HarfBuzzNGFaceSkia.cpp revision 2a4db1327ea4ccf9592eb4d842ec7db5d5ed59f2 
1/*
2 * Copyright (c) 2012 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
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28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
29 */
30
31#define LOG_TAG "TextLayoutCache"
32
33#include "HarfBuzzNGFaceSkia.h"
34
35#include <stdlib.h>
36#include <cutils/log.h>
37#include <SkPaint.h>
38#include <SkPath.h>
39#include <SkPoint.h>
40#include <SkRect.h>
41#include <SkTypeface.h>
42#include <SkUtils.h>
43
44#include <hb.h>
45
46namespace android {
47
48static const bool kDebugGlyphs = false;
49
50// Our implementation of the callbacks which Harfbuzz requires by using Skia
51// calls. See the Harfbuzz source for references about what these callbacks do.
52
53struct HarfBuzzFontData {
54    HarfBuzzFontData(SkPaint* paint) : m_paint(paint) { }
55    SkPaint* m_paint;
56};
57
58static void SkiaGetGlyphWidthAndExtents(SkPaint* paint, hb_codepoint_t codepoint, hb_position_t* width, hb_glyph_extents_t* extents)
59{
60    ALOG_ASSERT(codepoint <= 0xFFFF);
61    paint->setTextEncoding(SkPaint::kGlyphID_TextEncoding);
62
63    SkScalar skWidth;
64    SkRect skBounds;
65    uint16_t glyph = codepoint;
66
67    paint->getTextWidths(&glyph, sizeof(glyph), &skWidth, &skBounds);
68    if (kDebugGlyphs) {
69        ALOGD("returned glyph for %i: width = %f", codepoint, skWidth);
70    }
71    if (width)
72        *width = SkScalarToHBFixed(skWidth);
73    if (extents) {
74        // Invert y-axis because Skia is y-grows-down but we set up harfbuzz to be y-grows-up.
75        extents->x_bearing = SkScalarToHBFixed(skBounds.fLeft);
76        extents->y_bearing = SkScalarToHBFixed(-skBounds.fTop);
77        extents->width = SkScalarToHBFixed(skBounds.width());
78        extents->height = SkScalarToHBFixed(-skBounds.height());
79    }
80}
81
82static hb_bool_t harfbuzzGetGlyph(hb_font_t* hbFont, void* fontData, hb_codepoint_t unicode, hb_codepoint_t variationSelector, hb_codepoint_t* glyph, void* userData)
83{
84    HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
85
86    if (unicode > 0x10ffff) {
87        unicode = 0xfffd;
88    }
89    SkPaint* paint = hbFontData->m_paint;
90    // It would be better to use kUTF32_TextEncoding directly
91    paint->setTextEncoding(SkPaint::kUTF16_TextEncoding);
92    uint16_t glyph16;
93    uint16_t unichar[2];
94    size_t size = SkUTF16_FromUnichar(unicode, unichar);
95    paint->textToGlyphs(unichar, size * sizeof(*unichar), &glyph16);
96    *glyph = glyph16;
97    return !!*glyph;
98}
99
100static hb_position_t harfbuzzGetGlyphHorizontalAdvance(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, void* userData)
101{
102    HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
103    hb_position_t advance = 0;
104
105    SkiaGetGlyphWidthAndExtents(hbFontData->m_paint, glyph, &advance, 0);
106    return advance;
107}
108
109static hb_bool_t harfbuzzGetGlyphHorizontalOrigin(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, hb_position_t* x, hb_position_t* y, void* userData)
110{
111    // Just return true, following the way that Harfbuzz-FreeType
112    // implementation does.
113    return true;
114}
115
116static hb_bool_t harfbuzzGetGlyphExtents(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, hb_glyph_extents_t* extents, void* userData)
117{
118    HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
119
120    SkiaGetGlyphWidthAndExtents(hbFontData->m_paint, glyph, 0, extents);
121    return true;
122}
123
124static hb_font_funcs_t* harfbuzzSkiaGetFontFuncs()
125{
126    static hb_font_funcs_t* harfbuzzSkiaFontFuncs = 0;
127
128    // We don't set callback functions which we can't support.
129    // Harfbuzz will use the fallback implementation if they aren't set.
130    if (!harfbuzzSkiaFontFuncs) {
131        harfbuzzSkiaFontFuncs = hb_font_funcs_create();
132        hb_font_funcs_set_glyph_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyph, 0, 0);
133        hb_font_funcs_set_glyph_h_advance_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyphHorizontalAdvance, 0, 0);
134        hb_font_funcs_set_glyph_h_origin_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyphHorizontalOrigin, 0, 0);
135        hb_font_funcs_set_glyph_extents_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyphExtents, 0, 0);
136        hb_font_funcs_make_immutable(harfbuzzSkiaFontFuncs);
137    }
138    return harfbuzzSkiaFontFuncs;
139}
140
141hb_blob_t* harfbuzzSkiaReferenceTable(hb_face_t* face, hb_tag_t tag, void* userData)
142{
143    SkTypeface* typeface = reinterpret_cast<SkTypeface*>(userData);
144
145    const size_t tableSize = typeface->getTableSize(tag);
146    if (!tableSize)
147        return 0;
148
149    char* buffer = reinterpret_cast<char*>(malloc(tableSize));
150    if (!buffer)
151        return 0;
152    size_t actualSize = typeface->getTableData(tag, 0, tableSize, buffer);
153    if (tableSize != actualSize) {
154        free(buffer);
155        return 0;
156    }
157
158    return hb_blob_create(const_cast<char*>(buffer), tableSize,
159                          HB_MEMORY_MODE_WRITABLE, buffer, free);
160}
161
162static void destroyHarfBuzzFontData(void* data) {
163    delete (HarfBuzzFontData*)data;
164}
165
166hb_font_t* createFont(hb_face_t* face, SkPaint* paint, float sizeX, float sizeY) {
167    hb_font_t* font = hb_font_create(face);
168
169    // Note: this needs to be reworked when we do subpixels
170    int x_ppem = floor(sizeX + 0.5);
171    int y_ppem = floor(sizeY + 0.5);
172    hb_font_set_ppem(font, x_ppem, y_ppem);
173    hb_font_set_scale(font, HBFloatToFixed(sizeX), HBFloatToFixed(sizeY));
174
175    HarfBuzzFontData* data = new HarfBuzzFontData(paint);
176    hb_font_set_funcs(font, harfbuzzSkiaGetFontFuncs(), data, destroyHarfBuzzFontData);
177
178    return font;
179}
180
181} // namespace android
182