// 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.

#include "ui/gfx/platform_font_win.h"

#include <windows.h>
#include <dwrite.h>
#include <limits.h>
#include <math.h>
#include <stdint.h>
#include <wchar.h>

#include <algorithm>

#include "base/debug/alias.h"
#include "base/logging.h"
#include "base/macros.h"
#include "base/strings/string16.h"
#include "base/strings/string_util.h"
#include "base/strings/sys_string_conversions.h"
#include "base/strings/utf_string_conversions.h"
#include "base/win/scoped_comptr.h"
#include "base/win/scoped_gdi_object.h"
#include "base/win/scoped_hdc.h"
#include "base/win/scoped_select_object.h"
#include "base/win/win_util.h"
#include "third_party/skia/include/core/SkFontLCDConfig.h"
#include "third_party/skia/include/core/SkRefCnt.h"
#include "third_party/skia/include/core/SkTypeface.h"
#include "ui/gfx/canvas.h"
#include "ui/gfx/font.h"
#include "ui/gfx/font_render_params.h"
#include "ui/gfx/win/scoped_set_map_mode.h"

namespace {

// Returns the minimum font size, using the minimum size callback, if set.
int GetMinimumFontSize() {
  int min_font_size = 0;
  if (gfx::PlatformFontWin::get_minimum_font_size_callback)
    min_font_size = gfx::PlatformFontWin::get_minimum_font_size_callback();
  return min_font_size;
}

// Returns either minimum font allowed for a current locale or
// lf_height + size_delta value.
int AdjustFontSize(int lf_height, int size_delta) {
  if (lf_height < 0) {
    lf_height -= size_delta;
  } else {
    lf_height += size_delta;
  }
  const int min_font_size = GetMinimumFontSize();
  // Make sure lf_height is not smaller than allowed min font size for current
  // locale.
  if (abs(lf_height) < min_font_size) {
    return lf_height < 0 ? -min_font_size : min_font_size;
  } else {
    return lf_height;
  }
}

// Sets style properties on |font_info| based on |font_style|.
void SetLogFontStyle(int font_style, LOGFONT* font_info) {
  font_info->lfUnderline = (font_style & gfx::Font::UNDERLINE) != 0;
  font_info->lfItalic = (font_style & gfx::Font::ITALIC) != 0;
}

gfx::Font::Weight ToGfxFontWeight(int weight) {
  return static_cast<gfx::Font::Weight>(weight);
}

// Uses the GDI interop functionality exposed by DirectWrite to find a
// matching DirectWrite font for the LOGFONT passed in. If we fail to
// find a direct match then we try the DirectWrite font substitution
// route to find a match.
// The contents of the LOGFONT pointer |font_info| may be modified on
// return.
HRESULT FindDirectWriteFontForLOGFONT(IDWriteFactory* factory,
                                      LOGFONT* font_info,
                                      IDWriteFont** dwrite_font) {
  base::win::ScopedComPtr<IDWriteGdiInterop> gdi_interop;
  HRESULT hr = factory->GetGdiInterop(gdi_interop.Receive());
  if (FAILED(hr)) {
    CHECK(false);
    return hr;
  }

  hr = gdi_interop->CreateFontFromLOGFONT(font_info, dwrite_font);
  if (SUCCEEDED(hr))
    return hr;

  base::win::ScopedComPtr<IDWriteFontCollection> font_collection;
  hr = factory->GetSystemFontCollection(font_collection.Receive());
  if (FAILED(hr)) {
    CHECK(false);
    return hr;
  }

  // We try to find a matching font by triggering DirectWrite to substitute the
  // font passed in with a matching font (FontSubstitutes registry key)
  // If this succeeds we return the matched font.
  base::win::ScopedGDIObject<HFONT> font(::CreateFontIndirect(font_info));
  base::win::ScopedGetDC screen_dc(NULL);
  base::win::ScopedSelectObject scoped_font(screen_dc, font.get());

  base::win::ScopedComPtr<IDWriteFontFace> font_face;
  hr = gdi_interop->CreateFontFaceFromHdc(screen_dc, font_face.Receive());
  if (FAILED(hr))
    return hr;

  LOGFONT converted_font = {0};
  hr = gdi_interop->ConvertFontFaceToLOGFONT(font_face.get(), &converted_font);
  if (SUCCEEDED(hr)) {
    hr = font_collection->GetFontFromFontFace(font_face.get(), dwrite_font);
    if (SUCCEEDED(hr)) {
      wcscpy_s(font_info->lfFaceName, arraysize(font_info->lfFaceName),
               converted_font.lfFaceName);
    }
  }
  return hr;
}

// Returns a matching IDWriteFont for the |font_info| passed in. If we fail
// to find a matching font, then we return the IDWriteFont corresponding to
// the default font on the system.
// Returns S_OK on success.
// The contents of the LOGFONT pointer |font_info| may be modified on
// return.
HRESULT GetMatchingDirectWriteFont(LOGFONT* font_info,
                                   bool italic,
                                   IDWriteFactory* factory,
                                   IDWriteFont** dwrite_font) {
  // First try the GDI compat route to get a matching DirectWrite font.
  // If that succeeds then we are good. If that fails then try and find a
  // match from the DirectWrite font collection.
  HRESULT hr = FindDirectWriteFontForLOGFONT(factory, font_info, dwrite_font);
  if (SUCCEEDED(hr))
    return hr;

  // Get a matching font from the system font collection exposed by
  // DirectWrite.
  base::win::ScopedComPtr<IDWriteFontCollection> font_collection;
  hr = factory->GetSystemFontCollection(font_collection.Receive());
  if (FAILED(hr)) {
    CHECK(false);
    return hr;
  }

  // Steps as below:-
  // This mirrors skia.
  // 1. Attempt to find a DirectWrite font family based on the face name in the
  //    font. That may not work at all times, as the face name could be random
  //    GDI has its own font system where in it creates a font matching the
  //    characteristics in the LOGFONT structure passed into
  //    CreateFontIndirect. DirectWrite does not do that. If this succeeds then
  //    return the matching IDWriteFont from the family.
  // 2. If step 1 fails then repeat with the default system font. This has the
  //    same limitations with the face name as mentioned above.
  // 3. If step 2 fails then return the first family from the collection and
  //    use that.
  base::win::ScopedComPtr<IDWriteFontFamily> font_family;
  BOOL exists = FALSE;
  uint32_t index = 0;
  hr = font_collection->FindFamilyName(font_info->lfFaceName, &index, &exists);
  // If we fail to find a match then try fallback to the default font on the
  // system. This is what skia does as well.
  if (FAILED(hr) || (index == UINT_MAX) || !exists) {
    NONCLIENTMETRICS metrics = {0};
    metrics.cbSize = sizeof(metrics);
    if (!SystemParametersInfoW(SPI_GETNONCLIENTMETRICS,
                               sizeof(metrics),
                               &metrics,
                               0)) {
      CHECK(false);
      return E_FAIL;
    }

    if (wcsncmp(font_info->lfFaceName, metrics.lfMessageFont.lfFaceName,
                arraysize(font_info->lfFaceName))) {
      // First try the GDI compat route to get a matching DirectWrite font. If
      // that succeeds we are good. If not find a matching font from the font
      // collection.
      wcscpy_s(font_info->lfFaceName, arraysize(font_info->lfFaceName),
                metrics.lfMessageFont.lfFaceName);
      hr = FindDirectWriteFontForLOGFONT(factory, font_info, dwrite_font);
      if (SUCCEEDED(hr))
        return hr;

      // Best effort to find a matching font from the system font collection.
      hr = font_collection->FindFamilyName(metrics.lfMessageFont.lfFaceName,
                                           &index,
                                           &exists);
    }
  }

  if (index != UINT_MAX && exists) {
    hr = font_collection->GetFontFamily(index, font_family.Receive());
  } else {
    // If we fail to find a matching font, then fallback to the first font in
    // the list. This is what skia does as well.
    hr = font_collection->GetFontFamily(0, font_family.Receive());
  }

  if (FAILED(hr)) {
    CHECK(false);
    return hr;
  }

  DWRITE_FONT_WEIGHT weight =
      static_cast<DWRITE_FONT_WEIGHT>(font_info->lfWeight);
  DWRITE_FONT_STRETCH stretch = DWRITE_FONT_STRETCH_NORMAL;
  DWRITE_FONT_STYLE style =
      (italic) ? DWRITE_FONT_STYLE_ITALIC : DWRITE_FONT_STYLE_NORMAL;

  // The IDWriteFontFamily::GetFirstMatchingFont call fails on certain machines
  // for fonts like MS UI Gothic, Segoe UI, etc. It is not clear why these
  // fonts could be accessible to GDI and not to DirectWrite.
  // The code below adds some debug fields to help track down these failures.
  // 1. We get the matching font list for the font attributes passed in.
  // 2. We get the font count in the family with a debug alias variable.
  // 3. If GetFirstMatchingFont fails then we CHECK as before.
  // Next step would be to remove the CHECKs in this function and fallback to
  // GDI.
  // http://crbug.com/434425
  // TODO(ananta)
  // Remove the GetMatchingFonts and related code here once we get to a stable
  // state in canary.
  base::win::ScopedComPtr<IDWriteFontList> matching_font_list;
  hr = font_family->GetMatchingFonts(weight, stretch, style,
                                     matching_font_list.Receive());
  uint32_t matching_font_count = 0;
  if (SUCCEEDED(hr))
    matching_font_count = matching_font_list->GetFontCount();

  hr = font_family->GetFirstMatchingFont(weight, stretch, style, dwrite_font);
  if (FAILED(hr)) {
    base::debug::Alias(&matching_font_count);
    CHECK(false);
  }

  base::string16 font_name;
  gfx::GetFamilyNameFromDirectWriteFont(*dwrite_font, &font_name);
  wcscpy_s(font_info->lfFaceName, arraysize(font_info->lfFaceName),
           font_name.c_str());
  return hr;
}

}  // namespace

namespace gfx {

// static
PlatformFontWin::HFontRef* PlatformFontWin::base_font_ref_;

// static
PlatformFontWin::AdjustFontCallback
    PlatformFontWin::adjust_font_callback = nullptr;
PlatformFontWin::GetMinimumFontSizeCallback
    PlatformFontWin::get_minimum_font_size_callback = NULL;

IDWriteFactory* PlatformFontWin::direct_write_factory_ = nullptr;

// TODO(ananta)
// Remove the CHECKs in this function once this stabilizes on the field.
HRESULT GetFamilyNameFromDirectWriteFont(IDWriteFont* dwrite_font,
                                         base::string16* family_name) {
  base::win::ScopedComPtr<IDWriteFontFamily> font_family;
  HRESULT hr = dwrite_font->GetFontFamily(font_family.Receive());
  if (FAILED(hr))
    CHECK(false);

  base::win::ScopedComPtr<IDWriteLocalizedStrings> family_names;
  hr = font_family->GetFamilyNames(family_names.Receive());
  if (FAILED(hr))
    CHECK(false);

  // TODO(ananta)
  // Add support for retrieving the family for the current locale.
  wchar_t family_name_for_locale[MAX_PATH] = {0};
  hr = family_names->GetString(0, family_name_for_locale,
                               arraysize(family_name_for_locale));
  if (FAILED(hr))
    CHECK(false);

  *family_name = family_name_for_locale;
  return hr;
}

////////////////////////////////////////////////////////////////////////////////
// PlatformFontWin, public

PlatformFontWin::PlatformFontWin() : font_ref_(GetBaseFontRef()) {
}

PlatformFontWin::PlatformFontWin(NativeFont native_font) {
  InitWithCopyOfHFONT(native_font);
}

PlatformFontWin::PlatformFontWin(const std::string& font_name,
                                 int font_size) {
  InitWithFontNameAndSize(font_name, font_size);
}

////////////////////////////////////////////////////////////////////////////////
// PlatformFontWin, PlatformFont implementation:

Font PlatformFontWin::DeriveFont(int size_delta,
                                 int style,
                                 Font::Weight weight) const {
  LOGFONT font_info;
  GetObject(GetNativeFont(), sizeof(LOGFONT), &font_info);
  const int requested_font_size = font_ref_->requested_font_size();
  font_info.lfHeight = AdjustFontSize(-requested_font_size, size_delta);
  font_info.lfWeight = static_cast<LONG>(weight);
  SetLogFontStyle(style, &font_info);

  HFONT hfont = CreateFontIndirect(&font_info);
  return Font(new PlatformFontWin(CreateHFontRef(hfont)));
}

int PlatformFontWin::GetHeight() {
  return font_ref_->height();
}

Font::Weight PlatformFontWin::GetWeight() const {
  return font_ref_->weight();
}

int PlatformFontWin::GetBaseline() {
  return font_ref_->baseline();
}

int PlatformFontWin::GetCapHeight() {
  return font_ref_->cap_height();
}

int PlatformFontWin::GetExpectedTextWidth(int length) {
  return length * std::min(font_ref_->GetDluBaseX(),
                           font_ref_->ave_char_width());
}

int PlatformFontWin::GetStyle() const {
  return font_ref_->style();
}

const std::string& PlatformFontWin::GetFontName() const {
  return font_ref_->font_name();
}

std::string PlatformFontWin::GetActualFontNameForTesting() const {
  // With the current implementation on Windows, HFontRef::font_name() returns
  // the font name taken from the HFONT handle, but it's not the name that comes
  // from the font's metadata.  See http://crbug.com/327287
  return font_ref_->font_name();
}

std::string PlatformFontWin::GetLocalizedFontName() const {
  base::win::ScopedCreateDC memory_dc(CreateCompatibleDC(NULL));
  if (!memory_dc.Get())
    return GetFontName();

  // When a font has a localized name for a language matching the system
  // locale, GetTextFace() returns the localized name.
  base::win::ScopedSelectObject font(memory_dc.Get(), font_ref_->hfont());
  wchar_t localized_font_name[LF_FACESIZE];
  int length = GetTextFace(memory_dc.Get(), arraysize(localized_font_name),
                           &localized_font_name[0]);
  if (length <= 0)
    return GetFontName();
  return base::SysWideToUTF8(localized_font_name);
}

int PlatformFontWin::GetFontSize() const {
  return font_ref_->font_size();
}

const FontRenderParams& PlatformFontWin::GetFontRenderParams() {
  CR_DEFINE_STATIC_LOCAL(const FontRenderParams, params,
      (gfx::GetFontRenderParams(FontRenderParamsQuery(), NULL)));
  return params;
}

NativeFont PlatformFontWin::GetNativeFont() const {
  return font_ref_->hfont();
}

// static
void PlatformFontWin::SetDirectWriteFactory(IDWriteFactory* factory) {
  // We grab a reference on the DirectWrite factory. This reference is
  // leaked, which is ok because skia leaks it as well.
  factory->AddRef();
  direct_write_factory_ = factory;
}

// static
void PlatformFontWin::GetTextMetricsForFont(HDC hdc,
                                            HFONT font,
                                            TEXTMETRIC* text_metrics) {
  base::win::ScopedSelectObject scoped_font(hdc, font);
  GetTextMetrics(hdc, text_metrics);
}

// static
int PlatformFontWin::GetFontSize(const LOGFONT& font_info) {
  if (font_info.lfHeight < 0)
    return -font_info.lfHeight;

  base::win::ScopedGetDC screen_dc(NULL);
  base::win::ScopedGDIObject<HFONT> font(CreateFontIndirect(&font_info));

  TEXTMETRIC font_metrics = {0};
  PlatformFontWin::GetTextMetricsForFont(screen_dc, font.get(), &font_metrics);
  return font_metrics.tmAscent;
}

////////////////////////////////////////////////////////////////////////////////
// Font, private:

void PlatformFontWin::InitWithCopyOfHFONT(HFONT hfont) {
  DCHECK(hfont);
  LOGFONT font_info;
  GetObject(hfont, sizeof(LOGFONT), &font_info);
  font_ref_ = CreateHFontRef(CreateFontIndirect(&font_info));
}

void PlatformFontWin::InitWithFontNameAndSize(const std::string& font_name,
                                              int font_size) {
  HFONT hf = ::CreateFont(-font_size, 0, 0, 0, FW_DONTCARE, FALSE, FALSE, FALSE,
                          DEFAULT_CHARSET,
                          OUT_DEFAULT_PRECIS,
                          CLIP_DEFAULT_PRECIS,
                          DEFAULT_QUALITY,
                          DEFAULT_PITCH | FF_DONTCARE,
                          base::UTF8ToUTF16(font_name).c_str());
  font_ref_ = CreateHFontRef(hf);
}

// static
PlatformFontWin::HFontRef* PlatformFontWin::GetBaseFontRef() {
  if (base_font_ref_ == NULL) {
    NONCLIENTMETRICS_XP metrics;
    base::win::GetNonClientMetrics(&metrics);

    if (adjust_font_callback)
      adjust_font_callback(&metrics.lfMessageFont);
    metrics.lfMessageFont.lfHeight =
        AdjustFontSize(metrics.lfMessageFont.lfHeight, 0);
    HFONT font = CreateFontIndirect(&metrics.lfMessageFont);
    DLOG_ASSERT(font);
    base_font_ref_ = PlatformFontWin::CreateHFontRef(font);
    // base_font_ref_ is global, up the ref count so it's never deleted.
    base_font_ref_->AddRef();
  }
  return base_font_ref_;
}

PlatformFontWin::HFontRef* PlatformFontWin::CreateHFontRef(HFONT font) {
  TEXTMETRIC font_metrics;

  {
    base::win::ScopedGetDC screen_dc(NULL);
    ScopedSetMapMode mode(screen_dc, MM_TEXT);
    GetTextMetricsForFont(screen_dc, font, &font_metrics);
  }

  if (direct_write_factory_)
    return CreateHFontRefFromSkia(font, font_metrics);

  return CreateHFontRefFromGDI(font, font_metrics);
}

PlatformFontWin::HFontRef* PlatformFontWin::CreateHFontRefFromGDI(
    HFONT font,
    const TEXTMETRIC& font_metrics) {
  const int height = std::max<int>(1, font_metrics.tmHeight);
  const int baseline = std::max<int>(1, font_metrics.tmAscent);
  const int cap_height =
      std::max<int>(1, font_metrics.tmAscent - font_metrics.tmInternalLeading);
  const int ave_char_width = std::max<int>(1, font_metrics.tmAveCharWidth);
  const int font_size =
      std::max<int>(1, font_metrics.tmHeight - font_metrics.tmInternalLeading);
  int style = 0;
  if (font_metrics.tmItalic)
    style |= Font::ITALIC;
  if (font_metrics.tmUnderlined)
    style |= Font::UNDERLINE;

  return new HFontRef(font, font_size, height, baseline, cap_height,
                      ave_char_width, ToGfxFontWeight(font_metrics.tmWeight),
                      style);
}

// static
PlatformFontWin::HFontRef* PlatformFontWin::CreateHFontRefFromSkia(
    HFONT gdi_font,
    const TEXTMETRIC& font_metrics) {
  LOGFONT font_info = {0};
  GetObject(gdi_font, sizeof(LOGFONT), &font_info);

  // If the font height is passed in as 0, assume the height to be -1 to ensure
  // that we return the metrics for a 1 point font.
  // If the font height is positive it represents the rasterized font's cell
  // height. Calculate the actual height accordingly.
  if (font_info.lfHeight > 0) {
    font_info.lfHeight =
        font_metrics.tmInternalLeading - font_metrics.tmHeight;
  } else if (font_info.lfHeight == 0) {
    font_info.lfHeight = -1;
  }

  if (font_info.lfWeight == 0) {
    font_info.lfWeight = static_cast<LONG>(Font::Weight::NORMAL);
  }

  const bool italic = font_info.lfItalic != 0;

  // Skia does not return all values we need for font metrics. For e.g.
  // the cap height which indicates the height of capital letters is not
  // returned even though it is returned by DirectWrite.
  // TODO(ananta)
  // Fix SkScalerContext_win_dw.cpp to return all metrics we need from
  // DirectWrite and remove the code here which retrieves metrics from
  // DirectWrite to calculate the cap height.
  base::win::ScopedComPtr<IDWriteFont> dwrite_font;
  HRESULT hr = GetMatchingDirectWriteFont(
      &font_info, italic, direct_write_factory_, dwrite_font.Receive());
  if (FAILED(hr)) {
    CHECK(false);
    return nullptr;
  }

  DWRITE_FONT_METRICS dwrite_font_metrics = {0};
  dwrite_font->GetMetrics(&dwrite_font_metrics);

  SkFontStyle skia_font_style(font_info.lfWeight, SkFontStyle::kNormal_Width,
                              font_info.lfItalic ? SkFontStyle::kItalic_Slant
                                                 : SkFontStyle::kUpright_Slant);
  sk_sp<SkTypeface> skia_face(
      SkTypeface::MakeFromName(
          base::SysWideToUTF8(font_info.lfFaceName).c_str(),
                              skia_font_style));

  FontRenderParams font_params =
      gfx::GetFontRenderParams(FontRenderParamsQuery(), nullptr);
  SkFontLCDConfig::SetSubpixelOrder(
      FontRenderParams::SubpixelRenderingToSkiaLCDOrder(
          font_params.subpixel_rendering));
  SkFontLCDConfig::SetSubpixelOrientation(
      FontRenderParams::SubpixelRenderingToSkiaLCDOrientation(
          font_params.subpixel_rendering));

  SkPaint paint;
  paint.setAntiAlias(font_params.antialiasing);
  paint.setTypeface(std::move(skia_face));
  paint.setTextSize(-font_info.lfHeight);
  SkPaint::FontMetrics skia_metrics;
  paint.getFontMetrics(&skia_metrics);

  // The calculations below are similar to those in the CreateHFontRef
  // function. The height, baseline and cap height are rounded up to ensure
  // that they match up closely with GDI.
  const int height = std::ceil(skia_metrics.fDescent - skia_metrics.fAscent);
  const int baseline = std::max<int>(1, std::ceil(-skia_metrics.fAscent));
  const int cap_height = std::ceil(paint.getTextSize() *
      static_cast<double>(dwrite_font_metrics.capHeight) /
          dwrite_font_metrics.designUnitsPerEm);

  // The metrics retrieved from skia don't have the average character width. In
  // any case if we get the average character width from skia then use that or
  // the average character width in the TEXTMETRIC structure.
  // TODO(ananta): Investigate whether it is possible to retrieve this value
  // from DirectWrite.
  const int ave_char_width =
      skia_metrics.fAvgCharWidth == 0 ? font_metrics.tmAveCharWidth
              : skia_metrics.fAvgCharWidth;

  int style = 0;
  if (italic)
    style |= Font::ITALIC;
  if (font_info.lfUnderline)
    style |= Font::UNDERLINE;

  // DirectWrite may have substituted the GDI font name with a fallback
  // font. Ensure that it is updated here.
  DeleteObject(gdi_font);
  gdi_font = ::CreateFontIndirect(&font_info);
  return new HFontRef(gdi_font, -font_info.lfHeight, height, baseline,
                      cap_height, ave_char_width,
                      ToGfxFontWeight(font_info.lfWeight), style);
}

PlatformFontWin::PlatformFontWin(HFontRef* hfont_ref) : font_ref_(hfont_ref) {
}

PlatformFontWin::~PlatformFontWin() {
}

////////////////////////////////////////////////////////////////////////////////
// PlatformFontWin::HFontRef:

PlatformFontWin::HFontRef::HFontRef(HFONT hfont,
                                    int font_size,
                                    int height,
                                    int baseline,
                                    int cap_height,
                                    int ave_char_width,
                                    Font::Weight weight,
                                    int style)
    : hfont_(hfont),
      font_size_(font_size),
      height_(height),
      baseline_(baseline),
      cap_height_(cap_height),
      ave_char_width_(ave_char_width),
      weight_(weight),
      style_(style),
      dlu_base_x_(-1),
      requested_font_size_(font_size) {
  DLOG_ASSERT(hfont);

  LOGFONT font_info;
  GetObject(hfont_, sizeof(LOGFONT), &font_info);
  font_name_ = base::UTF16ToUTF8(base::string16(font_info.lfFaceName));

  // Retrieve the font size from the GetTextMetrics API instead of referencing
  // it from the LOGFONT structure. This is because the height as reported by
  // the LOGFONT structure is not always correct. For small fonts with size 1
  // the LOGFONT structure reports the height as -1, while the actual font size
  // is different. (2 on my XP machine).
  base::win::ScopedGetDC screen_dc(NULL);
  TEXTMETRIC font_metrics = {0};
  PlatformFontWin::GetTextMetricsForFont(screen_dc, hfont_, &font_metrics);
  requested_font_size_ = font_metrics.tmHeight - font_metrics.tmInternalLeading;
}

int PlatformFontWin::HFontRef::GetDluBaseX() {
  if (dlu_base_x_ != -1)
    return dlu_base_x_;

  dlu_base_x_ = GetAverageCharWidthInDialogUnits(hfont_);
  return dlu_base_x_;
}

// static
int PlatformFontWin::HFontRef::GetAverageCharWidthInDialogUnits(
    HFONT gdi_font) {
  base::win::ScopedGetDC screen_dc(NULL);
  base::win::ScopedSelectObject font(screen_dc, gdi_font);
  ScopedSetMapMode mode(screen_dc, MM_TEXT);

  // Yes, this is how Microsoft recommends calculating the dialog unit
  // conversions. See: http://support.microsoft.com/kb/125681
  SIZE ave_text_size;
  GetTextExtentPoint32(screen_dc,
                       L"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz",
                       52, &ave_text_size);
  int dlu_base_x = (ave_text_size.cx / 26 + 1) / 2;

  DCHECK_NE(dlu_base_x, -1);
  return dlu_base_x;
}

PlatformFontWin::HFontRef::~HFontRef() {
  DeleteObject(hfont_);
}

////////////////////////////////////////////////////////////////////////////////
// PlatformFont, public:

// static
PlatformFont* PlatformFont::CreateDefault() {
  return new PlatformFontWin;
}

// static
PlatformFont* PlatformFont::CreateFromNativeFont(NativeFont native_font) {
  return new PlatformFontWin(native_font);
}

// static
PlatformFont* PlatformFont::CreateFromNameAndSize(const std::string& font_name,
                                                  int font_size) {
  return new PlatformFontWin(font_name, font_size);
}

}  // namespace gfx