HarfBuzzNGFaceSkia.cpp revision 177612335aa5df21d8c21125608413d02289a6b3 
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
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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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 <cutils/log.h>
36#include <SkPaint.h>
37#include <SkPath.h>
38#include <SkPoint.h>
39#include <SkRect.h>
40#include <SkTypeface.h>
41#include <SkUtils.h>
42
43#include <hb.h>
44
45namespace android {
46
47static const bool kDebugGlyphs = false;
48
49// Our implementation of the callbacks which Harfbuzz requires by using Skia
50// calls. See the Harfbuzz source for references about what these callbacks do.
51
52struct HarfBuzzFontData {
53    HarfBuzzFontData(SkPaint* paint) : m_paint(paint) { }
54    SkPaint* m_paint;
55};
56
57static void SkiaGetGlyphWidthAndExtents(SkPaint* paint, hb_codepoint_t codepoint, hb_position_t* width, hb_glyph_extents_t* extents)
58{
59    ALOG_ASSERT(codepoint <= 0xFFFF);
60    paint->setTextEncoding(SkPaint::kGlyphID_TextEncoding);
61
62    SkScalar skWidth;
63    SkRect skBounds;
64    uint16_t glyph = codepoint;
65
66    paint->getTextWidths(&glyph, sizeof(glyph), &skWidth, &skBounds);
67    if (kDebugGlyphs) {
68        ALOGD("returned glyph for %i: width = %f", codepoint, skWidth);
69    }
70    if (width)
71        *width = SkScalarToHBFixed(skWidth);
72    if (extents) {
73        // Invert y-axis because Skia is y-grows-down but we set up harfbuzz to be y-grows-up.
74        extents->x_bearing = SkScalarToHBFixed(skBounds.fLeft);
75        extents->y_bearing = SkScalarToHBFixed(-skBounds.fTop);
76        extents->width = SkScalarToHBFixed(skBounds.width());
77        extents->height = SkScalarToHBFixed(-skBounds.height());
78    }
79}
80
81static hb_bool_t harfbuzzGetGlyph(hb_font_t* hbFont, void* fontData, hb_codepoint_t unicode, hb_codepoint_t variationSelector, hb_codepoint_t* glyph, void* userData)
82{
83    HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
84
85    if (unicode > 0x10ffff) {
86        unicode = 0xfffd;
87    }
88    SkPaint* paint = hbFontData->m_paint;
89    // It would be better to use kUTF32_TextEncoding directly
90    paint->setTextEncoding(SkPaint::kUTF16_TextEncoding);
91    uint16_t glyph16;
92    uint16_t unichar[2];
93    size_t size = SkUTF16_FromUnichar(unicode, unichar);
94    paint->textToGlyphs(unichar, size * sizeof(*unichar), &glyph16);
95    *glyph = glyph16;
96    return !!*glyph;
97}
98
99static hb_position_t harfbuzzGetGlyphHorizontalAdvance(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, void* userData)
100{
101    HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
102    hb_position_t advance = 0;
103
104    SkiaGetGlyphWidthAndExtents(hbFontData->m_paint, glyph, &advance, 0);
105    return advance;
106}
107
108static hb_bool_t harfbuzzGetGlyphHorizontalOrigin(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, hb_position_t* x, hb_position_t* y, void* userData)
109{
110    // Just return true, following the way that Harfbuzz-FreeType
111    // implementation does.
112    return true;
113}
114
115static hb_bool_t harfbuzzGetGlyphExtents(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, hb_glyph_extents_t* extents, void* userData)
116{
117    HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
118
119    SkiaGetGlyphWidthAndExtents(hbFontData->m_paint, glyph, 0, extents);
120    return true;
121}
122
123static hb_font_funcs_t* harfbuzzSkiaGetFontFuncs()
124{
125    static hb_font_funcs_t* harfbuzzSkiaFontFuncs = 0;
126
127    // We don't set callback functions which we can't support.
128    // Harfbuzz will use the fallback implementation if they aren't set.
129    if (!harfbuzzSkiaFontFuncs) {
130        harfbuzzSkiaFontFuncs = hb_font_funcs_create();
131        hb_font_funcs_set_glyph_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyph, 0, 0);
132        hb_font_funcs_set_glyph_h_advance_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyphHorizontalAdvance, 0, 0);
133        hb_font_funcs_set_glyph_h_origin_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyphHorizontalOrigin, 0, 0);
134        hb_font_funcs_set_glyph_extents_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyphExtents, 0, 0);
135        hb_font_funcs_make_immutable(harfbuzzSkiaFontFuncs);
136    }
137    return harfbuzzSkiaFontFuncs;
138}
139
140hb_blob_t* harfbuzzSkiaReferenceTable(hb_face_t* face, hb_tag_t tag, void* userData)
141{
142    SkTypeface* typeface = reinterpret_cast<SkTypeface*>(userData);
143
144    const size_t tableSize = typeface->getTableSize(tag);
145    if (!tableSize)
146        return 0;
147
148    char* buffer = reinterpret_cast<char*>(malloc(tableSize));
149    if (!buffer)
150        return 0;
151    size_t actualSize = typeface->getTableData(tag, 0, tableSize, buffer);
152    if (tableSize != actualSize) {
153        free(buffer);
154        return 0;
155    }
156
157    return hb_blob_create(const_cast<char*>(buffer), tableSize,
158                          HB_MEMORY_MODE_WRITABLE, buffer, free);
159}
160
161static void destroyHarfBuzzFontData(void* data) {
162    delete (HarfBuzzFontData*)data;
163}
164
165hb_font_t* createFont(hb_face_t* face, SkPaint* paint, float sizeX, float sizeY) {
166    hb_font_t* font = hb_font_create(face);
167
168    // Note: this needs to be reworked when we do subpixels
169    int x_ppem = floor(sizeX + 0.5);
170    int y_ppem = floor(sizeY + 0.5);
171    hb_font_set_ppem(font, x_ppem, y_ppem);
172    hb_font_set_scale(font, HBFloatToFixed(sizeX), HBFloatToFixed(sizeY));
173
174    HarfBuzzFontData* data = new HarfBuzzFontData(paint);
175    hb_font_set_funcs(font, harfbuzzSkiaGetFontFuncs(), data, destroyHarfBuzzFontData);
176
177    return font;
178}
179
180} // namespace android
181