indicate empty categories in single-palette mode

HISTORY.md

@@ -68,6 +68,7 @@
 * gui, translations: removed old hidden "virtual keyboard" setting
 * gui: removed old hidden "project urls" setting
 * gui: removed hidden "cache inputs" setting (only used for debugging the evaluator)
+* gui, objects: indicate empty categories in single-palette mode 
 
 ### 2021-11-14
 * locale: contextualize translations

src/gui.js

@@ -1276,6 +1276,14 @@ IDE_Morph.prototype.createCategories = function () {
             if (cat.state) {
                 cat.scrollIntoView();
             }
+
+            // indicate whether a category is empty of blocks to show
+            // currently only supported in unified palette mode
+            if (myself.currentSprite.emptyCategoriesCache[cat.category]) {
+                cat.disable();
+            } else {
+                cat.enable();
+            }
         });
     };
 
@@ -1322,6 +1330,7 @@ IDE_Morph.prototype.createCategories = function () {
             true // has preview
         );
 
+        button.category = category;
         button.corner = 8;
         button.padding = 0;
         button.labelShadowOffset = new Point(-1, -1);
@@ -1358,6 +1367,7 @@ IDE_Morph.prototype.createCategories = function () {
             true // has preview
         );
 
+        button.category = category;
         button.corner = 8;
         button.padding = 0;
         button.labelShadowOffset = new Point(-1, -1);
@@ -2806,6 +2816,7 @@ IDE_Morph.prototype.selectSprite = function (sprite) {
     }
     this.currentSprite = sprite;
     this.scene.currentSprite = sprite;
+    this.categories.refresh(); // indicate empty categories in unified palette
     this.createPalette();
     this.createSpriteBar();
     this.createSpriteEditor();
@@ -6256,6 +6267,7 @@ IDE_Morph.prototype.toggleStageSize = function (isSmall, forcedRatio) {
 
 IDE_Morph.prototype.toggleUnifiedPalette = function () {
     this.setUnifiedPalette(!this.scene.unifiedPalette);
+    this.categories.refresh(); // update empty categories in single palette mode
 };
 
 IDE_Morph.prototype.setUnifiedPalette = function (bool) {

src/objects.js

@@ -1870,6 +1870,7 @@ SpriteMorph.prototype.init = function (globals) {
 
     this.primitivesCache = {}; // not to be serialized (!)
     this.paletteCache = {}; // not to be serialized (!)
+    this.emptyCategoriesCache = {}; // not to be serialized;
     this.rotationOffset = ZERO; // not to be serialized (!)
     this.idx = 0; // not to be serialized (!) - used for de-serialization
 
@@ -1935,6 +1936,7 @@ SpriteMorph.prototype.fullCopy = function (forClone) {
     c.freqPlayer = null;
     c.primitivesCache = {};
     c.paletteCache = {};
+    c.emptyCategoriesCache = {};
     c.imageData = {};
     c.cachedColorDimensions = c.color[this.penColorModel]();
     arr = [];
@@ -3011,6 +3013,14 @@ SpriteMorph.prototype.freshPalette = function (category) {
         searchButton,
         makeButton;
 
+    function isEmptyCategory(blocks) {
+        return blocks.filter(each =>
+            each instanceof BlockMorph && !myself.isHidingBlock(each)
+        ).length === 0;
+    }
+
+    this.emptyCategoriesCache = {};
+
     palette.owner = this;
     palette.padding = unit / 2;
     palette.color = this.paletteColor;
@@ -3088,7 +3098,7 @@ SpriteMorph.prototype.freshPalette = function (category) {
         // In a Unified Palette custom blocks appear following each category,
         // but there is only 1 make a block button (at the end).
         showCategories = this.parentThatIsA(IDE_Morph).scene.showCategories;
-        blocks = SpriteMorph.prototype.allCategories().reduce( // +++
+        blocks = SpriteMorph.prototype.allCategories().reduce(
             (blocks, category) => {
                 let header = [this.categoryText(category), '-'],
                     primitives = this.getPrimitiveTemplates(category),
@@ -3103,6 +3113,11 @@ SpriteMorph.prototype.freshPalette = function (category) {
                         each !== '-' && each !== '=');
                 }
 
+                // update the empty categories cache
+                if (isEmptyCategory(primitives) &&  isEmptyCategory(customs)) {
+                    this.emptyCategoriesCache[category] = true;
+                }
+
                 return blocks.concat(
                     showHeader ? header : [],
                     primitives,
@@ -7772,6 +7787,7 @@ StageMorph.prototype.init = function (globals) {
     this.keysPressed = {}; // for handling keyboard events, do not persist
     this.primitivesCache = {}; // not to be serialized (!)
     this.paletteCache = {}; // not to be serialized (!)
+    this.emptyCategoriesCache = {}; // not to be serialized (!)
     this.lastAnswer = ''; // last user input, do not persist
     this.activeSounds = []; // do not persist