feat(editor): add block button for hovering blocks (#14879)

This PR implements [feature request] #14845 

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Add-block control that appears when hovering blocks in page mode to
insert and auto-focus a new paragraph; control hides after insertion.

* **Improvements**
* Improved hover and interaction handling to avoid accidental triggers
when interacting with the drag handle or add-block control.
* Consistent sizing, positioning, and visibility behavior for the
add-block control.

* **Style**
  * Moved heading icon slightly for improved visual alignment.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Co-authored-by: DarkSky <25152247+darkskygit@users.noreply.github.com>

blocksuite/affine/blocks/paragraph/src/heading-icon.ts

@@ -42,7 +42,7 @@ export class ParagraphHeadingIcon extends SignalWatcher(
       margin-top: 0.3em;
       position: absolute;
       left: 0;
-      transform: translateX(-64px);
+      transform: translateX(-80px);
       border-radius: 4px;
       padding: 2px;
       cursor: pointer;

blocksuite/affine/widgets/drag-handle/package.json

@@ -19,6 +19,7 @@
     "@blocksuite/affine-components": "workspace:*",
     "@blocksuite/affine-ext-loader": "workspace:*",
     "@blocksuite/affine-model": "workspace:*",
+    "@blocksuite/affine-rich-text": "workspace:*",
     "@blocksuite/affine-shared": "workspace:*",
     "@blocksuite/global": "workspace:*",
     "@blocksuite/icons": "^2.2.17",

blocksuite/affine/widgets/drag-handle/src/components/add-block-widget.ts

@@ -0,0 +1,78 @@
+import { PlusIcon } from '@blocksuite/icons/lit';
+import { css, html, LitElement } from 'lit';
+import { property } from 'lit/decorators.js';
+
+import type { AFFINE_ADD_BLOCK_WIDGET } from '../consts.js';
+
+export class AffineAddBlockWidget extends LitElement {
+  static override styles = css`
+    :host {
+      display: block;
+      pointer-events: none;
+    }
+
+    .affine-add-block-widget {
+      display: flex;
+      align-items: center;
+      justify-content: center;
+      width: 18px;
+      height: 18px;
+      margin-top: 8px;
+      cursor: pointer;
+      border-radius: 4px;
+      color: var(--affine-placeholder-color);
+      background: transparent;
+      border: none;
+      padding: 0;
+      transition:
+        color 0.2s ease,
+        background 0.2s ease;
+      pointer-events: auto;
+      user-select: none;
+      box-sizing: border-box;
+    }
+
+    .affine-add-block-widget:hover {
+      background: var(--affine-hover-color);
+      color: var(--affine-text-primary-color);
+    }
+
+    .affine-add-block-widget svg {
+      width: 12px;
+      height: 12px;
+      flex-shrink: 0;
+    }
+  `;
+
+  @property({ type: Boolean })
+  accessor visible = false;
+
+  private readonly _handleClick = (e: MouseEvent) => {
+    e.stopPropagation();
+    e.preventDefault();
+    this.dispatchEvent(
+      new CustomEvent('add-block', { bubbles: true, composed: true })
+    );
+  };
+
+  override render() {
+    if (!this.visible) return html``;
+
+    return html`
+      <button
+        class="affine-add-block-widget"
+        title="Click to add a block below"
+        aria-label="Add block below"
+        @click=${this._handleClick}
+      >
+        ${PlusIcon({ width: '12', height: '12' })}
+      </button>
+    `;
+  }
+}
+
+declare global {
+  interface HTMLElementTagNameMap {
+    [AFFINE_ADD_BLOCK_WIDGET]: AffineAddBlockWidget;
+  }
+}

blocksuite/affine/widgets/drag-handle/src/config.ts

@@ -1,3 +1,4 @@
+export const ADD_BLOCK_WIDGET_WIDTH = 16;
 export const DRAG_HANDLE_CONTAINER_HEIGHT = 24;
 export const DRAG_HANDLE_CONTAINER_WIDTH = 16;
 export const DRAG_HANDLE_CONTAINER_WIDTH_TOP_LEVEL = 8;

blocksuite/affine/widgets/drag-handle/src/consts.ts

@@ -1 +1,2 @@
 export const AFFINE_DRAG_HANDLE_WIDGET = 'affine-drag-handle-widget';
+export const AFFINE_ADD_BLOCK_WIDGET = 'affine-add-block-widget';

blocksuite/affine/widgets/drag-handle/src/drag-handle.ts

@@ -1,5 +1,8 @@
+import './components/add-block-widget.js';
+
 import { EdgelessCRUDIdentifier } from '@blocksuite/affine-block-surface';
 import type { RootBlockModel } from '@blocksuite/affine-model';
+import { focusTextModel } from '@blocksuite/affine-rich-text';
 import { DocModeProvider } from '@blocksuite/affine-shared/services';
 import {
   isInsideEdgelessEditor,
@@ -15,6 +18,7 @@ import { query, state } from 'lit/decorators.js';
 import { classMap } from 'lit/directives/class-map.js';
 import { styleMap } from 'lit/directives/style-map.js';
 
+//focustextmodel rich text should be added in package.json file and import from there
 import type { AFFINE_DRAG_HANDLE_WIDGET } from './consts.js';
 import { RectHelper } from './helpers/rect-helper.js';
 import { SelectionHelper } from './helpers/selection-helper.js';
@@ -51,9 +55,48 @@ export class AffineDragHandleWidget extends WidgetComponent<RootBlockModel> {
     this.pointerEventWatcher.reset();
   };
 
+  /**
+   * Insert a new empty paragraph block below the currently hovered block
+   * and move the cursor into it.
+   */
+  private readonly _handleAddBlock = () => {
+    const anchorBlockId = this.anchorBlockId.peek();
+    if (!anchorBlockId) return;
+
+    const block = this.anchorBlockComponent.peek();
+    if (!block) return;
+
+    const { store } = this;
+    const parent = store.getParent(block.model);
+    if (!parent) return;
+
+    const index = parent.children.indexOf(block.model);
+    if (index < 0) return;
+    store.captureSync();
+    const newBlockId = store.addBlock(
+      'affine:paragraph',
+      {},
+      parent,
+      index + 1
+    );
+
+    if (!newBlockId) return;
+
+    this.host.updateComplete
+      .then(() => {
+        focusTextModel(this.std, newBlockId);
+      })
+      .catch(console.error);
+
+    this.hide();
+  };
+
   @state()
   accessor activeDragHandle: 'block' | 'gfx' | null = null;
 
+  @state()
+  accessor showAddBlockWidget = false;
+
   anchorBlockId = signal<string | null>(null);
 
   anchorBlockComponent = computed<BlockComponent | null>(() => {
@@ -115,6 +158,7 @@ export class AffineDragHandleWidget extends WidgetComponent<RootBlockModel> {
     this.anchorBlockId.value = null;
     this.dragHoverRect = null;
     this.activeDragHandle = null;
+    this.showAddBlockWidget = false;
 
     if (this.dragHandleContainer) {
       this.dragHandleContainer.removeAttribute('style');
@@ -123,6 +167,10 @@ export class AffineDragHandleWidget extends WidgetComponent<RootBlockModel> {
     if (this.dragHandleGrabber) {
       this.dragHandleGrabber.removeAttribute('style');
     }
+    if (this.addBlockWidgetContainer) {
+      this.addBlockWidgetContainer.removeAttribute('style');
+      this.addBlockWidgetContainer.style.display = 'none';
+    }
 
     if (force) {
       this._reset();
@@ -211,6 +259,12 @@ export class AffineDragHandleWidget extends WidgetComponent<RootBlockModel> {
 
     return html`
       <div class="affine-drag-handle-widget">
+        <div class="affine-add-block-widget-container">
+          <affine-add-block-widget
+            .visible=${this.showAddBlockWidget && this.mode === 'page'}
+            @add-block=${this._handleAddBlock}
+          ></affine-add-block-widget>
+        </div>
         <div class="affine-drag-handle-container">
           <div class=${classMap(classes)}>
             ${isGfx
@@ -236,6 +290,9 @@ export class AffineDragHandleWidget extends WidgetComponent<RootBlockModel> {
   @query('.affine-drag-handle-grabber')
   accessor dragHandleGrabber!: HTMLDivElement;
 
+  @query('.affine-add-block-widget-container')
+  accessor addBlockWidgetContainer!: HTMLDivElement;
+
   @state()
   accessor dragHoverRect: {
     width: number;

blocksuite/affine/widgets/drag-handle/src/effects.ts

@@ -1,12 +1,14 @@
+import { AffineAddBlockWidget } from './components/add-block-widget';
 import {
   EDGELESS_DND_PREVIEW_ELEMENT,
   EdgelessDndPreviewElement,
 } from './components/edgeless-preview/preview';
-import { AFFINE_DRAG_HANDLE_WIDGET } from './consts';
+import { AFFINE_ADD_BLOCK_WIDGET, AFFINE_DRAG_HANDLE_WIDGET } from './consts';
 import { AffineDragHandleWidget } from './drag-handle';
 
 export function effects() {
   customElements.define(AFFINE_DRAG_HANDLE_WIDGET, AffineDragHandleWidget);
+  customElements.define(AFFINE_ADD_BLOCK_WIDGET, AffineAddBlockWidget);
   customElements.define(
     EDGELESS_DND_PREVIEW_ELEMENT,
     EdgelessDndPreviewElement

blocksuite/affine/widgets/drag-handle/src/styles.ts

@@ -1,7 +1,10 @@
 import { unsafeCSSVarV2 } from '@blocksuite/affine-shared/theme';
 import { css } from 'lit';
 
-import { DRAG_HANDLE_CONTAINER_WIDTH } from './config.js';
+import {
+  ADD_BLOCK_WIDGET_WIDTH,
+  DRAG_HANDLE_CONTAINER_WIDTH,
+} from './config.js';
 
 export const styles = css`
   .affine-drag-handle-widget {
@@ -10,6 +13,20 @@ export const styles = css`
     left: 0;
     top: 0;
     contain: size layout;
+    pointer-events: none;
+  }
+
+  .affine-add-block-widget-container {
+    top: 0;
+    left: 0;
+    position: absolute;
+    display: flex;
+    justify-content: center;
+    width: ${ADD_BLOCK_WIDGET_WIDTH}px;
+    min-height: 12px;
+    pointer-events: none;
+    user-select: none;
+    box-sizing: border-box;
   }
 
   .affine-drag-handle-container {

blocksuite/affine/widgets/drag-handle/src/watchers/pointer-event-watcher.ts

@@ -12,6 +12,7 @@ import { computed } from '@preact/signals-core';
 import throttle from 'lodash-es/throttle';
 
 import {
+  ADD_BLOCK_WIDGET_WIDTH,
   DRAG_HANDLE_CONTAINER_WIDTH,
   DRAG_HANDLE_GRABBER_BORDER_RADIUS,
   DRAG_HANDLE_GRABBER_HEIGHT,
@@ -199,6 +200,7 @@ export class PointerEventWatcher {
       !this.widget.isDragHandleHovered
     ) {
       this.showDragHandleOnHoverBlock();
+      this.widget.showAddBlockWidget = true;
       this._lastHoveredBlockId = this.widget.anchorBlockId.peek();
     }
   };
@@ -251,8 +253,13 @@ export class PointerEventWatcher {
         return;
       }
 
-      // When pointer on drag handle, should do nothing
-      if (element.closest('.affine-drag-handle-container')) return;
+      // When pointer on drag handle or add-block widget, should do nothing
+      if (
+        element.closest('.affine-drag-handle-container') ||
+        element.closest('.affine-add-block-widget-container')
+      ) {
+        return;
+      }
 
       if (!this.widget.rootComponent) return;
 
@@ -317,6 +324,7 @@ export class PointerEventWatcher {
 
     const container = this.widget.dragHandleContainer;
     const grabber = this.widget.dragHandleGrabber;
+    const addBlockWidgetContainer = this.widget.addBlockWidgetContainer;
     if (!container || !grabber) return;
 
     this.widget.activeDragHandle = 'block';
@@ -336,6 +344,21 @@ export class PointerEventWatcher {
       Object.assign(container.style, containerStyle);
 
       container.style.display = 'flex';
+
+      // Position the add-block widget beside the drag handle, aligned to the first line.
+      if (
+        addBlockWidgetContainer &&
+        this.widget.showAddBlockWidget &&
+        this.widget.mode === 'page'
+      ) {
+        const posTop = this._getTopWithBlockComponent(block);
+        addBlockWidgetContainer.style.left = `${draggingAreaRect.left - ADD_BLOCK_WIDGET_WIDTH}px`;
+        addBlockWidgetContainer.style.top = `${posTop}px`;
+        addBlockWidgetContainer.style.height = 'auto';
+        addBlockWidgetContainer.style.display = 'flex';
+      } else if (addBlockWidgetContainer) {
+        addBlockWidgetContainer.style.display = 'none';
+      }
     };
 
     if (isBlockIdEqual(block.blockId, this._lastShowedBlock?.id)) {

blocksuite/affine/widgets/drag-handle/tsconfig.json

@@ -16,6 +16,7 @@
     { "path": "../../components" },
     { "path": "../../ext-loader" },
     { "path": "../../model" },
+    { "path": "../../rich-text" },
     { "path": "../../shared" },
     { "path": "../../../framework/global" },
     { "path": "../../../framework/std" },

tools/utils/src/workspace.gen.ts

@@ -828,6 +828,7 @@ export const PackageList = [
       'blocksuite/affine/components',
       'blocksuite/affine/ext-loader',
       'blocksuite/affine/model',
+      'blocksuite/affine/rich-text',
       'blocksuite/affine/shared',
       'blocksuite/framework/global',
       'blocksuite/framework/std',

yarn.lock

@@ -2932,6 +2932,7 @@ __metadata:
     "@blocksuite/affine-components": "workspace:*"
     "@blocksuite/affine-ext-loader": "workspace:*"
     "@blocksuite/affine-model": "workspace:*"
+    "@blocksuite/affine-rich-text": "workspace:*"
     "@blocksuite/affine-shared": "workspace:*"
     "@blocksuite/global": "workspace:*"
     "@blocksuite/icons": "npm:^2.2.17"