don't start refresh until we know bus is available

Author: dhalbert

shared-module/busdisplay/BusDisplay.c

@@ -309,14 +309,15 @@ static bool _refresh_area(busdisplay_busdisplay_obj_t *self, const displayio_are
 }
 
 static void _refresh_display(busdisplay_busdisplay_obj_t *self) {
-    if (!displayio_display_core_start_refresh(&self->core)) {
-        // Refresh for this display already in progress.
-        return;
-    }
     if (!displayio_display_bus_is_free(&self->bus)) {
         // A refresh on this bus is already in progress.  Try next display.
         return;
     }
+    if (!displayio_display_core_start_refresh(&self->core)) {
+        // Refresh for this display already in progress.
+        return;
+    }
+
     const displayio_area_t *current_area = _get_refresh_areas(self);
     while (current_area != NULL) {
         _refresh_area(self, current_area);

shared-module/epaperdisplay/EPaperDisplay.c

@@ -187,15 +187,14 @@ void epaperdisplay_epaperdisplay_change_refresh_mode_parameters(epaperdisplay_ep
 }
 
 static void epaperdisplay_epaperdisplay_start_refresh(epaperdisplay_epaperdisplay_obj_t *self) {
-    if (!displayio_display_core_start_refresh(&self->core)) {
-        // Refresh on this display already in progress.
-        return;
-    }
-
     if (!displayio_display_bus_is_free(&self->bus)) {
         // Can't acquire display bus; skip updating this display. Try next display.
         return;
     }
+    if (!displayio_display_core_start_refresh(&self->core)) {
+        // Refresh on this display already in progress.
+        return;
+    }
 
     // run start sequence
     self->bus.bus_reset(self->bus.bus);