Only show the "message" upvar in the "When I receive" hat if "any message" is selected

HISTORY.md

@@ -43,6 +43,9 @@
     * German
     * Chinese, thanks, Simon!
 
+### 2021-10-22
+* blocks, objects: Only show the "message" upvar in the "When I receive" hat if "any message" is selected
+
 ### 2021-10-21
 * threads, objects: make "when I receive 'any message'" hat scripts threadsafe (uninterruptable by other messages)
 * threads: enabled sending atomic lists to other scenes

snap.html

@@ -16,9 +16,9 @@
         <script src="src/morphic.js?version=2021-07-09"></script>
         <script src="src/symbols.js?version=2021-03-03"></script>
         <script src="src/widgets.js?version=2021-07-21"></script>
-        <script src="src/blocks.js?version=2021-10-20"></script>
+        <script src="src/blocks.js?version=2021-10-22"></script>
         <script src="src/threads.js?version=2021-10-21"></script>
-        <script src="src/objects.js?version=2021-10-21"></script>
+        <script src="src/objects.js?version=2021-10-22"></script>
         <script src="src/scenes.js?version=2021-10-12"></script>
         <script src="src/gui.js?version=2021-10-20"></script>
         <script src="src/paint.js?version=2021-07-05"></script>

src/blocks.js

@@ -160,7 +160,7 @@ CustomCommandBlockMorph, ToggleButtonMorph, DialMorph, SnapExtensions*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.blocks = '2021-October-21';
+modules.blocks = '2021-October-22';
 
 var SyntaxElementMorph;
 var BlockMorph;
@@ -311,6 +311,7 @@ SyntaxElementMorph.prototype.labelParts = {
         type: 'input'
         tags: 'numeric read-only unevaluated landscape static'
         menu: dictionary or selector
+        react: selector
     */
     '%s': {
         type: 'input'
@@ -596,7 +597,8 @@ SyntaxElementMorph.prototype.labelParts = {
     '%msgHat': {
         type: 'input',
         tags: 'read-only static',
-        menu: 'messagesReceivedMenu'
+        menu: 'messagesReceivedMenu',
+        react: 'updateMessageUpvar'
     },
     '%msgSend': {
         type: 'input',
@@ -1610,6 +1612,7 @@ SyntaxElementMorph.prototype.labelPart = function (spec) {
         switch (info.type) {
         case 'input':
             part = new InputSlotMorph(null, null, info.menu);
+            part.onSetContents = info.react || null;
             break;
         case 'text entry':
             part = new TextSlotMorph();
@@ -8985,6 +8988,7 @@ InputSlotMorph.prototype.init = function (
     this.isReadOnly = isReadOnly || false;
     this.minWidth = 0; // can be chaged for text-type inputs ("landscape")
     this.constant = null;
+    this.onSetContents = null;
 
     InputSlotMorph.uber.init.call(this, null, true);
     this.color = WHITE;
@@ -9069,6 +9073,11 @@ InputSlotMorph.prototype.setContents = function (data) {
     if (this.isReadOnly && (this.parent instanceof BlockMorph)) {
         this.parent.fixLabelColor();
     }
+
+    // run onSetContents if any
+    if (this.onSetContents) {
+        this[this.onSetContents](data);
+    }
 };
 
 InputSlotMorph.prototype.userSetContents = function (aStringOrFloat) {
@@ -10006,6 +10015,31 @@ InputSlotMorph.prototype.userMenu = function () {
     return menu;
 };
 
+// InputSlotMorph reacting to user choices
+
+/*
+    if selecting an option from a dropdown menu might affect the visibility
+    or contents of another input slot, the methods in this section can
+    offer functionality that can be specified externally by setting
+    the "onSetContents" property to the name of the according method
+*/
+
+InputSlotMorph.prototype.updateMessageUpvar = function (data) {
+    // assumes a second multi-arg input slot to my right that is
+    // either shown or hidden and collapsed based on whether
+    // "any message" is selected as choice.
+
+    var trg = this.parent.inputs()[1];
+    if (data instanceof Array && data[0] === 'any message') {
+        trg.show();
+    } else {
+        trg.removeInput();
+        trg.hide();
+    }
+    this.parent.fixLayout();
+};
+
+
 // InputSlotMorph code mapping
 
 /*

src/objects.js

@@ -87,7 +87,7 @@ BlockVisibilityDialogMorph*/
 
 /*jshint esversion: 6*/
 
-modules.objects = '2021-October-21';
+modules.objects = '2021-October-22';
 
 var SpriteMorph;
 var StageMorph;
@@ -744,7 +744,8 @@ SpriteMorph.prototype.initBlocks = function () {
         receiveMessage: {
             type: 'hat',
             category: 'control',
-            spec: 'when I receive %msgHat %message'
+            spec: 'when I receive %msgHat %message',
+            defaults: [''] // trigger the "message" expansion to refresh
         },
         receiveCondition: {
             type: 'hat',