SkGlyph.h revision b4c29ac173e6f8844327338687248b98bc94132d 
1/*
2 * Copyright 2006 The Android Open Source Project
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#ifndef SkGlyph_DEFINED
9#define SkGlyph_DEFINED
10
11#include "SkTypes.h"
12#include "SkFixed.h"
13#include "SkMask.h"
14
15class SkPath;
16
17// needs to be != to any valid SkMask::Format
18#define MASK_FORMAT_UNKNOWN         (0xFF)
19#define MASK_FORMAT_JUST_ADVANCE    MASK_FORMAT_UNKNOWN
20
21#define kMaxGlyphWidth (1<<13)
22
23struct SkGlyph {
24    void*       fImage;
25    SkPath*     fPath;
26    SkFixed     fAdvanceX, fAdvanceY;
27
28    uint32_t    fID;
29    uint16_t    fWidth, fHeight;
30    int16_t     fTop, fLeft;
31
32    uint8_t     fMaskFormat;
33    int8_t      fRsbDelta, fLsbDelta;  // used by auto-kerning
34    int8_t      fForceBW;
35
36    void init(uint32_t id) {
37        fID             = id;
38        fImage          = NULL;
39        fPath           = NULL;
40        fMaskFormat     = MASK_FORMAT_UNKNOWN;
41        fForceBW        = 0;
42    }
43
44    /**
45     *  Compute the rowbytes for the specified width and mask-format.
46     */
47    static unsigned ComputeRowBytes(unsigned width, SkMask::Format format) {
48        unsigned rb = width;
49        if (SkMask::kBW_Format == format) {
50            rb = (rb + 7) >> 3;
51        } else if (SkMask::kARGB32_Format == format) {
52            rb <<= 2;
53        } else if (SkMask::kLCD16_Format == format) {
54            rb = SkAlign4(rb << 1);
55        } else {
56            rb = SkAlign4(rb);
57        }
58        return rb;
59    }
60
61    unsigned rowBytes() const {
62        return ComputeRowBytes(fWidth, (SkMask::Format)fMaskFormat);
63    }
64
65    bool isJustAdvance() const {
66        return MASK_FORMAT_JUST_ADVANCE == fMaskFormat;
67    }
68
69    bool isFullMetrics() const {
70        return MASK_FORMAT_JUST_ADVANCE != fMaskFormat;
71    }
72
73    uint16_t getGlyphID() const {
74        return ID2Code(fID);
75    }
76
77    unsigned getSubX() const {
78        return ID2SubX(fID);
79    }
80
81    SkFixed getSubXFixed() const {
82        return SubToFixed(ID2SubX(fID));
83    }
84
85    SkFixed getSubYFixed() const {
86        return SubToFixed(ID2SubY(fID));
87    }
88
89    size_t computeImageSize() const;
90
91    /** Call this to set all of the metrics fields to 0 (e.g. if the scaler
92        encounters an error measuring a glyph). Note: this does not alter the
93        fImage, fPath, fID, fMaskFormat fields.
94     */
95    void zeroMetrics();
96
97    enum {
98        kSubBits = 2,
99        kSubMask = ((1 << kSubBits) - 1),
100        kSubShift = 24, // must be large enough for glyphs and unichars
101        kCodeMask = ((1 << kSubShift) - 1),
102        // relative offsets for X and Y subpixel bits
103        kSubShiftX = kSubBits,
104        kSubShiftY = 0
105    };
106
107    // The code is increased by one in MakeID. Adjust back. This allows the zero
108    // id to be the invalid id.
109    static unsigned ID2Code(uint32_t id) {
110        return (id & kCodeMask) - 1;
111    }
112
113    static unsigned ID2SubX(uint32_t id) {
114        return id >> (kSubShift + kSubShiftX);
115    }
116
117    static unsigned ID2SubY(uint32_t id) {
118        return (id >> (kSubShift + kSubShiftY)) & kSubMask;
119    }
120
121    static unsigned FixedToSub(SkFixed n) {
122        return (n >> (16 - kSubBits)) & kSubMask;
123    }
124
125    static SkFixed SubToFixed(unsigned sub) {
126        SkASSERT(sub <= kSubMask);
127        return sub << (16 - kSubBits);
128    }
129
130    // This and the MakeID below must not return an id of zero. Zero is used as
131    // the invalid id.
132    static uint32_t MakeID(unsigned code) {
133        SkASSERT(code + 1 <= kCodeMask);
134        return code + 1;
135    }
136
137    // See comment for MakeID above.
138    static uint32_t MakeID(unsigned code, SkFixed x, SkFixed y) {
139        SkASSERT(code + 1 <= kCodeMask);
140        x = FixedToSub(x);
141        y = FixedToSub(y);
142        return (x << (kSubShift + kSubShiftX)) |
143               (y << (kSubShift + kSubShiftY)) |
144               (code + 1);
145    }
146
147    void toMask(SkMask* mask) const;
148};
149
150#endif
151