ui/gfx: Allow for font-specific rendering settings.

ui/gfx/platform_font_pango.cc

Index: ui/gfx/platform_font_pango.cc
diff --git a/ui/gfx/platform_font_pango.cc b/ui/gfx/platform_font_pango.cc
index 2120d3311bfdbc0ba7df7d6c4f4de38e3f0abc24..1f311f19696f875108d6e5377f7ea977a97a3654 100644
--- a/ui/gfx/platform_font_pango.cc
+++ b/ui/gfx/platform_font_pango.cc
@@ -31,32 +31,6 @@ namespace {
 // IsFallbackFontAllowed function in skia/ext/SkFontHost_fontconfig_direct.cpp.
 const char* kFallbackFontFamilyName = "sans";
 
-// Returns the available font family that best (in FontConfig's eyes) matches
-// the supplied list of family names.
-std::string FindBestMatchFontFamilyName(
-    const std::vector<std::string>& family_names) {
-  FcPattern* pattern = FcPatternCreate();
-  for (std::vector<std::string>::const_iterator it = family_names.begin();
-       it != family_names.end(); ++it) {
-    FcValue fcvalue;
-    fcvalue.type = FcTypeString;
-    fcvalue.u.s = reinterpret_cast<const FcChar8*>(it->c_str());
-    FcPatternAdd(pattern, FC_FAMILY, fcvalue, FcTrue /* append */);
-  }
-
-  FcConfigSubstitute(0, pattern, FcMatchPattern);
-  FcDefaultSubstitute(pattern);
-  FcResult result;
-  FcPattern* match = FcFontMatch(0, pattern, &result);
-  DCHECK(match) << "Could not find font";
-  FcChar8* match_family = NULL;
-  FcPatternGetString(match, FC_FAMILY, 0, &match_family);
-  std::string font_family(reinterpret_cast<char*>(match_family));
-  FcPatternDestroy(pattern);
-  FcPatternDestroy(match);
-  return font_family;
-}
-
 }  // namespace
 
 namespace gfx {
@@ -94,10 +68,20 @@ PlatformFontPango::PlatformFontPango() {
 }
 
 PlatformFontPango::PlatformFontPango(NativeFont native_font) {
+  const int pango_size =
+      pango_font_description_get_size(native_font) / PANGO_SCALE;

[msw, 2014/07/12 00:27:33]

Hmm, can you consolidate this with pango_util's GetPangoFontSizeInPixels?
(perhaps only send/accept pixel sizes in GetCustomFontRenderParams?)

[Daniel Erat, 2014/07/12 01:55:33]

i don't think so. i was hoping to go this route at first, but fontconfig seems
to only e.g. apply point-based matches to queries using points, even if given a
pixel-based size that should fall within the range.

you can see this using https://github.com/derat/font-config-info. when i have a
fontconfig match for a "size" (i.e. points) >= 0 and <= 9 that disables
antialiasing, i see the following:

./font-config-info -f 'Arial 8'  # i.e. 8-point
...
Fontconfig (Arial 8):
requested size       8 points at 96.00 DPI
family               Arial
pixelsize            8.33 pixels
size                 8 points
antialias            0
hinting              1
autohint             0
hintstyle            1 (slight)
rgba                 5 (none)

./font-config-info -f 'Arial 4px'
...
Fontconfig (Arial 4px):
requested size       4.00 pixels at 96.00 DPI
family               Arial
pixelsize            4.00 pixels
size                 [no match]
antialias            1
hinting              1
autohint             0
hintstyle            3 (full)
rgba                 5 (none)

[msw, 2014/07/12 02:26:40]

Acknowledged.

+  const bool pango_using_pixels =
+      pango_font_description_get_size_is_absolute(native_font);
+
+  std::string font_family;
   std::vector<std::string> family_names;
   base::SplitString(pango_font_description_get_family(native_font), ',',
                     &family_names);
-  std::string font_family = FindBestMatchFontFamilyName(family_names);
+  const FontRenderParams params = GetCustomFontRenderParams(
+      false, &family_names,
+      pango_using_pixels ? &pango_size : NULL /* pixel_size */,
+      !pango_using_pixels ? &pango_size : NULL /* point_size */,
+      &font_family);
 
   int style = 0;
   // TODO(davemoore) What should we do about other weights? We currently only
@@ -109,13 +93,16 @@ PlatformFontPango::PlatformFontPango(NativeFont native_font) {
     style |= gfx::Font::ITALIC;
 
   InitFromDetails(skia::RefPtr<SkTypeface>(), font_family,
-                  gfx::GetPangoFontSizeInPixels(native_font), style);
+                  gfx::GetPangoFontSizeInPixels(native_font), style, params);
 }
 
 PlatformFontPango::PlatformFontPango(const std::string& font_name,
                                      int font_size) {
+  const std::vector<std::string> font_list(1, font_name);
+  const FontRenderParams params =
+      GetCustomFontRenderParams(false, &font_list, &font_size, NULL, NULL);
   InitFromDetails(skia::RefPtr<SkTypeface>(), font_name, font_size,
-                  SkTypeface::kNormal);
+                  SkTypeface::kNormal, params);
 }
 
 double PlatformFontPango::underline_position() const {
@@ -148,34 +135,32 @@ void PlatformFontPango::SetDefaultFontDescription(
 #endif
 
 Font PlatformFontPango::DeriveFont(int size_delta, int style) const {
-  // If the delta is negative, if must not push the size below 1
+  // If the delta is negative, it must not push the size below 1.
   if (size_delta < 0)
     DCHECK_LT(-size_delta, font_size_pixels_);
 
-  if (style == style_) {
-    // Fast path, we just use the same typeface at a different size
-    return Font(new PlatformFontPango(typeface_,
-                                      font_family_,
-                                      font_size_pixels_ + size_delta,
-                                      style_));
+  skia::RefPtr<SkTypeface> typeface = typeface_;
+  if (style != style_) {
+    // If the style has changed we may need to load a new face.
+    int skstyle = SkTypeface::kNormal;
+    if (gfx::Font::BOLD & style)
+      skstyle |= SkTypeface::kBold;
+    if (gfx::Font::ITALIC & style)
+      skstyle |= SkTypeface::kItalic;
+    typeface = skia::AdoptRef(SkTypeface::CreateFromName(
+        font_family_.c_str(), static_cast<SkTypeface::Style>(skstyle)));
   }
 
-  // If the style has changed we may need to load a new face
-  int skstyle = SkTypeface::kNormal;
-  if (gfx::Font::BOLD & style)
-    skstyle |= SkTypeface::kBold;
-  if (gfx::Font::ITALIC & style)
-    skstyle |= SkTypeface::kItalic;
-
-  skia::RefPtr<SkTypeface> typeface = skia::AdoptRef(
-      SkTypeface::CreateFromName(
-          font_family_.c_str(),
-          static_cast<SkTypeface::Style>(skstyle)));
+  const int new_size = font_size_pixels_ + size_delta;
+  const std::vector<std::string> family_list(1, font_family_);
+  const FontRenderParams render_params =
+      GetCustomFontRenderParams(false, &family_list, &new_size, NULL, NULL);

[Daniel Erat, 2014/07/11 18:08:40]

calling this is only necessary when |size_delta| is nonzero. i'll update this in
the next revision.

[msw, 2014/07/12 00:27:33]

Really? What if the style (bold/italic) differs?
Please add a comment explaining why that's the case.

[Daniel Erat, 2014/07/12 01:55:33]

to be clear, i mean that the call to GetCustomFontRenderParams() is only
necessary if the size changed, since we only pass the family list and the size
to it. we can just use the previously-queried params otherwise.

[msw, 2014/07/12 02:26:40]

Acknowledged.

 
   return Font(new PlatformFontPango(typeface,
                                     font_family_,
-                                    font_size_pixels_ + size_delta,
-                                    style));
+                                    new_size,
+                                    style,
+                                    render_params));
 }
 
 int PlatformFontPango::GetHeight() const {
@@ -213,6 +198,10 @@ int PlatformFontPango::GetFontSize() const {
   return font_size_pixels_;
 }
 
+const FontRenderParams& PlatformFontPango::GetFontRenderParams() const {
+  return font_render_params_;
+}
+
 NativeFont PlatformFontPango::GetNativeFont() const {
   PangoFontDescription* pfd = pango_font_description_new();
   pango_font_description_set_family(pfd, GetFontName().c_str());
@@ -248,8 +237,9 @@ NativeFont PlatformFontPango::GetNativeFont() const {
 PlatformFontPango::PlatformFontPango(const skia::RefPtr<SkTypeface>& typeface,
                                      const std::string& name,
                                      int size,
-                                     int style) {
-  InitFromDetails(typeface, name, size, style);
+                                     int style,
+                                     const FontRenderParams& render_params) {
+  InitFromDetails(typeface, name, size, style, render_params);
 }
 
 PlatformFontPango::~PlatformFontPango() {}
@@ -258,7 +248,8 @@ void PlatformFontPango::InitFromDetails(
     const skia::RefPtr<SkTypeface>& typeface,
     const std::string& font_family,
     int font_size,
-    int style) {
+    int style,
+    const FontRenderParams& render_params) {
   DCHECK_GT(font_size, 0);
 
   typeface_ = typeface;
@@ -279,6 +270,7 @@ void PlatformFontPango::InitFromDetails(
 
   font_size_pixels_ = font_size;
   style_ = style;
+  font_render_params_ = render_params;
 
   SkPaint paint;
   SkPaint::FontMetrics metrics;
@@ -299,6 +291,7 @@ void PlatformFontPango::InitFromPlatformFont(const PlatformFontPango* other) {
   font_family_ = other->font_family_;
   font_size_pixels_ = other->font_size_pixels_;
   style_ = other->style_;
+  font_render_params_ = other->font_render_params_;
   ascent_pixels_ = other->ascent_pixels_;
   height_pixels_ = other->height_pixels_;
   cap_height_pixels_ = other->cap_height_pixels_;