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..1aa1328e729320d88aff3c799612e4f19e5edd77 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 +30,32 @@ namespace {
 // in |Dispatch()|.
 const int64 kConfigureDelayMs = 500;
 
+float GetDeviceScaleFactor(int screen_dim, int screen_dim_mm) {
+  const int kCSSPixelsPerInch = 96;

[kenneth.r.christiansen, 2013/10/14 08:20:54]

kDefaultCSSPixelsPerInch ?

[Mikhail, 2013/10/14 09:15:52]

Yeah, I would even say kDefaultDIPPerInch to be more aligned with the rest of
the code.

+  const float kMillimetersPerInch = 25.4f;
+  float screen_DPI = (screen_dim * kMillimetersPerInch)
+                    / screen_dim_mm;
+
+  float scale = screen_DPI / kCSSPixelsPerInch;
+
+  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);
 
-  return std::vector<gfx::Display>(
-      1, gfx::Display(0, gfx::Rect(0, 0, width, height)));
+  gfx::Rect bounds_in_pixels(0, 0, width, height);

[kenneth.r.christiansen, 2013/10/14 08:20:54]

device pixels? or css pixels? not obvious

[Mikhail, 2013/10/14 09:15:52]

Device pixels. From what I saw postfix "_in_pixels" always means device pixels
within the chromium codebase.

+  gfx::Display gfx_display(0, bounds_in_pixels);

[kenneth.r.christiansen, 2013/10/14 08:20:54]

Why are we assuming screen 0 here?

[Mikhail, 2013/10/14 09:15:52]

Guess, this is just a fallback display number. Anyway this is not something
introduced by the patch.

+  if (!gfx::Display::HasForceDeviceScaleFactor()) {
+    float device_scale_factor = GetDeviceScaleFactor(width,
+                                                     WidthMMOfScreen(screen));
+    gfx_display.SetScaleAndBounds(device_scale_factor, bounds_in_pixels);
+  }
+
+  return std::vector<gfx::Display>(1, gfx_display);
 }
 
 }  // namespace
@@ -128,7 +147,7 @@ void DesktopScreenX11::ProcessDisplayChange(
 // DesktopScreenX11, gfx::Screen implementation:
 
 bool DesktopScreenX11::IsDIPEnabled() {
-  return false;
+  return true;
 }
 
 gfx::Point DesktopScreenX11::GetCursorScreenPoint() {
@@ -317,6 +336,13 @@ 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()) {
+        float device_scale_factor = GetDeviceScaleFactor(crtc->width,
+                                                         output_info->mm_width);
+        display.SetScaleAndBounds(device_scale_factor, crtc_bounds);
+      }
+
       if (has_work_area) {
         gfx::Rect intersection = crtc_bounds;
         intersection.Intersect(work_area);