Modifies the threshold for hidpi displays.

ash/display/display_change_observer_chromeos.cc

 // Copyright 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 "ash/display/display_change_observer_chromeos.h"
 
 #include <algorithm>
 #include <map>
 #include <set>
 #include <vector>
@@ skipping 16 matching lines @@
 namespace ash {
 
 using ui::OutputConfigurator;
 
 namespace {
 
 // The DPI threshold to detect high density screen.
 // Higher DPI than this will use device_scale_factor=2.
 const unsigned int kHighDensityDPIThreshold = 170;
 
+// The HiDPI threshold for bigger (usually external) monitors. Lower threshold

[oshima, 2014/04/08 20:39:47]

"Large" is probably better term. Can you update the one above to XxxSmall ?

[Jun Mukai, 2014/04/09 20:20:07]

Done.

+// makes sense for bigger monitors, because such monitors should be located
+// farther from the user's face usually. See http://crbug.com/348279
+const unsigned int kHighDensityDPIThresholdBigger = 150;
+
+// The width threshold in mm for "bigger" monitors.
+const int kBiggerDisplayWidthThresholdMM = 500;
+
 // 1 inch in mm.
 const float kInchInMm = 25.4f;
 
 // Display mode list is sorted by (in descending priority):
 //  * the area in pixels.
 //  * refresh rate.
 struct DisplayModeSorter {
   bool operator()(const DisplayMode& a, const DisplayMode& b) {
     if (a.size.GetArea() == b.size.GetArea())
       return (a.refresh_rate > b.refresh_rate);
     return (a.size.GetArea() > b.size.GetArea());
   }
 };
 
+bool ShouldBeHiDPI(const gfx::Size& physical_size,

[oshima, 2014/04/08 20:39:47]

Can you change this to return scale factor (like GetScaleFactor(...))
and write unit tests?

[Jun Mukai, 2014/04/09 20:20:07]

Done.

+                   const ui::DisplayMode& mode_info) {
+  if (ui::IsDisplaySizeBlackListed(physical_size))
+    return false;
+
+  const unsigned int dpi = (kInchInMm * mode_info.size().width() /
+                            physical_size.width());
+  const unsigned int threshold =
+      (physical_size.width() >= kBiggerDisplayWidthThresholdMM) ?
+      kHighDensityDPIThresholdBigger : kHighDensityDPIThreshold;
+  return dpi > threshold;
+}
+
 }  // namespace
 
 // static
 std::vector<DisplayMode> DisplayChangeObserver::GetDisplayModeList(
     const OutputConfigurator::DisplayState& output) {
   typedef std::map<std::pair<int, int>, DisplayMode> DisplayModeMap;
   DisplayModeMap display_mode_map;
 
   for (std::vector<const ui::DisplayMode*>::const_iterator it =
            output.display->modes().begin();
@@ skipping 66 matching lines @@
     if (output.display->type() == ui::OUTPUT_TYPE_INTERNAL &&
         gfx::Display::InternalDisplayId() == gfx::Display::kInvalidDisplayID) {
       gfx::Display::SetInternalDisplayId(output.display->display_id());
     }
 
     const ui::DisplayMode* mode_info = output.display->current_mode();
     if (!mode_info)
       continue;
 
     float device_scale_factor = 1.0f;
-    if (!ui::IsDisplaySizeBlackListed(output.display->physical_size()) &&
-        (kInchInMm * mode_info->size().width() /
-         output.display->physical_size().width()) > kHighDensityDPIThreshold) {
+    if (ShouldBeHiDPI(output.display->physical_size(), *mode_info))
       device_scale_factor = 2.0f;
-    }
+
     gfx::Rect display_bounds(output.display->origin(), mode_info->size());
 
     std::vector<DisplayMode> display_modes = GetDisplayModeList(output);
 
     std::string name =
         output.display->type() == ui::OUTPUT_TYPE_INTERNAL
             ? l10n_util::GetStringUTF8(IDS_ASH_INTERNAL_DISPLAY_NAME) :
               output.display->display_name();
     if (name.empty())
       name = l10n_util::GetStringUTF8(IDS_ASH_STATUS_TRAY_UNKNOWN_DISPLAY_NAME);
@@ skipping 22 matching lines @@
 
 void DisplayChangeObserver::OnAppTerminating() {
 #if defined(USE_ASH)
   // Stop handling display configuration events once the shutdown
   // process starts. crbug.com/177014.
   Shell::GetInstance()->output_configurator()->PrepareForExit();
 #endif
 }
 
 }  // namespace ash