ui/gfx/platform_font_win.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/platform_font_win.h"
   6
   7 #include <algorithm>
   8 #include <dwrite.h>
   9 #include <math.h>
  10 #include <windows.h>
  11
  12 #include "base/debug/alias.h"
  13 #include "base/logging.h"
  14 #include "base/macros.h"
  15 #include "base/strings/string_util.h"
  16 #include "base/strings/sys_string_conversions.h"
  17 #include "base/strings/utf_string_conversions.h"
  18 #include "base/win/scoped_comptr.h"
  19 #include "base/win/scoped_gdi_object.h"
  20 #include "base/win/scoped_hdc.h"
  21 #include "base/win/scoped_select_object.h"
  22 #include "base/win/win_util.h"
  23 #include "third_party/skia/include/core/SkTypeface.h"
  24 #include "ui/gfx/canvas.h"
  25 #include "ui/gfx/font.h"
  26 #include "ui/gfx/font_render_params.h"
  27 #include "ui/gfx/win/scoped_set_map_mode.h"
  28
  29 namespace {
  30
  31 // If the tmWeight field of a TEXTMETRIC structure has a value >= this, the
  32 // font is bold.
  33 const int kTextMetricWeightBold = 700;
  34
  35 // Returns the minimum font size, using the minimum size callback, if set.
  36 int GetMinimumFontSize() {
  37   int min_font_size = 0;
  38   if (gfx::PlatformFontWin::get_minimum_font_size_callback)
  39     min_font_size = gfx::PlatformFontWin::get_minimum_font_size_callback();
  40   return min_font_size;
  41 }
  42
  43 // Returns either minimum font allowed for a current locale or
  44 // lf_height + size_delta value.
  45 int AdjustFontSize(int lf_height, int size_delta) {
  46   if (lf_height < 0) {
  47     lf_height -= size_delta;
  48   } else {
  49     lf_height += size_delta;
  50   }
  51   const int min_font_size = GetMinimumFontSize();
  52   // Make sure lf_height is not smaller than allowed min font size for current
  53   // locale.
  54   if (abs(lf_height) < min_font_size) {
  55     return lf_height < 0 ? -min_font_size : min_font_size;
  56   } else {
  57     return lf_height;
  58   }
  59 }
  60
  61 // Sets style properties on |font_info| based on |font_style|.
  62 void SetLogFontStyle(int font_style, LOGFONT* font_info) {
  63   font_info->lfUnderline = (font_style & gfx::Font::UNDERLINE) != 0;
  64   font_info->lfItalic = (font_style & gfx::Font::ITALIC) != 0;
  65   font_info->lfWeight = (font_style & gfx::Font::BOLD) ? FW_BOLD : FW_NORMAL;
  66 }
  67
  68 // Returns a matching IDWriteFont for the |font_info| passed in. If we fail
  69 // to find a matching font, then we return the IDWriteFont corresponding to
  70 // the default font on the system.
  71 // Returns S_OK on success.
  72 HRESULT GetMatchingDirectWriteFont(const LOGFONT& font_info,
  73                                    int font_style,
  74                                    IDWriteFactory* factory,
  75                                    IDWriteFont** dwrite_font) {
  76   // First try the GDI compat route to convert the LOGFONT to a IDWriteFont
  77   // If that succeeds then we are good. If that fails then try and find a
  78   // match from the DirectWrite font collection.
  79   base::win::ScopedComPtr<IDWriteGdiInterop> gdi_interop;
  80   HRESULT hr = factory->GetGdiInterop(gdi_interop.Receive());
  81   if (FAILED(hr)) {
  82     CHECK(false);
  83     return hr;
  84   }
  85
  86   hr = gdi_interop->CreateFontFromLOGFONT(&font_info, dwrite_font);
  87   if (SUCCEEDED(hr))
  88     return hr;
  89
  90   // Get the matching font from the system font collection exposed by
  91   // DirectWrite.
  92   base::win::ScopedComPtr<IDWriteFontCollection> font_collection;
  93   hr = factory->GetSystemFontCollection(font_collection.Receive());
  94   if (FAILED(hr)) {
  95     CHECK(false);
  96     return hr;
  97   }
  98
  99   // Steps as below:-
 100   // This mirrors skia.
 101   // 1. Attempt to find a DirectWrite font family based on the face name in the
 102   //    font. That may not work at all times, as the face name could be random
 103   //    GDI has its own font system where in it creates a font matching the
 104   //    characteristics in the LOGFONT structure passed into
 105   //    CreateFontIndirect. DirectWrite does not do that. If this succeeds then
 106   //    return the matching IDWriteFont from the family.
 107   // 2. If step 1 fails then repeat with the default system font. This has the
 108   //    same limitations with the face name as mentioned above.
 109   // 3. If step 2 fails then return the first family from the collection and
 110   //    use that.
 111   base::win::ScopedComPtr<IDWriteFontFamily> font_family;
 112   BOOL exists = FALSE;
 113   uint32 index = 0;
 114   hr = font_collection->FindFamilyName(font_info.lfFaceName, &index, &exists);
 115   // If we fail to find a match then try fallback to the default font on the
 116   // system. This is what skia does as well.
 117   if (FAILED(hr) || (index == UINT_MAX) || !exists) {
 118     NONCLIENTMETRICS metrics = {0};
 119     metrics.cbSize = sizeof(metrics);
 120     if (!SystemParametersInfoW(SPI_GETNONCLIENTMETRICS,
 121                                sizeof(metrics),
 122                                &metrics,
 123                                0)) {
 124       CHECK(false);
 125       return E_FAIL;
 126     }
 127     hr = font_collection->FindFamilyName(metrics.lfMessageFont.lfFaceName,
 128                                          &index,
 129                                          &exists);
 130   }
 131
 132   if (index != UINT_MAX && exists) {
 133     hr = font_collection->GetFontFamily(index, font_family.Receive());
 134   } else {
 135     // If we fail to find a matching font, then fallback to the first font in
 136     // the list. This is what skia does as well.
 137     hr = font_collection->GetFontFamily(0, font_family.Receive());
 138   }
 139
 140   if (FAILED(hr)) {
 141     CHECK(false);
 142     return hr;
 143   }
 144
 145   DWRITE_FONT_WEIGHT weight = (font_style & SkTypeface::kBold)
 146                             ? DWRITE_FONT_WEIGHT_BOLD
 147                             : DWRITE_FONT_WEIGHT_NORMAL;
 148   DWRITE_FONT_STRETCH stretch = DWRITE_FONT_STRETCH_NORMAL;
 149   DWRITE_FONT_STYLE italic = (font_style & SkTypeface::kItalic)
 150                             ? DWRITE_FONT_STYLE_ITALIC
 151                             : DWRITE_FONT_STYLE_NORMAL;
 152
 153   // The IDWriteFontFamily::GetFirstMatchingFont call fails on certain machines
 154   // for fonts like MS UI Gothic, Segoe UI, etc. It is not clear why these
 155   // fonts could be accessible to GDI and not to DirectWrite.
 156   // The code below adds some debug fields to help track down these failures.
 157   // 1. We get the matching font list for the font attributes passed in.
 158   // 2. We get the font count in the family with a debug alias variable.
 159   // 3. If GetFirstMatchingFont fails then we CHECK as before.
 160   // Next step would be to remove the CHECKs in this function and fallback to
 161   // GDI.
 162   // http://crbug.com/434425
 163   // TODO(ananta)
 164   // Remove the GetMatchingFonts and related code here once we get to a stable
 165   // state in canary.
 166   base::win::ScopedComPtr<IDWriteFontList> matching_font_list;
 167   hr = font_family->GetMatchingFonts(weight, stretch, italic,
 168                                      matching_font_list.Receive());
 169   uint32 matching_font_count = 0;
 170   if (SUCCEEDED(hr))
 171     matching_font_count = matching_font_list->GetFontCount();
 172
 173   hr = font_family->GetFirstMatchingFont(weight, stretch, italic,
 174                                          dwrite_font);
 175   if (FAILED(hr)) {
 176     base::debug::Alias(&matching_font_count);
 177     CHECK(false);
 178   }
 179   return hr;
 180 }
 181
 182 }  // namespace
 183
 184 namespace gfx {
 185
 186 // static
 187 PlatformFontWin::HFontRef* PlatformFontWin::base_font_ref_;
 188
 189 // static
 190 PlatformFontWin::AdjustFontCallback
 191     PlatformFontWin::adjust_font_callback = nullptr;
 192 PlatformFontWin::GetMinimumFontSizeCallback
 193     PlatformFontWin::get_minimum_font_size_callback = NULL;
 194
 195 IDWriteFactory* PlatformFontWin::direct_write_factory_ = nullptr;
 196
 197 ////////////////////////////////////////////////////////////////////////////////
 198 // PlatformFontWin, public
 199
 200 PlatformFontWin::PlatformFontWin() : font_ref_(GetBaseFontRef()) {
 201 }
 202
 203 PlatformFontWin::PlatformFontWin(NativeFont native_font) {
 204   InitWithCopyOfHFONT(native_font);
 205 }
 206
 207 PlatformFontWin::PlatformFontWin(const std::string& font_name,
 208                                  int font_size) {
 209   InitWithFontNameAndSize(font_name, font_size);
 210 }
 211
 212 Font PlatformFontWin::DeriveFontWithHeight(int height, int style) {
 213   DCHECK_GE(height, 0);
 214   if (GetHeight() == height && GetStyle() == style)
 215     return Font(this);
 216
 217   // CreateFontIndirect() doesn't return the largest size for the given height
 218   // when decreasing the height. Iterate to find it.
 219   if (GetHeight() > height) {
 220     const int min_font_size = GetMinimumFontSize();
 221     Font font = DeriveFont(-1, style);
 222     int font_height = font.GetHeight();
 223     int font_size = font.GetFontSize();
 224     while (font_height > height && font_size != min_font_size) {
 225       font = font.Derive(-1, style);
 226       if (font_height == font.GetHeight() && font_size == font.GetFontSize())
 227         break;
 228       font_height = font.GetHeight();
 229       font_size = font.GetFontSize();
 230     }
 231     return font;
 232   }
 233
 234   LOGFONT font_info;
 235   GetObject(GetNativeFont(), sizeof(LOGFONT), &font_info);
 236   font_info.lfHeight = height;
 237   SetLogFontStyle(style, &font_info);
 238
 239   HFONT hfont = CreateFontIndirect(&font_info);
 240   return DeriveWithCorrectedSize(hfont);
 241 }
 242
 243 ////////////////////////////////////////////////////////////////////////////////
 244 // PlatformFontWin, PlatformFont implementation:
 245
 246 Font PlatformFontWin::DeriveFont(int size_delta, int style) const {
 247   LOGFONT font_info;
 248   GetObject(GetNativeFont(), sizeof(LOGFONT), &font_info);
 249   const int requested_font_size = font_ref_->requested_font_size();
 250   font_info.lfHeight = AdjustFontSize(-requested_font_size, size_delta);
 251   SetLogFontStyle(style, &font_info);
 252
 253   HFONT hfont = CreateFontIndirect(&font_info);
 254   return Font(new PlatformFontWin(CreateHFontRef(hfont)));
 255 }
 256
 257 int PlatformFontWin::GetHeight() const {
 258   return font_ref_->height();
 259 }
 260
 261 int PlatformFontWin::GetBaseline() const {
 262   return font_ref_->baseline();
 263 }
 264
 265 int PlatformFontWin::GetCapHeight() const {
 266   return font_ref_->cap_height();
 267 }
 268
 269 int PlatformFontWin::GetExpectedTextWidth(int length) const {
 270   return length * std::min(font_ref_->GetDluBaseX(),
 271                            font_ref_->ave_char_width());
 272 }
 273
 274 int PlatformFontWin::GetStyle() const {
 275   return font_ref_->style();
 276 }
 277
 278 std::string PlatformFontWin::GetFontName() const {
 279   return font_ref_->font_name();
 280 }
 281
 282 std::string PlatformFontWin::GetActualFontNameForTesting() const {
 283   // With the current implementation on Windows, HFontRef::font_name() returns
 284   // the font name taken from the HFONT handle, but it's not the name that comes
 285   // from the font's metadata.  See http://crbug.com/327287
 286   return font_ref_->font_name();
 287 }
 288
 289 std::string PlatformFontWin::GetLocalizedFontName() const {
 290   base::win::ScopedCreateDC memory_dc(CreateCompatibleDC(NULL));
 291   if (!memory_dc.Get())
 292     return GetFontName();
 293
 294   // When a font has a localized name for a language matching the system
 295   // locale, GetTextFace() returns the localized name.
 296   base::win::ScopedSelectObject font(memory_dc.Get(), font_ref_->hfont());
 297   wchar_t localized_font_name[LF_FACESIZE];
 298   int length = GetTextFace(memory_dc.Get(), arraysize(localized_font_name),
 299                            &localized_font_name[0]);
 300   if (length <= 0)
 301     return GetFontName();
 302   return base::SysWideToUTF8(localized_font_name);
 303 }
 304
 305 int PlatformFontWin::GetFontSize() const {
 306   return font_ref_->font_size();
 307 }
 308
 309 const FontRenderParams& PlatformFontWin::GetFontRenderParams() {
 310   CR_DEFINE_STATIC_LOCAL(const gfx::FontRenderParams, params,
 311       (gfx::GetFontRenderParams(gfx::FontRenderParamsQuery(false), NULL)));
 312   return params;
 313 }
 314
 315 NativeFont PlatformFontWin::GetNativeFont() const {
 316   return font_ref_->hfont();
 317 }
 318
 319 void PlatformFontWin::SetDirectWriteFactory(IDWriteFactory* factory) {
 320   // We grab a reference on the DirectWrite factory. This reference is
 321   // leaked, which is ok because skia leaks it as well.
 322   factory->AddRef();
 323   direct_write_factory_ = factory;
 324 }
 325
 326 void PlatformFontWin::GetTextMetricsForFont(HDC hdc,
 327                                             HFONT font,
 328                                             TEXTMETRIC* text_metrics) {
 329   base::win::ScopedSelectObject scoped_font(hdc, font);
 330   GetTextMetrics(hdc, text_metrics);
 331 }
 332
 333 ////////////////////////////////////////////////////////////////////////////////
 334 // Font, private:
 335
 336 void PlatformFontWin::InitWithCopyOfHFONT(HFONT hfont) {
 337   DCHECK(hfont);
 338   LOGFONT font_info;
 339   GetObject(hfont, sizeof(LOGFONT), &font_info);
 340   font_ref_ = CreateHFontRef(CreateFontIndirect(&font_info));
 341 }
 342
 343 void PlatformFontWin::InitWithFontNameAndSize(const std::string& font_name,
 344                                               int font_size) {
 345   HFONT hf = ::CreateFont(-font_size, 0, 0, 0, FW_DONTCARE, FALSE, FALSE, FALSE,
 346                           DEFAULT_CHARSET,
 347                           OUT_DEFAULT_PRECIS,
 348                           CLIP_DEFAULT_PRECIS,
 349                           DEFAULT_QUALITY,
 350                           DEFAULT_PITCH | FF_DONTCARE,
 351                           base::UTF8ToUTF16(font_name).c_str());
 352   font_ref_ = CreateHFontRef(hf);
 353 }
 354
 355 // static
 356 PlatformFontWin::HFontRef* PlatformFontWin::GetBaseFontRef() {
 357   if (base_font_ref_ == NULL) {
 358     NONCLIENTMETRICS_XP metrics;
 359     base::win::GetNonClientMetrics(&metrics);
 360
 361     if (adjust_font_callback)
 362       adjust_font_callback(&metrics.lfMessageFont);
 363     metrics.lfMessageFont.lfHeight =
 364         AdjustFontSize(metrics.lfMessageFont.lfHeight, 0);
 365     HFONT font = CreateFontIndirect(&metrics.lfMessageFont);
 366     DLOG_ASSERT(font);
 367     base_font_ref_ = PlatformFontWin::CreateHFontRef(font);
 368     // base_font_ref_ is global, up the ref count so it's never deleted.
 369     base_font_ref_->AddRef();
 370   }
 371   return base_font_ref_;
 372 }
 373
 374 PlatformFontWin::HFontRef* PlatformFontWin::CreateHFontRef(HFONT font) {
 375   TEXTMETRIC font_metrics;
 376
 377   {
 378     base::win::ScopedGetDC screen_dc(NULL);
 379     gfx::ScopedSetMapMode mode(screen_dc, MM_TEXT);
 380     GetTextMetricsForFont(screen_dc, font, &font_metrics);
 381   }
 382
 383   if (direct_write_factory_)
 384     return CreateHFontRefFromSkia(font, font_metrics);
 385
 386   return CreateHFontRefFromGDI(font, font_metrics);
 387 }
 388
 389 PlatformFontWin::HFontRef* PlatformFontWin::CreateHFontRefFromGDI(
 390     HFONT font,
 391     const TEXTMETRIC& font_metrics) {
 392   const int height = std::max<int>(1, font_metrics.tmHeight);
 393   const int baseline = std::max<int>(1, font_metrics.tmAscent);
 394   const int cap_height =
 395       std::max<int>(1, font_metrics.tmAscent - font_metrics.tmInternalLeading);
 396   const int ave_char_width = std::max<int>(1, font_metrics.tmAveCharWidth);
 397   const int font_size =
 398       std::max<int>(1, font_metrics.tmHeight - font_metrics.tmInternalLeading);
 399   int style = 0;
 400   if (font_metrics.tmItalic)
 401     style |= Font::ITALIC;
 402   if (font_metrics.tmUnderlined)
 403     style |= Font::UNDERLINE;
 404   if (font_metrics.tmWeight >= kTextMetricWeightBold)
 405     style |= Font::BOLD;
 406
 407   return new HFontRef(font, font_size, height, baseline, cap_height,
 408                       ave_char_width, style);
 409 }
 410
 411 Font PlatformFontWin::DeriveWithCorrectedSize(HFONT base_font) {
 412   base::win::ScopedGetDC screen_dc(NULL);
 413   gfx::ScopedSetMapMode mode(screen_dc, MM_TEXT);
 414
 415   base::win::ScopedGDIObject<HFONT> best_font(base_font);
 416   TEXTMETRIC best_font_metrics;
 417   GetTextMetricsForFont(screen_dc, best_font, &best_font_metrics);
 418
 419   LOGFONT font_info;
 420   GetObject(base_font, sizeof(LOGFONT), &font_info);
 421
 422   // Set |lfHeight| to negative value to indicate it's the size, not the height.
 423   font_info.lfHeight =
 424       -(best_font_metrics.tmHeight - best_font_metrics.tmInternalLeading);
 425
 426   do {
 427     // Increment font size. Prefer font with greater size if its height isn't
 428     // greater than height of base font.
 429     font_info.lfHeight = AdjustFontSize(font_info.lfHeight, 1);
 430     base::win::ScopedGDIObject<HFONT> font(CreateFontIndirect(&font_info));
 431     TEXTMETRIC font_metrics;
 432     GetTextMetricsForFont(screen_dc, font, &font_metrics);
 433     if (font_metrics.tmHeight > best_font_metrics.tmHeight)
 434       break;
 435     best_font.Set(font.release());
 436     best_font_metrics = font_metrics;
 437   } while (true);
 438
 439   return Font(new PlatformFontWin(CreateHFontRef(best_font.release())));
 440 }
 441
 442 // static
 443 PlatformFontWin::HFontRef* PlatformFontWin::CreateHFontRefFromSkia(
 444     HFONT gdi_font,
 445     const TEXTMETRIC& font_metrics) {
 446   LOGFONT font_info = {0};
 447   GetObject(gdi_font, sizeof(LOGFONT), &font_info);
 448
 449   // If the font height is passed in as 0, assume the height to be -1 to ensure
 450   // that we return the metrics for a 1 point font.
 451   // If the font height is positive it represents the rasterized font's cell
 452   // height. Calculate the actual height accordingly.
 453   if (font_info.lfHeight > 0) {
 454     font_info.lfHeight =
 455         font_metrics.tmInternalLeading - font_metrics.tmHeight;
 456   } else if (font_info.lfHeight == 0) {
 457     font_info.lfHeight = -1;
 458   }
 459
 460   int skia_style = SkTypeface::kNormal;
 461   if (font_info.lfWeight >= FW_SEMIBOLD &&
 462       font_info.lfWeight <= FW_ULTRABOLD) {
 463     skia_style |= SkTypeface::kBold;
 464   }
 465   if (font_info.lfItalic)
 466     skia_style |= SkTypeface::kItalic;
 467
 468   // Skia does not return all values we need for font metrics. For e.g.
 469   // the cap height which indicates the height of capital letters is not
 470   // returned even though it is returned by DirectWrite.
 471   // TODO(ananta)
 472   // Fix SkScalerContext_win_dw.cpp to return all metrics we need from
 473   // DirectWrite and remove the code here which retrieves metrics from
 474   // DirectWrite to calculate the cap height.
 475   base::win::ScopedComPtr<IDWriteFont> dwrite_font;
 476   HRESULT hr = GetMatchingDirectWriteFont(font_info,
 477                                           skia_style,
 478                                           direct_write_factory_,
 479                                           dwrite_font.Receive());
 480   if (FAILED(hr)) {
 481     CHECK(false);
 482     return nullptr;
 483   }
 484
 485   DWRITE_FONT_METRICS dwrite_font_metrics = {0};
 486   dwrite_font->GetMetrics(&dwrite_font_metrics);
 487
 488   skia::RefPtr<SkTypeface> skia_face = skia::AdoptRef(
 489       SkTypeface::CreateFromName(
 490           base::SysWideToUTF8(font_info.lfFaceName).c_str(),
 491                               static_cast<SkTypeface::Style>(skia_style)));
 492
 493   BOOL antialiasing = TRUE;
 494   SystemParametersInfo(SPI_GETFONTSMOOTHING, 0, &antialiasing, 0);
 495
 496   SkPaint paint;
 497   paint.setAntiAlias(!!antialiasing);
 498   paint.setTypeface(skia_face.get());
 499   paint.setTextSize(-font_info.lfHeight);
 500   SkPaint::FontMetrics skia_metrics;
 501   paint.getFontMetrics(&skia_metrics);
 502
 503   // The calculations below are similar to those in the CreateHFontRef
 504   // function. The height, baseline and cap height are rounded up to ensure
 505   // that they match up closely with GDI.
 506   const int height = std::ceil(
 507       skia_metrics.fDescent - skia_metrics.fAscent + skia_metrics.fLeading);
 508   const int baseline = std::max<int>(1, std::ceil(-skia_metrics.fAscent));
 509   const int cap_height = std::ceil(paint.getTextSize() *
 510       static_cast<double>(dwrite_font_metrics.capHeight) /
 511           dwrite_font_metrics.designUnitsPerEm);
 512
 513   // The metrics retrieved from skia don't have the average character width. In
 514   // any case if we get the average character width from skia then use that or
 515   // use the text extent technique as documented by microsoft. See
 516   // GetAverageCharWidthInDialogUnits for details.
 517   const int ave_char_width =
 518       skia_metrics.fAvgCharWidth == 0 ?
 519           HFontRef::GetAverageCharWidthInDialogUnits(gdi_font)
 520               : skia_metrics.fAvgCharWidth;
 521
 522   int style = 0;
 523   if (skia_style & SkTypeface::kItalic)
 524     style |= Font::ITALIC;
 525   if (font_info.lfUnderline)
 526     style |= Font::UNDERLINE;
 527   if (font_info.lfWeight >= kTextMetricWeightBold)
 528     style |= Font::BOLD;
 529   return new HFontRef(gdi_font, -font_info.lfHeight, height, baseline,
 530                       cap_height, ave_char_width, style);
 531 }
 532
 533 PlatformFontWin::PlatformFontWin(HFontRef* hfont_ref) : font_ref_(hfont_ref) {
 534 }
 535
 536 ////////////////////////////////////////////////////////////////////////////////
 537 // PlatformFontWin::HFontRef:
 538
 539 PlatformFontWin::HFontRef::HFontRef(HFONT hfont,
 540                                     int font_size,
 541                                     int height,
 542                                     int baseline,
 543                                     int cap_height,
 544                                     int ave_char_width,
 545                                     int style)
 546     : hfont_(hfont),
 547       font_size_(font_size),
 548       height_(height),
 549       baseline_(baseline),
 550       cap_height_(cap_height),
 551       ave_char_width_(ave_char_width),
 552       style_(style),
 553       dlu_base_x_(-1),
 554       requested_font_size_(font_size) {
 555   DLOG_ASSERT(hfont);
 556
 557   LOGFONT font_info;
 558   GetObject(hfont_, sizeof(LOGFONT), &font_info);
 559   font_name_ = base::UTF16ToUTF8(base::string16(font_info.lfFaceName));
 560   if (font_info.lfHeight < 0)
 561     requested_font_size_ = -font_info.lfHeight;
 562 }
 563
 564 int PlatformFontWin::HFontRef::GetDluBaseX() {
 565   if (dlu_base_x_ != -1)
 566     return dlu_base_x_;
 567
 568   dlu_base_x_ = GetAverageCharWidthInDialogUnits(hfont_);
 569   return dlu_base_x_;
 570 }
 571
 572 // static
 573 int PlatformFontWin::HFontRef::GetAverageCharWidthInDialogUnits(
 574     HFONT gdi_font) {
 575   base::win::ScopedGetDC screen_dc(NULL);
 576   base::win::ScopedSelectObject font(screen_dc, gdi_font);
 577   gfx::ScopedSetMapMode mode(screen_dc, MM_TEXT);
 578
 579   // Yes, this is how Microsoft recommends calculating the dialog unit
 580   // conversions. See: http://support.microsoft.com/kb/125681
 581   SIZE ave_text_size;
 582   GetTextExtentPoint32(screen_dc,
 583                        L"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz",
 584                        52, &ave_text_size);
 585   int dlu_base_x = (ave_text_size.cx / 26 + 1) / 2;
 586
 587   DCHECK_NE(dlu_base_x, -1);
 588   return dlu_base_x;
 589 }
 590
 591 PlatformFontWin::HFontRef::~HFontRef() {
 592   DeleteObject(hfont_);
 593 }
 594
 595 ////////////////////////////////////////////////////////////////////////////////
 596 // PlatformFont, public:
 597
 598 // static
 599 PlatformFont* PlatformFont::CreateDefault() {
 600   return new PlatformFontWin;
 601 }
 602
 603 // static
 604 PlatformFont* PlatformFont::CreateFromNativeFont(NativeFont native_font) {
 605   return new PlatformFontWin(native_font);
 606 }
 607
 608 // static
 609 PlatformFont* PlatformFont::CreateFromNameAndSize(const std::string& font_name,
 610                                                   int font_size) {
 611   return new PlatformFontWin(font_name, font_size);
 612 }
 613
 614 }  // namespace gfx