🎨 Improve automatic scrolling when dragging items in the outline (siyuan-note#16161)

fix siyuan-note#15846 (comment)

Author: TCOTC

app/src/boot/globalEvent/dragover.ts

@@ -18,5 +18,7 @@ export const cancelDrag = () => {
         }
         ghostElement.remove();
         document.onmousemove = null;
+        // 通知取消拖拽，供相关模块停止滚动动画等
+        window.dispatchEvent(new CustomEvent("drag-cancel"));
     }
 };

app/src/layout/dock/Outline.ts

@@ -36,6 +36,9 @@ export class Outline extends Model {
     public blockId: string;
     public isPreview: boolean;
     private preFilterExpandIds: string[] | null = null;
+    private scrollAnimationId: number | null = null;
+    private scrollLastFrameTime: number = 0;
+    private scrollCurrentFPS: number = 60;
 
     constructor(options: {
         app: App,
@@ -331,6 +334,21 @@ export class Outline extends Model {
         }, response => {
             this.update(response);
         });
+
+        window.addEventListener("drag-cancel", () => {
+            this.stopScrollAnimation();
+        });
+    }
+
+    private stopScrollAnimation() {
+        if (this.scrollAnimationId) {
+            if (typeof cancelAnimationFrame !== "undefined") {
+                cancelAnimationFrame(this.scrollAnimationId);
+            } else {
+                clearTimeout(this.scrollAnimationId);
+            }
+            this.scrollAnimationId = null;
+        }
     }
 
     private bindSort() {
@@ -368,18 +386,68 @@ export class Outline extends Model {
                 }
                 ghostElement.style.top = moveEvent.clientY + "px";
                 ghostElement.style.left = moveEvent.clientX + "px";
+                // 检查是否在滚动边界区域
+                if (moveEvent.clientY < contentRect.top + Constants.SIZE_SCROLL_TB || moveEvent.clientY > contentRect.bottom - Constants.SIZE_SCROLL_TB) {
+                    // 如果还没有开始滚动，则开始持续滚动
+                    if (!this.scrollAnimationId) {
+                        const scrollDirection = moveEvent.clientY < contentRect.top + Constants.SIZE_SCROLL_TB ? -1 : 1;
+                        this.scrollLastFrameTime = performance.now();
+                        let scrollFrameCount = 0;
+                        
+                        const scrollAnimation = (currentTime: number) => {
+                            if (!this.scrollAnimationId) {
+                                return;
+                            }
+
+                            // 每隔 20 帧重新计算一次帧率
+                            if (scrollFrameCount % 20 === 0) {
+                                const deltaTime = currentTime - this.scrollLastFrameTime;
+                                this.scrollLastFrameTime = currentTime;
+                                // 计算过去 20 帧的平均帧率
+                                this.scrollCurrentFPS = deltaTime > 0 ? (20 * 1000) / deltaTime : 60;
+                            }
+                            scrollFrameCount++;
+
+                            // 基于当前帧率计算滚动步长，确保等效于 60fps 时的 16px/帧
+                            const baseScrollStep = 16;
+                            const targetFPS = 60;
+                            const scrollStep = baseScrollStep * (targetFPS / this.scrollCurrentFPS);
+
+                            this.element.scroll({
+                                top: this.element.scrollTop + scrollStep * scrollDirection
+                            });
+
+                            // 使用 requestAnimationFrame 继续动画
+                            this.scrollAnimationId = requestAnimationFrame(scrollAnimation);
+                        };
+
+                        // 检查浏览器是否支持 requestAnimationFrame
+                        if (typeof requestAnimationFrame !== "undefined") {
+                            this.scrollAnimationId = requestAnimationFrame(scrollAnimation);
+                        } else {
+                            // 回退到 setTimeout 方法
+                            const scrollInterval = 16; // 约 60fps
+                            const scrollStep = 16; // 每次滚动的距离
+
+                            const scrollAnimationFallback = () => {
+                                this.element.scroll({
+                                    top: this.element.scrollTop + scrollStep * scrollDirection
+                                });
+                                this.scrollAnimationId = window.setTimeout(scrollAnimationFallback, scrollInterval);
+                            };
+                            this.scrollAnimationId = window.setTimeout(scrollAnimationFallback, scrollInterval);
+                        }
+                    }
+                } else {
+                    // 离开滚动区域时停止滚动
+                    this.stopScrollAnimation();
+                }
                 if (!this.element.contains(moveEvent.target as Element)) {
                     this.element.querySelectorAll(".dragover__top, .dragover__bottom, .dragover, .dragover__current").forEach(item => {
                         item.classList.remove("dragover__top", "dragover__bottom", "dragover", "dragover__current");
                     });
                     return;
                 }
-                if (moveEvent.clientY < contentRect.top + Constants.SIZE_SCROLL_TB || moveEvent.clientY > contentRect.bottom - Constants.SIZE_SCROLL_TB) {
-                    this.element.scroll({
-                        top: this.element.scrollTop + (moveEvent.clientY < contentRect.top + Constants.SIZE_SCROLL_TB ? -Constants.SIZE_SCROLL_STEP : Constants.SIZE_SCROLL_STEP),
-                        behavior: "smooth"
-                    });
-                }
                 selectItem = hasClosestByClassName(moveEvent.target as HTMLElement, "b3-list-item") as HTMLElement;
                 if (!selectItem || selectItem.tagName !== "LI" || selectItem.style.position === "fixed") {
                     return;
@@ -410,6 +478,8 @@ export class Outline extends Model {
                 documentSelf.onselect = null;
                 ghostElement?.remove();
                 item.style.opacity = "";
+                // 清理滚动动画
+                this.stopScrollAnimation();
                 if (!selectItem) {
                     selectItem = this.element.querySelector(".dragover__top, .dragover__bottom, .dragover");
                 }