Area: automatically request a repaint when showing up for the first time

Author: emilk

egui/src/containers/area.rs

@@ -204,10 +204,13 @@ impl Area {
 
         let state = ctx.memory().areas.get(id).cloned();
         let is_new = state.is_none();
-        let mut state = state.unwrap_or_else(|| State {
-            pos: default_pos.unwrap_or_else(|| automatic_area_position(ctx)),
-            size: Vec2::ZERO,
-            interactable,
+        let mut state = state.unwrap_or_else(|| {
+            ctx.request_repaint(); // if we don't know the previous size we are likely drawing the area in the wrong place
+            State {
+                pos: default_pos.unwrap_or_else(|| automatic_area_position(ctx)),
+                size: Vec2::ZERO,
+                interactable,
+            }
         });
         state.pos = new_pos.unwrap_or(state.pos);