Disable subpixel font rendering on OLED panel

Default FreeType geometry doesn't work well with OLED's pixel layout.

Bug: 377929384
Test: covered by unittests

Change-Id: I83dfb9085a0538e432e4f75b5ba7ab0589617730
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6221115
Commit-Queue: Mitsuru Oshima <oshima@chromium.org>
Reviewed-by: Vincent Chiang <vincentchiang@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1414495}

ash/display/display_manager_unittest.cc

@@ -40,6 +40,7 @@
 #include "base/run_loop.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/stringprintf.h"
+#include "base/test/scoped_feature_list.h"
 #include "build/build_config.h"
 #include "chromeos/ui/base/app_types.h"
 #include "chromeos/ui/base/window_properties.h"
@@ -50,6 +51,7 @@
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/compositor/layer.h"
 #include "ui/display/display.h"
+#include "ui/display/display_features.h"
 #include "ui/display/display_layout.h"
 #include "ui/display/display_layout_builder.h"
 #include "ui/display/display_observer.h"
@@ -70,6 +72,7 @@
 #include "ui/events/devices/touchscreen_device.h"
 #include "ui/events/test/event_generator.h"
 #include "ui/gfx/font_render_params.h"
+#include "ui/gfx/font_render_params_linux.h"
 #include "ui/gfx/geometry/rect_conversions.h"
 #include "ui/gfx/overlay_transform.h"
 #include "ui/wm/core/compound_event_filter.h"
@@ -5530,4 +5533,25 @@ TEST_F(DisplayManagerTest, VirtualDisplayUtilAddRemove) {
   EXPECT_EQ(screen->GetNumDisplays(), initial_display_count);
 }
 
+TEST_F(DisplayManagerTest, FontConfig) {
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  command_line->AppendSwitchASCII("form-factor", "CHROMEBOX");
+  display_manager()->RefreshFontParams();
+  EXPECT_TRUE(gfx::GetFontRenderParamsSubpixelRenderingEnabledForTesting());
+
+  command_line->AppendSwitchASCII("form-factor", "CLAMSHELL");
+  display_manager()->RefreshFontParams();
+  EXPECT_FALSE(gfx::GetFontRenderParamsSubpixelRenderingEnabledForTesting());
+
+  {
+    base::test::ScopedFeatureList feature_list_;
+    feature_list_.InitAndEnableFeature(
+        display::features::kOledScaleFactorEnabled);
+    display_manager()->RefreshFontParams();
+    EXPECT_TRUE(gfx::GetFontRenderParamsSubpixelRenderingEnabledForTesting());
+  }
+  display_manager()->RefreshFontParams();
+  EXPECT_FALSE(gfx::GetFontRenderParamsSubpixelRenderingEnabledForTesting());
+}
+
 }  // namespace ash

ui/display/manager/display_manager.cc

@@ -538,10 +538,16 @@ void DisplayManager::UpdateInternalDisplay(
 }
 
 void DisplayManager::RefreshFontParams() {
+  bool force_disable_subpixel_font_rendering = false;
   if (features::DoesFormFactorControlSubpixelRendering()) {
-    gfx::SetForceDisableSubpixelFontRendering(
-        chromeos::GetFormFactor() != chromeos::form_factor::kClamshell);
+    force_disable_subpixel_font_rendering =
+        chromeos::GetFormFactor() != chromeos::form_factor::kClamshell;
   }
+  if (features::IsOledScaleFactorEnabled()) {
+    force_disable_subpixel_font_rendering = true;
+  }
+  gfx::SetForceDisableSubpixelFontRendering(
+      force_disable_subpixel_font_rendering);
 
   gfx::SetFontRenderParamsDeviceScaleFactor(
       chromeos::GetRepresentativeDeviceScaleFactor(active_display_list_));

ui/gfx/font_render_params_linux.cc

@@ -188,6 +188,10 @@ void SetForceDisableSubpixelFontRendering(bool disable) {
   force_disable_subpixel_font_rendering = disable;
 }
 
+bool GetFontRenderParamsSubpixelRenderingEnabledForTesting() {
+  return force_disable_subpixel_font_rendering;
+}
+
 FontRenderParams GetFontRenderParams(const FontRenderParamsQuery& query,
                                      std::string* family_out) {
   TRACE_EVENT0("fonts", "gfx::GetFontRenderParams");

ui/gfx/font_render_params_linux.h

@@ -20,6 +20,9 @@ bool QueryFontconfig(const FontRenderParamsQuery& query,
 COMPONENT_EXPORT(GFX)
 void SetForceDisableSubpixelFontRendering(bool disable);
 
+COMPONENT_EXPORT(GFX)
+bool GetFontRenderParamsSubpixelRenderingEnabledForTesting();
+
 }  // namespace gfx
 
 #endif  // UI_GFX_FONT_RENDER_PARAMS_LINUX_H_