linux_aura: Enable HIDPI support

ui/views/widget/desktop_aura/desktop_screen_x11.cc

Index: ui/views/widget/desktop_aura/desktop_screen_x11.cc
diff --git a/ui/views/widget/desktop_aura/desktop_screen_x11.cc b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
index 9358875895ac0bd2f1aadb30c27df4f1fd018773..8bf3e9f85f767829831a54db100cc7dab3be7997 100644
--- a/ui/views/widget/desktop_aura/desktop_screen_x11.cc
+++ b/ui/views/widget/desktop_aura/desktop_screen_x11.cc
@@ -14,6 +14,7 @@
 #include "base/x11/edid_parser_x11.h"
 #include "ui/aura/root_window.h"
 #include "ui/aura/root_window_host.h"
+#include "ui/base/layout.h"
 #include "ui/base/x/x11_util.h"
 #include "ui/gfx/display.h"
 #include "ui/gfx/display_observer.h"
@@ -29,14 +30,65 @@ namespace {
 // in |Dispatch()|.
 const int64 kConfigureDelayMs = 500;
 
+float g_device_scale_factor = 1.0f;
+
+// A list of bogus sizes in mm that X detects that should be ignored.
+// See crbug.com/136533. The first element maintains the minimum
+// size required to be valid size.
+// (Taken from ash/display/display_change_observer_chromeos.cc)
+const unsigned long kInvalidDisplaySizeList[][2] = {
+  {40, 30},
+  {50, 40},
+  {160, 90},
+  {160, 100},
+};
+
+bool ShouldIgnoreScreen(unsigned long mm_width, unsigned long mm_height) {

[oshima, 2013/10/23 18:10:59]

I thought I left the comment, but apparently not, sorry.

I believe you took this from ash/display/display_change_observer_chromeos.cc.
Can you
move this utility function to ui/base/x/x11_util and use it instead of
duplicating the code?

The name should be someting like

IsDisplaySizeBlackListed

+  // Ignore if the reported display is smaller than minimum size.
+  if (mm_width <= kInvalidDisplaySizeList[0][0] ||
+      mm_height <= kInvalidDisplaySizeList[0][1]) {
+    LOG(WARNING) << "Smaller than minimum display size";
+    return true;
+  }
+  for (unsigned long i = 1 ; i < arraysize(kInvalidDisplaySizeList); ++i) {
+    const unsigned long* size = kInvalidDisplaySizeList[i];
+    if (mm_width == size[0] && mm_height == size[1]) {
+      LOG(WARNING) << "Black listed display size detected:"
+                   << size[0] << "x" << size[1];
+      return true;
+    }
+  }
+  return false;
+}
+
+float GetDeviceScaleFactor(int screen_dim, int mm_screen_dim) {
+  const int kCSSDefaultDIPCountPerInch = 96;
+  const float kInchInMm = 25.4f;
+
+  float screen_DPI = (screen_dim * kInchInMm) / mm_screen_dim;
+  float scale = screen_DPI / kCSSDefaultDIPCountPerInch;
+
+  return ui::GetImageScale(ui::GetSupportedScaleFactor(scale));
+}
+
 std::vector<gfx::Display> GetFallbackDisplayList() {
   ::XDisplay* display = gfx::GetXDisplay();
   ::Screen* screen = DefaultScreenOfDisplay(display);
   int width = WidthOfScreen(screen);
   int height = HeightOfScreen(screen);
+  int mm_width = WidthMMOfScreen(screen);
+  int mm_height = HeightMMOfScreen(screen);
+
+  gfx::Rect bounds_in_pixels(0, 0, width, height);
+  gfx::Display gfx_display(0, bounds_in_pixels);
+  if (!gfx::Display::HasForceDeviceScaleFactor()
+      && !ShouldIgnoreScreen(mm_width, mm_height)) {

[Elliot Glaysher, 2013/10/23 17:51:19]

&& on previous line.

+    g_device_scale_factor = GetDeviceScaleFactor(width, mm_width);
+    DCHECK_LE(1.0f, g_device_scale_factor);
+    gfx_display.SetScaleAndBounds(g_device_scale_factor, bounds_in_pixels);
+  }
 
-  return std::vector<gfx::Display>(
-      1, gfx::Display(0, gfx::Rect(0, 0, width, height)));
+  return std::vector<gfx::Display>(1, gfx_display);
 }
 
 }  // namespace
@@ -128,7 +180,7 @@ void DesktopScreenX11::ProcessDisplayChange(
 // DesktopScreenX11, gfx::Screen implementation:
 
 bool DesktopScreenX11::IsDIPEnabled() {
-  return false;
+  return true;
 }
 
 gfx::Point DesktopScreenX11::GetCursorScreenPoint() {
@@ -317,6 +369,19 @@ std::vector<gfx::Display> DesktopScreenX11::BuildDisplaysFromXRandRInfo() {
 
       gfx::Rect crtc_bounds(crtc->x, crtc->y, crtc->width, crtc->height);
       gfx::Display display(display_id, crtc_bounds);
+
+      if (!gfx::Display::HasForceDeviceScaleFactor()) {
+        if (i == 0 && !ShouldIgnoreScreen(output_info->mm_width,
+                                          output_info->mm_height)) {
+          // As per display scale factor is not supported right now,
+          // the primary display's scale factor is always used.
+          g_device_scale_factor = GetDeviceScaleFactor(crtc->width,
+                                                       output_info->mm_width);
+        }
+        DCHECK_LE(1.0f, g_device_scale_factor);
+        display.SetScaleAndBounds(g_device_scale_factor, crtc_bounds);
+      }
+
       if (has_work_area) {
         gfx::Rect intersection = crtc_bounds;
         intersection.Intersect(work_area);