feat: use small stage in an iframe

Author: mikebarkmin

packages/scratch-gui/src/playground/index.css

@@ -7,7 +7,7 @@ body,
     margin: 0;
 
     /* Setting min height/width makes the UI scroll below those sizes */
-    min-width: 1024px;
+    min-width: 960px;
     min-height: 640px; /* Min height to fit sprite/backdrop button */
 }
 

packages/scratch-gui/src/reducers/stage-size.js

@@ -2,8 +2,10 @@ import {STAGE_DISPLAY_SIZES} from '../lib/layout-constants.js';
 
 const SET_STAGE_SIZE = 'scratch-gui/StageSize/SET_STAGE_SIZE';
 
+const isInIframe = typeof window !== 'undefined' && window.self !== window.top;
+
 const initialState = {
-    stageSize: STAGE_DISPLAY_SIZES.large
+    stageSize: isInIframe ? STAGE_DISPLAY_SIZES.small : STAGE_DISPLAY_SIZES.large
 };
 
 const reducer = function (state, action) {