From 21d714ab6e09eff6a6c103387efa32f54f68b1d1 Mon Sep 17 00:00:00 2001
From: Marshall Greenblatt <magreenblatt@gmail.com>
Date: Fri, 5 Aug 2022 14:58:31 -0400
Subject: [PATCH] Fix issues with browser focus assignment (fixes issue #3306,
 fixes issue #3116, see issue #3040)

DesktopWindowTreeHostWin ("Chrome_WidgetWin_0") focus needs to be set
synchronously in response to the parent window WM_SETFOCUS message and
before the associated call to WebContents::Focus. See updated comments in
CefBrowserPlatformDelegateNativeWin::SetFocus.
---
 libcef/browser/browser_host_base.cc           | 11 +++---
 libcef/browser/browser_host_base.h            |  2 --
 .../browser_platform_delegate_native_win.cc   | 34 +++++++++++++------
 3 files changed, 28 insertions(+), 19 deletions(-)

diff --git a/libcef/browser/browser_host_base.cc b/libcef/browser/browser_host_base.cc
index c2bad10db..6c7e8df08 100644
--- a/libcef/browser/browser_host_base.cc
+++ b/libcef/browser/browser_host_base.cc
@@ -233,13 +233,12 @@ bool CefBrowserHostBase::HasView() {
 }
 
 void CefBrowserHostBase::SetFocus(bool focus) {
-  // Always execute asynchronously to work around issue #3040.
-  CEF_POST_TASK(CEF_UIT, base::BindOnce(&CefBrowserHostBase::SetFocusInternal,
-                                        this, focus));
-}
+  if (!CEF_CURRENTLY_ON_UIT()) {
+    CEF_POST_TASK(CEF_UIT,
+                  base::BindOnce(&CefBrowserHostBase::SetFocus, this, focus));
+    return;
+  }
 
-void CefBrowserHostBase::SetFocusInternal(bool focus) {
-  CEF_REQUIRE_UIT();
   if (focus)
     OnSetFocus(FOCUS_SOURCE_SYSTEM);
   else if (platform_delegate_)
diff --git a/libcef/browser/browser_host_base.h b/libcef/browser/browser_host_base.h
index 58778891f..3a9d29fac 100644
--- a/libcef/browser/browser_host_base.h
+++ b/libcef/browser/browser_host_base.h
@@ -337,8 +337,6 @@ class CefBrowserHostBase : public CefBrowserHost,
   // Called from LoadMainFrameURL to perform the actual navigation.
   virtual bool Navigate(const content::OpenURLParams& params);
 
-  void SetFocusInternal(bool focus);
-
   // Create the CefFileDialogManager if it doesn't already exist.
   bool EnsureFileDialogManager();
 
diff --git a/libcef/browser/native/browser_platform_delegate_native_win.cc b/libcef/browser/native/browser_platform_delegate_native_win.cc
index ccd5315ce..599f530d7 100644
--- a/libcef/browser/native/browser_platform_delegate_native_win.cc
+++ b/libcef/browser/native/browser_platform_delegate_native_win.cc
@@ -350,15 +350,12 @@ void CefBrowserPlatformDelegateNativeWin::SetFocus(bool setFocus) {
   if (!setFocus)
     return;
 
-  if (web_contents_) {
-    // Give logical focus to the RenderWidgetHostViewAura in the views
-    // hierarchy. This does not change the native keyboard focus.
-    web_contents_->Focus();
-  }
-
   if (window_widget_) {
-    // Give native focus to the DesktopWindowTreeHostWin associated with the
-    // root window.
+    // Give native focus to the DesktopWindowTreeHostWin ("Chrome_WidgetWin_0")
+    // associated with the root window. The currently focused HWND may be
+    // "CefBrowserWindow" if we're called in response to our WndProc receiving
+    // the WM_SETFOCUS event, or some other HWND if the client calls
+    // CefBrowserHost::SetFocus(true) directly.
     //
     // The DesktopWindowTreeHostWin HandleNativeFocus/HandleNativeBlur methods
     // are called in response to WM_SETFOCUS/WM_KILLFOCUS respectively. The
@@ -369,9 +366,17 @@ void CefBrowserPlatformDelegateNativeWin::SetFocus(bool setFocus) {
     //    rings, flashing caret, onFocus/onBlur JS events, etc.) to work as
     //    expected (see issue #1677).
     // 2. Update focus state of the ui::InputMethod. If this does not occur
-    //    then InputMethodBase::GetTextInputClient will return NULL and
-    //    InputMethodWin::OnChar will fail to sent character events to the
-    //    renderer (see issue #1700).
+    //    then:
+    //    (a) InputMethodBase::GetTextInputClient will return NULL and
+    //    InputMethodWin::OnChar will fail to send character events to the
+    //    renderer (see issue #1700); and
+    //    (b) InputMethodWinBase::IsWindowFocused will return false due to
+    //    ::GetFocus() returning the currently focused HWND (e.g.
+    //    "CefBrowserWindow") instead of the expected "Chrome_WidgetWin_0" HWND,
+    //    causing TSF not to handle IME events (see issue #3306). For this same
+    //    reason, ::SetFocus needs to be called before WebContents::Focus which
+    //    sends the InputMethod OnWillChangeFocusedClient notification that then
+    //    calls IsWindowFocused.
     //
     // This differs from activation in Chrome which is handled via
     // HWNDMessageHandler::PostProcessActivateMessage (Widget::Show indirectly
@@ -387,6 +392,13 @@ void CefBrowserPlatformDelegateNativeWin::SetFocus(bool setFocus) {
     // discovered.
     ::SetFocus(HWNDForWidget(window_widget_));
   }
+
+  if (web_contents_) {
+    // Give logical focus to the RenderWidgetHostViewAura in the views
+    // hierarchy. This does not change the native keyboard focus. See above
+    // comments about InputMethod notifications.
+    web_contents_->Focus();
+  }
 }
 
 void CefBrowserPlatformDelegateNativeWin::NotifyMoveOrResizeStarted() {