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gecko-dev/gfx/thebes/gfxFT2Utils.cpp

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/* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla Foundation code.
*
* The Initial Developer of the Original Code is Mozilla Foundation.
* Portions created by the Initial Developer are Copyright (C) 2009
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Vladimir Vukicevic <vladimir@mozilla.com>
* Masayuki Nakano <masayuki@d-toybox.com>
* Behdad Esfahbod <behdad@gnome.org>
* Mats Palmgren <mats.palmgren@bredband.net>
* Karl Tomlinson <karlt+@karlt.net>, Mozilla Corporation
* Takuro Ashie <ashie@clear-code.com>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#include "gfxFT2FontBase.h"
#include "gfxFT2Utils.h"
#include FT_TRUETYPE_TAGS_H
#include FT_TRUETYPE_TABLES_H
#ifdef HAVE_FONTCONFIG_FCFREETYPE_H
#include <fontconfig/fcfreetype.h>
#endif
#include "prlink.h"
// aScale is intended for a 16.16 x/y_scale of an FT_Size_Metrics
static inline FT_Long
ScaleRoundDesignUnits(FT_Short aDesignMetric, FT_Fixed aScale)
{
FT_Long fixed26dot6 = FT_MulFix(aDesignMetric, aScale);
return ROUND_26_6_TO_INT(fixed26dot6);
}
// Snap a line to pixels while keeping the center and size of the line as
// close to the original position as possible.
//
// Pango does similar snapping for underline and strikethrough when fonts are
// hinted, but nsCSSRendering::GetTextDecorationRectInternal always snaps the
// top and size of lines. Optimizing the distance between the line and
// baseline is probably good for the gap between text and underline, but
// optimizing the center of the line is better for positioning strikethough.
static void
SnapLineToPixels(gfxFloat& aOffset, gfxFloat& aSize)
{
gfxFloat snappedSize = NS_MAX(NS_floor(aSize + 0.5), 1.0);
// Correct offset for change in size
gfxFloat offset = aOffset - 0.5 * (aSize - snappedSize);
// Snap offset
aOffset = NS_floor(offset + 0.5);
aSize = snappedSize;
}
void
gfxFT2LockedFace::GetMetrics(gfxFont::Metrics* aMetrics,
PRUint32* aSpaceGlyph)
{
NS_PRECONDITION(aMetrics != NULL, "aMetrics must not be NULL");
NS_PRECONDITION(aSpaceGlyph != NULL, "aSpaceGlyph must not be NULL");
if (NS_UNLIKELY(!mFace)) {
// No face. This unfortunate situation might happen if the font
// file is (re)moved at the wrong time.
aMetrics->emHeight = mGfxFont->GetStyle()->size;
aMetrics->emAscent = 0.8 * aMetrics->emHeight;
aMetrics->emDescent = 0.2 * aMetrics->emHeight;
aMetrics->maxAscent = aMetrics->emAscent;
aMetrics->maxDescent = aMetrics->maxDescent;
aMetrics->maxHeight = aMetrics->emHeight;
aMetrics->internalLeading = 0.0;
aMetrics->externalLeading = 0.2 * aMetrics->emHeight;
aSpaceGlyph = 0;
aMetrics->spaceWidth = 0.5 * aMetrics->emHeight;
aMetrics->maxAdvance = aMetrics->spaceWidth;
aMetrics->aveCharWidth = aMetrics->spaceWidth;
aMetrics->zeroOrAveCharWidth = aMetrics->spaceWidth;
aMetrics->xHeight = 0.5 * aMetrics->emHeight;
aMetrics->underlineSize = aMetrics->emHeight / 14.0;
aMetrics->underlineOffset = -aMetrics->underlineSize;
aMetrics->strikeoutOffset = 0.25 * aMetrics->emHeight;
aMetrics->strikeoutSize = aMetrics->underlineSize;
aMetrics->superscriptOffset = aMetrics->xHeight;
aMetrics->subscriptOffset = aMetrics->xHeight;
return;
}
const FT_Size_Metrics& ftMetrics = mFace->size->metrics;
gfxFloat emHeight;
// Scale for vertical design metric conversion: pixels per design unit.
gfxFloat yScale;
if (FT_IS_SCALABLE(mFace)) {
// Prefer FT_Size_Metrics::x_scale to x_ppem as x_ppem does not
// have subpixel accuracy.
//
// FT_Size_Metrics::y_scale is in 16.16 fixed point format. Its
// (fractional) value is a factor that converts vertical metrics from
// design units to units of 1/64 pixels, so that the result may be
// interpreted as pixels in 26.6 fixed point format.
yScale = FLOAT_FROM_26_6(FLOAT_FROM_16_16(ftMetrics.y_scale));
emHeight = mFace->units_per_EM * yScale;
} else { // Not scalable.
// FT_Size_Metrics doc says x_scale is "only relevant for scalable
// font formats".
gfxFloat emUnit = mFace->units_per_EM;
emHeight = ftMetrics.y_ppem;
yScale = emHeight / emUnit;
}
TT_OS2 *os2 =
static_cast<TT_OS2*>(FT_Get_Sfnt_Table(mFace, ft_sfnt_os2));
aMetrics->maxAscent = FLOAT_FROM_26_6(ftMetrics.ascender);
aMetrics->maxDescent = -FLOAT_FROM_26_6(ftMetrics.descender);
aMetrics->maxAdvance = FLOAT_FROM_26_6(ftMetrics.max_advance);
gfxFloat lineHeight;
if (os2 && os2->sTypoAscender) {
aMetrics->emAscent = os2->sTypoAscender * yScale;
aMetrics->emDescent = -os2->sTypoDescender * yScale;
FT_Short typoHeight =
os2->sTypoAscender - os2->sTypoDescender + os2->sTypoLineGap;
lineHeight = typoHeight * yScale;
// maxAscent/maxDescent get used for frame heights, and some fonts
// don't have the HHEA table ascent/descent set (bug 279032).
if (aMetrics->emAscent > aMetrics->maxAscent)
aMetrics->maxAscent = aMetrics->emAscent;
if (aMetrics->emDescent > aMetrics->maxDescent)
aMetrics->maxDescent = aMetrics->emDescent;
} else {
aMetrics->emAscent = aMetrics->maxAscent;
aMetrics->emDescent = aMetrics->maxDescent;
lineHeight = FLOAT_FROM_26_6(ftMetrics.height);
}
cairo_text_extents_t extents;
*aSpaceGlyph = GetCharExtents(' ', &extents);
if (*aSpaceGlyph) {
aMetrics->spaceWidth = extents.x_advance;
} else {
aMetrics->spaceWidth = aMetrics->maxAdvance; // guess
}
aMetrics->zeroOrAveCharWidth = 0.0;
if (GetCharExtents('0', &extents)) {
aMetrics->zeroOrAveCharWidth = extents.x_advance;
}
// Prefering a measured x over sxHeight because sxHeight doesn't consider
// hinting, but maybe the x extents are not quite right in some fancy
// script fonts. CSS 2.1 suggests possibly using the height of an "o",
// which would have a more consistent glyph across fonts.
if (GetCharExtents('x', &extents) && extents.y_bearing < 0.0) {
aMetrics->xHeight = -extents.y_bearing;
aMetrics->aveCharWidth = extents.x_advance;
} else {
if (os2 && os2->sxHeight) {
aMetrics->xHeight = os2->sxHeight * yScale;
} else {
// CSS 2.1, section 4.3.2 Lengths: "In the cases where it is
// impossible or impractical to determine the x-height, a value of
// 0.5em should be used."
aMetrics->xHeight = 0.5 * emHeight;
}
aMetrics->aveCharWidth = 0.0; // updated below
}
// aveCharWidth is used for the width of text input elements so be
// liberal rather than conservative in the estimate.
if (os2 && os2->xAvgCharWidth) {
// Round to pixels as this is compared with maxAdvance to guess
// whether this is a fixed width font.
gfxFloat avgCharWidth =
ScaleRoundDesignUnits(os2->xAvgCharWidth, ftMetrics.x_scale);
aMetrics->aveCharWidth =
NS_MAX(aMetrics->aveCharWidth, avgCharWidth);
}
aMetrics->aveCharWidth =
NS_MAX(aMetrics->aveCharWidth, aMetrics->zeroOrAveCharWidth);
if (aMetrics->aveCharWidth == 0.0) {
aMetrics->aveCharWidth = aMetrics->spaceWidth;
}
if (aMetrics->zeroOrAveCharWidth == 0.0) {
aMetrics->zeroOrAveCharWidth = aMetrics->aveCharWidth;
}
// Apparently hinting can mean that max_advance is not always accurate.
aMetrics->maxAdvance =
NS_MAX(aMetrics->maxAdvance, aMetrics->aveCharWidth);
// gfxFont::Metrics::underlineOffset is the position of the top of the
// underline.
//
// FT_FaceRec documentation describes underline_position as "the
// center of the underlining stem". This was the original definition
// of the PostScript metric, but in the PostScript table of OpenType
// fonts the metric is "the top of the underline"
// (http://www.microsoft.com/typography/otspec/post.htm), and FreeType
// (up to version 2.3.7) doesn't make any adjustment.
//
// Therefore get the underline position directly from the table
// ourselves when this table exists. Use FreeType's metrics for
// other (including older PostScript) fonts.
if (mFace->underline_position && mFace->underline_thickness) {
aMetrics->underlineSize = mFace->underline_thickness * yScale;
TT_Postscript *post = static_cast<TT_Postscript*>
(FT_Get_Sfnt_Table(mFace, ft_sfnt_post));
if (post && post->underlinePosition) {
aMetrics->underlineOffset = post->underlinePosition * yScale;
} else {
aMetrics->underlineOffset = mFace->underline_position * yScale
+ 0.5 * aMetrics->underlineSize;
}
} else { // No underline info.
// Imitate Pango.
aMetrics->underlineSize = emHeight / 14.0;
aMetrics->underlineOffset = -aMetrics->underlineSize;
}
if (os2 && os2->yStrikeoutSize && os2->yStrikeoutPosition) {
aMetrics->strikeoutSize = os2->yStrikeoutSize * yScale;
aMetrics->strikeoutOffset = os2->yStrikeoutPosition * yScale;
} else { // No strikeout info.
aMetrics->strikeoutSize = aMetrics->underlineSize;
// Use OpenType spec's suggested position for Roman font.
aMetrics->strikeoutOffset = emHeight * 409.0 / 2048.0
+ 0.5 * aMetrics->strikeoutSize;
}
SnapLineToPixels(aMetrics->strikeoutOffset, aMetrics->strikeoutSize);
if (os2 && os2->ySuperscriptYOffset) {
gfxFloat val = ScaleRoundDesignUnits(os2->ySuperscriptYOffset,
ftMetrics.y_scale);
aMetrics->superscriptOffset = NS_MAX(1.0, val);
} else {
aMetrics->superscriptOffset = aMetrics->xHeight;
}
if (os2 && os2->ySubscriptYOffset) {
gfxFloat val = ScaleRoundDesignUnits(os2->ySubscriptYOffset,
ftMetrics.y_scale);
// some fonts have the incorrect sign.
val = fabs(val);
aMetrics->subscriptOffset = NS_MAX(1.0, val);
} else {
aMetrics->subscriptOffset = aMetrics->xHeight;
}
aMetrics->maxHeight = aMetrics->maxAscent + aMetrics->maxDescent;
// Make the line height an integer number of pixels so that lines will be
// equally spaced (rather than just being snapped to pixels, some up and
// some down). Layout calculates line height from the emHeight +
// internalLeading + externalLeading, but first each of these is rounded
// to layout units. To ensure that the result is an integer number of
// pixels, round each of the components to pixels.
aMetrics->emHeight = NS_floor(emHeight + 0.5);
// maxHeight will normally be an integer, but round anyway in case
// FreeType is configured differently.
aMetrics->internalLeading =
NS_floor(aMetrics->maxHeight - aMetrics->emHeight + 0.5);
// Text input boxes currently don't work well with lineHeight
// significantly less than maxHeight (with Verdana, for example).
lineHeight = NS_floor(NS_MAX(lineHeight, aMetrics->maxHeight) + 0.5);
aMetrics->externalLeading =
lineHeight - aMetrics->internalLeading - aMetrics->emHeight;
// Ensure emAscent + emDescent == emHeight
gfxFloat sum = aMetrics->emAscent + aMetrics->emDescent;
aMetrics->emAscent = sum > 0.0 ?
aMetrics->emAscent * aMetrics->emHeight / sum : 0.0;
aMetrics->emDescent = aMetrics->emHeight - aMetrics->emAscent;
}
PRUint32
gfxFT2LockedFace::GetGlyph(PRUint32 aCharCode)
{
if (NS_UNLIKELY(!mFace))
return 0;
#ifdef HAVE_FONTCONFIG_FCFREETYPE_H
// FcFreeTypeCharIndex will search starting from the most recently
// selected charmap. This can cause non-determistic behavior when more
// than one charmap supports a character but with different glyphs, as
// with older versions of MS Gothic, for example. Always prefer a Unicode
// charmap, if there is one. (FcFreeTypeCharIndex usually does the
// appropriate Unicode conversion, but some fonts have non-Roman glyphs
// for FT_ENCODING_APPLE_ROMAN characters.)
if (!mFace->charmap || mFace->charmap->encoding != FT_ENCODING_UNICODE) {
FT_Select_Charmap(mFace, FT_ENCODING_UNICODE);
}
return FcFreeTypeCharIndex(mFace, aCharCode);
#else
return FT_Get_Char_Index(mFace, aCharCode);
#endif
}
typedef FT_UInt (*GetCharVariantFunction)(FT_Face face,
FT_ULong charcode,
FT_ULong variantSelector);
PRUint32
gfxFT2LockedFace::GetUVSGlyph(PRUint32 aCharCode, PRUint32 aVariantSelector)
{
NS_PRECONDITION(aVariantSelector, "aVariantSelector should not be NULL");
if (NS_UNLIKELY(!mFace))
return 0;
// This function is available from FreeType 2.3.6 (June 2008).
static CharVariantFunction sGetCharVariantPtr = FindCharVariantFunction();
if (!sGetCharVariantPtr)
return 0;
#ifdef HAVE_FONTCONFIG_FCFREETYPE_H
// FcFreeTypeCharIndex may have changed the selected charmap.
// FT_Face_GetCharVariantIndex needs a unicode charmap.
if (!mFace->charmap || mFace->charmap->encoding != FT_ENCODING_UNICODE) {
FT_Select_Charmap(mFace, FT_ENCODING_UNICODE);
}
#endif
return (*sGetCharVariantPtr)(mFace, aCharCode, aVariantSelector);
}
PRBool
gfxFT2LockedFace::GetFontTable(PRUint32 aTag, FallibleTArray<PRUint8>& aBuffer)
{
if (!mFace || !FT_IS_SFNT(mFace))
return PR_FALSE;
FT_ULong length = 0;
// TRUETYPE_TAG is defined equivalent to FT_MAKE_TAG
FT_Error error = FT_Load_Sfnt_Table(mFace, aTag, 0, NULL, &length);
if (error != 0)
return PR_FALSE;
if (NS_UNLIKELY(length > static_cast<FallibleTArray<PRUint8>::size_type>(-1))
|| NS_UNLIKELY(!aBuffer.SetLength(length)))
return PR_FALSE;
error = FT_Load_Sfnt_Table(mFace, aTag, 0, aBuffer.Elements(), &length);
if (NS_UNLIKELY(error != 0)) {
aBuffer.Clear();
return PR_FALSE;
}
return PR_TRUE;
}
PRUint32
gfxFT2LockedFace::GetCharExtents(char aChar, cairo_text_extents_t* aExtents)
{
NS_PRECONDITION(aExtents != NULL, "aExtents must not be NULL");
if (!mFace)
return 0;
FT_UInt gid = mGfxFont->GetGlyph(aChar);
if (gid) {
mGfxFont->GetGlyphExtents(gid, aExtents);
}
return gid;
}
gfxFT2LockedFace::CharVariantFunction
gfxFT2LockedFace::FindCharVariantFunction()
{
// This function is available from FreeType 2.3.6 (June 2008).
PRLibrary *lib = nsnull;
CharVariantFunction function =
reinterpret_cast<CharVariantFunction>
(PR_FindFunctionSymbolAndLibrary("FT_Face_GetCharVariantIndex", &lib));
if (!lib) {
return nsnull;
}
FT_Int major;
FT_Int minor;
FT_Int patch;
FT_Library_Version(mFace->glyph->library, &major, &minor, &patch);
// Versions 2.4.0 to 2.4.3 crash if configured with
// FT_CONFIG_OPTION_OLD_INTERNALS. Presence of the symbol FT_Alloc
// indicates FT_CONFIG_OPTION_OLD_INTERNALS.
if (major == 2 && minor == 4 && patch < 4 &&
PR_FindFunctionSymbol(lib, "FT_Alloc")) {
function = nsnull;
}
// Decrement the reference count incremented in
// PR_FindFunctionSymbolAndLibrary.
PR_UnloadLibrary(lib);
return function;
}
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