Bug 1770878: Don't fire collapsed selection events on the container of a focused text field. r=morgan

These events were clobbering the text field selection in the cache.
They aren't useful to clients anyway.

Differential Revision: https://phabricator.services.mozilla.com/D151004

accessible/base/SelectionManager.cpp

@@ -127,9 +127,17 @@ void SelectionManager::RemoveDocSelectionListener(PresShell* aPresShell) {
 
 void SelectionManager::ProcessTextSelChangeEvent(AccEvent* aEvent) {
   // Fire selection change event if it's not pure caret-move selection change,
-  // i.e. the accessible has or had not collapsed selection.
+  // i.e. the accessible has or had not collapsed selection. Also, it must not
+  // be a collapsed selection on the container of a focused text field, since
+  // the text field has an independent selection and will thus fire its own
+  // selection events.
   AccTextSelChangeEvent* event = downcast_accEvent(aEvent);
-  if (!event->IsCaretMoveOnly()) nsEventShell::FireEvent(aEvent);
+  if (!event->IsCaretMoveOnly() &&
+      !(event->mSel->IsCollapsed() && event->mSel != mCurrCtrlNormalSel &&
+        FocusMgr() && FocusMgr()->FocusedAccessible() &&
+        FocusMgr()->FocusedAccessible()->IsTextField())) {
+    nsEventShell::FireEvent(aEvent);
+  }
 
   // Fire caret move event if there's a caret in the selection.
   nsINode* caretCntrNode = nsCoreUtils::GetDOMNodeFromDOMPoint(

accessible/tests/browser/e10s/browser_caching_text.js

@@ -1136,3 +1136,54 @@ addAccessibleTask(
     remoteIframe: !isWinNoCache,
   }
 );
+
+/**
+ * Tabbing to an input selects all its text. Test that the cached selection
+ *reflects this. This has to be done separately from the other selection tests
+ * because prior contentEditable selection changes the events that get fired.
+ */
+addAccessibleTask(
+  `
+<button id="before">Before</button>
+<input id="input" value="test">
+  `,
+  async function(browser, docAcc) {
+    // The tab order is different when there's an iframe, so focus a control
+    // before the input to make tab consistent.
+    info("Focusing before");
+    const before = findAccessibleChildByID(docAcc, "before");
+    // Focusing a button fires a selection event. We must swallow this to
+    // avoid confusing the later test.
+    let events = waitForOrderedEvents([
+      [EVENT_FOCUS, before],
+      [EVENT_TEXT_SELECTION_CHANGED, docAcc],
+    ]);
+    before.takeFocus();
+    await events;
+
+    const input = findAccessibleChildByID(docAcc, "input", [nsIAccessibleText]);
+    info("Tabbing to input");
+    events = waitForEvents(
+      {
+        expected: [
+          [EVENT_FOCUS, input],
+          [EVENT_TEXT_SELECTION_CHANGED, input],
+        ],
+        unexpected: [[EVENT_TEXT_SELECTION_CHANGED, docAcc]],
+      },
+      "input",
+      false,
+      (args, task) => invokeContentTask(browser, args, task)
+    );
+    EventUtils.synthesizeKey("KEY_Tab");
+    await events;
+    testSelectionRange(browser, input, input, 0, input, 4);
+    testTextGetSelection(input, 0, 4, 0);
+  },
+  {
+    chrome: true,
+    topLevel: !isWinNoCache,
+    iframe: !isWinNoCache,
+    remoteIframe: !isWinNoCache,
+  }
+);