feat: implement horizontal drag-to-scroll functionality in board views (#326)

apps/web/src/hooks/useDragToScroll.ts

@@ -0,0 +1,113 @@
+import { useEffect, useRef, useState } from "react";
+
+interface UseDragToScrollOptions {
+  /**
+   * Whether drag-to-scroll is enabled
+   */
+  enabled?: boolean;
+  /**
+   * The direction to scroll
+   */
+  direction?: "horizontal" | "vertical" | "both";
+}
+
+/**
+ * Hook to enable drag-to-scroll functionality on a scrollable element
+ * @param options Configuration options
+ * @returns Ref to attach to the scrollable element and mouse event handlers
+ */
+export function useDragToScroll({
+  enabled = true,
+  direction = "horizontal",
+}: UseDragToScrollOptions = {}) {
+  const scrollRef = useRef<HTMLDivElement>(null);
+  const [isDragging, setIsDragging] = useState(false);
+  const startPosRef = useRef({ x: 0, y: 0 });
+  const scrollStartRef = useRef({ x: 0, y: 0 });
+
+  useEffect(() => {
+    if (!enabled || !isDragging) return;
+
+    const handleMouseMove = (e: MouseEvent) => {
+      if (!scrollRef.current) return;
+
+      const deltaX = e.clientX - startPosRef.current.x;
+      const deltaY = e.clientY - startPosRef.current.y;
+
+      if (direction === "horizontal" || direction === "both") {
+        scrollRef.current.scrollLeft = scrollStartRef.current.x - deltaX;
+      }
+      if (direction === "vertical" || direction === "both") {
+        scrollRef.current.scrollTop = scrollStartRef.current.y - deltaY;
+      }
+    };
+
+    const handleMouseUp = () => {
+      setIsDragging(false);
+    };
+
+    document.addEventListener("mousemove", handleMouseMove);
+    document.addEventListener("mouseup", handleMouseUp);
+    document.body.style.cursor = "grabbing";
+    document.body.style.userSelect = "none";
+
+    return () => {
+      document.removeEventListener("mousemove", handleMouseMove);
+      document.removeEventListener("mouseup", handleMouseUp);
+      document.body.style.cursor = "";
+      document.body.style.userSelect = "";
+    };
+  }, [enabled, isDragging, direction]);
+
+  const handleMouseDown = (e: React.MouseEvent<HTMLDivElement>) => {
+    if (!scrollRef.current) return;
+
+    const target = e.target as HTMLElement;
+    const container = scrollRef.current;
+
+    // Check if the click is on an interactive or draggable element
+    // We need to be careful not to interfere with react-beautiful-dnd dragging
+    const isInteractiveElement =
+      target.closest("a") ||
+      target.closest("button") ||
+      target.closest("input") ||
+      target.closest("textarea") ||
+      target.closest("[role='button']") ||
+      target.closest("[draggable='true']") ||
+      target.closest(".react-beautiful-dnd-drag-handle") ||
+      target.closest("[data-rbd-drag-handle-draggable-id]") ||
+      target.closest("[data-rbd-draggable-id]");
+
+    // Don't start dragging if clicking on interactive elements
+    if (isInteractiveElement) return;
+
+    // Check if clicking directly on the container (background)
+    const isContainer = target === container;
+    
+    // Check if clicking on a spacer div (empty space between lists)
+    // Spacer divs are direct children with minimal/no content
+    const isDirectChild = container.contains(target) && target.parentElement === container;
+    const isSpacer = 
+      isDirectChild &&
+      target.textContent?.trim() === "" &&
+      target.children.length === 0 &&
+      !target.closest("[data-rbd-droppable-id]");
+
+    // Allow dragging if clicking on the container background or spacer elements
+    if (isContainer || isSpacer) {
+      e.preventDefault();
+      setIsDragging(true);
+      startPosRef.current = { x: e.clientX, y: e.clientY };
+      scrollStartRef.current = {
+        x: container.scrollLeft,
+        y: container.scrollTop,
+      };
+    }
+  };
+
+  return {
+    ref: scrollRef,
+    onMouseDown: handleMouseDown,
+    isDragging,
+  };
+}