1
2/*
3 * Copyright 2009 The Android Open Source Project
4 *
5 * Use of this source code is governed by a BSD-style license that can be
6 * found in the LICENSE file.
7 */
8
9
10#include "SkHarfBuzzFont.h"
11#include "SkFontHost.h"
12#include "SkPaint.h"
13#include "SkPath.h"
14
15// HB_Fixed is a 26.6 fixed point format.
16static inline HB_Fixed SkScalarToHarfbuzzFixed(SkScalar value) {
17#ifdef SK_SCALAR_IS_FLOAT
18    return static_cast<HB_Fixed>(value * 64);
19#else
20    // convert .16 to .6
21    return value >> (16 - 6);
22#endif
23}
24
25static HB_Bool stringToGlyphs(HB_Font hbFont, const HB_UChar16* characters,
26                              hb_uint32 length, HB_Glyph* glyphs,
27                              hb_uint32* glyphsSize, HB_Bool isRTL) {
28    SkHarfBuzzFont* font = reinterpret_cast<SkHarfBuzzFont*>(hbFont->userData);
29    SkPaint paint;
30
31    paint.setTypeface(font->getTypeface());
32    paint.setTextEncoding(SkPaint::kUTF16_TextEncoding);
33    int numGlyphs = paint.textToGlyphs(characters, length * sizeof(uint16_t),
34                                       reinterpret_cast<uint16_t*>(glyphs));
35
36    // HB_Glyph is 32-bit, but Skia outputs only 16-bit numbers. So our
37    // |glyphs| array needs to be converted.
38    for (int i = numGlyphs - 1; i >= 0; --i) {
39        uint16_t value;
40        // We use a memcpy to avoid breaking strict aliasing rules.
41        memcpy(&value, reinterpret_cast<char*>(glyphs) + sizeof(uint16_t) * i, sizeof(uint16_t));
42        glyphs[i] = value;
43    }
44
45    *glyphsSize = numGlyphs;
46    return 1;
47}
48
49static void glyphsToAdvances(HB_Font hbFont, const HB_Glyph* glyphs,
50                         hb_uint32 numGlyphs, HB_Fixed* advances, int flags) {
51    SkHarfBuzzFont* font = reinterpret_cast<SkHarfBuzzFont*>(hbFont->userData);
52    SkPaint paint;
53
54    font->setupPaint(&paint);
55    paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
56
57    SkAutoMalloc storage(numGlyphs * (sizeof(SkScalar) + sizeof(uint16_t)));
58    SkScalar* scalarWidths = reinterpret_cast<SkScalar*>(storage.get());
59    uint16_t* glyphs16 = reinterpret_cast<uint16_t*>(scalarWidths + numGlyphs);
60
61    // convert HB 32bit glyphs to skia's 16bit
62    for (hb_uint32 i = 0; i < numGlyphs; ++i) {
63        glyphs16[i] = SkToU16(glyphs[i]);
64    }
65    paint.getTextWidths(glyphs16, numGlyphs * sizeof(uint16_t), scalarWidths);
66
67    for (hb_uint32 i = 0; i < numGlyphs; ++i) {
68        advances[i] = SkScalarToHarfbuzzFixed(scalarWidths[i]);
69    }
70}
71
72static HB_Bool canRender(HB_Font hbFont, const HB_UChar16* characters,
73                         hb_uint32 length) {
74    SkHarfBuzzFont* font = reinterpret_cast<SkHarfBuzzFont*>(hbFont->userData);
75    SkPaint paint;
76
77    paint.setTypeface(font->getTypeface());
78    paint.setTextEncoding(SkPaint::kUTF16_TextEncoding);
79    return paint.containsText(characters, length * sizeof(uint16_t));
80}
81
82static HB_Error getOutlinePoint(HB_Font hbFont, HB_Glyph glyph, int flags,
83                                hb_uint32 index, HB_Fixed* xPos, HB_Fixed* yPos,
84                                hb_uint32* resultingNumPoints) {
85    SkHarfBuzzFont* font = reinterpret_cast<SkHarfBuzzFont*>(hbFont->userData);
86    SkPaint paint;
87
88    font->setupPaint(&paint);
89    paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
90    if (flags & HB_ShaperFlag_UseDesignMetrics) {
91        paint.setHinting(SkPaint::kNo_Hinting);
92    }
93
94    SkPath path;
95    uint16_t glyph16 = SkToU16(glyph);
96    paint.getTextPath(&glyph16, sizeof(glyph16), 0, 0, &path);
97    int numPoints = path.countPoints();
98    if (index >= numPoints) {
99        return HB_Err_Invalid_SubTable;
100    }
101
102    SkPoint pt = path.getPoint(index);
103    *xPos = SkScalarToHarfbuzzFixed(pt.fX);
104    *yPos = SkScalarToHarfbuzzFixed(pt.fY);
105    *resultingNumPoints = numPoints;
106
107    return HB_Err_Ok;
108}
109
110static void getGlyphMetrics(HB_Font hbFont, HB_Glyph glyph,
111                            HB_GlyphMetrics* metrics) {
112    SkHarfBuzzFont* font = reinterpret_cast<SkHarfBuzzFont*>(hbFont->userData);
113    SkPaint paint;
114
115    font->setupPaint(&paint);
116    paint.setTextEncoding(SkPaint::kGlyphID_TextEncoding);
117
118    SkScalar width;
119    SkRect bounds;
120    uint16_t glyph16 = SkToU16(glyph);
121    paint.getTextWidths(&glyph16, sizeof(glyph16), &width, &bounds);
122
123    metrics->x = SkScalarToHarfbuzzFixed(bounds.fLeft);
124    metrics->y = SkScalarToHarfbuzzFixed(bounds.fTop);
125    metrics->width = SkScalarToHarfbuzzFixed(bounds.width());
126    metrics->height = SkScalarToHarfbuzzFixed(bounds.height());
127
128    metrics->xOffset = SkScalarToHarfbuzzFixed(width);
129    // We can't actually get the |y| correct because Skia doesn't export
130    // the vertical advance. However, nor we do ever render vertical text at
131    // the moment so it's unimportant.
132    metrics->yOffset = 0;
133}
134
135static HB_Fixed getFontMetric(HB_Font hbFont, HB_FontMetric metric)
136{
137    SkHarfBuzzFont* font = reinterpret_cast<SkHarfBuzzFont*>(hbFont->userData);
138    SkPaint paint;
139    SkPaint::FontMetrics skiaMetrics;
140
141    font->setupPaint(&paint);
142    paint.getFontMetrics(&skiaMetrics);
143
144    switch (metric) {
145    case HB_FontAscent:
146        return SkScalarToHarfbuzzFixed(-skiaMetrics.fAscent);
147    default:
148        SkDebugf("--- unknown harfbuzz metric enum %d\n", metric);
149        return 0;
150    }
151}
152
153static HB_FontClass gSkHarfBuzzFontClass = {
154    stringToGlyphs,
155    glyphsToAdvances,
156    canRender,
157    getOutlinePoint,
158    getGlyphMetrics,
159    getFontMetric,
160};
161
162const HB_FontClass& SkHarfBuzzFont::GetFontClass() {
163    return gSkHarfBuzzFontClass;
164}
165
166HB_Error SkHarfBuzzFont::GetFontTableFunc(void* voidface, const HB_Tag tag,
167                                          HB_Byte* buffer, HB_UInt* len) {
168    SkHarfBuzzFont* font = reinterpret_cast<SkHarfBuzzFont*>(voidface);
169    uint32_t uniqueID = SkTypeface::UniqueID(font->getTypeface());
170
171    const size_t tableSize = SkFontHost::GetTableSize(uniqueID, tag);
172    if (!tableSize) {
173        return HB_Err_Invalid_Argument;
174    }
175    // If Harfbuzz specified a NULL buffer then it's asking for the size.
176    if (!buffer) {
177        *len = tableSize;
178        return HB_Err_Ok;
179    }
180
181    if (*len < tableSize) {
182        // is this right, or should we just copy less than the full table?
183        return HB_Err_Invalid_Argument;
184    }
185    SkFontHost::GetTableData(uniqueID, tag, 0, tableSize, buffer);
186    return HB_Err_Ok;
187}
188
189