monitor-manager: Flip transform

The transform we get from the DBus protocol is flipped
regarding Waylands view on it. This is similar to what
was done in wlroots to preserve config changes.
Signed-off-by: Guido Günther <guido.gunther@puri.sm>

src/monitor-manager.c

@@ -98,6 +98,33 @@ phosh_monitor_manager_get_head_from_monitor (PhoshMonitorManager *self, PhoshMon
   return NULL;
 }
 
+static gint32
+phosh_monitor_manager_flip_transform (PhoshMonitorTransform transform)
+{
+  /* Wayland rotation is opposite from DBus */
+  switch (transform) {
+  case PHOSH_MONITOR_TRANSFORM_90:
+    return WL_OUTPUT_TRANSFORM_270;
+    break;
+  case PHOSH_MONITOR_TRANSFORM_270:
+    return WL_OUTPUT_TRANSFORM_90;
+    break;
+  case PHOSH_MONITOR_TRANSFORM_FLIPPED_90:
+    return WL_OUTPUT_TRANSFORM_FLIPPED_270;
+    break;
+  case PHOSH_MONITOR_TRANSFORM_FLIPPED_270:
+    return WL_OUTPUT_TRANSFORM_FLIPPED_90;
+    break;
+  case PHOSH_MONITOR_TRANSFORM_NORMAL:
+  case PHOSH_MONITOR_TRANSFORM_180:
+  case PHOSH_MONITOR_TRANSFORM_FLIPPED:
+  case PHOSH_MONITOR_TRANSFORM_FLIPPED_180:
+  default:
+    /* Nothing to be done */
+    return transform;
+  }
+}
+
 /*
  * DBus Interface
  */
@@ -705,7 +732,7 @@ config_head_config_from_logical_monitor_variant (PhoshMonitorManager *self,
     head->pending.scale = scale;
     head->pending.x = x;
     head->pending.y = y;
-    head->pending.transform = transform;
+    head->pending.transform = phosh_monitor_manager_flip_transform (transform);
     head->pending.enabled = TRUE;
     head->pending.seen = TRUE;
   }