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
  11 using namespace mozilla::gfx;
  12
  13 gfxFT2FontBase::gfxFT2FontBase(cairo_scaled_font_t *aScaledFont,
  14                                gfxFontEntry *aFontEntry,
  15                                const gfxFontStyle *aFontStyle)
  16     : gfxFont(aFontEntry, aFontStyle, kAntialiasDefault, aScaledFont),
  17       mSpaceGlyph(0),
  18       mHasMetrics(false)
  19 {
  20     cairo_scaled_font_reference(mScaledFont);
  21     ConstructFontOptions();
  22 }
  23
  24 gfxFT2FontBase::~gfxFT2FontBase()
  25 {
  26     cairo_scaled_font_destroy(mScaledFont);
  27 }
  28
  29 uint32_t
  30 gfxFT2FontBase::GetGlyph(uint32_t aCharCode)
  31 {
  32     // FcFreeTypeCharIndex needs to lock the FT_Face and can end up searching
  33     // through all the postscript glyph names in the font.  Therefore use a
  34     // lightweight cache, which is stored on the cairo_font_face_t.
  35
  36     cairo_font_face_t *face =
  37         cairo_scaled_font_get_font_face(CairoScaledFont());
  38
  39     if (cairo_font_face_status(face) != CAIRO_STATUS_SUCCESS)
  40         return 0;
  41
  42     // This cache algorithm and size is based on what is done in
  43     // cairo_scaled_font_text_to_glyphs and pango_fc_font_real_get_glyph.  I
  44     // think the concept is that adjacent characters probably come mostly from
  45     // one Unicode block.  This assumption is probably not so valid with
  46     // scripts with large character sets as used for East Asian languages.
  47
  48     struct CmapCacheSlot {
  49         uint32_t mCharCode;
  50         uint32_t mGlyphIndex;
  51     };
  52     const uint32_t kNumSlots = 256;
  53     static cairo_user_data_key_t sCmapCacheKey;
  54
  55     CmapCacheSlot *slots = static_cast<CmapCacheSlot*>
  56         (cairo_font_face_get_user_data(face, &sCmapCacheKey));
  57
  58     if (!slots) {
  59         // cairo's caches can keep some cairo_font_faces alive past our last
  60         // destroy, so the destroy function (free) for the cache must be
  61         // callable from cairo without any assumptions about what other
  62         // modules have not been shutdown.
  63         slots = static_cast<CmapCacheSlot*>
  64             (calloc(kNumSlots, sizeof(CmapCacheSlot)));
  65         if (!slots)
  66             return 0;
  67
  68         cairo_status_t status =
  69             cairo_font_face_set_user_data(face, &sCmapCacheKey, slots, free);
  70         if (status != CAIRO_STATUS_SUCCESS) { // OOM
  71             free(slots);
  72             return 0;
  73         }
  74
  75         // Invalidate slot 0 by setting its char code to something that would
  76         // never end up in slot 0.  All other slots are already invalid
  77         // because they have mCharCode = 0 and a glyph for char code 0 will
  78         // always be in the slot 0.
  79         slots[0].mCharCode = 1;
  80     }
  81
  82     CmapCacheSlot *slot = &slots[aCharCode % kNumSlots];
  83     if (slot->mCharCode != aCharCode) {
  84         slot->mCharCode = aCharCode;
  85         slot->mGlyphIndex = gfxFT2LockedFace(this).GetGlyph(aCharCode);
  86     }
  87
  88     return slot->mGlyphIndex;
  89 }
  90
  91 void
  92 gfxFT2FontBase::GetGlyphExtents(uint32_t aGlyph, cairo_text_extents_t* aExtents)
  93 {
  94     NS_PRECONDITION(aExtents != NULL, "aExtents must not be NULL");
  95
  96     cairo_glyph_t glyphs[1];
  97     glyphs[0].index = aGlyph;
  98     glyphs[0].x = 0.0;
  99     glyphs[0].y = 0.0;
 100     // cairo does some caching for us here but perhaps a small gain could be
 101     // made by caching more.  It is usually only the advance that is needed,
 102     // so caching only the advance could allow many requests to be cached with
 103     // little memory use.  Ideally this cache would be merged with
 104     // gfxGlyphExtents.
 105     cairo_scaled_font_glyph_extents(CairoScaledFont(), glyphs, 1, aExtents);
 106 }
 107
 108 const gfxFont::Metrics&
 109 gfxFT2FontBase::GetMetrics()
 110 {
 111     if (mHasMetrics)
 112         return mMetrics;
 113
 114     if (MOZ_UNLIKELY(GetStyle()->size <= 0.0)) {
 115         new(&mMetrics) gfxFont::Metrics(); // zero initialize
 116         mSpaceGlyph = 0;
 117     } else {
 118         gfxFT2LockedFace(this).GetMetrics(&mMetrics, &mSpaceGlyph);
 119     }
 120
 121     SanitizeMetrics(&mMetrics, false);
 122
 123 #if 0
 124     //    printf("font name: %s %f\n", NS_ConvertUTF16toUTF8(GetName()).get(), GetStyle()->size);
 125     //    printf ("pango font %s\n", pango_font_description_to_string (pango_font_describe (font)));
 126
 127     fprintf (stderr, "Font: %s\n", NS_ConvertUTF16toUTF8(GetName()).get());
 128     fprintf (stderr, "    emHeight: %f emAscent: %f emDescent: %f\n", mMetrics.emHeight, mMetrics.emAscent, mMetrics.emDescent);
 129     fprintf (stderr, "    maxAscent: %f maxDescent: %f\n", mMetrics.maxAscent, mMetrics.maxDescent);
 130     fprintf (stderr, "    internalLeading: %f externalLeading: %f\n", mMetrics.externalLeading, mMetrics.internalLeading);
 131     fprintf (stderr, "    spaceWidth: %f aveCharWidth: %f xHeight: %f\n", mMetrics.spaceWidth, mMetrics.aveCharWidth, mMetrics.xHeight);
 132     fprintf (stderr, "    uOff: %f uSize: %f stOff: %f stSize: %f suOff: %f suSize: %f\n", mMetrics.underlineOffset, mMetrics.underlineSize, mMetrics.strikeoutOffset, mMetrics.strikeoutSize, mMetrics.superscriptOffset, mMetrics.subscriptOffset);
 133 #endif
 134
 135     mHasMetrics = true;
 136     return mMetrics;
 137 }
 138
 139 // Get the glyphID of a space
 140 uint32_t
 141 gfxFT2FontBase::GetSpaceGlyph()
 142 {
 143     NS_ASSERTION(GetStyle()->size != 0,
 144                  "forgot to short-circuit a text run with zero-sized font?");
 145     GetMetrics();
 146     return mSpaceGlyph;
 147 }
 148
 149 hb_blob_t *
 150 gfxFT2FontBase::GetFontTable(uint32_t aTag)
 151 {
 152     hb_blob_t *blob;
 153     if (mFontEntry->GetExistingFontTable(aTag, &blob))
 154         return blob;
 155
 156     FallibleTArray<uint8_t> buffer;
 157     bool haveTable = gfxFT2LockedFace(this).GetFontTable(aTag, buffer);
 158
 159     // Cache even when there is no table to save having to open the FT_Face
 160     // again.
 161     return mFontEntry->ShareFontTableAndGetBlob(aTag,
 162                                                 haveTable ? &buffer : nullptr);
 163 }
 164
 165 uint32_t
 166 gfxFT2FontBase::GetGlyph(uint32_t unicode, uint32_t variation_selector)
 167 {
 168     if (variation_selector) {
 169         uint32_t id =
 170             gfxFT2LockedFace(this).GetUVSGlyph(unicode, variation_selector);
 171         if (id)
 172             return id;
 173     }
 174
 175     return GetGlyph(unicode);
 176 }
 177
 178 int32_t
 179 gfxFT2FontBase::GetGlyphWidth(gfxContext *aCtx, uint16_t aGID)
 180 {
 181     cairo_text_extents_t extents;
 182     GetGlyphExtents(aGID, &extents);
 183     // convert to 16.16 fixed point
 184     return NS_lround(0x10000 * extents.x_advance);
 185 }
 186
 187 bool
 188 gfxFT2FontBase::SetupCairoFont(gfxContext *aContext)
 189 {
 190     cairo_t *cr = aContext->GetCairo();
 191
 192     // The scaled font ctm is not relevant right here because
 193     // cairo_set_scaled_font does not record the scaled font itself, but
 194     // merely the font_face, font_matrix, font_options.  The scaled_font used
 195     // for the target can be different from the scaled_font passed to
 196     // cairo_set_scaled_font.  (Unfortunately we have measured only for an
 197     // identity ctm.)
 198     cairo_scaled_font_t *cairoFont = CairoScaledFont();
 199
 200     if (cairo_scaled_font_status(cairoFont) != CAIRO_STATUS_SUCCESS) {
 201         // Don't cairo_set_scaled_font as that would propagate the error to
 202         // the cairo_t, precluding any further drawing.
 203         return false;
 204     }
 205     // Thoughts on which font_options to set on the context:
 206     //
 207     // cairoFont has been created for screen rendering.
 208     //
 209     // When the context is being used for screen rendering, we should set
 210     // font_options such that the same scaled_font gets used (when the ctm is
 211     // the same).  The use of explicit font_options recorded in
 212     // CreateScaledFont ensures that this will happen.
 213     //
 214     // XXXkt: For pdf and ps surfaces, I don't know whether it's better to
 215     // remove surface-specific options, or try to draw with the same
 216     // scaled_font that was used to measure.  As the same font_face is being
 217     // used, its font_options will often override some values anyway (unless
 218     // perhaps we remove those from the FcPattern at face creation).
 219     //
 220     // I can't see any significant difference in printing, irrespective of
 221     // what is set here.  It's too late to change things here as measuring has
 222     // already taken place.  We should really be measuring with a different
 223     // font for pdf and ps surfaces (bug 403513).
 224     cairo_set_scaled_font(cr, cairoFont);
 225     return true;
 226 }
 227
 228 void
 229 gfxFT2FontBase::ConstructFontOptions()
 230 {
 231   NS_LossyConvertUTF16toASCII name(this->GetName());
 232   mFontOptions.mName = name.get();
 233
 234   const gfxFontStyle* style = this->GetStyle();
 235   if (style->style == NS_FONT_STYLE_ITALIC) {
 236     if (style->weight == NS_FONT_WEIGHT_BOLD) {
 237       mFontOptions.mStyle = FONT_STYLE_BOLD_ITALIC;
 238     } else {
 239       mFontOptions.mStyle = FONT_STYLE_ITALIC;
 240     }
 241   } else {
 242     if (style->weight == NS_FONT_WEIGHT_BOLD) {
 243       mFontOptions.mStyle = FONT_STYLE_BOLD;
 244     } else {
 245       mFontOptions.mStyle = FONT_STYLE_NORMAL;
 246     }
 247   }
 248 }