fix: do not allow the window to grab focus when tabbing / shift+tabbing (#16042)

* fix: do not allow the window to grab focus when tabbing / shift+tabbing

* test: add tests.

spec/chromium-spec.js

@@ -1410,6 +1410,111 @@ describe('chromium feature', () => {
       await new Promise((resolve) => { utter.onend = resolve })
     })
   })
+
+  describe('focus handling', () => {
+    let webviewContents = null
+
+    beforeEach(async () => {
+      w = new BrowserWindow({
+        show: true
+      })
+
+      const webviewReady = emittedOnce(w.webContents, 'did-attach-webview')
+      await w.loadFile(path.join(fixtures, 'pages', 'tab-focus-loop-elements.html'))
+      const [, wvContents] = await webviewReady
+      webviewContents = wvContents
+      await emittedOnce(webviewContents, 'did-finish-load')
+      w.focus()
+    })
+
+    afterEach(() => {
+      webviewContents = null
+    })
+
+    const expectFocusChange = async () => {
+      const [, focusedElementId] = await emittedOnce(ipcMain, 'focus-changed')
+      return focusedElementId
+    }
+
+    describe('a TAB press', () => {
+      const tabPressEvent = {
+        type: 'keyDown',
+        keyCode: 'Tab'
+      }
+
+      it('moves focus to the next focusable item', async () => {
+        let focusChange = expectFocusChange()
+        w.webContents.sendInputEvent(tabPressEvent)
+        let focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-element-1', `should start focused in element-1, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        w.webContents.sendInputEvent(tabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-element-2', `focus should've moved to element-2, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        w.webContents.sendInputEvent(tabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-wv-element-1', `focus should've moved to the webview's element-1, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        webviewContents.sendInputEvent(tabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-wv-element-2', `focus should've moved to the webview's element-2, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        webviewContents.sendInputEvent(tabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-element-3', `focus should've moved to element-3, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        w.webContents.sendInputEvent(tabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-element-1', `focus should've looped back to element-1, it's instead in ${focusedElementId}`)
+      })
+    })
+
+    describe('a SHIFT + TAB press', () => {
+      const shiftTabPressEvent = {
+        type: 'keyDown',
+        modifiers: ['Shift'],
+        keyCode: 'Tab'
+      }
+
+      it('moves focus to the previous focusable item', async () => {
+        let focusChange = expectFocusChange()
+        w.webContents.sendInputEvent(shiftTabPressEvent)
+        let focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-element-3', `should start focused in element-3, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        w.webContents.sendInputEvent(shiftTabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-wv-element-2', `focus should've moved to the webview's element-2, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        webviewContents.sendInputEvent(shiftTabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-wv-element-1', `focus should've moved to the webview's element-1, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        webviewContents.sendInputEvent(shiftTabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-element-2', `focus should've moved to element-2, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        w.webContents.sendInputEvent(shiftTabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-element-1', `focus should've moved to element-1, it's instead in ${focusedElementId}`)
+
+        focusChange = expectFocusChange()
+        w.webContents.sendInputEvent(shiftTabPressEvent)
+        focusedElementId = await focusChange
+        assert.strictEqual(focusedElementId, 'BUTTON-element-3', `focus should've looped back to element-3, it's instead in ${focusedElementId}`)
+      })
+    })
+  })
 })
 
 describe('font fallback', () => {