(const SkGlyph& glyph) {
     SkAutoMutexAcquire  ac(gFTMutex);
 
     if (this->setupSize()) {
         clear_glyph_image(glyph);
         return;
     }
 
     FT_Error err = FT_Load_Glyph(fFace, glyph.getGlyphID(), fLoadGlyphFlags);
     if (err != 0) {
         SkDEBUGF(("SkScalerContext_FreeType::generateImage: FT_Load_Glyph(glyph:%d width:%d height:%d rb:%d flags:%d) returned 0x%x\n",
                   glyph.getGlyphID(), glyph.fWidth, glyph.fHeight, glyph.rowBytes(), fLoadGlyphFlags, err));
         clear_glyph_image(glyph);
         return;
     }
 
     emboldenIfNeeded(fFace, fFace->glyph);
-    generateGlyphImage(fFace, glyph);
+    generateGlyphImage(fFace, glyph, fMatrix22Scalar);
 }
 
 
 void SkScalerContext_FreeType::generatePath(const SkGlyph& glyph, SkPath* path) {
     SkAutoMutexAcquire  ac(gFTMutex);
 
     SkASSERT(path);
 
     if (this->setupSize()) {
         path->reset();
@@ skipping 35 matching lines @@
     SkAutoMutexAcquire ac(gFTMutex);
 
     if (this->setupSize()) {
         sk_bzero(metrics, sizeof(*metrics));
         return;
     }
 
     FT_Face face = fFace;
     SkScalar scaleX = fScale.x();
     SkScalar scaleY = fScale.y();
-    SkScalar mxy = fMatrix22Scalar.getSkewX() * scaleY;
+    SkScalar mxy = -fMatrix22Scalar.getSkewX() * scaleY;
     SkScalar myy = fMatrix22Scalar.getScaleY() * scaleY;
 
     // fetch units/EM from "head" table if needed (ie for bitmap fonts)
     SkScalar upem = SkIntToScalar(face->units_per_EM);
     if (!upem) {
         TT_Header* ttHeader = (TT_Header*)FT_Get_Sfnt_Table(face, ft_sfnt_head);
         if (ttHeader) {
             upem = SkIntToScalar(ttHeader->Units_Per_EM);
         }
     }
@@ skipping 501 matching lines @@
                 SkDEBUGF(("Requested font axis not found: %s '%c%c%c%c'\n",
                           name.c_str(),
                           (skTag >> 24) & 0xFF,
                           (skTag >> 16) & 0xFF,
                           (skTag >>  8) & 0xFF,
                           (skTag)       & 0xFF));
             }
         }
     )
 }