I can select range with visual feedback

src/myfasthtml/assets/core/mouse.js

@@ -671,12 +671,8 @@
             const element = document.getElementById(candidate.elementId);
             const dynamicValues = func(event, element, candidate.node.combinationStr);
             if (dynamicValues && typeof dynamicValues === 'object') {
-              // Suffix each key with _mousedown
-              const suffixed = {};
-              for (const [key, value] of Object.entries(dynamicValues)) {
-                suffixed[key + '_mousedown'] = value;
-              }
-              mousedownJsValues[candidate.elementId] = suffixed;
+              // Store raw values - _mousedown suffix added at mouseup time
+              mousedownJsValues[candidate.elementId] = dynamicValues;
             }
           }
         } catch (e) {
@@ -699,12 +695,39 @@
     // Clear pending state
     MouseRegistry.mousedownPending = null;
 
-    // Remove mousemove listener (no longer needed)
+    // Remove mousemove listener (threshold detection no longer needed)
     if (MouseRegistry.mousemoveHandler) {
       document.removeEventListener('mousemove', MouseRegistry.mousemoveHandler);
       MouseRegistry.mousemoveHandler = null;
     }
 
+    // Attach on_move handler if any candidate has 'on-move' config
+    const onMoveCandidates = MouseRegistry.mousedownState.candidates.filter(
+      c => c.node.config && c.node.config['on-move']
+    );
+    if (onMoveCandidates.length > 0) {
+      let rafId = null;
+      MouseRegistry.mousemoveHandler = (moveEvent) => {
+        if (rafId) return;
+        rafId = requestAnimationFrame(() => {
+          for (const candidate of onMoveCandidates) {
+            const funcName = candidate.node.config['on-move'];
+            try {
+              const func = window[funcName];
+              if (typeof func === 'function') {
+                const mousedownValues = mousedownJsValues[candidate.elementId] || null;
+                func(moveEvent, candidate.node.combinationStr, mousedownValues);
+              }
+            } catch (e) {
+              console.error('Error calling on_move function:', e);
+            }
+          }
+          rafId = null;
+        });
+      };
+      document.addEventListener('mousemove', MouseRegistry.mousemoveHandler);
+    }
+
     // For right button: prevent context menu during drag
     if (pendingData.button === 2) {
       const preventContextMenu = (e) => {
@@ -907,9 +930,11 @@
       Object.assign(values, config['hx-vals']);
     }
 
-    // 2. Merge mousedown JS values (already suffixed with _mousedown)
+    // 2. Merge mousedown JS values with _mousedown suffix
     if (match.mousedownJsValues) {
-      Object.assign(values, match.mousedownJsValues);
+      for (const [key, value] of Object.entries(match.mousedownJsValues)) {
+        values[key + '_mousedown'] = value;
+      }
     }
 
     // 3. Call JS function at mouseup time, suffix with _mouseup