[gnome-settings-daemon] xsettings: Enable hidpi scaling on 4K monitors

[Owen Taylor <otaylor src gnome org>]

commit 5efbd21fe649383de3dd4b15c014b55a27304e18
Author: Bastien Nocera <hadess hadess net>
Date:   Wed Nov 20 13:25:54 2013 +0100

    xsettings: Enable hidpi scaling on 4K monitors
    
    Even if HDMI is used.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=709859

 plugins/xsettings/gsd-xsettings-manager.c |   19 +++++++++++++++++--
 1 files changed, 17 insertions(+), 2 deletions(-)
---
diff --git a/plugins/xsettings/gsd-xsettings-manager.c b/plugins/xsettings/gsd-xsettings-manager.c
index 5dd9118..91f1eb5 100644
--- a/plugins/xsettings/gsd-xsettings-manager.c
+++ b/plugins/xsettings/gsd-xsettings-manager.c
@@ -229,6 +229,9 @@
 
 #define HIDPI_LIMIT (DPI_FALLBACK * 2)
 
+/* From http://en.wikipedia.org/wiki/4K_resolution#Resolutions_of_common_formats */
+#define SMALLEST_4K_WIDTH 3656
+
 typedef struct _TranslationEntry TranslationEntry;
 typedef void (* TranslationFunc) (GnomeXSettingsManager *manager,
                                   TranslationEntry      *trans,
@@ -475,6 +478,17 @@ primary_monitor_at_native_resolution (GnomeRROutput *primary)
 }
 
 static gboolean
+primary_monitor_is_4k (GnomeRROutput *primary)
+{
+        GnomeRRMode *mode;
+
+        mode = gnome_rr_output_get_current_mode (primary);
+        if (gnome_rr_mode_get_width (mode) >= SMALLEST_4K_WIDTH)
+                return TRUE;
+        return FALSE;
+}
+
+static gboolean
 primary_monitor_on_hdmi (GnomeRROutput *primary)
 {
         const char *name;
@@ -514,8 +528,9 @@ get_window_scale (GnomeXSettingsManager *manager)
                 output = get_primary_output (rr_screen);
                 if (!output)
                         goto out;
-                if (!primary_monitor_at_native_resolution (output) ||
-                    primary_monitor_on_hdmi (output))
+                if (!primary_monitor_at_native_resolution (output))
+                        goto out;
+                if (!primary_monitor_is_4k (output) && primary_monitor_on_hdmi (output))
                         goto out;
 
                 display = gdk_display_get_default ();