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..44a89f5189dbe964fc5599cd0f42bd7b9fe22e70 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 +30,36 @@ namespace {
 // in |Dispatch()|.
 const int64 kConfigureDelayMs = 500;
 
+float g_device_scale_factor = 1.0f;

[Daniel Erat, 2013/10/29 14:28:25]

why does this need to be global? it looks like it gets assigned by
GetFallbackDisplayList() (which is called by BuildDisplaysFromXRandRInfo() if
the XRandR call fails) and later by BuildDisplaysFromXRandRInfo() if the first
display isn't blacklisted, but i don't see where it's being read.

[Mikhail, 2013/10/29 14:50:55]

Indeed! Thanks for noticing it!

+
+float GetDeviceScaleFactor(int screen_dim, int mm_screen_dim) {

[Daniel Erat, 2013/10/29 14:28:25]

what does "dim" stand for here?

[Mikhail, 2013/10/29 14:50:55]

dimention, probably I should put the whole word.

+  const int kCSSDefaultDIPCountPerInch = 96;

[Daniel Erat, 2013/10/29 14:28:25]

where does this number come from?

[Mikhail, 2013/10/29 14:50:55]

We always assume 96 CSS pixels in an inch

+  const float kInchInMm = 25.4f;
+
+  float screen_DPI = (screen_dim * kInchInMm) / mm_screen_dim;

[Daniel Erat, 2013/10/29 14:28:25]

nit: screen_dpi

+  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() &&
+      !ui::IsXDisplaySizeBlackListed(mm_width, mm_height)) {
+    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 +151,7 @@ void DesktopScreenX11::ProcessDisplayChange(
 // DesktopScreenX11, gfx::Screen implementation:
 
 bool DesktopScreenX11::IsDIPEnabled() {
-  return false;
+  return true;
 }
 
 gfx::Point DesktopScreenX11::GetCursorScreenPoint() {
@@ -317,6 +340,19 @@ 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 && !ui::IsXDisplaySizeBlackListed(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);