ui/gfx/platform_font_win.h

// Copyright (c) 2012 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.

#ifndef UI_GFX_PLATFORM_FONT_WIN_H_
#define UI_GFX_PLATFORM_FONT_WIN_H_

#include <windows.h>

#include <string>

#include "base/compiler_specific.h"
#include "base/gtest_prod_util.h"
#include "base/macros.h"
#include "base/memory/ref_counted.h"
#include "ui/gfx/gfx_export.h"
#include "ui/gfx/platform_font.h"

struct IDWriteFactory;
struct IDWriteFont;

namespace gfx {

namespace internal {
class SystemFonts;
}

class GFX_EXPORT PlatformFontWin : public PlatformFont {
 public:
  enum class SystemFont : int {
    kCaption = 0,
    kSmallCaption,
    kMenu,
    kStatus,
    kMessage
  };

  // Represents an optional override of system font and scale.
  struct FontAdjustment {
    base::string16 font_family_override;
    double font_scale = 1.0;
  };

  PlatformFontWin();
  explicit PlatformFontWin(NativeFont native_font);
  PlatformFontWin(const std::string& font_name, int font_size);

  // Dialog units to pixels conversion.
  // See http://support.microsoft.com/kb/145994 for details.
  int horizontal_dlus_to_pixels(int dlus) const {
    return dlus * font_ref_->GetDluBaseX() / 4;
  }
  int vertical_dlus_to_pixels(int dlus)  const {
    return dlus * font_ref_->height() / 8;
  }

  // Callback that returns the minimum height that should be used for
  // gfx::Fonts. Optional. If not specified, the minimum font size is 0.
  typedef int (*GetMinimumFontSizeCallback)();
  static void SetGetMinimumFontSizeCallback(
      GetMinimumFontSizeCallback callback);

  // Callback that adjusts a SystemFontInfo to meet suitability requirements
  // of the embedding application. Optional. If not specified, no adjustments
  // are performed other than clamping to a minimum font size if
  // |get_minimum_font_size_callback| is specified.
  typedef void (*AdjustFontCallback)(FontAdjustment* font_adjustment);
  static void SetAdjustFontCallback(AdjustFontCallback callback);

  // Returns the font name for the system locale. Some fonts, particularly
  // East Asian fonts, have different names per locale. If the localized font
  // name could not be retrieved, returns GetFontName().
  std::string GetLocalizedFontName() const;

  // Overridden from PlatformFont:
  Font DeriveFont(int size_delta,
                  int style,
                  Font::Weight weight) const override;
  int GetHeight() override;
  Font::Weight GetWeight() const override;
  int GetBaseline() override;
  int GetCapHeight() override;
  int GetExpectedTextWidth(int length) override;
  int GetStyle() const override;
  const std::string& GetFontName() const override;
  std::string GetActualFontNameForTesting() const override;
  int GetFontSize() const override;
  const FontRenderParams& GetFontRenderParams() override;
  NativeFont GetNativeFont() const override;

  // Called once during initialization if we should be retrieving font metrics
  // from skia and DirectWrite.
  static void SetDirectWriteFactory(IDWriteFactory* factory);

  static bool IsDirectWriteEnabled();

  // Returns the specified Windows system font, suitable for drawing on screen
  // elements.
  static const Font& GetSystemFont(SystemFont system_font);

  // Apply a font adjustment to an existing font.
  static Font AdjustExistingFont(NativeFont existing_font,
                                 const FontAdjustment& font_adjustment);

 private:
  friend class internal::SystemFonts;
  FRIEND_TEST_ALL_PREFIXES(RenderTextTest, HarfBuzz_UniscribeFallback);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, Metrics_SkiaVersusGDI);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, DirectWriteFontSubstitution);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, AdjustFontSize);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest,
                           AdjustFontSize_MinimumSizeSpecified);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, AdjustLOGFONT_NoAdjustment);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, AdjustLOGFONT_ChangeFace);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, AdjustLOGFONT_ScaleDown);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest,
                           AdjustLOGFONT_ScaleDownWithRounding);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest,
                           AdjustLOGFONT_ScaleUpWithFaceChange);
  FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest,
                           AdjustLOGFONT_ScaleUpWithRounding);

  ~PlatformFontWin() override;

  // Chrome text drawing bottoms out in the Windows GDI functions that take an
  // HFONT (an opaque handle into Windows). To avoid lots of GDI object
  // allocation and destruction, Font indirectly refers to the HFONT by way of
  // an HFontRef. That is, every Font has an HFontRef, which has an HFONT.
  //
  // HFontRef is reference counted. Upon deletion, it deletes the HFONT.
  // By making HFontRef maintain the reference to the HFONT, multiple
  // HFontRefs can share the same HFONT, and Font can provide value semantics.
  class GFX_EXPORT HFontRef : public base::RefCounted<HFontRef> {
   public:
    // This constructor takes control of the HFONT, and will delete it when
    // the HFontRef is deleted.
    HFontRef(HFONT hfont,
             int font_size,
             int height,
             int baseline,
             int cap_height,
             int ave_char_width,
             Font::Weight weight,
             int style);

    // Accessors
    HFONT hfont() const { return hfont_; }
    int height() const { return height_; }
    int baseline() const { return baseline_; }
    int cap_height() const { return cap_height_; }
    int ave_char_width() const { return ave_char_width_; }
    Font::Weight weight() const { return weight_; }
    int style() const { return style_; }
    const std::string& font_name() const { return font_name_; }
    int font_size() const { return font_size_; }
    int requested_font_size() const { return requested_font_size_; }

    // Returns the average character width in dialog units.
    int GetDluBaseX();

    // Helper to return the average character width using the text extent
    // technique mentioned here. http://support.microsoft.com/kb/125681.
    static int GetAverageCharWidthInDialogUnits(HFONT gdi_font);

   private:
    friend class base::RefCounted<HFontRef>;
    FRIEND_TEST_ALL_PREFIXES(RenderTextTest, HarfBuzz_UniscribeFallback);
    FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, Metrics_SkiaVersusGDI);
    FRIEND_TEST_ALL_PREFIXES(PlatformFontWinTest, DirectWriteFontSubstitution);

    ~HFontRef();

    const HFONT hfont_;
    const int font_size_;
    const int height_;
    const int baseline_;
    const int cap_height_;
    const int ave_char_width_;
    const Font::Weight weight_;
    const int style_;
    // Average character width in dialog units. This is queried lazily from the
    // system, with an initial value of -1 meaning it hasn't yet been queried.
    int dlu_base_x_;
    std::string font_name_;

    // If the requested font size is not possible for the font, |font_size_|
    // will be different than |requested_font_size_|. This is stored separately
    // so that code that increases the font size in a loop will not cause the
    // loop to get stuck on the same size.
    int requested_font_size_;

    DISALLOW_COPY_AND_ASSIGN(HFontRef);
  };

  // Initializes this object with a copy of the specified HFONT.
  void InitWithCopyOfHFONT(HFONT hfont);

  // Initializes this object with the specified font name and size.
  void InitWithFontNameAndSize(const std::string& font_name,
                               int font_size);

  // Returns the GDI metrics for the font passed in.
  static void GetTextMetricsForFont(HDC hdc,
                                    HFONT font,
                                    TEXTMETRIC* text_metrics);

  // Returns the base font ref. This should ONLY be invoked on the
  // UI thread.
  static HFontRef* GetBaseFontRef();

  // Creates and returns a new HFontRef from the specified HFONT.
  static HFontRef* CreateHFontRef(HFONT font);

  // Creates and returns a new HFontRef from the specified HFONT. Uses provided
  // |font_metrics| instead of calculating new one.
  static HFontRef* CreateHFontRefFromGDI(HFONT font,
                                         const TEXTMETRIC& font_metrics);

  // Creates and returns a new HFontRef from the specified HFONT using metrics
  // from skia. Currently this is only used if we use DirectWrite for font
  // metrics.
  // |gdi_font| : Handle to the GDI font created via CreateFontIndirect.
  // |font_metrics| : The GDI font metrics retrieved via the GetTextMetrics
  // API. This is currently used to calculate the correct height of the font
  // in case we get a font created with a positive height.
  // A positive height represents the cell height (ascent + descent).
  // A negative height represents the character Em height which is cell
  // height minus the internal leading value.
  static PlatformFontWin::HFontRef* CreateHFontRefFromSkia(
      HFONT gdi_font,
      const TEXTMETRIC& font_metrics);

  // Adjust a font smaller or larger, subject to the global minimum size.
  // |lf_height| is the height as reported by the LOGFONT structure, and may
  // be positive or negative (but is typically negative, indicating character
  // size rather than cell size). The absolute value of |lf_size| will be
  // adjusted by |size_delta| and then returned with the original sign.
  static int AdjustFontSize(int lf_height, int size_delta);

  // Adjust a LOGFONT structure for optional size scale and face override.
  static void AdjustLOGFONT(const FontAdjustment& font_adjustment,
                            LOGFONT* logfont);

  // Takes control of a native font (e.g. from CreateFontIndirect()) and wraps
  // it in a Font object to manage its lifespan. Note that |hfont| may not be
  // valid after the call; use the returned Font object instead.
  static Font HFontToFont(HFONT hfont);

  // Creates a new PlatformFontWin with the specified HFontRef. Used when
  // constructing a Font from a HFONT we don't want to copy.
  explicit PlatformFontWin(HFontRef* hfont_ref);

    // Reference to the base font all fonts are derived from.
  static HFontRef* base_font_ref_;

  // Indirect reference to the HFontRef, which references the underlying HFONT.
  scoped_refptr<HFontRef> font_ref_;

  // Pointer to the global IDWriteFactory interface.
  static IDWriteFactory* direct_write_factory_;

  // Font adjustment callback.
  static AdjustFontCallback adjust_font_callback_;

  // Minimum size callback.
  static GetMinimumFontSizeCallback get_minimum_font_size_callback_;

  DISALLOW_COPY_AND_ASSIGN(PlatformFontWin);
};

// Returns the family name for the |IDWriteFont| interface passed in.
// The family name is returned in the |family_name| parameter.
// Returns S_OK on success.
HRESULT GetFamilyNameFromDirectWriteFont(IDWriteFont* dwrite_font,
                                         base::string16* family_name);

}  // namespace gfx

#endif  // UI_GFX_PLATFORM_FONT_WIN_H_