gecko-dev/gfx/thebes/gfxUnicodeProperties.cpp

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#include "gfxUnicodeProperties.h"

#include "gfxUnicodePropertyData.cpp"

#include "harfbuzz/hb-unicode.h"

#define UNICODE_BMP_LIMIT 0x10000
#define UNICODE_LIMIT     0x110000

/*
To store properties for a million Unicode codepoints compactly, we use
a three-level array structure, with the Unicode values considered as
three elements: Plane, Page, and Char.

Space optimization happens because multiple Planes can refer to the same
Page array, and multiple Pages can refer to the same Char array holding
the actual values. In practice, most of the higher planes are empty and
thus share the same data; and within the BMP, there are also many pages
that repeat the same data for any given property.

Plane is usually zero, so we skip a lookup in this case, and require
that the Plane 0 pages are always the first set of entries in the Page
array.

The division of the remaining 16 bits into Page and Char fields is
adjusted for each property (by experiment using the generation tool)
to provide the most compact storage, depending on the distribution
of values.
*/

PRUint32
gfxUnicodeProperties::GetMirroredChar(PRUint32 aCh)
{
    // all mirrored chars are in plane 0
    if (aCh < UNICODE_BMP_LIMIT) {
        int v = sMirrorValues[sMirrorPages[0][aCh >> kMirrorCharBits]]
                             [aCh & ((1 << kMirrorCharBits) - 1)];
        // The mirror value is stored as either an offset (if less than
        // kSmallMirrorOffset) from the input character code, or as
        // an index into the sDistantMirrors list. This allows the
        // mirrored codes to be stored as 8-bit values, as most of them
        // are references to nearby character codes.
        if (v < kSmallMirrorOffset) {
            return aCh + v;
        }
        return sDistantMirrors[v - kSmallMirrorOffset];
    }
    return aCh;
}

PRUint8
gfxUnicodeProperties::GetCombiningClass(PRUint32 aCh)
{
    if (aCh < UNICODE_BMP_LIMIT) {
        return sCClassValues[sCClassPages[0][aCh >> kCClassCharBits]]
                            [aCh & ((1 << kCClassCharBits) - 1)];
    }
    if (aCh >= UNICODE_LIMIT) {
        return 0;
    }
    return sCClassValues[sCClassPages[sCClassPlanes[(aCh >> 16) - 1]]
                                     [(aCh & 0xffff) >> kCClassCharBits]]
                        [aCh & ((1 << kCClassCharBits) - 1)];
}

PRUint8
gfxUnicodeProperties::GetGeneralCategory(PRUint32 aCh)
{
    if (aCh < UNICODE_BMP_LIMIT) {
        return sCatEAWValues[sCatEAWPages[0][aCh >> kCatEAWCharBits]]
                            [aCh & ((1 << kCatEAWCharBits) - 1)].mCategory;
    }
    if (aCh >= UNICODE_LIMIT) {
        return PRUint8(HB_CATEGORY_UNASSIGNED);
    }
    return sCatEAWValues[sCatEAWPages[sCatEAWPlanes[(aCh >> 16) - 1]]
                                     [(aCh & 0xffff) >> kCatEAWCharBits]]
                        [aCh & ((1 << kCatEAWCharBits) - 1)].mCategory;
}

PRUint8
gfxUnicodeProperties::GetEastAsianWidth(PRUint32 aCh)
{
    if (aCh < UNICODE_BMP_LIMIT) {
        return sCatEAWValues[sCatEAWPages[0][aCh >> kCatEAWCharBits]]
                            [aCh & ((1 << kCatEAWCharBits) - 1)].mEAW;
    }
    if (aCh >= UNICODE_LIMIT) {
        return 0;
    }
    return sCatEAWValues[sCatEAWPages[sCatEAWPlanes[(aCh >> 16) - 1]]
                                     [(aCh & 0xffff) >> kCatEAWCharBits]]
                        [aCh & ((1 << kCatEAWCharBits) - 1)].mEAW;
}

PRInt32
gfxUnicodeProperties::GetScriptCode(PRUint32 aCh)
{
    if (aCh < UNICODE_BMP_LIMIT) {
        return sScriptValues[sScriptPages[0][aCh >> kScriptCharBits]]
                            [aCh & ((1 << kScriptCharBits) - 1)];
    }
    if (aCh >= UNICODE_LIMIT) {
        return PRInt32(HB_SCRIPT_UNKNOWN);
    }
    return sScriptValues[sScriptPages[sScriptPlanes[(aCh >> 16) - 1]]
                                     [(aCh & 0xffff) >> kScriptCharBits]]
                        [aCh & ((1 << kScriptCharBits) - 1)];
}

// TODO: replace this with a properties file or similar;
// expect this to evolve as harfbuzz shaping support matures.
//
// The "shaping level" of each script run, as returned by this
// function, is compared to the gfx.font_rendering.harfbuzz.level
// preference to decide whether to use the harfbuzz shaper.
//
// Currently, we only distinguish "simple" (level 1) scripts
// and "the rest" (level 2), but may subdivide this further in
// the future.
PRInt32
gfxUnicodeProperties::ScriptShapingLevel(PRInt32 aScriptCode)
{
    switch (aScriptCode) {
    case HB_SCRIPT_LATIN:
    case HB_SCRIPT_CYRILLIC:
    case HB_SCRIPT_HAN:
    case HB_SCRIPT_HIRAGANA:
    case HB_SCRIPT_KATAKANA:
    case HB_SCRIPT_COMMON:
    case HB_SCRIPT_INHERITED:
    case HB_SCRIPT_UNKNOWN:
        return 1; // level 1: common scripts that can use "generic" shaping
    }

    return 2; // all others are considered level 2
}