From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: clavin <clavin@electronjs.org>
Date: Mon, 11 Dec 2023 20:43:34 -0300
Subject: fix: activate background material on windows

This patch adds a condition to the HWND message handler to allow windows
with translucent background materials to become activated.

It also ensures the lParam of WM_NCACTIVATE is set to -1 so as to not repaint
the client area, which can lead to a title bar incorrectly being displayed in
frameless windows.

This patch likely can't be upstreamed as-is, as Chromium doesn't have
this use case in mind currently.

diff --git a/ui/views/win/hwnd_message_handler.cc b/ui/views/win/hwnd_message_handler.cc
index 72fa8b61c41e54b06b87f2b6750021fb99e65fea..b6c9210890d88d21b1aeb5ee2b513d1efd29b4b3 100644
--- a/ui/views/win/hwnd_message_handler.cc
+++ b/ui/views/win/hwnd_message_handler.cc
@@ -907,13 +907,13 @@ void HWNDMessageHandler::FrameTypeChanged() {
 
 void HWNDMessageHandler::PaintAsActiveChanged() {
   if (!delegate_->HasNonClientView() || !delegate_->CanActivate() ||
-      !delegate_->HasFrame() ||
+      (!delegate_->HasFrame() && !is_translucent_) ||
       (delegate_->GetFrameMode() == FrameMode::CUSTOM_DRAWN)) {
     return;
   }
 
   DefWindowProcWithRedrawLock(WM_NCACTIVATE, delegate_->ShouldPaintAsActive(),
-                              0);
+                              delegate_->HasFrame() ? 0 : -1);
 }
 
 void HWNDMessageHandler::SetWindowIcons(const gfx::ImageSkia& window_icon,
@@ -2252,17 +2252,18 @@ LRESULT HWNDMessageHandler::OnNCActivate(UINT message,
   if (IsVisible())
     delegate_->SchedulePaint();
 
-  // Calling DefWindowProc is only necessary if there's a system frame being
-  // drawn. Otherwise it can draw an incorrect title bar and cause visual
-  // corruption.
-  if (!delegate_->HasFrame() ||
+  // If the window is translucent, it may have the Mica background.
+  // In that case, it's necessary to call |DefWindowProc|, but we can
+  // pass -1 in the lParam to prevent any non-client area elements from
+  // being displayed.
+  if ((!delegate_->HasFrame() && !is_translucent_) ||
       delegate_->GetFrameMode() == FrameMode::CUSTOM_DRAWN) {
     SetMsgHandled(TRUE);
     return TRUE;
   }
 
   return DefWindowProcWithRedrawLock(WM_NCACTIVATE, paint_as_active || active,
-                                     0);
+                                     delegate_->HasFrame() ? 0 : -1);
 }
 
 LRESULT HWNDMessageHandler::OnNCCalcSize(BOOL mode, LPARAM l_param) {
