support bulk-file-drop for importing scenes

HISTORY.md

@@ -8,6 +8,7 @@
 
 ### 2021-04-12
 * blocks, objects, threads, gui: new "switch to scene _" command primitive
+* morphic, gui: support bulk-file-drop for importing scenes
 
 ### 2021-04-08
 * gui: scroll selected scene icon into view

snap.html

@@ -5,7 +5,7 @@
         <meta name="viewport" content="width=device-width, initial-scale=1">
         <title>Snap! 7 - dev - Build Your Own Blocks</title>
         <link rel="icon" href="src/favicon.ico">
-        <script src="src/morphic.js?version=2021-02-10"></script>
+        <script src="src/morphic.js?version=2021-04-12"></script>
         <script src="src/symbols.js?version=2021-03-03"></script>
         <script src="src/widgets.js?version=2021-01-05"></script>
         <script src="src/blocks.js?version=2021-04-12"></script>

src/gui.js

@@ -293,6 +293,9 @@ IDE_Morph.prototype.init = function (isAutoFill) {
 
     this.savingPreferences = true; // for bh's infamous "Eisenbergification"
 
+    this.bulkDropInProgress = false; // for handling multiple file-drops
+    this.cachedSceneFlag = null; // for importing multiple scenes at once
+
     // initialize inherited properties:
     IDE_Morph.uber.init.call(this);
 
@@ -2196,6 +2199,17 @@ IDE_Morph.prototype.reactToWorldResize = function (rect) {
     }
 };
 
+IDE_Morph.prototype.beginBulkDrop = function () {
+    this.bulkDropInProgress = true;
+    this.cachedSceneFlag = this.isAddingScenes;
+    this.isAddingScenes = true;
+};
+
+IDE_Morph.prototype.endBulkDrop = function () {
+    this.isAddingScenes = this.cachedSceneFlag;
+    this.bulkDropInProgress = false;
+};
+
 IDE_Morph.prototype.droppedImage = function (aCanvas, name) {
     var costume = new Costume(
         aCanvas,
@@ -5111,6 +5125,11 @@ IDE_Morph.prototype.exportProjectSummary = function (useDropShadows) {
 
 IDE_Morph.prototype.openProjectString = function (str, callback) {
     var msg;
+    if (this.bulkDropInProgress) {
+            this.rawOpenProjectString(str);
+            if (callback) {callback(); }
+            return;
+    }
     this.nextSteps([
         () => msg = this.showMessage('Opening project...'),
         () => {