From 118abffdeaa323c391b2e709e46c70bbfc3f3b4d Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?R=C5=ABdolfs=20O=C5=A1i=C5=86=C5=A1?= <rudolfs@osins.org>
Date: Fri, 25 Sep 2026 17:11:17 +0200
Subject: [PATCH] Drop files only into the textarea under the cursor

---
 crates/radicle-tauri/tauri.conf.json     |   3 +-
 src/components/ExtendedTextarea.svelte   | 102 ++++++++++++++---------
 src/lib/disableDropNavigation.ts         |  25 ++++++
 src/main.ts                              |   2 +
 tests/e2e/repo/fileDrop.spec.ts          |  88 +++++++++++++++++++
 tests/unit/disableDropNavigation.test.ts |  77 +++++++++++++++++
 6 files changed, 255 insertions(+), 42 deletions(-)
 create mode 100644 src/lib/disableDropNavigation.ts
 create mode 100644 tests/e2e/repo/fileDrop.spec.ts
 create mode 100644 tests/unit/disableDropNavigation.test.ts

diff --git a/crates/radicle-tauri/tauri.conf.json b/crates/radicle-tauri/tauri.conf.json
index 5bbf6effd..29c9aab2d 100644
--- a/crates/radicle-tauri/tauri.conf.json
+++ b/crates/radicle-tauri/tauri.conf.json
@@ -16,7 +16,8 @@
         "minWidth": 960,
         "minHeight": 600,
         "titleBarStyle": "Overlay",
-        "hiddenTitle": true
+        "hiddenTitle": true,
+        "dragDropEnabled": false
       }
     ],
     "security": {
diff --git a/src/components/ExtendedTextarea.svelte b/src/components/ExtendedTextarea.svelte
index 5a79bf3be..5aa36530b 100644
--- a/src/components/ExtendedTextarea.svelte
+++ b/src/components/ExtendedTextarea.svelte
@@ -1,13 +1,10 @@
 <script lang="ts">
   import type { MentionInsertion } from "@app/components/MentionAutocomplete.svelte";
   import type { Embed } from "@bindings/cob/thread/Embed";
-  import type { UnlistenFn } from "@tauri-apps/api/event";
   import type { ComponentProps, Snippet } from "svelte";
 
-  import { listen } from "@tauri-apps/api/event";
   import { open } from "@tauri-apps/plugin-dialog";
   import debounce from "lodash/debounce";
-  import { onDestroy, onMount } from "svelte";
   import { SvelteMap } from "svelte/reactivity";
 
   import { basename } from "@app/lib/embeds";
@@ -123,9 +120,10 @@
     $state(undefined);
   let draggingOver = $state(false);
   let embedUploadError: string | undefined = $state();
-  let dragEnterUnlistenFn: UnlistenFn | undefined = undefined;
-  let dragLeaveUnlistenFn: UnlistenFn | undefined = undefined;
-  let dragDropUnlistenFn: UnlistenFn | undefined = undefined;
+  let dragDepth = 0;
+
+  // Mirrors `MAX_EMBED_SIZE` in `crates/radicle-types/src/traits/thread.rs`.
+  const MAX_EMBED_SIZE = 10_485_760;
 
   const restoreDragDropText = debounce(() => {
     embedUploadError = undefined;
@@ -178,33 +176,60 @@
     textareaElement?.setSelectionRange(selectionStart, selectionEnd);
   }
 
-  onMount(async () => {
-    if (window.__TAURI_INTERNALS__) {
-      if (attachEnabled) {
-        dragEnterUnlistenFn = await listen("tauri://drag-enter", () => {
-          draggingOver = true;
-        });
-
-        dragLeaveUnlistenFn = await listen("tauri://drag-leave", () => {
-          draggingOver = false;
-        });
-
-        dragDropUnlistenFn = await listen<{
-          paths: string[];
-          position: { x: number; y: number };
-        }>("tauri://drag-drop", async event => {
-          draggingOver = false;
-          await uploadEmbeds(event.payload.paths, basename, saveByPath);
-        });
-      }
+  async function saveFileBytes(file: File) {
+    if (file.size > MAX_EMBED_SIZE) {
+      throw new Error(`${file.name} exceeds the embed size limit`);
     }
-  });
+    return invoke<string>("save_embed_by_bytes", {
+      rid,
+      name: file.name,
+      bytes: new Uint8Array(await file.arrayBuffer()),
+    });
+  }
 
-  onDestroy(() => {
-    if (dragEnterUnlistenFn) dragEnterUnlistenFn();
-    if (dragLeaveUnlistenFn) dragLeaveUnlistenFn();
-    if (dragDropUnlistenFn) dragDropUnlistenFn();
-  });
+  function hasFiles(event: DragEvent): boolean {
+    return event.dataTransfer?.types.includes("Files") ?? false;
+  }
+
+  function acceptsDrop(event: DragEvent): boolean {
+    return attachEnabled && !preview && hasFiles(event);
+  }
+
+  function handleDragEnter(event: DragEvent) {
+    if (!hasFiles(event)) return;
+    dragDepth += 1;
+    if (acceptsDrop(event)) {
+      event.preventDefault();
+      draggingOver = true;
+    }
+  }
+
+  function handleDragOver(event: DragEvent) {
+    if (!acceptsDrop(event) || !event.dataTransfer) return;
+    event.preventDefault();
+    event.dataTransfer.dropEffect = "copy";
+  }
+
+  function handleDragLeave(event: DragEvent) {
+    if (!hasFiles(event)) return;
+    dragDepth = Math.max(0, dragDepth - 1);
+    if (dragDepth === 0) {
+      draggingOver = false;
+    }
+  }
+
+  function handleDrop(event: DragEvent) {
+    if (!hasFiles(event)) return;
+    dragDepth = 0;
+    draggingOver = false;
+    if (!acceptsDrop(event) || !event.dataTransfer) return;
+    event.preventDefault();
+    void uploadEmbeds(
+      Array.from(event.dataTransfer.files),
+      file => file.name,
+      saveFileBytes,
+    );
+  }
 
   async function attachEmbedsByPaths(paths: string[]) {
     await uploadEmbeds(paths, basename, saveByPath);
@@ -228,16 +253,7 @@
             invoke<string>("save_embed_by_clipboard", { name: file.name, rid }),
         );
       } else {
-        await uploadEmbeds(
-          files,
-          file => file.name,
-          async file =>
-            invoke<string>("save_embed_by_bytes", {
-              rid,
-              name: file.name,
-              bytes: new Uint8Array(await file.arrayBuffer()),
-            }),
-        );
+        await uploadEmbeds(files, file => file.name, saveFileBytes);
       }
     }
   }
@@ -410,6 +426,10 @@
 <div
   class="comment-section"
   aria-label="extended-textarea"
+  ondragenter={handleDragEnter}
+  ondragover={handleDragOver}
+  ondragleave={handleDragLeave}
+  ondrop={handleDrop}
   class:inline
   onkeydown={event => {
     if (!preview) return;
diff --git a/src/lib/disableDropNavigation.ts b/src/lib/disableDropNavigation.ts
new file mode 100644
index 000000000..7086bb7b3
--- /dev/null
+++ b/src/lib/disableDropNavigation.ts
@@ -0,0 +1,25 @@
+export function disableDropNavigation(): void {
+  const isNativeTextDrop = (event: DragEvent) =>
+    !(event.dataTransfer?.types.includes("Files") ?? false) &&
+    event.target instanceof Element &&
+    event.target.closest(
+      'input, textarea, [contenteditable]:not([contenteditable="false"])',
+    ) !== null;
+
+  window.addEventListener("dragover", event => {
+    if (
+      event.defaultPrevented ||
+      isNativeTextDrop(event) ||
+      !event.dataTransfer
+    ) {
+      return;
+    }
+    event.preventDefault();
+    event.dataTransfer.dropEffect = "none";
+  });
+  window.addEventListener("drop", event => {
+    if (!isNativeTextDrop(event)) {
+      event.preventDefault();
+    }
+  });
+}
diff --git a/src/main.ts b/src/main.ts
index 07af9d025..f3ae2816f 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -2,10 +2,12 @@ import "overlayscrollbars/overlayscrollbars.css";
 import { mount } from "svelte";
 
 import App from "./App.svelte";
+import { disableDropNavigation } from "./lib/disableDropNavigation";
 import { disableNativeContextMenu } from "./lib/disableNativeContextMenu";
 
 const app = mount(App, { target: document.body });
 
 disableNativeContextMenu();
+disableDropNavigation();
 
 export default app;
diff --git a/tests/e2e/repo/fileDrop.spec.ts b/tests/e2e/repo/fileDrop.spec.ts
new file mode 100644
index 000000000..fb438796c
--- /dev/null
+++ b/tests/e2e/repo/fileDrop.spec.ts
@@ -0,0 +1,88 @@
+import type { JSHandle, Locator, Page } from "@playwright/test";
+import type { RadiclePeer } from "@tests/support/peerManager.js";
+
+import { createProject } from "@tests/support/collaboration.js";
+import { expect, test, waitForCommand } from "@tests/support/fixtures.js";
+
+async function openIssue(page: Page, peer: RadiclePeer) {
+  const { rid, issueId } = await createProject(peer);
+  await page.goto(`/repos/${rid}/issues/${issueId}`);
+  await expect(page.getByText("Nobody reads them.")).toBeVisible();
+}
+
+function fileTransfer(
+  page: Page,
+  name: string,
+): Promise<JSHandle<DataTransfer>> {
+  return page.evaluateHandle(name => {
+    const dataTransfer = new DataTransfer();
+    dataTransfer.items.add(new File(["loud"], name, { type: "text/plain" }));
+    return dataTransfer;
+  }, name);
+}
+
+async function dropFile(target: Locator, dataTransfer: JSHandle<DataTransfer>) {
+  for (const type of ["dragenter", "dragover", "drop"]) {
+    await target.dispatchEvent(type, { dataTransfer });
+  }
+}
+
+test("a dropped file only goes into the textarea under it", async ({
+  page,
+  peer,
+}) => {
+  await openIssue(page, peer);
+
+  await page.getByText("Nobody reads them.").hover();
+  await page.getByTitle("Edit description").click();
+  const description = page.getByPlaceholder("Leave your comment");
+  await expect(description).toHaveValue("Nobody reads them.");
+
+  const composer = page.getByPlaceholder("Leave a comment");
+  await waitForCommand(page, "save_embed_by_bytes", () =>
+    fileTransfer(page, "notes.txt").then(transfer =>
+      dropFile(composer, transfer),
+    ),
+  );
+  await expect(composer).toHaveValue(/\[notes\.txt\]\(\w+\)/);
+  await expect(description).toHaveValue("Nobody reads them.");
+});
+
+test("a file dropped while previewing is refused", async ({ page, peer }) => {
+  await openIssue(page, peer);
+  let uploads = 0;
+  page.on("request", request => {
+    if (new URL(request.url()).pathname === "/save_embed_by_bytes") {
+      uploads++;
+    }
+  });
+
+  await page.getByPlaceholder("Leave a comment").fill("Draft");
+  const composer = page.getByLabel("extended-textarea");
+  await composer.getByRole("button", { name: "Preview" }).click();
+  await dropFile(composer, await fileTransfer(page, "notes.txt"));
+
+  await composer.getByRole("button", { name: "Edit" }).click();
+  await expect(page.getByPlaceholder("Leave a comment")).toHaveValue("Draft");
+  expect(uploads).toBe(0);
+});
+
+test("the drop highlight clears once the file leaves", async ({
+  page,
+  peer,
+}) => {
+  await openIssue(page, peer);
+  const transfer = await fileTransfer(page, "notes.txt");
+  const composer = page.getByPlaceholder("Leave a comment");
+  const highlight = page.getByText("Drop files to add them as embeds.");
+
+  await composer.dispatchEvent("dragenter", { dataTransfer: transfer });
+  await expect(highlight).toBeVisible();
+  // The highlight covers the textarea, so it is entered before that is left.
+  await highlight.dispatchEvent("dragenter", { dataTransfer: transfer });
+  await composer.dispatchEvent("dragleave", { dataTransfer: transfer });
+  await expect(highlight).toBeVisible();
+
+  await highlight.dispatchEvent("dragleave", { dataTransfer: transfer });
+  await expect(highlight).toBeHidden();
+});
diff --git a/tests/unit/disableDropNavigation.test.ts b/tests/unit/disableDropNavigation.test.ts
new file mode 100644
index 000000000..5b2769a60
--- /dev/null
+++ b/tests/unit/disableDropNavigation.test.ts
@@ -0,0 +1,77 @@
+import { beforeAll, describe, expect, test } from "vitest";
+
+import { disableDropNavigation } from "@app/lib/disableDropNavigation";
+
+// happy-dom's DragEvent ignores `dataTransfer`, so it is attached by hand.
+function drag(type: "dragover" | "drop", target: Element, types: string[]) {
+  const dataTransfer = { types, dropEffect: "copy" };
+  const event = new DragEvent(type, { bubbles: true, cancelable: true });
+  Object.defineProperty(event, "dataTransfer", { value: dataTransfer });
+  target.dispatchEvent(event);
+  return {
+    prevented: event.defaultPrevented,
+    dropEffect: dataTransfer.dropEffect,
+  };
+}
+
+function element(html: string): Element {
+  const template = document.createElement("template");
+  template.innerHTML = html;
+  const node = template.content.firstElementChild as Element;
+  document.body.append(node);
+  return node;
+}
+
+beforeAll(() => {
+  disableDropNavigation();
+});
+
+describe("disableDropNavigation", () => {
+  test.each([
+    ["a link", ["text/uri-list", "text/plain"]],
+    ["a file", ["Files"]],
+  ])("refuses %s dropped on the page", (_, types) => {
+    const page = element("<div>page</div>");
+    expect(drag("dragover", page, types)).toEqual({
+      prevented: true,
+      dropEffect: "none",
+    });
+    expect(drag("drop", page, types).prevented).toBe(true);
+  });
+
+  test.each([
+    ["a textarea", "<textarea></textarea>"],
+    ["an input", "<input>"],
+    ["an editable element", '<div contenteditable="true">x</div>'],
+  ])("leaves text dropped into %s to the webview", (_, html) => {
+    const field = element(html);
+    const types = ["text/plain"];
+    expect(drag("dragover", field, types)).toEqual({
+      prevented: false,
+      dropEffect: "copy",
+    });
+    expect(drag("drop", field, types).prevented).toBe(false);
+  });
+
+  test("refuses text dropped on an element that isn't editable", () => {
+    const field = element('<div contenteditable="false">x</div>');
+    expect(drag("drop", field, ["text/plain"]).prevented).toBe(true);
+  });
+
+  test("refuses a file over a field that didn't accept it", () => {
+    const field = element("<textarea></textarea>");
+    expect(drag("dragover", field, ["Files"])).toEqual({
+      prevented: true,
+      dropEffect: "none",
+    });
+  });
+
+  test("keeps the drop effect of a field that accepted the file", () => {
+    const field = element("<div></div>");
+    field.addEventListener("dragover", event => event.preventDefault());
+    expect(drag("dragover", field, ["Files"])).toEqual({
+      prevented: true,
+      dropEffect: "copy",
+    });
+  });
+});