gfx/thebes/gfxFT2FontBase.cpp

   1 /* -*- Mode: C++; tab-width: 20; indent-tabs-mode: nil; c-basic-offset: 4 -*-
   2  * This Source Code Form is subject to the terms of the Mozilla Public
   3  * License, v. 2.0. If a copy of the MPL was not distributed with this
   4  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
   5
   6 #include "gfxFT2FontBase.h"
   7 #include "gfxFT2Utils.h"
   8 #include "harfbuzz/hb.h"
   9 #include "mozilla/Likely.h"
  10 #include "gfxFontConstants.h"
  11 #include "gfxFontUtils.h"
  12
  13 using namespace mozilla::gfx;
  14
  15 gfxFT2FontBase::gfxFT2FontBase(cairo_scaled_font_t *aScaledFont,
  16                                gfxFontEntry *aFontEntry,
  17                                const gfxFontStyle *aFontStyle)
  18     : gfxFont(aFontEntry, aFontStyle, kAntialiasDefault, aScaledFont),
  19       mSpaceGlyph(0),
  20       mHasMetrics(false)
  21 {
  22     cairo_scaled_font_reference(mScaledFont);
  23     ConstructFontOptions();
  24 }
  25
  26 gfxFT2FontBase::~gfxFT2FontBase()
  27 {
  28     cairo_scaled_font_destroy(mScaledFont);
  29 }
  30
  31 uint32_t
  32 gfxFT2FontBase::GetGlyph(uint32_t aCharCode)
  33 {
  34     // FcFreeTypeCharIndex needs to lock the FT_Face and can end up searching
  35     // through all the postscript glyph names in the font.  Therefore use a
  36     // lightweight cache, which is stored on the cairo_font_face_t.
  37
  38     cairo_font_face_t *face =
  39         cairo_scaled_font_get_font_face(CairoScaledFont());
  40
  41     if (cairo_font_face_status(face) != CAIRO_STATUS_SUCCESS)
  42         return 0;
  43
  44     // This cache algorithm and size is based on what is done in
  45     // cairo_scaled_font_text_to_glyphs and pango_fc_font_real_get_glyph.  I
  46     // think the concept is that adjacent characters probably come mostly from
  47     // one Unicode block.  This assumption is probably not so valid with
  48     // scripts with large character sets as used for East Asian languages.
  49
  50     struct CmapCacheSlot {
  51         uint32_t mCharCode;
  52         uint32_t mGlyphIndex;
  53     };
  54     const uint32_t kNumSlots = 256;
  55     static cairo_user_data_key_t sCmapCacheKey;
  56
  57     CmapCacheSlot *slots = static_cast<CmapCacheSlot*>
  58         (cairo_font_face_get_user_data(face, &sCmapCacheKey));
  59
  60     if (!slots) {
  61         // cairo's caches can keep some cairo_font_faces alive past our last
  62         // destroy, so the destroy function (free) for the cache must be
  63         // callable from cairo without any assumptions about what other
  64         // modules have not been shutdown.
  65         slots = static_cast<CmapCacheSlot*>
  66             (calloc(kNumSlots, sizeof(CmapCacheSlot)));
  67         if (!slots)
  68             return 0;
  69
  70         cairo_status_t status =
  71             cairo_font_face_set_user_data(face, &sCmapCacheKey, slots, free);
  72         if (status != CAIRO_STATUS_SUCCESS) { // OOM
  73             free(slots);
  74             return 0;
  75         }
  76
  77         // Invalidate slot 0 by setting its char code to something that would
  78         // never end up in slot 0.  All other slots are already invalid
  79         // because they have mCharCode = 0 and a glyph for char code 0 will
  80         // always be in the slot 0.
  81         slots[0].mCharCode = 1;
  82     }
  83
  84     CmapCacheSlot *slot = &slots[aCharCode % kNumSlots];
  85     if (slot->mCharCode != aCharCode) {
  86         slot->mCharCode = aCharCode;
  87         slot->mGlyphIndex = gfxFT2LockedFace(this).GetGlyph(aCharCode);
  88     }
  89
  90     return slot->mGlyphIndex;
  91 }
  92
  93 void
  94 gfxFT2FontBase::GetGlyphExtents(uint32_t aGlyph, cairo_text_extents_t* aExtents)
  95 {
  96     NS_PRECONDITION(aExtents != nullptr, "aExtents must not be NULL");
  97
  98     cairo_glyph_t glyphs[1];
  99     glyphs[0].index = aGlyph;
 100     glyphs[0].x = 0.0;
 101     glyphs[0].y = 0.0;
 102     // cairo does some caching for us here but perhaps a small gain could be
 103     // made by caching more.  It is usually only the advance that is needed,
 104     // so caching only the advance could allow many requests to be cached with
 105     // little memory use.  Ideally this cache would be merged with
 106     // gfxGlyphExtents.
 107     cairo_scaled_font_glyph_extents(CairoScaledFont(), glyphs, 1, aExtents);
 108 }
 109
 110 const gfxFont::Metrics&
 111 gfxFT2FontBase::GetMetrics()
 112 {
 113     if (mHasMetrics)
 114         return mMetrics;
 115
 116     if (MOZ_UNLIKELY(GetStyle()->size <= 0.0)) {
 117         new(&mMetrics) gfxFont::Metrics(); // zero initialize
 118         mSpaceGlyph = 0;
 119     } else {
 120         gfxFT2LockedFace face(this);
 121         mFUnitsConvFactor = face.XScale();
 122         face.GetMetrics(&mMetrics, &mSpaceGlyph);
 123     }
 124
 125     SanitizeMetrics(&mMetrics, false);
 126
 127 #if 0
 128     //    printf("font name: %s %f\n", NS_ConvertUTF16toUTF8(GetName()).get(), GetStyle()->size);
 129     //    printf ("pango font %s\n", pango_font_description_to_string (pango_font_describe (font)));
 130
 131     fprintf (stderr, "Font: %s\n", NS_ConvertUTF16toUTF8(GetName()).get());
 132     fprintf (stderr, "    emHeight: %f emAscent: %f emDescent: %f\n", mMetrics.emHeight, mMetrics.emAscent, mMetrics.emDescent);
 133     fprintf (stderr, "    maxAscent: %f maxDescent: %f\n", mMetrics.maxAscent, mMetrics.maxDescent);
 134     fprintf (stderr, "    internalLeading: %f externalLeading: %f\n", mMetrics.externalLeading, mMetrics.internalLeading);
 135     fprintf (stderr, "    spaceWidth: %f aveCharWidth: %f xHeight: %f\n", mMetrics.spaceWidth, mMetrics.aveCharWidth, mMetrics.xHeight);
 136     fprintf (stderr, "    uOff: %f uSize: %f stOff: %f stSize: %f\n", mMetrics.underlineOffset, mMetrics.underlineSize, mMetrics.strikeoutOffset, mMetrics.strikeoutSize);
 137 #endif
 138
 139     mHasMetrics = true;
 140     return mMetrics;
 141 }
 142
 143 // Get the glyphID of a space
 144 uint32_t
 145 gfxFT2FontBase::GetSpaceGlyph()
 146 {
 147     NS_ASSERTION(GetStyle()->size != 0,
 148                  "forgot to short-circuit a text run with zero-sized font?");
 149     GetMetrics();
 150     return mSpaceGlyph;
 151 }
 152
 153 uint32_t
 154 gfxFT2FontBase::GetGlyph(uint32_t unicode, uint32_t variation_selector)
 155 {
 156     if (variation_selector) {
 157         uint32_t id =
 158             gfxFT2LockedFace(this).GetUVSGlyph(unicode, variation_selector);
 159         if (id)
 160             return id;
 161         id = gfxFontUtils::GetUVSFallback(unicode, variation_selector);
 162         if (id) {
 163             unicode = id;
 164         }
 165     }
 166
 167     return GetGlyph(unicode);
 168 }
 169
 170 int32_t
 171 gfxFT2FontBase::GetGlyphWidth(gfxContext *aCtx, uint16_t aGID)
 172 {
 173     cairo_text_extents_t extents;
 174     GetGlyphExtents(aGID, &extents);
 175     // convert to 16.16 fixed point
 176     return NS_lround(0x10000 * extents.x_advance);
 177 }
 178
 179 bool
 180 gfxFT2FontBase::SetupCairoFont(gfxContext *aContext)
 181 {
 182     cairo_t *cr = aContext->GetCairo();
 183
 184     // The scaled font ctm is not relevant right here because
 185     // cairo_set_scaled_font does not record the scaled font itself, but
 186     // merely the font_face, font_matrix, font_options.  The scaled_font used
 187     // for the target can be different from the scaled_font passed to
 188     // cairo_set_scaled_font.  (Unfortunately we have measured only for an
 189     // identity ctm.)
 190     cairo_scaled_font_t *cairoFont = CairoScaledFont();
 191
 192     if (cairo_scaled_font_status(cairoFont) != CAIRO_STATUS_SUCCESS) {
 193         // Don't cairo_set_scaled_font as that would propagate the error to
 194         // the cairo_t, precluding any further drawing.
 195         return false;
 196     }
 197     // Thoughts on which font_options to set on the context:
 198     //
 199     // cairoFont has been created for screen rendering.
 200     //
 201     // When the context is being used for screen rendering, we should set
 202     // font_options such that the same scaled_font gets used (when the ctm is
 203     // the same).  The use of explicit font_options recorded in
 204     // CreateScaledFont ensures that this will happen.
 205     //
 206     // XXXkt: For pdf and ps surfaces, I don't know whether it's better to
 207     // remove surface-specific options, or try to draw with the same
 208     // scaled_font that was used to measure.  As the same font_face is being
 209     // used, its font_options will often override some values anyway (unless
 210     // perhaps we remove those from the FcPattern at face creation).
 211     //
 212     // I can't see any significant difference in printing, irrespective of
 213     // what is set here.  It's too late to change things here as measuring has
 214     // already taken place.  We should really be measuring with a different
 215     // font for pdf and ps surfaces (bug 403513).
 216     cairo_set_scaled_font(cr, cairoFont);
 217     return true;
 218 }
 219
 220 void
 221 gfxFT2FontBase::ConstructFontOptions()
 222 {
 223   NS_LossyConvertUTF16toASCII name(this->GetName());
 224   mFontOptions.mName = name.get();
 225
 226   const gfxFontStyle* style = this->GetStyle();
 227   if (style->style == NS_FONT_STYLE_ITALIC) {
 228     if (style->weight == NS_FONT_WEIGHT_BOLD) {
 229       mFontOptions.mStyle = FontStyle::BOLD_ITALIC;
 230     } else {
 231       mFontOptions.mStyle = FontStyle::ITALIC;
 232     }
 233   } else {
 234     if (style->weight == NS_FONT_WEIGHT_BOLD) {
 235       mFontOptions.mStyle = FontStyle::BOLD;
 236     } else {
 237       mFontOptions.mStyle = FontStyle::NORMAL;
 238     }
 239   }
 240 }