From 2aef6570bbaa11505e97d9b89f1fc15316d9ec3c Mon Sep 17 00:00:00 2001
From: Vadim Zeitlin <vadim@wxwidgets.org>
Date: Thu, 25 Apr 2019 17:12:41 +0200
Subject: [PATCH] Add TempHWNDSetter RAII helper to wxMSW and use it

No real changes, just replace pairs of SetHWND(hwnd)/SetHWND(0) calls
with the use of TempHWNDSetter.
---
 include/wx/msw/private.h | 23 +++++++++++++++++++++++
 src/msw/colordlg.cpp     |  5 +----
 src/msw/filedlg.cpp      | 11 +++--------
 src/msw/msgdlg.cpp       |  5 +----
 4 files changed, 28 insertions(+), 16 deletions(-)

diff --git a/include/wx/msw/private.h b/include/wx/msw/private.h
index 9b47c6f528..95dbe03b9e 100644
--- a/include/wx/msw/private.h
+++ b/include/wx/msw/private.h
@@ -374,6 +374,29 @@ inline RECT wxGetClientRect(HWND hwnd)
 // small helper classes
 // ---------------------------------------------------------------------------
 
+// Temporarily assign the given HWND to the window in ctor and unset it back to
+// the original value (usually 0) in dtor.
+class TempHWNDSetter
+{
+public:
+    TempHWNDSetter(wxWindow* win, WXHWND hWnd)
+        : m_win(win), m_hWndOrig(m_win->GetHWND())
+    {
+        m_win->SetHWND(hWnd);
+    }
+
+    ~TempHWNDSetter()
+    {
+        m_win->SetHWND(m_hWndOrig);
+    }
+
+private:
+    wxWindow* const m_win;
+    WXHWND const m_hWndOrig;
+
+    wxDECLARE_NO_COPY_CLASS(TempHWNDSetter);
+};
+
 // create an instance of this class and use it as the HDC for screen, will
 // automatically release the DC going out of scope
 class ScreenHDC
diff --git a/src/msw/colordlg.cpp b/src/msw/colordlg.cpp
index fb9c89d16c..9b4d9e55ee 100644
--- a/src/msw/colordlg.cpp
+++ b/src/msw/colordlg.cpp
@@ -255,7 +255,7 @@ void wxColourDialog::DoGetClientSize(int *width, int *height) const
 void wxColourDialog::MSWOnInitDone(WXHWND hDlg)
 {
     // set HWND so that our DoMoveWindow() works correctly
-    SetHWND(hDlg);
+    TempHWNDSetter set(this, hDlg);
 
     if ( m_centreDir )
     {
@@ -272,9 +272,6 @@ void wxColourDialog::MSWOnInitDone(WXHWND hDlg)
     {
         SetPosition(GetPosition());
     }
-
-    // we shouldn't destroy hDlg, so disassociate from it
-    SetHWND(NULL);
 }
 
 #endif // wxUSE_COLOURDLG
diff --git a/src/msw/filedlg.cpp b/src/msw/filedlg.cpp
index 5a0b7bd17a..2e96f37d5c 100644
--- a/src/msw/filedlg.cpp
+++ b/src/msw/filedlg.cpp
@@ -312,7 +312,7 @@ void wxFileDialog::MSWOnInitDone(WXHWND hDlg)
     HWND hFileDlg = ::GetParent((HWND)hDlg);
 
     // set HWND so that our DoMoveWindow() works correctly
-    SetHWND((WXHWND)hFileDlg);
+    TempHWNDSetter set(this, (WXHWND)hFileDlg);
 
     if ( m_centreDir )
     {
@@ -333,9 +333,6 @@ void wxFileDialog::MSWOnInitDone(WXHWND hDlg)
     // Call selection change handler so that update handler will be
     // called once with no selection.
     MSWOnSelChange(hDlg);
-
-    // we shouldn't destroy this HWND
-    SetHWND(NULL);
 }
 
 void wxFileDialog::MSWOnSelChange(WXHWND hDlg)
@@ -402,11 +399,9 @@ static bool ShowCommFileDialog(OPENFILENAME *of, long style)
 
 void wxFileDialog::MSWOnInitDialogHook(WXHWND hwnd)
 {
-   SetHWND(hwnd);
+    TempHWNDSetter set(this, hwnd);
 
-   CreateExtraControl();
-
-   SetHWND(NULL);
+    CreateExtraControl();
 }
 
 int wxFileDialog::ShowModal()
diff --git a/src/msw/msgdlg.cpp b/src/msw/msgdlg.cpp
index 6ffc80b43d..6da44d822b 100644
--- a/src/msw/msgdlg.cpp
+++ b/src/msw/msgdlg.cpp
@@ -136,7 +136,7 @@ wxMessageDialog::HookFunction(int code, WXWPARAM wParam, WXLPARAM lParam)
         wnd->m_hook = NULL;
         HookMap().erase(tid);
 
-        wnd->SetHWND((HWND)wParam);
+        TempHWNDSetter set(wnd, (WXHWND)wParam);
 
         // replace the static text with an edit control if the message box is
         // too big to fit the display
@@ -151,9 +151,6 @@ wxMessageDialog::HookFunction(int code, WXWPARAM wParam, WXLPARAM lParam)
         if ( wnd->GetMessageDialogStyle() & wxCENTER )
             wnd->Center(); // center on parent
         //else: default behaviour, center on screen
-
-        // there seems to be no reason to leave it set
-        wnd->SetHWND(NULL);
     }
 
     return rc;