ENG-1507: Drag and drop files from wikilinks (#960)

* widget approach

* ENG-1507: Add debug logging to wikilink drag handler

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* clean up

* address PR comment

* clean further

* PR comment

* Update apps/obsidian/src/utils/wikilinkDragHandler.ts

Co-authored-by: graphite-app[bot] <96075541+graphite-app[bot]@users.noreply.github.com>

* fix

* hide/show the widget

* PR comment

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-authored-by: graphite-app[bot] <96075541+graphite-app[bot]@users.noreply.github.com>

Author: 3 people

apps/obsidian/src/index.ts

@@ -17,6 +17,7 @@ import {
   openConvertImageToNodeModal,
 } from "~/utils/editorMenuUtils";
 import { createImageEmbedHoverExtension } from "~/utils/imageEmbedHoverIcon";
+import { createWikilinkDragExtension } from "~/utils/wikilinkDragHandler";
 import { registerCommands } from "~/utils/registerCommands";
 import { DiscourseContextView } from "~/components/DiscourseContextView";
 import { VIEW_TYPE_TLDRAW_DG_PREVIEW, FRONTMATTER_KEY } from "~/constants";
@@ -232,6 +233,32 @@ export default class DiscourseGraphPlugin extends Plugin {
       }),
     );
 
+    type EditorWithCm = { cm: EditorView };
+    const hasCodeMirrorView = (editor: unknown): editor is EditorWithCm => {
+      if (!editor || typeof editor !== "object") return false;
+      return "cm" in editor;
+    };
+
+    // Dispatch a no-op CM6 transaction to every markdown editor so their
+    // ViewPlugin re-evaluates hasVisibleCanvasLeaf and shows/hides widgets.
+    // layout-change covers splits/moves, active-leaf-change covers tab switches.
+    const refreshMarkdownEditors = (): void => {
+      this.app.workspace.iterateAllLeaves((leaf) => {
+        if (
+          leaf.view instanceof MarkdownView &&
+          hasCodeMirrorView(leaf.view.editor)
+        ) {
+          leaf.view.editor.cm.dispatch({});
+        }
+      });
+    };
+    this.registerEvent(
+      this.app.workspace.on("layout-change", refreshMarkdownEditors),
+    );
+    this.registerEvent(
+      this.app.workspace.on("active-leaf-change", refreshMarkdownEditors),
+    );
+
     // Register editor keydown listener for node tag hotkey
     this.setupNodeTagHotkey();
   }
@@ -281,6 +308,9 @@ export default class DiscourseGraphPlugin extends Plugin {
 
     // eslint-disable-next-line @typescript-eslint/no-unsafe-argument
     this.registerEditorExtension(createImageEmbedHoverExtension(this));
+
+    // eslint-disable-next-line @typescript-eslint/no-unsafe-argument
+    this.registerEditorExtension(createWikilinkDragExtension(this));
   }
 
   private createStyleElement() {

apps/obsidian/src/utils/wikilinkDragHandler.ts

@@ -0,0 +1,188 @@
+import {
+  type PluginValue,
+  ViewPlugin,
+  type ViewUpdate,
+  WidgetType,
+  Decoration,
+  type DecorationSet,
+  EditorView,
+} from "@codemirror/view";
+import { TFile, WorkspaceLeaf } from "obsidian";
+import { VIEW_TYPE_TLDRAW_DG_PREVIEW } from "~/constants";
+import type DiscourseGraphPlugin from "~/index";
+
+const buildObsidianUrl = (vaultName: string, filePath: string): string => {
+  return `obsidian://open?vault=${encodeURIComponent(vaultName)}&file=${encodeURIComponent(filePath)}`;
+};
+
+const resolveFileFromLinkText = (
+  linkText: string,
+  plugin: DiscourseGraphPlugin,
+): TFile | null => {
+  const activeFile = plugin.app.workspace.getActiveFile();
+  if (!activeFile) return null;
+
+  const resolved = plugin.app.metadataCache.getFirstLinkpathDest(
+    linkText,
+    activeFile.path,
+  );
+  return resolved instanceof TFile ? resolved : null;
+};
+
+const setDragData = (
+  e: DragEvent,
+  file: TFile,
+  plugin: DiscourseGraphPlugin,
+): void => {
+  const vaultName = plugin.app.vault.getName();
+  const url = buildObsidianUrl(vaultName, file.path);
+  e.dataTransfer?.setData("text/uri-list", url);
+  e.dataTransfer?.setData("text/plain", url);
+};
+
+// --- Live Preview ---
+
+/**
+ * Extract the file path from a link match.
+ * Handles wikilinks (`[[path]]`, `[[path|alias]]`) and
+ * markdown links (`[text](path.md)`), decoding URL-encoded paths.
+ */
+const extractLinkPath = (match: string): string => {
+  // Wikilink: [[path]] or [[path|alias]]
+  if (match.startsWith("[[")) {
+    const inner = match.slice(2, -2);
+    const pipeIndex = inner.indexOf("|");
+    return pipeIndex >= 0 ? inner.slice(0, pipeIndex) : inner;
+  }
+
+  // Markdown link: [text](path)
+  const parenOpen = match.lastIndexOf("(");
+  const rawPath = match.slice(parenOpen + 1, -1);
+  try {
+    return decodeURIComponent(rawPath);
+  } catch (error) {
+    return rawPath;
+  }
+};
+
+/**
+ * Widget that renders a small drag handle next to an internal link.
+ * CM6 widgets get `ignoreEvent() → true` by default, which means
+ * the editor completely ignores mouse events on them — native drag works.
+ */
+class WikilinkDragHandleWidget extends WidgetType {
+  constructor(
+    private linkPath: string,
+    private plugin: DiscourseGraphPlugin,
+  ) {
+    super();
+  }
+
+  eq(other: WikilinkDragHandleWidget): boolean {
+    return this.linkPath === other.linkPath;
+  }
+
+  toDOM(): HTMLElement {
+    const handle = document.createElement("span");
+    handle.className =
+      "inline-block cursor-grab opacity-30 text-[10px] text-[var(--text-muted)] align-middle ml-0.5 transition-opacity duration-150 ease-in-out select-none";
+    handle.draggable = true;
+    handle.setAttribute("aria-label", "Drag to canvas");
+    handle.textContent = "⠿";
+
+    handle.addEventListener("mouseenter", () => {
+      handle.style.opacity = "1";
+    });
+    handle.addEventListener("mouseleave", () => {
+      handle.style.opacity = "";
+    });
+
+    handle.addEventListener("dragstart", (e) => {
+      const file = resolveFileFromLinkText(this.linkPath, this.plugin);
+      if (!file) {
+        e.preventDefault();
+        return;
+      }
+      setDragData(e, file, this.plugin);
+    });
+
+    return handle;
+  }
+}
+
+// Matches wikilinks [[...]] and markdown links [text](path.md).
+// Embed exclusion (![[...]] and ![text](...)) is handled in the loop.
+const INTERNAL_LINK_RE = /\[\[([^\]]+)\]\]|\[([^\]]+)\]\(([^)]+\.md)\)/g;
+
+const hasVisibleCanvasLeaf = (plugin: DiscourseGraphPlugin): boolean =>
+  plugin.app.workspace
+    .getLeavesOfType(VIEW_TYPE_TLDRAW_DG_PREVIEW)
+    .some((leaf) =>
+      (leaf as WorkspaceLeaf & { isVisible(): boolean }).isVisible(),
+    );
+const buildWidgetDecorations = (
+  view: EditorView,
+  plugin: DiscourseGraphPlugin,
+): DecorationSet => {
+  if (!hasVisibleCanvasLeaf(plugin)) return Decoration.none;
+
+  const widgets = [];
+
+  for (const { from, to } of view.visibleRanges) {
+    const text = view.state.doc.sliceString(from, to);
+    let match: RegExpExecArray | null;
+    INTERNAL_LINK_RE.lastIndex = 0;
+
+    while ((match = INTERNAL_LINK_RE.exec(text)) !== null) {
+      const checkPos = from + match.index - 1;
+      const isEmbed =
+        checkPos >= 0 &&
+        view.state.doc.sliceString(checkPos, checkPos + 1) === "!";
+      if (isEmbed) continue;
+      const matchEnd = from + match.index + match[0].length;
+      const linkPath = extractLinkPath(match[0]);
+      const widget = new WikilinkDragHandleWidget(linkPath, plugin);
+      widgets.push(Decoration.widget({ widget, side: 1 }).range(matchEnd));
+    }
+  }
+
+  // Decorations must be sorted by position
+  widgets.sort((a, b) => a.from - b.from);
+  return Decoration.set(widgets);
+};
+
+/**
+ * CM6 ViewPlugin that adds a draggable grip icon after each internal link
+ * in Live Preview. Matches both wikilinks (`[[...]]`) and markdown links
+ * (`[text](path.md)`), inserting a widget decoration after each match.
+ */
+export const createWikilinkDragExtension = (
+  plugin: DiscourseGraphPlugin,
+): ViewPlugin<PluginValue> => {
+  return ViewPlugin.fromClass(
+    class {
+      decorations: DecorationSet;
+      private canvasVisible: boolean;
+
+      constructor(view: EditorView) {
+        this.canvasVisible = hasVisibleCanvasLeaf(plugin);
+        this.decorations = buildWidgetDecorations(view, plugin);
+      }
+
+      update(update: ViewUpdate): void {
+        const canvasVisible = hasVisibleCanvasLeaf(plugin);
+        if (
+          update.docChanged ||
+          update.viewportChanged ||
+          canvasVisible !== this.canvasVisible
+        ) {
+          this.canvasVisible = canvasVisible;
+          this.decorations = buildWidgetDecorations(update.view, plugin);
+        }
+      }
+    },
+    {
+      decorations: (v) => v.decorations,
+    },
+  );
+};