// gfxOS2Font::GetMetrics()
// return the metrics of the current font using the gfxFont metrics structure.
// If the metrics are not available yet, compute them using the FreeType
// function on the font. (This is partly based on the respective function from
// gfxPangoFonts)
const gfxFont::Metrics& gfxOS2Font::GetMetrics()
{
#ifdef DEBUG_thebes_1
printf("gfxOS2Font[%#x]::GetMetrics()\n", (unsigned)this);
#endif
if (mMetrics) {
return *mMetrics;
}
// whatever happens below, we can always create the metrics
mMetrics = new gfxFont::Metrics;
mSpaceGlyph = 0;
// round size to integer pixels, this is to get full pixels for layout
// together with internal/external leading (see below)
mMetrics->emHeight = NS_floor(GetStyle()->size + 0.5);
FT_Face face = cairo_ft_scaled_font_lock_face(CairoScaledFont());
if (!face) {
// Abort here already, otherwise we crash in the following
// this can happen if the font-size requested is zero.
FillMetricsDefaults(mMetrics);
return *mMetrics;
}
if (!face->charmap) {
// Also abort, if the charmap isn't loaded; then the char
// lookups won't work. This happens for fonts without Unicode
// charmap.
cairo_ft_scaled_font_unlock_face(CairoScaledFont());
FillMetricsDefaults(mMetrics);
return *mMetrics;
}
// compute font scaling factors
gfxFloat emUnit = 1.0 * face->units_per_EM;
gfxFloat xScale = face->size->metrics.x_ppem / emUnit;
gfxFloat yScale = face->size->metrics.y_ppem / emUnit;
FT_UInt gid; // glyph ID
// properties of space
gid = FT_Get_Char_Index(face, ' ');
if (gid) {
// Load glyph into glyph slot. Use load_default here to get results in
// 26.6 fractional pixel format which is what is used for all other
// characters in gfxOS2FontGroup::CreateGlyphRunsFT.
FT_Load_Glyph(face, gid, FT_LOAD_DEFAULT);
// glyph width doesn't work for spaces, use advance instead
mMetrics->spaceWidth = face->glyph->advance.x >> 6;
// save the space glyph
mSpaceGlyph = gid;
} else {
PRBool
gfxDWriteFont::SetupCairoFont(gfxContext *aContext)
{
cairo_scaled_font_t *scaledFont = CairoScaledFont();
if (cairo_scaled_font_status(scaledFont) != CAIRO_STATUS_SUCCESS) {
// Don't cairo_set_scaled_font as that would propagate the error to
// the cairo_t, precluding any further drawing.
return PR_FALSE;
}
cairo_set_scaled_font(aContext->GetCairo(), scaledFont);
return PR_TRUE;
}
void
gfxFT2FontBase::GetGlyphExtents(PRUint32 aGlyph, cairo_text_extents_t* aExtents)
{
NS_PRECONDITION(aExtents != NULL, "aExtents must not be NULL");
cairo_glyph_t glyphs[1];
glyphs[0].index = aGlyph;
glyphs[0].x = 0.0;
glyphs[0].y = 0.0;
// cairo does some caching for us here but perhaps a small gain could be
// made by caching more. It is usually only the advance that is needed,
// so caching only the advance could allow many requests to be cached with
// little memory use. Ideally this cache would be merged with
// gfxGlyphExtents.
cairo_scaled_font_glyph_extents(CairoScaledFont(), glyphs, 1, aExtents);
}
bool
gfxFT2FontBase::SetupCairoFont(gfxContext *aContext)
{
cairo_t *cr = aContext->GetCairo();
// The scaled font ctm is not relevant right here because
// cairo_set_scaled_font does not record the scaled font itself, but
// merely the font_face, font_matrix, font_options. The scaled_font used
// for the target can be different from the scaled_font passed to
// cairo_set_scaled_font. (Unfortunately we have measured only for an
// identity ctm.)
cairo_scaled_font_t *cairoFont = CairoScaledFont();
if (cairo_scaled_font_status(cairoFont) != CAIRO_STATUS_SUCCESS) {
// Don't cairo_set_scaled_font as that would propagate the error to
// the cairo_t, precluding any further drawing.
return PR_FALSE;
}
// Thoughts on which font_options to set on the context:
//
// cairoFont has been created for screen rendering.
//
// When the context is being used for screen rendering, we should set
// font_options such that the same scaled_font gets used (when the ctm is
// the same). The use of explicit font_options recorded in
// CreateScaledFont ensures that this will happen.
//
// XXXkt: For pdf and ps surfaces, I don't know whether it's better to
// remove surface-specific options, or try to draw with the same
// scaled_font that was used to measure. As the same font_face is being
// used, its font_options will often override some values anyway (unless
// perhaps we remove those from the FcPattern at face creation).
//
// I can't see any significant difference in printing, irrespective of
// what is set here. It's too late to change things here as measuring has
// already taken place. We should really be measuring with a different
// font for pdf and ps surfaces (bug 403513).
cairo_set_scaled_font(cr, cairoFont);
return PR_TRUE;
}
PRUint32
gfxFT2FontBase::GetGlyph(PRUint32 aCharCode)
{
// FcFreeTypeCharIndex needs to lock the FT_Face and can end up searching
// through all the postscript glyph names in the font. Therefore use a
// lightweight cache, which is stored on the cairo_font_face_t.
cairo_font_face_t *face =
cairo_scaled_font_get_font_face(CairoScaledFont());
if (cairo_font_face_status(face) != CAIRO_STATUS_SUCCESS)
return 0;
// This cache algorithm and size is based on what is done in
// cairo_scaled_font_text_to_glyphs and pango_fc_font_real_get_glyph. I
// think the concept is that adjacent characters probably come mostly from
// one Unicode block. This assumption is probably not so valid with
// scripts with large character sets as used for East Asian languages.
struct CmapCacheSlot {
PRUint32 mCharCode;
PRUint32 mGlyphIndex;
};
const PRUint32 kNumSlots = 256;
static cairo_user_data_key_t sCmapCacheKey;
CmapCacheSlot *slots = static_cast<CmapCacheSlot*>
(cairo_font_face_get_user_data(face, &sCmapCacheKey));
if (!slots) {
// cairo's caches can keep some cairo_font_faces alive past our last
// destroy, so the destroy function (free) for the cache must be
// callable from cairo without any assumptions about what other
// modules have not been shutdown.
slots = static_cast<CmapCacheSlot*>
(calloc(kNumSlots, sizeof(CmapCacheSlot)));
if (!slots)
return 0;
cairo_status_t status =
cairo_font_face_set_user_data(face, &sCmapCacheKey, slots, free);
if (status != CAIRO_STATUS_SUCCESS) { // OOM
free(slots);
return 0;
}
// Invalidate slot 0 by setting its char code to something that would
// never end up in slot 0. All other slots are already invalid
// because they have mCharCode = 0 and a glyph for char code 0 will
// always be in the slot 0.
slots[0].mCharCode = 1;
}
CmapCacheSlot *slot = &slots[aCharCode % kNumSlots];
if (slot->mCharCode != aCharCode) {
slot->mCharCode = aCharCode;
slot->mGlyphIndex = gfxFT2LockedFace(this).GetGlyph(aCharCode);
}
return slot->mGlyphIndex;
}
