Clamp the max size of fonts used by skia/chrome canvas.

app/gfx/font_gtk.cc

 // Copyright (c) 2006-2008 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "app/gfx/font.h"
 
+#include <algorithm>
 #include <fontconfig/fontconfig.h>
 #include <gtk/gtk.h>
 
 #include "base/logging.h"
 #include "base/string_piece.h"
 #include "base/utf_string_conversions.h"
 
 namespace gfx {
 
 Font* Font::default_font_ = NULL;
@@ skipping 24 matching lines @@
   FcPatternGetString(match, FC_FAMILY, 0, &match_family);
 
   std::wstring font_family = UTF8ToWide(
       reinterpret_cast<char*>(match_family));
   FcPatternDestroy(match);
   FcPatternDestroy(pattern);
   free(family_name_copy);
   return font_family;
 }
 
+// Pango scales font sizes. This returns the scale factor. See
+// pango_cairo_context_set_resolution for details.
+// NOTE: this isn't entirely accurate, in that Pango also consults the
+// FC_PIXEL_SIZE first (see get_font_size in pangocairo-fcfont), but this
+// seems to give us the same sizes as used by Pango for all our fonts in both
+// English and Thai.
+float Font::GetPangoScaleFactor() {
+  static float scale_factor = 0;
+  static bool determined_scale = false;
+  if (!determined_scale) {
+    PangoContext* context = gdk_pango_context_get();
+    scale_factor = pango_cairo_context_get_resolution(context);
+    // Until we switch to vector graphics, force the max DPI to 96.0.
+    scale_factor = std::min(scale_factor, 96.f);

[Evan Martin, 2010/03/19 04:56:56]

This is the new code, right?

[tony, 2010/03/19 04:59:36]

Yes.

+    g_object_unref(context);
+    if (scale_factor <= 0)
+      scale_factor = 1;
+    else
+      scale_factor /= 72.0;
+    determined_scale = true;
+  }
+  return scale_factor;
+}
+
 // static
 Font Font::CreateFont(PangoFontDescription* desc) {
   gint size = pango_font_description_get_size(desc);
   const char* family_name = pango_font_description_get_family(desc);
 
   // Find best match font for |family_name| to make sure we can get
   // a SkTypeface for the default font.
   // TODO(agl): remove this.
   std::wstring font_family = FindBestMatchFontFamilyName(family_name);
 
@@ skipping 37 matching lines @@
 
   CopyFont(*default_font_);
 }
 
 // static
 PangoFontDescription* Font::PangoFontFromGfxFont(
     const gfx::Font& gfx_font) {
   gfx::Font font = gfx_font;  // Copy so we can call non-const methods.
   PangoFontDescription* pfd = pango_font_description_new();
   pango_font_description_set_family(pfd, WideToUTF8(font.FontName()).c_str());
-  pango_font_description_set_size(pfd, font.FontSize() * PANGO_SCALE);
+  // Set the absolute size to avoid overflowing UI elements.
+  pango_font_description_set_absolute_size(pfd,
+      font.FontSize() * PANGO_SCALE * Font::GetPangoScaleFactor());

[sky, 2010/03/23 20:33:32]

You also need to change Canvas::SetupPangoLayout otherwise we're not symmetrical
if we actually draw.

 
   switch (font.style()) {
     case gfx::Font::NORMAL:
       // Nothing to do, should already be PANGO_STYLE_NORMAL.
       break;
     case gfx::Font::BOLD:
       pango_font_description_set_weight(pfd, PANGO_WEIGHT_BOLD);
       break;
     case gfx::Font::ITALIC:
       pango_font_description_set_style(pfd, PANGO_STYLE_ITALIC);
       break;
     case gfx::Font::UNDERLINED:
       // TODO(deanm): How to do underlined?  Where do we use it?  Probably have
       // to paint it ourselves, see pango_font_metrics_get_underline_position.
       break;
   }
 
   return pfd;
 }
 
 }  // namespace gfx