[gtk/broadway-display-scale] broadway: Add a setter for display scale

[Matthias Clasen <matthiasc src gnome org>]

commit 6837e6e565b6dd871e223f356845f1be463f8f9d
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun May 9 19:42:42 2021 -0400

    broadway: Add a setter for display scale
    
    This is useful when using Broadway as a headless
    display server.
    
    Fixes: #3934

 gdk/broadway/gdkbroadwaydisplay.h  |  4 ++++
 gdk/broadway/gdkdisplay-broadway.c | 38 ++++++++++++++++++++++++++++++++++++--
 gdk/broadway/gdkdisplay-broadway.h |  1 +
 3 files changed, 41 insertions(+), 2 deletions(-)
---
diff --git a/gdk/broadway/gdkbroadwaydisplay.h b/gdk/broadway/gdkbroadwaydisplay.h
index b7293dc932..79e78c9a62 100644
--- a/gdk/broadway/gdkbroadwaydisplay.h
+++ b/gdk/broadway/gdkbroadwaydisplay.h
@@ -48,6 +48,10 @@ void                    gdk_broadway_display_show_keyboard       (GdkBroadwayDis
 GDK_AVAILABLE_IN_ALL
 void                    gdk_broadway_display_hide_keyboard       (GdkBroadwayDisplay *display);
 
+GDK_AVAILABLE_IN_4_4
+void                    gdk_broadway_display_set_surface_scale   (GdkDisplay *display,
+                                                                  int         scale);
+
 G_END_DECLS
 
 #endif /* __GDK_BROADWAY_DISPLAY_H__ */
diff --git a/gdk/broadway/gdkdisplay-broadway.c b/gdk/broadway/gdkdisplay-broadway.c
index 86e299d13a..c4b54d53d4 100644
--- a/gdk/broadway/gdkdisplay-broadway.c
+++ b/gdk/broadway/gdkdisplay-broadway.c
@@ -94,10 +94,12 @@ _gdk_broadway_display_size_changed (GdkDisplay                      *display,
 
   if (msg->width == current_size.width &&
       msg->height == current_size.height &&
-      msg->scale == broadway_display->scale_factor)
+      (msg->scale == broadway_display->scale_factor ||
+       broadway_display->fixed_scale))
     return;
 
-  broadway_display->scale_factor = msg->scale;
+  if (!broadway_display->fixed_scale)
+    broadway_display->scale_factor = msg->scale;
 
   gdk_monitor_set_geometry (monitor, &(GdkRectangle) { 0, 0, msg->width, msg->height });
   gdk_monitor_set_scale_factor (monitor, msg->scale);
@@ -328,6 +330,38 @@ gdk_broadway_display_hide_keyboard (GdkBroadwayDisplay *display)
   _gdk_broadway_server_set_show_keyboard (display->server, FALSE);
 }
 
+/**
+ * gdk_broadway_display_set_surface_scale:
+ * @display: (type GdkBroadwayDisplay): the display
+ * @scale: The new scale value, as an integer >= 1
+ *
+ * Forces a specific window scale for all windows on this display,
+ * instead of using the default or user configured scale. This
+ * is can be used to disable scaling support by setting @scale to
+ * 1, or to programmatically set the window scale.
+ *
+ * Once the scale is set by this call it will not change in
+ * response to later user configuration changes.
+ *
+ * Since: 4.4
+ */
+void
+gdk_broadway_display_set_surface_scale (GdkDisplay *display,
+                                        int         scale)
+{
+  GdkMonitor *monitor;
+
+  g_return_if_fail (GDK_IS_BROADWAY_DISPLAY (display));
+  g_return_if_fail (scale > 0);
+
+  monitor = broadway_display->monitor;
+
+  broadway_display->scale_factor = msg->scale;
+  broadway_display->fixed_scale = TRUE;
+
+  gdk_monitor_set_scale_factor (monitor, msg->scale);
+}
+
 static GListModel *
 gdk_broadway_display_get_monitors (GdkDisplay *display)
 {
diff --git a/gdk/broadway/gdkdisplay-broadway.h b/gdk/broadway/gdkdisplay-broadway.h
index 78dfce9a06..1747f2cb0b 100644
--- a/gdk/broadway/gdkdisplay-broadway.h
+++ b/gdk/broadway/gdkdisplay-broadway.h
@@ -57,6 +57,7 @@ struct _GdkBroadwayDisplay
   GListStore *monitors;
   GdkMonitor *monitor;
   int scale_factor;
+  gboolean fixed_scale;
 
   GHashTable *texture_cache;