Revert "Bug 1824053 - [2/4] Cloak and clear new windows on creation r=win-reviewers,handyman"

This reverts commit 8ef94cf.

Author: K4sum1

widget/windows/nsWindow.cpp

@@ -1705,64 +1705,6 @@ void nsWindow::Show(bool aState) {
         // top level windows:
         syncInvalidate = true;
 
-        // Cloak (or uncloak) the window.
-        //
-        // (DWMWA_CLOAK is effectively orthogonal to any cloaking done by the
-        // shell to implement virtual desktops; we don't have to worry about
-        // accidentally forcing something on another desktop to become visible.)
-        constexpr static const auto CloakWindow = [](HWND hwnd, BOOL state) {
-          ::DwmSetWindowAttribute(hwnd, DWMWA_CLOAK, &state, sizeof(state));
-        };
-
-        // Clear the window using a theme-appropriate color.
-        constexpr static const auto ClearWindow = [](HWND hwnd) {
-          // default background color from current theme
-          auto const bgcolor = LookAndFeel::Color(
-              StyleSystemColor::Window, PreferenceSheet::ColorSchemeForChrome(),
-              LookAndFeel::UseStandins::No, NS_RGB(0, 0, 0));
-
-          HBRUSH brush = ::CreateSolidBrush(NSRGB_2_COLOREF(bgcolor));
-          if (NS_WARN_IF(!brush)) {
-            // GDI object cap hit, possibly?
-            return;
-          }
-          auto const _releaseBrush =
-              MakeScopeExit([&] { ::DeleteObject(brush); });
-
-          HDC hdc = ::GetWindowDC(hwnd);
-          MOZ_ASSERT(hdc);
-          auto const _cleanupDC =
-              MakeScopeExit([&] { ::ReleaseDC(hwnd, hdc); });
-
-          RECT rect;
-          ::GetWindowRect(hwnd, &rect);  // includes non-client area
-
-          // Convert from screen- to client-coordinates, accounting for the
-          // desktop (or, in theory, us) possibly being WS_EX_LAYOUTRTL...
-          ::MapWindowPoints(HWND_DESKTOP, hwnd, (LPPOINT)&rect, 2);
-          // ... then convert from client- to window- coordinates, with no
-          // separate RTL-handling needed.
-          ::OffsetRect(&rect, -rect.left, -rect.top);
-
-          ::FillRect(hdc, &rect, brush);
-        };
-
-        if (!mHasBeenShown) {
-          // On creation, the window's content is not specified; in practice,
-          // it's observed to usually be full of bright white, regardless of any
-          // window-class options. DWM will happily render that unspecified
-          // content to the screen before we get a chance to process a
-          // WM_ERASEBKGND event (or, indeed, anything else). To avoid dark-mode
-          // users being assaulted with a bright white flash, we need to draw
-          // something on top of that at least once before showing the window.
-          //
-          // Unfortunately, there's a bit of a catch-22 here: until the window
-          // has been set "visible" at least once, it doesn't have a backing
-          // surface, so we can't draw anything to it! To work around this, we
-          // cloak the window before "showing" it.
-          CloakWindow(mWnd, TRUE);
-        }
-
         // Set the cursor before showing the window to avoid the default wait
         // cursor.
         SetCursor(Cursor{eCursor_standard});
@@ -1789,16 +1731,6 @@ void nsWindow::Show(bool aState) {
             }
             break;
         }
-
-        if (!mHasBeenShown) {
-          // Now that ::ShowWindow() has been called once, the window surface
-          // actually exists, so we can draw to it. Fill it with the theme's
-          // background color before uncloaking it to complete the Show().
-          ClearWindow(mWnd);
-          CloakWindow(mWnd, FALSE);
-          mHasBeenShown = false;
-        }
-
       } else {
         DWORD flags = SWP_NOSIZE | SWP_NOMOVE | SWP_SHOWWINDOW;
         if (wasVisible) {
@@ -5701,7 +5633,7 @@ bool nsWindow::ProcessMessageInternal(UINT msg, WPARAM& wParam, LPARAM& lParam,
     } break;
 
     // Say we've dealt with erasing the background. (This is actually handled in
-    // WM_PAINT or at window-creation time, as necessary.)
+    // WM_PAINT, where necessary.)
     case WM_ERASEBKGND: {
       *aRetValue = 1;
       result = true;

widget/windows/nsWindow.h

@@ -757,7 +757,6 @@ class nsWindow final : public nsBaseWidget {
   bool mIsEarlyBlankWindow = false;
   bool mIsShowingPreXULSkeletonUI = false;
   bool mResizable = false;
-  bool mHasBeenShown = false;
   // Whether we're an alert window. Alert windows don't have taskbar icons and
   // don't steal focus from other windows when opened. They're also expected to
   // be of type WindowType::Dialog.