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      1 /*
      2  * Copyright (c) 2009 Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions are
      6  * met:
      7  *
      8  *     * Redistributions of source code must retain the above copyright
      9  * notice, this list of conditions and the following disclaimer.
     10  *     * Redistributions in binary form must reproduce the above
     11  * copyright notice, this list of conditions and the following disclaimer
     12  * in the documentation and/or other materials provided with the
     13  * distribution.
     14  *     * Neither the name of Google Inc. nor the names of its
     15  * contributors may be used to endorse or promote products derived from
     16  * this software without specific prior written permission.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
     21  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
     22  * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     23  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
     24  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
     28  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #include "config.h"
     32 
     33 #include "FontPlatformData.h"
     34 #include "wtf/OwnArrayPtr.h"
     35 
     36 #include "SkFontHost.h"
     37 #include "SkPaint.h"
     38 #include "SkPath.h"
     39 #include "SkPoint.h"
     40 #include "SkRect.h"
     41 
     42 extern "C" {
     43 #include "harfbuzz-shaper.h"
     44 }
     45 
     46 // This file implements the callbacks which Harfbuzz requires by using Skia
     47 // calls. See the Harfbuzz source for references about what these callbacks do.
     48 
     49 namespace WebCore {
     50 
     51 static HB_Fixed SkiaScalarToHarfbuzzFixed(SkScalar value)
     52 {
     53     // HB_Fixed is a 26.6 fixed point format.
     54     return value * 64;
     55 }
     56 
     57 static HB_Bool stringToGlyphs(HB_Font hbFont, const HB_UChar16* characters, hb_uint32 length, HB_Glyph* glyphs, hb_uint32* glyphsSize, HB_Bool isRTL)
     58 {
     59     FontPlatformData* font = reinterpret_cast<FontPlatformData*>(hbFont->userData);
     60     SkPaint paint;
     61 
     62     font->setupPaint(&paint);
     63     paint.setTextEncoding(SkPaint::kUTF16_TextEncoding);
     64     int numGlyphs = paint.textToGlyphs(characters, length * sizeof(uint16_t), reinterpret_cast<uint16_t*>(glyphs));
     65 
     66     // HB_Glyph is 32-bit, but Skia outputs only 16-bit numbers. So our
     67     // |glyphs| array needs to be converted.
     68     for (int i = numGlyphs - 1; i >= 0; --i) {
     69         uint16_t value;
     70         // We use a memcpy to avoid breaking strict aliasing rules.
     71         memcpy(&value, reinterpret_cast<char*>(glyphs) + sizeof(uint16_t) * i, sizeof(uint16_t));
     72         glyphs[i] = value;
     73     }
     74 
     75     *glyphsSize = numGlyphs;
     76     return 1;
     77 }
     78 
     79 static void glyphsToAdvances(HB_Font hbFont, const HB_Glyph* glyphs, hb_uint32 numGlyphs, HB_Fixed* advances, int flags)
     80 {
     81     FontPlatformData* font = reinterpret_cast<FontPlatformData*>(hbFont->userData);
     82     SkPaint paint;
     83 
     84     font->setupPaint(&paint);
     85     paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
     86 
     87     OwnArrayPtr<uint16_t> glyphs16(new uint16_t[numGlyphs]);
     88     if (!glyphs16.get())
     89         return;
     90     for (unsigned i = 0; i < numGlyphs; ++i)
     91         glyphs16[i] = glyphs[i];
     92     paint.getTextWidths(glyphs16.get(), numGlyphs * sizeof(uint16_t), reinterpret_cast<SkScalar*>(advances));
     93 
     94     // The |advances| values which Skia outputs are SkScalars, which are floats
     95     // in Chromium. However, Harfbuzz wants them in 26.6 fixed point format.
     96     // These two formats are both 32-bits long.
     97     for (unsigned i = 0; i < numGlyphs; ++i) {
     98         float value;
     99         // We use a memcpy to avoid breaking strict aliasing rules.
    100         memcpy(&value, reinterpret_cast<char*>(advances) + sizeof(float) * i, sizeof(float));
    101         advances[i] = SkiaScalarToHarfbuzzFixed(value);
    102     }
    103 }
    104 
    105 static HB_Bool canRender(HB_Font hbFont, const HB_UChar16* characters, hb_uint32 length)
    106 {
    107     FontPlatformData* font = reinterpret_cast<FontPlatformData*>(hbFont->userData);
    108     SkPaint paint;
    109 
    110     font->setupPaint(&paint);
    111     paint.setTextEncoding(SkPaint::kUTF16_TextEncoding);
    112 
    113     OwnArrayPtr<uint16_t> glyphs16(new uint16_t[length]);
    114     if (!glyphs16.get())
    115         return 0;
    116     int numGlyphs = paint.textToGlyphs(characters, length * sizeof(uint16_t), glyphs16.get());
    117 
    118     bool canRender = true;
    119     for (int i = 0; i < numGlyphs; ++i) {
    120         if (!glyphs16[i]) {
    121             canRender = false;
    122             break;
    123         }
    124     }
    125 
    126     return canRender;
    127 }
    128 
    129 static HB_Error getOutlinePoint(HB_Font hbFont, HB_Glyph glyph, int flags, hb_uint32 point, HB_Fixed* xPos, HB_Fixed* yPos, hb_uint32* resultingNumPoints)
    130 {
    131     FontPlatformData* font = reinterpret_cast<FontPlatformData*>(hbFont->userData);
    132     SkPaint paint;
    133 
    134     if (flags & HB_ShaperFlag_UseDesignMetrics)
    135         return HB_Err_Invalid_Argument;  // This is requesting pre-hinted positions. We can't support this.
    136 
    137     font->setupPaint(&paint);
    138     paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
    139     uint16_t glyph16 = glyph;
    140     SkPath path;
    141     paint.getTextPath(&glyph16, sizeof(glyph16), 0, 0, &path);
    142     int numPoints = path.getPoints(NULL, 0);
    143     if (point >= numPoints)
    144         return HB_Err_Invalid_SubTable;
    145     SkPoint* points = reinterpret_cast<SkPoint*>(fastMalloc(sizeof(SkPoint) * (point + 1)));
    146     if (!points)
    147         return HB_Err_Invalid_SubTable;
    148     // Skia does let us get a single point from the path.
    149     path.getPoints(points, point + 1);
    150     *xPos = SkiaScalarToHarfbuzzFixed(points[point].fX);
    151     *yPos = SkiaScalarToHarfbuzzFixed(points[point].fY);
    152     *resultingNumPoints = numPoints;
    153     fastFree(points);
    154 
    155     return HB_Err_Ok;
    156 }
    157 
    158 static void getGlyphMetrics(HB_Font hbFont, HB_Glyph glyph, HB_GlyphMetrics* metrics)
    159 {
    160     FontPlatformData* font = reinterpret_cast<FontPlatformData*>(hbFont->userData);
    161     SkPaint paint;
    162 
    163     font->setupPaint(&paint);
    164     paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
    165     uint16_t glyph16 = glyph;
    166     SkScalar width;
    167     SkRect bounds;
    168     paint.getTextWidths(&glyph16, sizeof(glyph16), &width, &bounds);
    169 
    170     metrics->x = SkiaScalarToHarfbuzzFixed(bounds.fLeft);
    171     metrics->y = SkiaScalarToHarfbuzzFixed(bounds.fTop);
    172     metrics->width = SkiaScalarToHarfbuzzFixed(bounds.width());
    173     metrics->height = SkiaScalarToHarfbuzzFixed(bounds.height());
    174 
    175     metrics->xOffset = SkiaScalarToHarfbuzzFixed(width);
    176     // We can't actually get the |y| correct because Skia doesn't export
    177     // the vertical advance. However, nor we do ever render vertical text at
    178     // the moment so it's unimportant.
    179     metrics->yOffset = 0;
    180 }
    181 
    182 static HB_Fixed getFontMetric(HB_Font hbFont, HB_FontMetric metric)
    183 {
    184     FontPlatformData* font = reinterpret_cast<FontPlatformData*>(hbFont->userData);
    185     SkPaint paint;
    186 
    187     font->setupPaint(&paint);
    188     SkPaint::FontMetrics skiaMetrics;
    189     paint.getFontMetrics(&skiaMetrics);
    190 
    191     switch (metric) {
    192     case HB_FontAscent:
    193         return SkiaScalarToHarfbuzzFixed(-skiaMetrics.fAscent);
    194     // We don't support getting the rest of the metrics and Harfbuzz doesn't seem to need them.
    195     default:
    196         return 0;
    197     }
    198 }
    199 
    200 HB_FontClass harfbuzzSkiaClass = {
    201     stringToGlyphs,
    202     glyphsToAdvances,
    203     canRender,
    204     getOutlinePoint,
    205     getGlyphMetrics,
    206     getFontMetric,
    207 };
    208 
    209 HB_Error harfbuzzSkiaGetTable(void* voidface, const HB_Tag tag, HB_Byte* buffer, HB_UInt* len)
    210 {
    211     FontPlatformData* font = reinterpret_cast<FontPlatformData*>(voidface);
    212 
    213     const size_t tableSize = SkFontHost::GetTableSize(font->uniqueID(), tag);
    214     if (!tableSize)
    215         return HB_Err_Invalid_Argument;
    216     // If Harfbuzz specified a NULL buffer then it's asking for the size of the table.
    217     if (!buffer) {
    218         *len = tableSize;
    219         return HB_Err_Ok;
    220     }
    221 
    222     if (*len < tableSize)
    223         return HB_Err_Invalid_Argument;
    224     SkFontHost::GetTableData(font->uniqueID(), tag, 0, tableSize, buffer);
    225     return HB_Err_Ok;
    226 }
    227 
    228 }  // namespace WebCore
    229