allow project-setting “Ternary Boolean slots” to be switched off

default is “on”. That way Boolean input slots can always be toggled
through “true”, “false” and “empty”. If this setting is switched off
Boolean input slots only toggle between “true” and “false” unless
inside a a ring (for implicit parameters)

blocks.js

@@ -8824,6 +8824,10 @@ BooleanSlotMorph.prototype = new ArgMorph();
 BooleanSlotMorph.prototype.constructor = BooleanSlotMorph;
 BooleanSlotMorph.uber = ArgMorph.prototype;
 
+// BooleanSlotMorph preferences settings
+
+BooleanSlotMorph.prototype.isTernary = true;
+
 // BooleanSlotMorph instance creation:
 
 function BooleanSlotMorph(initialValue) {
@@ -8851,7 +8855,8 @@ BooleanSlotMorph.prototype.isEmptySlot = function () {
 };
 
 BooleanSlotMorph.prototype.isBinary = function () {
-    return isNil(this.parentThatIsA(RingMorph)) &&
+    return !this.isTernary &&
+        isNil(this.parentThatIsA(RingMorph)) &&
         !isNil(this.parentThatIsA(ScriptsMorph));
 };
 

gui.js

@@ -70,11 +70,11 @@ fontHeight, hex_sha512, sb, CommentMorph, CommandBlockMorph,
 BlockLabelPlaceHolderMorph, Audio, SpeechBubbleMorph, ScriptFocusMorph,
 XML_Element, WatcherMorph, BlockRemovalDialogMorph, saveAs, TableMorph,
 isSnapObject, isRetinaEnabled, disableRetinaSupport, enableRetinaSupport,
-isRetinaSupported, SliderMorph, Animation*/
+isRetinaSupported, SliderMorph, Animation, BooleanSlotMorph*/
 
 // Global stuff ////////////////////////////////////////////////////////
 
-modules.gui = '2017-January-20';
+modules.gui = '2017-January-23';
 
 // Declarations
 
@@ -2733,6 +2733,16 @@ IDE_Morph.prototype.settingsMenu = function () {
         'uncheck for round ends of lines',
         'check for flat ends of lines'
     );
+    addPreference(
+        'Ternary Boolean slots',
+        function () {
+            BooleanSlotMorph.prototype.isTernary =
+                !BooleanSlotMorph.prototype.isTernary;
+        },
+        BooleanSlotMorph.prototype.isTernary,
+        'uncheck to only\ntoggle true / false\noutside of rings',
+        'check to enable toggling\nBoolean slots to empty'
+    );
     addPreference(
         'Codification support',
         function () {
@@ -3415,6 +3425,7 @@ IDE_Morph.prototype.newProject = function () {
     StageMorph.prototype.enableInheritance = false;
     StageMorph.prototype.enableSublistIDs = false;
     SpriteMorph.prototype.useFlatLineEnds = false;
+    BooleanSlotMorph.prototype.isTernary = true;
     Process.prototype.enableLiveCoding = false;
     this.setProjectName('');
     this.projectNotes = '';

history.txt

@@ -3324,4 +3324,5 @@ Fixes:
 
 170123
 ------
-* BYOB, Blocks, Store: added support for default values in custom block Boolean slots 
+* BYOB, Blocks, Store: added support for default values in custom block Boolean slots
+* GUI, Blocks, Store: allow project-setting “Ternary Boolean slots” to be switched off

store.js

@@ -412,6 +412,8 @@ SnapSerializer.prototype.rawLoadProjectModel = function (xmlNode) {
     project.stage.setExtent(StageMorph.prototype.dimensions);
     SpriteMorph.prototype.useFlatLineEnds =
         model.stage.attributes.lines === 'flat';
+    BooleanSlotMorph.prototype.isTernary =
+        model.stage.attributes.ternary !== 'false';
     project.stage.isThreadSafe =
         model.stage.attributes.threadsafe === 'true';
     StageMorph.prototype.enableCodeMapping =
@@ -1511,6 +1513,7 @@ StageMorph.prototype.toXML = function (serializer) {
             '<stage name="@" width="@" height="@" ' +
             'costume="@" tempo="@" threadsafe="@" ' +
             'lines="@" ' +
+            'ternary="@" ' +
             'codify="@" ' +
             'inheritance="@" ' +
             'sublistIDs="@" ' +
@@ -1540,6 +1543,7 @@ StageMorph.prototype.toXML = function (serializer) {
         this.getTempo(),
         this.isThreadSafe,
         SpriteMorph.prototype.useFlatLineEnds ? 'flat' : 'round',
+        BooleanSlotMorph.prototype.isTernary,
         this.enableCodeMapping,
         this.enableInheritance,
         this.enableSublistIDs,