logical-monitor: Track whether the logical monitor is transformed

Keep track of the logical monitor transform. When a logical monitor is
transformed, all of its monitors are also transformed in the same way.
A logical monitor can either be transformed on the CRTC level, or using
an offscreen intermediate buffer. In both cases will the logical
monitor be transformed, but only in the latter will the view be
transformed.

MetaCrtcs::transform currently does not represent whether the CRTC is
configured to be transformed or not; only when the backend can handle
it does it correctly correspond to the actual CRTC configuration. This
is intended to change with MetaMonitorConfigManager.

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

src/backends/meta-logical-monitor.c

@@ -92,6 +92,16 @@ meta_logical_monitor_new (MetaMonitorManager       *monitor_manager,
   return logical_monitor;
 }
 
+static MetaMonitorTransform
+derive_monitor_transform (MetaMonitor *monitor)
+{
+  MetaOutput *main_output;
+
+  main_output = meta_monitor_get_main_output (monitor);
+
+  return main_output->crtc->transform;
+}
+
 MetaLogicalMonitor *
 meta_logical_monitor_new_derived (MetaMonitorManager *monitor_manager,
                                   MetaMonitor        *monitor,
@@ -102,6 +112,7 @@ meta_logical_monitor_new_derived (MetaMonitorManager *monitor_manager,
   MetaOutput *main_output;
   MetaMonitorMode *monitor_mode;
   int scale;
+  MetaMonitorTransform transform;
 
   logical_monitor = g_object_new (META_TYPE_LOGICAL_MONITOR, NULL);
 
@@ -110,10 +121,13 @@ meta_logical_monitor_new_derived (MetaMonitorManager *monitor_manager,
                                                              monitor,
                                                              monitor_mode);
 
+  transform = derive_monitor_transform (monitor);
+
   main_output = meta_monitor_get_main_output (monitor);
   logical_monitor->number = monitor_number;
   logical_monitor->winsys_id = main_output->winsys_id;
   logical_monitor->scale = scale;
+  logical_monitor->transform = transform;
   logical_monitor->in_fullscreen = -1;
   logical_monitor->rect = *layout;
 

src/backends/meta-logical-monitor.h

@@ -41,6 +41,7 @@ struct _MetaLogicalMonitor
   gboolean is_presentation; /* XXX: not yet used */
   gboolean in_fullscreen;
   int scale;
+  MetaMonitorTransform transform;
 
   /* The primary or first output for this monitor, 0 if we can't figure out.
      It can be matched to a winsys_id of a MetaOutput.

src/backends/meta-monitor-manager.c

@@ -2734,17 +2734,13 @@ meta_monitor_manager_get_monitor_matrix (MetaMonitorManager *manager,
                                          MetaLogicalMonitor *logical_monitor,
                                          gfloat              matrix[6])
 {
-  MetaMonitor *main_monitor;
-  MetaOutput *main_output;
   MetaMonitorTransform transform;
   gfloat viewport[9];
 
   if (!calculate_viewport_matrix (manager, logical_monitor, viewport))
     return FALSE;
 
-  main_monitor = meta_logical_monitor_get_monitors (logical_monitor)->data;
+  transform = logical_monitor->transform;
-  main_output = meta_monitor_get_main_output (main_monitor);
-  transform = main_output->crtc->transform;
   multiply_matrix (viewport, transform_matrices[transform],
                    matrix);
   return TRUE;

src/backends/native/meta-renderer-native.c

@@ -1686,10 +1686,10 @@ calculate_view_transform (MetaMonitorManager *monitor_manager,
 
   if (meta_monitor_manager_is_transform_handled (monitor_manager,
                                                  main_output->crtc,
-                                                 main_output->crtc->transform))
+                                                 logical_monitor->transform))
     return META_MONITOR_TRANSFORM_NORMAL;
   else
-    return main_output->crtc->transform;
+    return logical_monitor->transform;
 }
 
 static MetaRendererView *

src/backends/x11/nested/meta-renderer-x11-nested.c

@@ -59,10 +59,10 @@ calculate_view_transform (MetaMonitorManager *monitor_manager,
 
   if (meta_monitor_manager_is_transform_handled (monitor_manager,
                                                  main_output->crtc,
-                                                 main_output->crtc->transform))
+                                                 logical_monitor->transform))
     return META_MONITOR_TRANSFORM_NORMAL;
   else
-    return main_output->crtc->transform;
+    return logical_monitor->transform;
 }
 
 static MetaRendererView *