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
 215   // Create a font with a height near that of the target height.
 216   LOGFONT font_info;
 217   GetObject(GetNativeFont(), sizeof(LOGFONT), &font_info);
 218   font_info.lfHeight = height;
 219   SetLogFontStyle(style, &font_info);
 220
 221   HFONT hfont = CreateFontIndirect(&font_info);
 222   Font font(new PlatformFontWin(CreateHFontRef(hfont)));
 223
 224   // Respect the minimum font size constraint.
 225   const int min_font_size = GetMinimumFontSize();
 226
 227   // Used to avoid shrinking the font and expanding it.
 228   bool ran_shrink_loop = false;
 229
 230   // Iterate to find the largest font with a height <= |height|.
 231   while ((font.GetHeight() > height) &&
 232          (font.GetFontSize() >= min_font_size)) {
 233     ran_shrink_loop = true;
 234     Font derived_font = font.Derive(-1, style);
 235     // Break the loop if the derived font is too small or hasn't shrunk at all.
 236     if ((derived_font.GetFontSize() < min_font_size) ||
 237         ((derived_font.GetFontSize() == font.GetFontSize()) &&
 238          (derived_font.GetHeight() == font.GetHeight())))
 239       break;
 240     font = derived_font;
 241   }
 242
 243   while ((!ran_shrink_loop && font.GetHeight() <= height) ||
 244          (font.GetFontSize() < min_font_size)) {
 245     Font derived_font = font.Derive(1, style);
 246     // Break the loop if the derived font is too large or hasn't grown at all.
 247     if (((derived_font.GetHeight() > height) &&
 248          (font.GetFontSize() >= min_font_size)) ||
 249         ((derived_font.GetFontSize() == font.GetFontSize()) &&
 250          (derived_font.GetHeight() == font.GetHeight())))
 251       break;
 252     font = derived_font;
 253   }
 254   return font;
 255 }
 256
 257 ////////////////////////////////////////////////////////////////////////////////
 258 // PlatformFontWin, PlatformFont implementation:
 259
 260 Font PlatformFontWin::DeriveFont(int size_delta, int style) const {
 261   LOGFONT font_info;
 262   GetObject(GetNativeFont(), sizeof(LOGFONT), &font_info);
 263   const int requested_font_size = font_ref_->requested_font_size();
 264   font_info.lfHeight = AdjustFontSize(-requested_font_size, size_delta);
 265   SetLogFontStyle(style, &font_info);
 266
 267   HFONT hfont = CreateFontIndirect(&font_info);
 268   return Font(new PlatformFontWin(CreateHFontRef(hfont)));
 269 }
 270
 271 int PlatformFontWin::GetHeight() const {
 272   return font_ref_->height();
 273 }
 274
 275 int PlatformFontWin::GetBaseline() const {
 276   return font_ref_->baseline();
 277 }
 278
 279 int PlatformFontWin::GetCapHeight() const {
 280   return font_ref_->cap_height();
 281 }
 282
 283 int PlatformFontWin::GetExpectedTextWidth(int length) const {
 284   return length * std::min(font_ref_->GetDluBaseX(),
 285                            font_ref_->ave_char_width());
 286 }
 287
 288 int PlatformFontWin::GetStyle() const {
 289   return font_ref_->style();
 290 }
 291
 292 std::string PlatformFontWin::GetFontName() const {
 293   return font_ref_->font_name();
 294 }
 295
 296 std::string PlatformFontWin::GetActualFontNameForTesting() const {
 297   // With the current implementation on Windows, HFontRef::font_name() returns
 298   // the font name taken from the HFONT handle, but it's not the name that comes
 299   // from the font's metadata.  See http://crbug.com/327287
 300   return font_ref_->font_name();
 301 }
 302
 303 std::string PlatformFontWin::GetLocalizedFontName() const {
 304   base::win::ScopedCreateDC memory_dc(CreateCompatibleDC(NULL));
 305   if (!memory_dc.Get())
 306     return GetFontName();
 307
 308   // When a font has a localized name for a language matching the system
 309   // locale, GetTextFace() returns the localized name.
 310   base::win::ScopedSelectObject font(memory_dc.Get(), font_ref_->hfont());
 311   wchar_t localized_font_name[LF_FACESIZE];
 312   int length = GetTextFace(memory_dc.Get(), arraysize(localized_font_name),
 313                            &localized_font_name[0]);
 314   if (length <= 0)
 315     return GetFontName();
 316   return base::SysWideToUTF8(localized_font_name);
 317 }
 318
 319 int PlatformFontWin::GetFontSize() const {
 320   return font_ref_->font_size();
 321 }
 322
 323 const FontRenderParams& PlatformFontWin::GetFontRenderParams() {
 324   CR_DEFINE_STATIC_LOCAL(const gfx::FontRenderParams, params,
 325       (gfx::GetFontRenderParams(gfx::FontRenderParamsQuery(false), NULL)));
 326   return params;
 327 }
 328
 329 NativeFont PlatformFontWin::GetNativeFont() const {
 330   return font_ref_->hfont();
 331 }
 332
 333 // static
 334 void PlatformFontWin::SetDirectWriteFactory(IDWriteFactory* factory) {
 335   // We grab a reference on the DirectWrite factory. This reference is
 336   // leaked, which is ok because skia leaks it as well.
 337   factory->AddRef();
 338   direct_write_factory_ = factory;
 339 }
 340
 341 // static
 342 void PlatformFontWin::GetTextMetricsForFont(HDC hdc,
 343                                             HFONT font,
 344                                             TEXTMETRIC* text_metrics) {
 345   base::win::ScopedSelectObject scoped_font(hdc, font);
 346   GetTextMetrics(hdc, text_metrics);
 347 }
 348
 349 // static
 350 int PlatformFontWin::GetFontSize(const LOGFONT& font_info) {
 351   if (font_info.lfHeight < 0)
 352     return -font_info.lfHeight;
 353
 354   base::win::ScopedGetDC screen_dc(NULL);
 355   base::win::ScopedGDIObject<HFONT> font(CreateFontIndirect(&font_info));
 356
 357   TEXTMETRIC font_metrics = {0};
 358   PlatformFontWin::GetTextMetricsForFont(screen_dc, font, &font_metrics);
 359   return font_metrics.tmAscent;
 360 }
 361
 362 ////////////////////////////////////////////////////////////////////////////////
 363 // Font, private:
 364
 365 void PlatformFontWin::InitWithCopyOfHFONT(HFONT hfont) {
 366   DCHECK(hfont);
 367   LOGFONT font_info;
 368   GetObject(hfont, sizeof(LOGFONT), &font_info);
 369   font_ref_ = CreateHFontRef(CreateFontIndirect(&font_info));
 370 }
 371
 372 void PlatformFontWin::InitWithFontNameAndSize(const std::string& font_name,
 373                                               int font_size) {
 374   HFONT hf = ::CreateFont(-font_size, 0, 0, 0, FW_DONTCARE, FALSE, FALSE, FALSE,
 375                           DEFAULT_CHARSET,
 376                           OUT_DEFAULT_PRECIS,
 377                           CLIP_DEFAULT_PRECIS,
 378                           DEFAULT_QUALITY,
 379                           DEFAULT_PITCH | FF_DONTCARE,
 380                           base::UTF8ToUTF16(font_name).c_str());
 381   font_ref_ = CreateHFontRef(hf);
 382 }
 383
 384 // static
 385 PlatformFontWin::HFontRef* PlatformFontWin::GetBaseFontRef() {
 386   if (base_font_ref_ == NULL) {
 387     NONCLIENTMETRICS_XP metrics;
 388     base::win::GetNonClientMetrics(&metrics);
 389
 390     if (adjust_font_callback)
 391       adjust_font_callback(&metrics.lfMessageFont);
 392     metrics.lfMessageFont.lfHeight =
 393         AdjustFontSize(metrics.lfMessageFont.lfHeight, 0);
 394     HFONT font = CreateFontIndirect(&metrics.lfMessageFont);
 395     DLOG_ASSERT(font);
 396     base_font_ref_ = PlatformFontWin::CreateHFontRef(font);
 397     // base_font_ref_ is global, up the ref count so it's never deleted.
 398     base_font_ref_->AddRef();
 399   }
 400   return base_font_ref_;
 401 }
 402
 403 PlatformFontWin::HFontRef* PlatformFontWin::CreateHFontRef(HFONT font) {
 404   TEXTMETRIC font_metrics;
 405
 406   {
 407     base::win::ScopedGetDC screen_dc(NULL);
 408     gfx::ScopedSetMapMode mode(screen_dc, MM_TEXT);
 409     GetTextMetricsForFont(screen_dc, font, &font_metrics);
 410   }
 411
 412   if (direct_write_factory_)
 413     return CreateHFontRefFromSkia(font, font_metrics);
 414
 415   return CreateHFontRefFromGDI(font, font_metrics);
 416 }
 417
 418 PlatformFontWin::HFontRef* PlatformFontWin::CreateHFontRefFromGDI(
 419     HFONT font,
 420     const TEXTMETRIC& font_metrics) {
 421   const int height = std::max<int>(1, font_metrics.tmHeight);
 422   const int baseline = std::max<int>(1, font_metrics.tmAscent);
 423   const int cap_height =
 424       std::max<int>(1, font_metrics.tmAscent - font_metrics.tmInternalLeading);
 425   const int ave_char_width = std::max<int>(1, font_metrics.tmAveCharWidth);
 426   const int font_size =
 427       std::max<int>(1, font_metrics.tmHeight - font_metrics.tmInternalLeading);
 428   int style = 0;
 429   if (font_metrics.tmItalic)
 430     style |= Font::ITALIC;
 431   if (font_metrics.tmUnderlined)
 432     style |= Font::UNDERLINE;
 433   if (font_metrics.tmWeight >= kTextMetricWeightBold)
 434     style |= Font::BOLD;
 435
 436   return new HFontRef(font, font_size, height, baseline, cap_height,
 437                       ave_char_width, style);
 438 }
 439
 440 // static
 441 PlatformFontWin::HFontRef* PlatformFontWin::CreateHFontRefFromSkia(
 442     HFONT gdi_font,
 443     const TEXTMETRIC& font_metrics) {
 444   LOGFONT font_info = {0};
 445   GetObject(gdi_font, sizeof(LOGFONT), &font_info);
 446
 447   // If the font height is passed in as 0, assume the height to be -1 to ensure
 448   // that we return the metrics for a 1 point font.
 449   // If the font height is positive it represents the rasterized font's cell
 450   // height. Calculate the actual height accordingly.
 451   if (font_info.lfHeight > 0) {
 452     font_info.lfHeight =
 453         font_metrics.tmInternalLeading - font_metrics.tmHeight;
 454   } else if (font_info.lfHeight == 0) {
 455     font_info.lfHeight = -1;
 456   }
 457
 458   int skia_style = SkTypeface::kNormal;
 459   if (font_info.lfWeight >= FW_SEMIBOLD &&
 460       font_info.lfWeight <= FW_ULTRABOLD) {
 461     skia_style |= SkTypeface::kBold;
 462   }
 463   if (font_info.lfItalic)
 464     skia_style |= SkTypeface::kItalic;
 465
 466   // Skia does not return all values we need for font metrics. For e.g.
 467   // the cap height which indicates the height of capital letters is not
 468   // returned even though it is returned by DirectWrite.
 469   // TODO(ananta)
 470   // Fix SkScalerContext_win_dw.cpp to return all metrics we need from
 471   // DirectWrite and remove the code here which retrieves metrics from
 472   // DirectWrite to calculate the cap height.
 473   base::win::ScopedComPtr<IDWriteFont> dwrite_font;
 474   HRESULT hr = GetMatchingDirectWriteFont(font_info,
 475                                           skia_style,
 476                                           direct_write_factory_,
 477                                           dwrite_font.Receive());
 478   if (FAILED(hr)) {
 479     CHECK(false);
 480     return nullptr;
 481   }
 482
 483   DWRITE_FONT_METRICS dwrite_font_metrics = {0};
 484   dwrite_font->GetMetrics(&dwrite_font_metrics);
 485
 486   skia::RefPtr<SkTypeface> skia_face = skia::AdoptRef(
 487       SkTypeface::CreateFromName(
 488           base::SysWideToUTF8(font_info.lfFaceName).c_str(),
 489                               static_cast<SkTypeface::Style>(skia_style)));
 490
 491   BOOL antialiasing = TRUE;
 492   SystemParametersInfo(SPI_GETFONTSMOOTHING, 0, &antialiasing, 0);
 493
 494   SkPaint paint;
 495   paint.setAntiAlias(!!antialiasing);
 496   paint.setTypeface(skia_face.get());
 497   paint.setTextSize(-font_info.lfHeight);
 498   SkPaint::FontMetrics skia_metrics;
 499   paint.getFontMetrics(&skia_metrics);
 500
 501   // The calculations below are similar to those in the CreateHFontRef
 502   // function. The height, baseline and cap height are rounded up to ensure
 503   // that they match up closely with GDI.
 504   const int height = std::ceil(skia_metrics.fDescent - skia_metrics.fAscent);
 505   const int baseline = std::max<int>(1, std::ceil(-skia_metrics.fAscent));
 506   const int cap_height = std::ceil(paint.getTextSize() *
 507       static_cast<double>(dwrite_font_metrics.capHeight) /
 508           dwrite_font_metrics.designUnitsPerEm);
 509
 510   // The metrics retrieved from skia don't have the average character width. In
 511   // any case if we get the average character width from skia then use that or
 512   // use the text extent technique as documented by microsoft. See
 513   // GetAverageCharWidthInDialogUnits for details.
 514   const int ave_char_width =
 515       skia_metrics.fAvgCharWidth == 0 ?
 516           HFontRef::GetAverageCharWidthInDialogUnits(gdi_font)
 517               : skia_metrics.fAvgCharWidth;
 518
 519   int style = 0;
 520   if (skia_style & SkTypeface::kItalic)
 521     style |= Font::ITALIC;
 522   if (font_info.lfUnderline)
 523     style |= Font::UNDERLINE;
 524   if (font_info.lfWeight >= kTextMetricWeightBold)
 525     style |= Font::BOLD;
 526   return new HFontRef(gdi_font, -font_info.lfHeight, height, baseline,
 527                       cap_height, ave_char_width, style);
 528 }
 529
 530 PlatformFontWin::PlatformFontWin(HFontRef* hfont_ref) : font_ref_(hfont_ref) {
 531 }
 532
 533 ////////////////////////////////////////////////////////////////////////////////
 534 // PlatformFontWin::HFontRef:
 535
 536 PlatformFontWin::HFontRef::HFontRef(HFONT hfont,
 537                                     int font_size,
 538                                     int height,
 539                                     int baseline,
 540                                     int cap_height,
 541                                     int ave_char_width,
 542                                     int style)
 543     : hfont_(hfont),
 544       font_size_(font_size),
 545       height_(height),
 546       baseline_(baseline),
 547       cap_height_(cap_height),
 548       ave_char_width_(ave_char_width),
 549       style_(style),
 550       dlu_base_x_(-1),
 551       requested_font_size_(font_size) {
 552   DLOG_ASSERT(hfont);
 553
 554   LOGFONT font_info;
 555   GetObject(hfont_, sizeof(LOGFONT), &font_info);
 556   font_name_ = base::UTF16ToUTF8(base::string16(font_info.lfFaceName));
 557
 558   // Retrieve the font size from the GetTextMetrics API instead of referencing
 559   // it from the LOGFONT structure. This is because the height as reported by
 560   // the LOGFONT structure is not always correct. For small fonts with size 1
 561   // the LOGFONT structure reports the height as -1, while the actual font size
 562   // is different. (2 on my XP machine).
 563   base::win::ScopedGetDC screen_dc(NULL);
 564   TEXTMETRIC font_metrics = {0};
 565   PlatformFontWin::GetTextMetricsForFont(screen_dc, hfont_, &font_metrics);
 566   requested_font_size_ = font_metrics.tmHeight - font_metrics.tmInternalLeading;
 567 }
 568
 569 int PlatformFontWin::HFontRef::GetDluBaseX() {
 570   if (dlu_base_x_ != -1)
 571     return dlu_base_x_;
 572
 573   dlu_base_x_ = GetAverageCharWidthInDialogUnits(hfont_);
 574   return dlu_base_x_;
 575 }
 576
 577 // static
 578 int PlatformFontWin::HFontRef::GetAverageCharWidthInDialogUnits(
 579     HFONT gdi_font) {
 580   base::win::ScopedGetDC screen_dc(NULL);
 581   base::win::ScopedSelectObject font(screen_dc, gdi_font);
 582   gfx::ScopedSetMapMode mode(screen_dc, MM_TEXT);
 583
 584   // Yes, this is how Microsoft recommends calculating the dialog unit
 585   // conversions. See: http://support.microsoft.com/kb/125681
 586   SIZE ave_text_size;
 587   GetTextExtentPoint32(screen_dc,
 588                        L"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz",
 589                        52, &ave_text_size);
 590   int dlu_base_x = (ave_text_size.cx / 26 + 1) / 2;
 591
 592   DCHECK_NE(dlu_base_x, -1);
 593   return dlu_base_x;
 594 }
 595
 596 PlatformFontWin::HFontRef::~HFontRef() {
 597   DeleteObject(hfont_);
 598 }
 599
 600 ////////////////////////////////////////////////////////////////////////////////
 601 // PlatformFont, public:
 602
 603 // static
 604 PlatformFont* PlatformFont::CreateDefault() {
 605   return new PlatformFontWin;
 606 }
 607
 608 // static
 609 PlatformFont* PlatformFont::CreateFromNativeFont(NativeFont native_font) {
 610   return new PlatformFontWin(native_font);
 611 }
 612
 613 // static
 614 PlatformFont* PlatformFont::CreateFromNameAndSize(const std::string& font_name,
 615                                                   int font_size) {
 616   return new PlatformFontWin(font_name, font_size);
 617 }
 618
 619 }  // namespace gfx