empty track (no knob) when board fits, add fit tolerance (v1.5.1)

Asset/js/top-scrollbar.js

@@ -26,6 +26,10 @@
     // Keep the thumb wide enough to grab, even on a very wide board.
     var MIN_THUMB = 24;
 
+    // Ignore a few px of residual overflow (padding / sub-pixel rounding) so a board that visually
+    // fits is treated as "no horizontal scroll" instead of showing an immovable near-full thumb.
+    var FIT_TOLERANCE = 4;
+
     function getContainer() {
         return document.getElementById("board-container");
     }
@@ -74,17 +78,29 @@
             thumb.style.transform = "translateX(" + Math.round(left) + "px)";
         }
 
-        // Recompute thumb width/position; hide the whole bar when nothing to scroll.
+        // The board needs scrolling only if its content exceeds the viewport by more than the
+        // tolerance (absorbs a residual px or two so a fitting board reads as "no scroll").
+        function needsScroll(m) {
+            return m && m.content - m.viewport > FIT_TOLERANCE;
+        }
+
+        // Recompute the thumb. The (light) track stays visible for a STABLE height; when the board
+        // fits, just drop the knob (thumb width 0) so it reads as "nothing to scroll" without the
+        // layout jump that hiding the whole bar would cause.
         function layout() {
             var m = metrics();
 
-            if (!m || m.content <= m.viewport || m.trackW <= 0) {
-                track.style.display = "none";
+            if (!m || m.trackW <= 0) {
                 return;
             }
 
             track.style.display = "";
 
+            if (!needsScroll(m)) {
+                thumb.style.width = "0px";
+                return;
+            }
+
             var thumbW = Math.round(m.trackW * m.viewport / m.content);
             if (thumbW < MIN_THUMB) { thumbW = MIN_THUMB; }
             if (thumbW > m.trackW) { thumbW = m.trackW; }
@@ -107,7 +123,7 @@
             if (dragging) { return; }
             if (e.target !== getContainer()) { return; }
             var m = metrics();
-            if (!m || m.content <= m.viewport) { return; }
+            if (!needsScroll(m)) { return; }
             positionThumb(m, thumb.offsetWidth);
         }, true);
 
@@ -153,7 +169,7 @@
         track.addEventListener("pointerdown", function (e) {
             if (e.target === thumb || dragging) { return; }
             var m = metrics();
-            if (!m || m.content <= m.viewport) { return; }
+            if (!needsScroll(m)) { return; }
 
             var thumbW = thumb.offsetWidth;
             var maxThumb = m.trackW - thumbW;