linux_aura: Enable HIDPI support

ui/views/widget/desktop_aura/desktop_screen_x11.cc

 // Copyright (c) 2012 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 "ui/views/widget/desktop_aura/desktop_screen_x11.h"
 
 #include <X11/extensions/Xrandr.h>
 #include <X11/Xlib.h>
 
 // It clashes with out RootWindow.
 #undef RootWindow
 
 #include "base/logging.h"
 #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"
 #include "ui/gfx/native_widget_types.h"
 #include "ui/gfx/screen.h"
 #include "ui/gfx/x/x11_types.h"
 #include "ui/views/widget/desktop_aura/desktop_root_window_host_x11.h"
 #include "ui/views/widget/desktop_aura/desktop_screen.h"
 
 namespace {
 
 // The delay to perform configuration after RRNotify.  See the comment
 // 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
 
 namespace views {
 
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopScreenX11, public:
 
 DesktopScreenX11::DesktopScreenX11()
@@ skipping 71 matching lines @@
     }
   }
 
   displays_ = incoming;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 // DesktopScreenX11, gfx::Screen implementation:
 
 bool DesktopScreenX11::IsDIPEnabled() {
-  return false;
+  return true;
 }
 
 gfx::Point DesktopScreenX11::GetCursorScreenPoint() {
   XDisplay* display = gfx::GetXDisplay();
 
   ::Window root, child;
   int root_x, root_y, win_x, win_y;
   unsigned int mask;
   XQueryPointer(display,
                 DefaultRootWindow(display),
@@ skipping 168 matching lines @@
 
       int64 display_id = -1;
       if (!base::GetDisplayId(output_id, i, &display_id)) {
         // It isn't ideal, but if we can't parse the EDID data, fallback on the
         // display number.
         display_id = i;
       }
 
       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);
         display.set_work_area(intersection);
       }
 
       displays.push_back(display);
 
       XRRFreeCrtcInfo(crtc);
     }
@@ skipping 14 matching lines @@
   ProcessDisplayChange(new_displays);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
 
 gfx::Screen* CreateDesktopScreen() {
   return new DesktopScreenX11;
 }
 
 }  // namespace views