meta-monitor-config: Pass logical monitor scale via config

The default (calculated) scale is derived from the output, but
ultimately set via the monitor scale. This will enable config files to
override the scale. Yet to be done is handling when a scale is not
supported by a backend (i.e. the X11 backend).

https://bugzilla.gnome.org/show_bug.cgi?id=777732

src/backends/meta-logical-monitor.c

@@ -78,7 +78,7 @@ meta_logical_monitor_new (MetaMonitorManager       *monitor_manager,
 
   logical_monitor->number = monitor_number;
   logical_monitor->winsys_id = main_output->winsys_id;
-  logical_monitor->scale = main_output->scale;
+  logical_monitor->scale = logical_monitor_config->scale,
   logical_monitor->in_fullscreen = -1;
   logical_monitor->rect = logical_monitor_config->layout;
 

src/backends/meta-monitor-config-manager.c

@@ -467,11 +467,14 @@ create_preferred_logical_monitor_config (MetaMonitor *monitor,
 {
   MetaMonitorMode *mode;
   int width, height;
+  int scale;
   MetaMonitorConfig *monitor_config;
   MetaLogicalMonitorConfig *logical_monitor_config;
 
   mode = meta_monitor_get_preferred_mode (monitor);
   meta_monitor_mode_get_resolution (mode, &width, &height);
+  scale = meta_monitor_get_calculated_scale (monitor);
+
   monitor_config = create_monitor_config (monitor, mode);
 
   logical_monitor_config = g_new0 (MetaLogicalMonitorConfig, 1);
@@ -482,6 +485,7 @@ create_preferred_logical_monitor_config (MetaMonitor *monitor,
       .width = width,
       .height = height
     },
+    .scale = scale,
     .monitor_configs = g_list_append (NULL, monitor_config)
   };
 

src/backends/meta-monitor-config-manager.h

@@ -40,6 +40,7 @@ typedef struct _MetaLogicalMonitorConfig
 {
   MetaRectangle layout;
   GList *monitor_configs;
+  int scale;
   gboolean is_primary;
   gboolean is_presentation;
 } MetaLogicalMonitorConfig;

src/backends/meta-monitor-config-store.c

@@ -405,6 +405,14 @@ static gboolean
 verify_logical_monitor_config (MetaLogicalMonitorConfig *logical_monitor_config,
                                GError                  **error)
 {
+  if (logical_monitor_config->scale < 1)
+    {
+      g_set_error (error, G_IO_ERROR, G_IO_ERROR_FAILED,
+                   "Invalid logical monitor config scale %d",
+                   logical_monitor_config->scale);
+      return FALSE;
+    }
+
   if (logical_monitor_config->layout.x < 0 ||
       logical_monitor_config->layout.y < 0)
     {
@@ -614,6 +622,8 @@ handle_end_element (GMarkupParseContext  *context,
 
         g_assert (g_str_equal (element_name, "logicalmonitor"));
 
+        logical_monitor_config->scale = 1;
+
         if (!verify_logical_monitor_config (logical_monitor_config, error))
           return;
 

src/backends/meta-monitor.c

@@ -196,6 +196,16 @@ meta_monitor_is_underscanning (MetaMonitor *monitor)
   return output->is_underscanning;
 }
 
+int
+meta_monitor_get_calculated_scale (MetaMonitor *monitor)
+{
+  MetaOutput *output;
+
+  output = meta_monitor_get_main_output (monitor);
+
+  return output->scale;
+}
+
 gboolean
 meta_monitor_is_laptop_panel (MetaMonitor *monitor)
 {

src/backends/meta-monitor.h

@@ -97,6 +97,8 @@ gboolean meta_monitor_is_underscanning (MetaMonitor *monitor);
 
 gboolean meta_monitor_is_laptop_panel (MetaMonitor *monitor);
 
+int meta_monitor_get_calculated_scale (MetaMonitor *monitor);
+
 GList * meta_monitor_get_outputs (MetaMonitor *monitor);
 
 void meta_monitor_get_current_resolution (MetaMonitor *monitor,