fix comments

src/zen/tests/moz.build

@@ -20,6 +20,7 @@ BROWSER_CHROME_MANIFESTS += [
     "ub-actions/browser.toml",
     "urlbar/browser.toml",
     "welcome/browser.toml",
+    "window_drag/browser.toml",
     "window_sync/browser.toml",
 ]
 

src/zen/tests/window_drag/browser.toml

@@ -0,0 +1,10 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+[DEFAULT]
+support-files = [
+  "head.js",
+]
+
+["browser_window_drag_basic.js"]

src/zen/tests/window_drag/browser_window_drag_basic.js

@@ -0,0 +1,109 @@
+/* Any copyright is dedicated to the Public Domain.
+   https://creativecommons.org/publicdomain/zero/1.0/ */
+
+"use strict";
+
+let gDragStartCount = 0;
+
+add_setup(async function () {
+  const observer = () => gDragStartCount++;
+  Services.obs.addObserver(observer, WINDOW_DRAG_TOPIC);
+  registerCleanupFunction(() => {
+    Services.obs.removeObserver(observer, WINDOW_DRAG_TOPIC);
+  });
+});
+
+add_task(async function test_drag_from_empty_top_area() {
+  await BrowserTestUtils.withNewTab(WINDOW_DRAG_TEST_PAGE, async browser => {
+    await synthesizeContentDrag(browser, 50, 50);
+    await TestUtils.waitForCondition(
+      () => gDragStartCount === 1,
+      "Dragging an empty area in the top region should start a window drag"
+    );
+    is(gDragStartCount, 1, "Exactly one window drag started");
+  });
+});
+
+add_task(async function test_no_drag_on_interactive_target() {
+  await BrowserTestUtils.withNewTab(WINDOW_DRAG_TEST_PAGE, async browser => {
+    // Start the gesture on top of the link. Messages from the same actor
+    // pair are ordered, so the control drag afterwards would arrive later.
+    await BrowserTestUtils.synthesizeMouse(
+      "#link",
+      5,
+      5,
+      { type: "mousedown" },
+      browser
+    );
+    await BrowserTestUtils.synthesizeMouse(
+      "#link",
+      35,
+      15,
+      { type: "mousemove", buttons: 1 },
+      browser
+    );
+    await BrowserTestUtils.synthesizeMouse(
+      "#link",
+      45,
+      20,
+      { type: "mouseup" },
+      browser
+    );
+
+    // Control drag from an eligible area.
+    await synthesizeContentDrag(browser, 50, 50);
+    await TestUtils.waitForCondition(
+      () => gDragStartCount >= 2,
+      "The control drag should start a window drag"
+    );
+    is(
+      gDragStartCount,
+      2,
+      "Dragging a link must not start a window drag (only the control did)"
+    );
+  });
+});
+
+add_task(async function test_no_drag_below_top_region() {
+  await BrowserTestUtils.withNewTab(WINDOW_DRAG_TEST_PAGE, async browser => {
+    const innerHeight = await getContentInnerHeight(browser);
+    await synthesizeContentDrag(browser, 50, Math.floor(innerHeight * 0.6));
+
+    // Control drag from inside the top region.
+    await synthesizeContentDrag(browser, 50, 50);
+    await TestUtils.waitForCondition(
+      () => gDragStartCount >= 3,
+      "The control drag should start a window drag"
+    );
+    is(
+      gDragStartCount,
+      3,
+      "Dragging below the top region must not start a window drag"
+    );
+  });
+});
+
+add_task(async function test_pref_disables_window_drag() {
+  await SpecialPowers.pushPrefEnv({
+    set: [["zen.view.drag-window-from-content", false]],
+  });
+  await BrowserTestUtils.withNewTab(WINDOW_DRAG_TEST_PAGE, async browser => {
+    await synthesizeContentDrag(browser, 50, 50);
+  });
+  await SpecialPowers.popPrefEnv();
+
+  // Control drag with the pref back on, in a fresh tab so the actor is
+  // created again.
+  await BrowserTestUtils.withNewTab(WINDOW_DRAG_TEST_PAGE, async browser => {
+    await synthesizeContentDrag(browser, 50, 50);
+    await TestUtils.waitForCondition(
+      () => gDragStartCount >= 4,
+      "The control drag should start a window drag"
+    );
+    is(
+      gDragStartCount,
+      4,
+      "Dragging with the pref disabled must not start a window drag"
+    );
+  });
+});

src/zen/tests/window_drag/head.js

@@ -0,0 +1,57 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+"use strict";
+
+const WINDOW_DRAG_TOPIC = "zen-window-drag-started";
+
+const WINDOW_DRAG_TEST_PAGE = `https://example.com/document-builder.sjs?html=${encodeURIComponent(`
+  <!doctype html>
+  <style>
+    body { margin: 0; }
+    #link {
+      position: fixed;
+      top: 20px;
+      left: 300px;
+      width: 100px;
+      height: 30px;
+      display: block;
+    }
+  </style>
+  <a id="link" href="https://example.com/">a link</a>
+`)}`;
+
+/**
+ * Synthesizes a primary-button drag gesture inside the content area,
+ * starting at (x, y) and moving well past the drag threshold.
+ */
+async function synthesizeContentDrag(browser, x, y) {
+  await BrowserTestUtils.synthesizeMouse(
+    null,
+    x,
+    y,
+    { type: "mousedown" },
+    browser
+  );
+  for (let i = 1; i <= 3; i++) {
+    await BrowserTestUtils.synthesizeMouse(
+      null,
+      x + i * 10,
+      y + i * 5,
+      { type: "mousemove", buttons: 1 },
+      browser
+    );
+  }
+  await BrowserTestUtils.synthesizeMouse(
+    null,
+    x + 40,
+    y + 20,
+    { type: "mouseup" },
+    browser
+  );
+}
+
+function getContentInnerHeight(browser) {
+  return SpecialPowers.spawn(browser, [], () => content.innerHeight);
+}

src/zen/window-drag/actors/ZenWindowDragChild.sys.mjs

@@ -103,6 +103,10 @@ export class ZenWindowDragChild extends JSWindowActorChild {
   #startScreenY = 0;
 
   handleEvent(event) {
+    // Never let pages spoof the gesture with synthetic events.
+    if (!event.isTrusted) {
+      return;
+    }
     switch (event.type) {
       case "mousedown":
         this.#onMouseDown(event);
@@ -321,7 +325,9 @@ export class ZenWindowDragChild extends JSWindowActorChild {
     if (!style) {
       return false;
     }
-    const cursor = style.cursor.split(",").pop().trim();
+    // The keyword is always the last component of the computed value.
+    // Don't split on "," as url() cursor images may contain commas.
+    const cursor = style.cursor.match(/[a-z-]+$/)?.[0];
     return kInteractiveCursors.has(cursor);
   }
 }

src/zen/window-drag/actors/ZenWindowDragParent.sys.mjs

@@ -22,6 +22,12 @@ export class ZenWindowDragParent extends JSWindowActorParent {
     if (!win || win.closed || win.windowState === win.STATE_FULLSCREEN) {
       return;
     }
+    if (Cu.isInAutomation) {
+      // Tests can't exercise a real OS drag session; let them observe the
+      // decision instead.
+      Services.obs.notifyObservers(win, "zen-window-drag-started");
+      return;
+    }
     lazy.zenDragAndDropService.beginNativeWindowMove(win);
   }
 }