Windows dark mode: fix button typography, make exclusive with high contrast

Bug: 931359
Change-Id: Id017e32692583f81fb30709bf7d26bb6bd2d731a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1506560Reviewed-by: Elly Fong-Jones <ellyjones@chromium.org>
Reviewed-by: Robert Liao <robliao@chromium.org>
Commit-Queue: Leonard Grey <lgrey@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638729}

chrome/browser/ui/views/chrome_typography_provider.cc

@@ -35,11 +35,11 @@ constexpr char kDefaultMonospacedTypeface[] = "DejaVu Sans Mono";
 #endif
 constexpr char kUnspecifiedTypeface[] = "";
 
-// If the default foreground color from the native theme isn't black, the rest
-// of the Harmony spec isn't going to work. Also skip Harmony if a Windows
-// High Contrast theme is enabled. One of the four standard High Contrast themes
-// in Windows 10 still has black text, but (since the user wants high contrast)
-// the grey text shades in Harmony should not be used.
+// If the default foreground color from the native theme isn't black and dark
+// mode is not on the rest of the Harmony spec isn't going to work. Also skip
+// Harmony if a Windows High Contrast theme is enabled. One of the four standard
+// High Contrast themes in Windows 10 still has black text, but (since the user
+// wants high contrast) the grey text shades in Harmony should not be used.
 bool ShouldIgnoreHarmonySpec(const ui::NativeTheme& theme) {
   // Mac provides users limited ways to customize the UI, including dark and
   // high contrast modes; all these are addressed elsewhere, so there's no need
@@ -50,6 +50,8 @@ bool ShouldIgnoreHarmonySpec(const ui::NativeTheme& theme) {
 #else
   if (theme.UsesHighContrastColors())
     return true;
+  if (theme.SystemDarkModeEnabled())
+    return false;
 
   // TODO(pbos): Revisit this check. Both GG900 and black are considered
   // "default black" as the common theme uses GG900 as primary color.

ui/native_theme/native_theme_win.cc

@@ -587,6 +587,11 @@ bool NativeThemeWin::UsesHighContrastColors() const {
 }
 
 bool NativeThemeWin::SystemDarkModeEnabled() const {
+  // Windows high contrast modes are entirely different themes,
+  // so let them take priority over dark mode.
+  // ...unless --force-dark-mode was specified in which case caveat emptor.
+  if (UsesHighContrastColors() && !NativeTheme::SystemDarkModeEnabled())
+    return false;
   bool fDarkModeEnabled = false;
   if (hkcu_themes_regkey_.Valid()) {
     DWORD apps_use_light_theme = 1;