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#ifndef UI_GFX_PLATFORM_FONT_WIN_H_
6#define UI_GFX_PLATFORM_FONT_WIN_H_
7
8#include <string>
9
10#include "base/compiler_specific.h"
11#include "base/memory/ref_counted.h"
12#include "ui/gfx/gfx_export.h"
13#include "ui/gfx/platform_font.h"
14
15namespace gfx {
16
17class GFX_EXPORT PlatformFontWin : public PlatformFont {
18 public:
19  PlatformFontWin();
20  explicit PlatformFontWin(NativeFont native_font);
21  PlatformFontWin(const std::string& font_name, int font_size);
22
23  // Dialog units to pixels conversion.
24  // See http://support.microsoft.com/kb/145994 for details.
25  int horizontal_dlus_to_pixels(int dlus) const {
26    return dlus * font_ref_->GetDluBaseX() / 4;
27  }
28  int vertical_dlus_to_pixels(int dlus)  const {
29    return dlus * font_ref_->height() / 8;
30  }
31
32  // Callback that returns the minimum height that should be used for
33  // gfx::Fonts. Optional. If not specified, the minimum font size is 0.
34  typedef int (*GetMinimumFontSizeCallback)();
35  static GetMinimumFontSizeCallback get_minimum_font_size_callback;
36
37  // Callback that adjusts a LOGFONT to meet suitability requirements of the
38  // embedding application. Optional. If not specified, no adjustments are
39  // performed other than clamping to a minimum font height if
40  // |get_minimum_font_size_callback| is specified.
41  typedef void (*AdjustFontCallback)(LOGFONT* lf);
42  static AdjustFontCallback adjust_font_callback;
43
44  // Returns the font name for the system locale. Some fonts, particularly
45  // East Asian fonts, have different names per locale. If the localized font
46  // name could not be retrieved, returns GetFontName().
47  std::string GetLocalizedFontName() const;
48
49  // Returns a derived Font with the specified |style| and with height at most
50  // |height|. If the height and style of the receiver already match, it is
51  // returned. Otherwise, the returned Font will have the largest size such that
52  // its height is less than or equal to |height| (since there may not exist a
53  // size that matches the exact |height| specified).
54  Font DeriveFontWithHeight(int height, int style);
55
56  // Overridden from PlatformFont:
57  virtual Font DeriveFont(int size_delta, int style) const OVERRIDE;
58  virtual int GetHeight() const OVERRIDE;
59  virtual int GetBaseline() const OVERRIDE;
60  virtual int GetCapHeight() const OVERRIDE;
61  virtual int GetExpectedTextWidth(int length) const OVERRIDE;
62  virtual int GetStyle() const OVERRIDE;
63  virtual std::string GetFontName() const OVERRIDE;
64  virtual std::string GetActualFontNameForTesting() const OVERRIDE;
65  virtual int GetFontSize() const OVERRIDE;
66  virtual NativeFont GetNativeFont() const OVERRIDE;
67
68 private:
69  virtual ~PlatformFontWin() {}
70
71  // Chrome text drawing bottoms out in the Windows GDI functions that take an
72  // HFONT (an opaque handle into Windows). To avoid lots of GDI object
73  // allocation and destruction, Font indirectly refers to the HFONT by way of
74  // an HFontRef. That is, every Font has an HFontRef, which has an HFONT.
75  //
76  // HFontRef is reference counted. Upon deletion, it deletes the HFONT.
77  // By making HFontRef maintain the reference to the HFONT, multiple
78  // HFontRefs can share the same HFONT, and Font can provide value semantics.
79  class HFontRef : public base::RefCounted<HFontRef> {
80   public:
81    // This constructor takes control of the HFONT, and will delete it when
82    // the HFontRef is deleted.
83    HFontRef(HFONT hfont,
84             int font_size,
85             int height,
86             int baseline,
87             int cap_height,
88             int ave_char_width,
89             int style);
90
91    // Accessors
92    HFONT hfont() const { return hfont_; }
93    int height() const { return height_; }
94    int baseline() const { return baseline_; }
95    int cap_height() const { return cap_height_; }
96    int ave_char_width() const { return ave_char_width_; }
97    int style() const { return style_; }
98    const std::string& font_name() const { return font_name_; }
99    int font_size() const { return font_size_; }
100    int requested_font_size() const { return requested_font_size_; }
101
102    // Returns the average character width in dialog units.
103    int GetDluBaseX();
104
105   private:
106    friend class base::RefCounted<HFontRef>;
107
108    ~HFontRef();
109
110    const HFONT hfont_;
111    const int font_size_;
112    const int height_;
113    const int baseline_;
114    const int cap_height_;
115    const int ave_char_width_;
116    const int style_;
117    // Average character width in dialog units. This is queried lazily from the
118    // system, with an initial value of -1 meaning it hasn't yet been queried.
119    int dlu_base_x_;
120    std::string font_name_;
121
122    // If the requested font size is not possible for the font, |font_size_|
123    // will be different than |requested_font_size_|. This is stored separately
124    // so that code that increases the font size in a loop will not cause the
125    // loop to get stuck on the same size.
126    int requested_font_size_;
127
128    DISALLOW_COPY_AND_ASSIGN(HFontRef);
129  };
130
131  // Initializes this object with a copy of the specified HFONT.
132  void InitWithCopyOfHFONT(HFONT hfont);
133
134  // Initializes this object with the specified font name and size.
135  void InitWithFontNameAndSize(const std::string& font_name,
136                               int font_size);
137
138  // Returns the base font ref. This should ONLY be invoked on the
139  // UI thread.
140  static HFontRef* GetBaseFontRef();
141
142  // Creates and returns a new HFONTRef from the specified HFONT.
143  static HFontRef* CreateHFontRef(HFONT font);
144
145  // Creates a new PlatformFontWin with the specified HFontRef. Used when
146  // constructing a Font from a HFONT we don't want to copy.
147  explicit PlatformFontWin(HFontRef* hfont_ref);
148
149    // Reference to the base font all fonts are derived from.
150  static HFontRef* base_font_ref_;
151
152  // Indirect reference to the HFontRef, which references the underlying HFONT.
153  scoped_refptr<HFontRef> font_ref_;
154
155  DISALLOW_COPY_AND_ASSIGN(PlatformFontWin);
156};
157
158}  // namespace gfx
159
160#endif  // UI_GFX_PLATFORM_FONT_WIN_H_
161