ui/gfx/pango_util.cc

   1 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "ui/gfx/pango_util.h"
   6
   7 #include <cairo/cairo.h>
   8 #include <pango/pango.h>
   9 #include <pango/pangocairo.h>
  10 #include <string>
  11
  12 #include <algorithm>
  13 #include <map>
  14
  15 #include "base/logging.h"
  16 #include "base/strings/utf_string_conversions.h"
  17 #include "ui/gfx/canvas.h"
  18 #include "ui/gfx/font_list.h"
  19 #include "ui/gfx/font_render_params.h"
  20 #include "ui/gfx/linux_font_delegate.h"
  21 #include "ui/gfx/platform_font_pango.h"
  22 #include "ui/gfx/text_utils.h"
  23
  24 namespace gfx {
  25
  26 namespace {
  27
  28 // Creates and returns a PangoContext. The caller owns the context.
  29 PangoContext* GetPangoContext() {
  30   PangoFontMap* font_map = pango_cairo_font_map_get_default();
  31   return pango_font_map_create_context(font_map);
  32 }
  33
  34 // Returns the DPI that should be used by Pango.
  35 double GetPangoDPI() {
  36   static double dpi = -1.0;
  37   if (dpi < 0.0) {
  38     const gfx::LinuxFontDelegate* delegate = gfx::LinuxFontDelegate::instance();
  39     if (delegate)
  40       dpi = delegate->GetFontDPI();
  41     if (dpi <= 0.0)
  42       dpi = 96.0;
  43   }
  44   return dpi;
  45 }
  46
  47 // Returns the number of pixels in a point.
  48 // - multiply a point size by this to get pixels ("device units")
  49 // - divide a pixel size by this to get points
  50 double GetPixelsInPoint() {
  51   static double pixels_in_point = GetPangoDPI() / 72.0;  // 72 points in an inch
  52   return pixels_in_point;
  53 }
  54
  55 }  // namespace
  56
  57 int GetPangoFontSizeInPixels(PangoFontDescription* pango_font) {
  58   // If the size is absolute, then it's in Pango units rather than points. There
  59   // are PANGO_SCALE Pango units in a device unit (pixel).
  60   if (pango_font_description_get_size_is_absolute(pango_font))
  61     return pango_font_description_get_size(pango_font) / PANGO_SCALE;
  62
  63   // Otherwise, we need to convert from points.
  64   return static_cast<int>(GetPixelsInPoint() *
  65       pango_font_description_get_size(pango_font) / PANGO_SCALE + 0.5);
  66 }
  67
  68 PangoFontMetrics* GetPangoFontMetrics(PangoFontDescription* desc) {
  69   static std::map<int, PangoFontMetrics*>* desc_to_metrics = NULL;
  70   static PangoContext* context = NULL;
  71
  72   if (!context) {
  73     context = GetPangoContext();
  74     pango_context_set_language(context, pango_language_get_default());
  75   }
  76
  77   if (!desc_to_metrics)
  78     desc_to_metrics = new std::map<int, PangoFontMetrics*>();
  79
  80   const int desc_hash = pango_font_description_hash(desc);
  81   std::map<int, PangoFontMetrics*>::iterator i =
  82       desc_to_metrics->find(desc_hash);
  83
  84   if (i == desc_to_metrics->end()) {
  85     PangoFontMetrics* metrics = pango_context_get_metrics(context, desc, NULL);
  86     desc_to_metrics->insert(std::make_pair(desc_hash, metrics));
  87     return metrics;
  88   }
  89   return i->second;
  90 }
  91
  92 }  // namespace gfx