Fix font sizes being incorrect when using --force-device-scale-factor.

ui/base/l10n/l10n_util_win_unittest.cc

 // Copyright (c) 2013 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/base/l10n/l10n_util_win.h"
 
 #include <windows.h>
 
+#include "base/command_line.h"
 #include "base/win/win_util.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/platform_test.h"
+#include "ui/display/display.h"
+#include "ui/display/display_switches.h"
+#include "ui/display/win/screen_win.h"
 
 typedef PlatformTest L10nUtilWinTest;
 
 TEST_F(L10nUtilWinTest, TestDPIScaling) {
   // Baseline font for comparison.
   NONCLIENTMETRICS_XP metrics;
   base::win::GetNonClientMetrics(&metrics);
   LOGFONT lf = metrics.lfMessageFont;
   l10n_util::AdjustUIFont(&lf);
   int size = lf.lfHeight;
   float rounding = size < 0 ? -0.5f : 0.5f;
 
   // Test that font size is properly normalized for DIP. In high-DPI mode, the
   // font metrics are scaled based on the DPI scale factor. For Windows 8, 140%
   // and 180% font scaling are supported. Simulate size normalization for a DPI-
   // aware process by manually scaling up the font and checking that it returns
   // to the expected size.
   lf.lfHeight = static_cast<int>(1.4 * size + rounding);
   l10n_util::AdjustUIFontForDIP(1.4f, &lf);
   EXPECT_NEAR(size, lf.lfHeight, 1);
 
   lf.lfHeight = static_cast<int>(1.8 * size + rounding);
   l10n_util::AdjustUIFontForDIP(1.8f, &lf);
   EXPECT_NEAR(size, lf.lfHeight, 1);
 }
+
+// Test for crbug.com/675933. Since font size is a Windows metric we need to
+// normalize to DIPs based on the real device scale factor, not the forced one.
+TEST_F(L10nUtilWinTest, TestForcedScaling) {
+  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      switches::kForceDeviceScaleFactor, "4");
+  display::Display::ResetForceDeviceScaleFactorForTesting();
+
+  NONCLIENTMETRICS_XP metrics;
+  base::win::GetNonClientMetrics(&metrics);
+  LOGFONT lf = metrics.lfMessageFont;
+
+  // Set the font size to an arbitrary value and make sure it comes through
+  // correctly on the other end.
+  constexpr int test_font_size = 18;
+  lf.lfHeight = test_font_size;
+  l10n_util::AdjustUIFont(&lf);
+  EXPECT_EQ(test_font_size / display::win::ScreenWin::GetSystemScaleFactor(),
+            lf.lfHeight);
+}