MSW: Fix dialog default positions under RTL locales

Toplevel windows use their parent's coordinate system as the reference
frame, not desktop's, so need to be adjusted accordingly if its
mirrored. Without these changes, default-positioned wxDialogs would end
to the right side of the parent window's right border (instead of being
slightly inside the window) and changing their size would move them as
well.

src/msw/toplevel.cpp

@@ -451,10 +451,11 @@ bool wxTopLevelWindowMSW::Create(wxWindow *parent,
         memset(dlgTemplate, 0, dlgsize);
 
         // these values are arbitrary, they won't be used normally anyhow
+        const LONG baseUnits = ::GetDialogBaseUnits();
         dlgTemplate->x = 34;
         dlgTemplate->y  = 22;
-        dlgTemplate->cx = 144;
+        dlgTemplate->cx = ::MulDiv(sizeReal.x, 4, LOWORD(baseUnits));
-        dlgTemplate->cy = 75;
+        dlgTemplate->cy = ::MulDiv(sizeReal.y, 8, HIWORD(baseUnits));
 
         // reuse the code in MSWGetStyle() but correct the results slightly for
         // the dialog

src/msw/window.cpp

@@ -1822,6 +1822,26 @@ wxWindowMSW::DoMoveSibling(WXHWND hwnd, int x, int y, int width, int height)
 
     // otherwise (or if deferring failed) move the window in place immediately
 #endif // wxUSE_DEFERRED_SIZING
+
+    // toplevel window's coordinates are mirrored if the TLW is a child of another
+    // RTL window and changing width without moving the position would enlarge the
+    // window in the wrong direction, so we need to adjust for it
+    if ( IsTopLevel() )
+    {
+        // note that this may be different from GetParent() for wxDialogs
+        HWND tlwParent = ::GetParent((HWND)hwnd);
+        if ( tlwParent && (::GetWindowLong(tlwParent, GWL_EXSTYLE) & WS_EX_LAYOUTRTL) != 0 )
+        {
+            RECT old;
+            ::GetWindowRect((HWND) hwnd, &old);
+            if ( old.left == x && old.right - old.left != width )
+            {
+                x -= width - (old.right - old.left);
+            }
+            // else: not a simple resize
+        }
+    }
+
     if ( !::MoveWindow((HWND)hwnd, x, y, width, height, IsShown()) )
     {
         wxLogLastError(wxT("MoveWindow"));
@@ -1967,10 +1987,25 @@ void wxWindowMSW::DoSetClientSize(int width, int height)
         const int widthWin = rectWin.right - rectWin.left,
                   heightWin = rectWin.bottom - rectWin.top;
 
+        if ( IsTopLevel() )
+        {
+            // toplevel window's coordinates are mirrored if the TLW is a child of another
+            // RTL window and changing width without moving the position would enlarge the
+            // window in the wrong direction, so we need to adjust for it
+
+            // note that this may be different from GetParent() for wxDialogs
+            HWND tlwParent = ::GetParent(GetHwnd());
+            if ( tlwParent && (::GetWindowLong(tlwParent, GWL_EXSTYLE) & WS_EX_LAYOUTRTL) != 0 )
+            {
+                const int diffWidth = width - (rectClient.right - rectClient.left);
+                rectWin.left -= diffWidth;
+                rectWin.right -= diffWidth;
+            }
+        }
+        else
+        {
             // MoveWindow positions the child windows relative to the parent, so
             // adjust if necessary
-        if ( !IsTopLevel() )
-        {
             wxWindow *parent = GetParent();
             if ( parent )
             {