HarfBuzzNGFaceSkia.cpp revision aaedde51b76901ff05f2a2348eb41f0f5323d954 
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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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#define LOG_TAG "TextLayoutCache"
32
33#include "HarfBuzzNGFaceSkia.h"
34
35#include <cutils/log.h>
36#include <SkFontHost.h>
37#include <SkPaint.h>
38#include <SkPath.h>
39#include <SkPoint.h>
40#include <SkRect.h>
41#include <SkUtils.h>
42
43#include <hb.h>
44
45namespace android {
46
47// Our implementation of the callbacks which Harfbuzz requires by using Skia
48// calls. See the Harfbuzz source for references about what these callbacks do.
49
50struct HarfBuzzFontData {
51    HarfBuzzFontData(SkPaint* paint) : m_paint(paint) { }
52    SkPaint* m_paint;
53};
54
55static void SkiaGetGlyphWidthAndExtents(SkPaint* paint, hb_codepoint_t codepoint, hb_position_t* width, hb_glyph_extents_t* extents)
56{
57    ALOG_ASSERT(codepoint <= 0xFFFF);
58    paint->setTextEncoding(SkPaint::kGlyphID_TextEncoding);
59
60    SkScalar skWidth;
61    SkRect skBounds;
62    uint16_t glyph = codepoint;
63
64    paint->getTextWidths(&glyph, sizeof(glyph), &skWidth, &skBounds);
65    ALOGD("returned glyph for %i: width = %f", codepoint, skWidth);
66    if (width)
67        *width = SkScalarToHBFixed(skWidth);
68    if (extents) {
69        // Invert y-axis because Skia is y-grows-down but we set up harfbuzz to be y-grows-up.
70        extents->x_bearing = SkScalarToHBFixed(skBounds.fLeft);
71        extents->y_bearing = SkScalarToHBFixed(-skBounds.fTop);
72        extents->width = SkScalarToHBFixed(skBounds.width());
73        extents->height = SkScalarToHBFixed(-skBounds.height());
74    }
75}
76
77static hb_bool_t harfbuzzGetGlyph(hb_font_t* hbFont, void* fontData, hb_codepoint_t unicode, hb_codepoint_t variationSelector, hb_codepoint_t* glyph, void* userData)
78{
79    HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
80
81    if (unicode > 0x10ffff) {
82        unicode = 0xfffd;
83    }
84    SkPaint* paint = hbFontData->m_paint;
85    // It would be better to use kUTF32_TextEncoding directly
86    paint->setTextEncoding(SkPaint::kUTF16_TextEncoding);
87    uint16_t glyph16;
88    uint16_t unichar[2];
89    size_t size = SkUTF16_FromUnichar(unicode, unichar);
90    paint->textToGlyphs(unichar, size * sizeof(*unichar), &glyph16);
91    *glyph = glyph16;
92    return !!*glyph;
93}
94
95static hb_position_t harfbuzzGetGlyphHorizontalAdvance(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, void* userData)
96{
97    HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
98    hb_position_t advance = 0;
99
100    SkiaGetGlyphWidthAndExtents(hbFontData->m_paint, glyph, &advance, 0);
101    return advance;
102}
103
104static hb_bool_t harfbuzzGetGlyphHorizontalOrigin(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, hb_position_t* x, hb_position_t* y, void* userData)
105{
106    // Just return true, following the way that Harfbuzz-FreeType
107    // implementation does.
108    return true;
109}
110
111static hb_bool_t harfbuzzGetGlyphExtents(hb_font_t* hbFont, void* fontData, hb_codepoint_t glyph, hb_glyph_extents_t* extents, void* userData)
112{
113    HarfBuzzFontData* hbFontData = reinterpret_cast<HarfBuzzFontData*>(fontData);
114
115    SkiaGetGlyphWidthAndExtents(hbFontData->m_paint, glyph, 0, extents);
116    return true;
117}
118
119static hb_font_funcs_t* harfbuzzSkiaGetFontFuncs()
120{
121    static hb_font_funcs_t* harfbuzzSkiaFontFuncs = 0;
122
123    // We don't set callback functions which we can't support.
124    // Harfbuzz will use the fallback implementation if they aren't set.
125    if (!harfbuzzSkiaFontFuncs) {
126        harfbuzzSkiaFontFuncs = hb_font_funcs_create();
127        hb_font_funcs_set_glyph_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyph, 0, 0);
128        hb_font_funcs_set_glyph_h_advance_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyphHorizontalAdvance, 0, 0);
129        hb_font_funcs_set_glyph_h_origin_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyphHorizontalOrigin, 0, 0);
130        hb_font_funcs_set_glyph_extents_func(harfbuzzSkiaFontFuncs, harfbuzzGetGlyphExtents, 0, 0);
131        hb_font_funcs_make_immutable(harfbuzzSkiaFontFuncs);
132    }
133    return harfbuzzSkiaFontFuncs;
134}
135
136hb_blob_t* harfbuzzSkiaReferenceTable(hb_face_t* face, hb_tag_t tag, void* userData)
137{
138    SkTypeface* typeface = reinterpret_cast<SkTypeface*>(userData);
139    SkFontID uniqueID = typeface->uniqueID();
140
141    const size_t tableSize = SkFontHost::GetTableSize(uniqueID, tag);
142    if (!tableSize)
143        return 0;
144
145    char* buffer = reinterpret_cast<char*>(malloc(tableSize));
146    if (!buffer)
147        return 0;
148    size_t actualSize = SkFontHost::GetTableData(uniqueID, tag, 0, tableSize, buffer);
149    if (tableSize != actualSize) {
150        free(buffer);
151        return 0;
152    }
153
154    return hb_blob_create(const_cast<char*>(buffer), tableSize,
155                          HB_MEMORY_MODE_WRITABLE, buffer, free);
156}
157
158static void destroyHarfBuzzFontData(void* data) {
159    delete (HarfBuzzFontData*)data;
160}
161
162hb_font_t* createFont(hb_face_t* face, SkPaint* paint, float sizeX, float sizeY) {
163    hb_font_t* font = hb_font_create(face);
164
165    // Note: this needs to be reworked when we do subpixels
166    int x_ppem = floor(sizeX + 0.5);
167    int y_ppem = floor(sizeY + 0.5);
168    hb_font_set_ppem(font, x_ppem, y_ppem);
169    hb_font_set_scale(font, HBFloatToFixed(sizeX), HBFloatToFixed(sizeY));
170
171    HarfBuzzFontData* data = new HarfBuzzFontData(paint);
172    hb_font_set_funcs(font, harfbuzzSkiaGetFontFuncs(), data, destroyHarfBuzzFontData);
173
174    return font;
175}
176
177} // namespace android
178