fix: track active bar element correctly for drag calculations

Fixed issue where dragged bars weren't updating visually because a single
barRef was shared across all bars. Now each bar passes its element reference
to the drag handlers, allowing proper width calculations during drag.

Changes:
- Renamed barRef to activeBarRef for clarity
- Updated handleMouseDown/handleTouchStart to accept bar element parameter
- Pass e.currentTarget as bar element in onMouseDown/onTouchStart handlers
- Clear activeBarRef on drag end (mouseup/touchend)

This fixes the visual feedback - bars now correctly resize as you drag them.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

components/converter/VisualComparison.tsx

@@ -18,7 +18,7 @@ export default function VisualComparison({
   const [draggingUnit, setDraggingUnit] = useState<string | null>(null);
   const dragStartX = useRef<number>(0);
   const dragStartWidth = useRef<number>(0);
-  const barRef = useRef<HTMLDivElement>(null);
+  const activeBarRef = useRef<HTMLDivElement | null>(null);
   // Calculate percentages for visual bars using logarithmic scale
   const withPercentages = useMemo(() => {
     if (conversions.length === 0) return [];
@@ -80,19 +80,20 @@ export default function VisualComparison({
   }, []);
 
   // Mouse drag handlers
-  const handleMouseDown = useCallback((e: React.MouseEvent, unit: string, currentPercentage: number) => {
+  const handleMouseDown = useCallback((e: React.MouseEvent, unit: string, currentPercentage: number, barElement: HTMLDivElement) => {
     if (!onValueChange) return;
 
     e.preventDefault();
     setDraggingUnit(unit);
     dragStartX.current = e.clientX;
     dragStartWidth.current = currentPercentage;
+    activeBarRef.current = barElement;
   }, [onValueChange]);
 
   const handleMouseMove = useCallback((e: MouseEvent) => {
-    if (!draggingUnit || !barRef.current || !onValueChange) return;
+    if (!draggingUnit || !activeBarRef.current || !onValueChange) return;
 
-    const barWidth = barRef.current.offsetWidth;
+    const barWidth = activeBarRef.current.offsetWidth;
     const deltaX = e.clientX - dragStartX.current;
     const deltaPercentage = (deltaX / barWidth) * 100;
 
@@ -116,24 +117,26 @@ export default function VisualComparison({
 
   const handleMouseUp = useCallback(() => {
     setDraggingUnit(null);
+    activeBarRef.current = null;
   }, []);
 
   // Touch drag handlers
-  const handleTouchStart = useCallback((e: React.TouchEvent, unit: string, currentPercentage: number) => {
+  const handleTouchStart = useCallback((e: React.TouchEvent, unit: string, currentPercentage: number, barElement: HTMLDivElement) => {
     if (!onValueChange) return;
 
     const touch = e.touches[0];
     setDraggingUnit(unit);
     dragStartX.current = touch.clientX;
     dragStartWidth.current = currentPercentage;
+    activeBarRef.current = barElement;
   }, [onValueChange]);
 
   const handleTouchMove = useCallback((e: TouchEvent) => {
-    if (!draggingUnit || !barRef.current || !onValueChange) return;
+    if (!draggingUnit || !activeBarRef.current || !onValueChange) return;
 
     e.preventDefault(); // Prevent scrolling while dragging
     const touch = e.touches[0];
-    const barWidth = barRef.current.offsetWidth;
+    const barWidth = activeBarRef.current.offsetWidth;
     const deltaX = touch.clientX - dragStartX.current;
     const deltaPercentage = (deltaX / barWidth) * 100;
 
@@ -154,6 +157,7 @@ export default function VisualComparison({
 
   const handleTouchEnd = useCallback(() => {
     setDraggingUnit(null);
+    activeBarRef.current = null;
   }, []);
 
   // Add/remove global event listeners for drag
@@ -202,15 +206,22 @@ export default function VisualComparison({
             </div>
             {/* Progress bar */}
             <div
-              ref={barRef}
               className={cn(
                 "w-full h-8 bg-muted rounded-lg overflow-hidden border border-border relative",
                 "transition-all duration-200",
                 isDraggable && "cursor-grab active:cursor-grabbing",
                 isDragging && "ring-2 ring-ring ring-offset-2 ring-offset-background scale-105"
               )}
-              onMouseDown={(e) => isDraggable && handleMouseDown(e, item.unit, item.percentage)}
-              onTouchStart={(e) => isDraggable && handleTouchStart(e, item.unit, item.percentage)}
+              onMouseDown={(e) => {
+                if (isDraggable && e.currentTarget instanceof HTMLDivElement) {
+                  handleMouseDown(e, item.unit, item.percentage, e.currentTarget);
+                }
+              }}
+              onTouchStart={(e) => {
+                if (isDraggable && e.currentTarget instanceof HTMLDivElement) {
+                  handleTouchStart(e, item.unit, item.percentage, e.currentTarget);
+                }
+              }}
             >
               {/* Colored fill */}
               <div