[gtk+] Add a fallback for unconverted backends

[Matthias Clasen <matthiasc src gnome org>]

commit b6c4ba0e2ad1e0a30a941594e4003399e74f5792
Author: Matthias Clasen <mclasen redhat com>
Date:   Mon Apr 25 09:07:56 2016 -0400

    Add a fallback for unconverted backends
    
    If the monitor vfuncs are not implemented in a display class,
    fall back to providing a single monitor object representing
    the entire screen. This is not meant to be 'good enough', it
    is just to provide some implementation until all backends
    implement the monitor vfuncs. When that is the case, the
    fallback should be removed.

 gdk/gdkdisplay.c |   33 +++++++++++++++++++++++++++++++++
 1 files changed, 33 insertions(+), 0 deletions(-)
---
diff --git a/gdk/gdkdisplay.c b/gdk/gdkdisplay.c
index d932b50..f26dd7e 100644
--- a/gdk/gdkdisplay.c
+++ b/gdk/gdkdisplay.c
@@ -33,6 +33,7 @@
 #include "gdkinternals.h"
 #include "gdkmarshalers.h"
 #include "gdkscreen.h"
+#include "gdkmonitorprivate.h"
 
 #include <math.h>
 #include <glib.h>
@@ -2520,9 +2521,38 @@ gdk_display_get_n_monitors (GdkDisplay *display)
 {
   g_return_val_if_fail (GDK_IS_DISPLAY (display), 0);
 
+  if (GDK_DISPLAY_GET_CLASS (display)->get_n_monitors == NULL)
+    return 1;
+
   return GDK_DISPLAY_GET_CLASS (display)->get_n_monitors (display);
 }
 
+static GdkMonitor *
+get_fallback_monitor (GdkDisplay *display)
+{
+  static GdkMonitor *monitor = NULL;
+  GdkScreen *screen;
+
+  if (monitor == NULL)
+    {
+      g_warning ("%s does not implement the monitor vfuncs", G_OBJECT_TYPE_NAME (display));
+      monitor = gdk_monitor_new (display);
+      gdk_monitor_set_manufacturer (monitor, "fallback");
+      gdk_monitor_set_position (monitor, 0, 0);
+      gdk_monitor_set_scale_factor (monitor, 1);
+    }
+
+  screen = gdk_display_get_default_screen (display);
+  gdk_monitor_set_size (monitor,
+                        gdk_screen_get_width (screen),
+                        gdk_screen_get_height (screen));
+  gdk_monitor_set_physical_size (monitor,
+                                 gdk_screen_get_width_mm (screen),
+                                 gdk_screen_get_height_mm (screen));
+
+  return monitor;
+}
+
 /**
  * gdk_display_get_monitor:
  * @display: a #GdkDisplay
@@ -2540,6 +2570,9 @@ gdk_display_get_monitor (GdkDisplay *display,
 {
   g_return_val_if_fail (GDK_IS_DISPLAY (display), NULL);
 
+  if (GDK_DISPLAY_GET_CLASS (display)->get_monitor == NULL)
+    return get_fallback_monitor (display);
+
   return GDK_DISPLAY_GET_CLASS (display)->get_monitor (display, monitor_num);
 }