Improve slot render stability & perf (#954)

- `draw` is now skipped for slots that should not be shown (prev. drawn
with 0 alpha)
- Fixes slot always rendered when widget not found in `node.widgets`
- Remove redundant check from `isWidgetInputSlot` - type is already
`INodeInputSlot`

src/LGraphNode.ts

@@ -3493,7 +3493,8 @@ export class LGraphNode implements Positionable, IPinnable, IColorable {
     return this.#getMouseOverSlot(slot) === slot
   }
 
-  #isMouseOverWidget(widget: IWidget): boolean {
+  #isMouseOverWidget(widget: IWidget | undefined): boolean {
+    if (!widget) return false
     return this.mouseOver?.overWidget === widget
   }
 
@@ -3535,19 +3536,20 @@ export class LGraphNode implements Positionable, IPinnable, IColorable {
       // - the mouse is over the widget
       // - the slot is valid during link drop
       // - the slot is connected
-      const showSlot = isMouseOverSlot ||
+      if (
+        isMouseOverSlot ||
         isValidTarget ||
         !slotInstance.isWidgetInputSlot ||
-        this.#isMouseOverWidget(this.getWidgetFromSlot(slotInstance)!) ||
+        this.#isMouseOverWidget(this.getWidgetFromSlot(slotInstance)) ||
         slotInstance.isConnected()
-
-      ctx.globalAlpha = showSlot ? (isValid ? editorAlpha : 0.4 * editorAlpha) : 0
-
-      slotInstance.draw(ctx, {
-        colorContext,
-        lowQuality,
-        highlight,
-      })
+      ) {
+        ctx.globalAlpha = isValid ? editorAlpha : 0.4 * editorAlpha
+        slotInstance.draw(ctx, {
+          colorContext,
+          lowQuality,
+          highlight,
+        })
+      }
     }
   }
 

src/NodeSlot.ts

@@ -72,11 +72,11 @@ export function toNodeSlotClass(slot: INodeInputSlot | INodeOutputSlot): NodeInp
 }
 
 /**
- * Whether this slot is an input slot and attached to a widget.
+ * Type guard: Whether this input slot is attached to a widget.
  * @param slot The slot to check.
  */
 export function isWidgetInputSlot(slot: INodeInputSlot): slot is IWidgetInputSlot {
-  return isINodeInputSlot(slot) && !!slot.widget
+  return !!slot.widget
 }
 
 export abstract class NodeSlot implements INodeSlot {