Linux: make gfx::Canvas honor GTK font settings.

app/gfx/canvas_linux.cc

Index: app/gfx/canvas_linux.cc
diff --git a/app/gfx/canvas_linux.cc b/app/gfx/canvas_linux.cc
index 091685edde0db67048abd16df025c2199f31287f..155221cde40f253e3c32b18f6caa9a3cbec69003 100644
--- a/app/gfx/canvas_linux.cc
+++ b/app/gfx/canvas_linux.cc
@@ -5,6 +5,7 @@
 #include "app/gfx/canvas.h"
 
 #include <cairo/cairo.h>
+#include <gtk/gtk.h>
 #include <pango/pango.h>
 #include <pango/pangocairo.h>
 
@@ -15,6 +16,10 @@
 
 namespace {
 
+// Font settings that we initialize once and then use when drawing text in
+// DrawStringInt().
+static cairo_font_options_t* cairo_font_options = NULL;

[Daniel Erat, 2009/08/05 22:36:03]

Is there a better place to be doing this?  I could make it a static var in
DrawStringInt(), but it seems plausible that another method could need this
someday.  Am I going to cause Valgrind warnings with a one-time "leak" like
this?

[agl, 2009/08/05 22:45:57]

I think it's ok where it is. You shouldn't trigger valgrind warnings as long as
you don't lose the pointer to it.

+
 // Returns a new pango font, free with pango_font_description_free().
 PangoFontDescription* PangoFontFromGfxFont(const gfx::Font& gfx_font) {
   gfx::Font font = gfx_font;  // Copy so we can call non-const methods.
@@ -41,6 +46,70 @@ PangoFontDescription* PangoFontFromGfxFont(const gfx::Font& gfx_font) {
   return pfd;
 }
 
+// Update |cairo_font_options| based on GtkSettings, allocating it if needed.
+static void UpdateCairoFontOptions() {
+  if (!cairo_font_options)
+    cairo_font_options = cairo_font_options_create();
+
+  GtkSettings* gtk_settings = gtk_settings_get_default();
+  gint antialias = 0;
+  gint hinting = 0;
+  gchar* hint_style = NULL;
+  gchar* rgba_style = NULL;
+  g_object_get(gtk_settings,
+               "gtk-xft-antialias", &antialias,
+               "gtk-xft-hinting", &hinting,
+               "gtk-xft-hintstyle", &hint_style,
+               "gtk-xft-rgba", &rgba_style,
+               NULL);
+
+  // g_object_get() doesn't tell us whether the properties were present or not,
+  // but if they aren't (because gnome-settings-daemon isn't running), we'll get
+  // NULL values for the strings.
+  if (hint_style && rgba_style) {
+    if (!antialias) {
+      cairo_font_options_set_antialias(cairo_font_options,
+                                       CAIRO_ANTIALIAS_NONE);
+    } else if (strcmp(rgba_style, "none") == 0) {
+      cairo_font_options_set_antialias(cairo_font_options,
+                                       CAIRO_ANTIALIAS_GRAY);
+    } else {
+      cairo_font_options_set_antialias(cairo_font_options,
+                                       CAIRO_ANTIALIAS_SUBPIXEL);
+      cairo_subpixel_order_t cairo_subpixel_order =
+          CAIRO_SUBPIXEL_ORDER_DEFAULT;
+      if (strcmp(rgba_style, "rgb") == 0) {
+        cairo_subpixel_order = CAIRO_SUBPIXEL_ORDER_RGB;
+      } else if (strcmp(rgba_style, "bgr") == 0) {
+        cairo_subpixel_order = CAIRO_SUBPIXEL_ORDER_BGR;
+      } else if (strcmp(rgba_style, "vrgb") == 0) {
+        cairo_subpixel_order = CAIRO_SUBPIXEL_ORDER_VRGB;
+      } else if (strcmp(rgba_style, "vbgr") == 0) {
+        cairo_subpixel_order = CAIRO_SUBPIXEL_ORDER_VBGR;
+      }
+      cairo_font_options_set_subpixel_order(cairo_font_options,
+                                            cairo_subpixel_order);
+    }
+
+    cairo_hint_style_t cairo_hint_style = CAIRO_HINT_STYLE_DEFAULT;
+    if (hinting == 0 || strcmp(hint_style, "hintnone") == 0) {
+      cairo_hint_style = CAIRO_HINT_STYLE_NONE;
+    } else if (strcmp(hint_style, "hintslight") == 0) {
+      cairo_hint_style = CAIRO_HINT_STYLE_SLIGHT;
+    } else if (strcmp(hint_style, "hintmedium") == 0) {
+      cairo_hint_style = CAIRO_HINT_STYLE_MEDIUM;
+    } else if (strcmp(hint_style, "hintfull") == 0) {
+      cairo_hint_style = CAIRO_HINT_STYLE_FULL;
+    }
+    cairo_font_options_set_hint_style(cairo_font_options, cairo_hint_style);
+  }
+
+  if (hint_style)
+    g_free(hint_style);
+  if (rgba_style)
+    g_free(rgba_style);
+}
+
 }  // namespace
 
 namespace gfx {
@@ -102,6 +171,13 @@ void Canvas::DrawStringInt(const std::wstring& text,
   cairo_t* cr = beginPlatformPaint();
   PangoLayout* layout = pango_cairo_create_layout(cr);
 
+  if (!cairo_font_options)
+    UpdateCairoFontOptions();
+  // This needs to be done early on; it has no effect when called just before
+  // pango_cairo_show_layout().
+  pango_cairo_context_set_font_options(
+      pango_layout_get_context(layout), cairo_font_options);
+
   // Callers of DrawStringInt handle RTL layout themselves, so tell pango to not
   // scope out RTL characters.
   pango_layout_set_auto_dir(layout, FALSE);