Add wxApp::GetMainTopWindow() wrapper

This trivial function just allows to avoid checking if wxTheApp is not
null before calling GetTopWindow() on it.

Replace the existing "wxTheApp && wxTheApp->GetTopWindow()" calls with
wxApp::GetMainTopWindow().

No real changes.

include/wx/app.h

@@ -622,6 +622,10 @@ public:
         // there are none, will return NULL)
     virtual wxWindow *GetTopWindow() const;
 
+        // convenient helper which is safe to use even if there is no wxApp at
+        // all, it will just return NULL in this case
+    static wxWindow *GetMainTopWindow();
+
         // control the exit behaviour: by default, the program will exit the
         // main loop (and so, usually, terminate) when the last top-level
         // program window is deleted. Beware that if you disable this behaviour

interface/wx/app.h

@@ -859,6 +859,18 @@ public:
     */
     bool GetUseBestVisual() const;
 
+    /**
+        Returns a pointer to the top application window if any.
+
+        This function is safe to call even before creating, or after
+        destroying, the application object, as it simply returns @NULL if it
+        doesn't exist. Otherwise it's equivalent to calling
+        @c wxTheApp->GetTopWindow().
+
+        @since 3.1.5
+     */
+    static wxWindow* GetMainTopWindow();
+
     /**
         Returns a pointer to the top window.
 

src/common/appcmn.cpp

@@ -189,6 +189,14 @@ wxWindow* wxAppBase::GetTopWindow() const
     return window;
 }
 
+/* static */
+wxWindow* wxAppBase::GetMainTopWindow()
+{
+    const wxAppBase* const app = static_cast<wxAppBase*>(GetInstance());
+
+    return app ? app->GetTopWindow() : NULL;
+}
+
 wxVideoMode wxAppBase::GetDisplayMode() const
 {
     return wxVideoMode();

src/common/dlgcmn.cpp

@@ -183,8 +183,8 @@ wxDialogBase::GetParentForModalDialog(wxWindow *parent, long style) const
                     wxGetTopLevelParent(wxGetActiveWindow()));
 
     // and finally the application main window
-    if ( !parent && wxTheApp )
-        parent = CheckIfCanBeUsedAsParent(wxTheApp->GetTopWindow());
+    if ( !parent )
+        parent = CheckIfCanBeUsedAsParent(wxApp::GetMainTopWindow());
 
     return parent;
 }

src/common/iconbndl.cpp

@@ -264,7 +264,7 @@ wxIcon wxIconBundle::GetIcon(const wxSize& size, int flags) const
             sysY = 0;
     if ( flags & FALLBACK_SYSTEM )
     {
-        wxWindow* win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+        wxWindow* win = wxApp::GetMainTopWindow();
         sysX = wxSystemSettings::GetMetric(wxSYS_ICON_X, win);
         sysY = wxSystemSettings::GetMetric(wxSYS_ICON_Y, win);
     }

src/common/sizer.cpp

@@ -104,7 +104,7 @@ float wxSizerFlags::DoGetDefaultBorderInPx()
     // We also have to use the DPI for the monitor showing the top window here
     // as we don't have any associated window -- but, again, without changes
     // in the API, there is nothing we can do about this.
-    const wxWindow* const win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+    const wxWindow* const win = wxApp::GetMainTopWindow();
     static wxPrivate::DpiDependentValue<float> s_defaultBorderInPx;
     if ( s_defaultBorderInPx.HasChanged(win) )
     {

src/generic/aboutdlgg.cpp

@@ -81,10 +81,10 @@ wxString wxAboutDialogInfo::GetDescriptionAndCredits() const
 wxIcon wxAboutDialogInfo::GetIcon() const
 {
     wxIcon icon = m_icon;
-    if ( !icon.IsOk() && wxTheApp )
+    if ( !icon.IsOk() )
     {
         const wxTopLevelWindow * const
-            tlw = wxDynamicCast(wxTheApp->GetTopWindow(), wxTopLevelWindow);
+            tlw = wxDynamicCast(wxApp::GetMainTopWindow(), wxTopLevelWindow);
         if ( tlw )
             icon = tlw->GetIcon();
     }

src/html/m_image.cpp

@@ -691,8 +691,8 @@ TAG_HANDLER_BEGIN(IMG, "IMG,MAP,AREA")
 #if defined(__WXOSX_COCOA__)
                 // Try to find a 2x resolution image with @2x appended before the file extension.
                 wxWindow* win = m_WParser->GetWindowInterface() ? m_WParser->GetWindowInterface()->GetHTMLWindow() : NULL;
-                if (!win && wxTheApp)
-                    win = wxTheApp->GetTopWindow();
+                if (!win)
+                    win = wxApp::GetMainTopWindow();
                 if (win && win->GetContentScaleFactor() > 1.0)
                 {
                     if (tmp.Find('.') != wxNOT_FOUND)

src/msw/artmsw.cpp

@@ -326,7 +326,7 @@ wxBitmap wxWindowsArtProvider::CreateBitmap(const wxArtID& id,
 /*static*/
 wxSize wxArtProvider::GetNativeSizeHint(const wxArtClient& client)
 {
-    const wxWindow* win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+    const wxWindow* win = wxApp::GetMainTopWindow();
     if ( client == wxART_TOOLBAR )
     {
         return wxWindow::FromDIP(wxSize(24, 24), win);

src/msw/cursor.cpp

@@ -109,13 +109,13 @@ public:
 
 wxCoord wxCursorRefData::GetStandardWidth()
 {
-    const wxWindow* win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+    const wxWindow* win = wxApp::GetMainTopWindow();
     return wxSystemSettings::GetMetric(wxSYS_CURSOR_X, win);
 }
 
 wxCoord wxCursorRefData::GetStandardHeight()
 {
-    const wxWindow* win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+    const wxWindow* win = wxApp::GetMainTopWindow();
     return wxSystemSettings::GetMetric(wxSYS_CURSOR_Y, win);
 }
 

src/msw/gdiimage.cpp

@@ -471,7 +471,7 @@ bool wxICOFileHandler::LoadIcon(wxIcon *icon,
     else
 #endif
     // were we asked for a large icon?
-    const wxWindow* win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+    const wxWindow* win = wxApp::GetMainTopWindow();
     if ( desiredWidth == wxGetSystemMetrics(SM_CXICON, win) &&
          desiredHeight == wxGetSystemMetrics(SM_CYICON, win) )
     {
@@ -666,7 +666,7 @@ wxSize wxGetHiconSize(HICON hicon)
     if ( !size.x )
     {
         // use default icon size on this hardware
-        const wxWindow* win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+        const wxWindow* win = wxApp::GetMainTopWindow();
         size.x = wxGetSystemMetrics(SM_CXICON, win);
         size.y = wxGetSystemMetrics(SM_CYICON, win);
     }

src/msw/helpchm.cpp

@@ -69,8 +69,8 @@ HTMLHELP GetHtmlHelpFunction()
 // fall back to the top level app window and then the desktop if it's NULL
 static HWND GetSuitableHWND(wxWindow *win)
 {
-    if ( !win && wxTheApp )
-        win = wxTheApp->GetTopWindow();
+    if ( !win )
+        win = wxApp::GetMainTopWindow();
 
     return win ? GetHwndOf(win) : ::GetDesktopWindow();
 }

src/msw/msgdlg.cpp

@@ -393,7 +393,7 @@ void wxMessageDialog::AdjustButtonLabels()
 /* static */
 wxFont wxMessageDialog::GetMessageFont()
 {
-    const wxWindow* win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+    const wxWindow* win = wxApp::GetMainTopWindow();
     const wxNativeFontInfo
         info(wxMSWImpl::GetNonClientMetrics(win).lfMessageFont, win);
 

src/msw/settings.cpp

@@ -179,7 +179,7 @@ wxFont wxSystemSettingsNative::GetFont(wxSystemFont index)
             // for most (simple) controls, e.g. buttons and such but other
             // controls may prefer to use lfStatusFont or lfCaptionFont if it
             // is more appropriate for them
-            const wxWindow* win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+            const wxWindow* win = wxApp::GetMainTopWindow();
             const wxNativeFontInfo
                 info(wxMSWImpl::GetNonClientMetrics(win).lfMessageFont, win);
 
@@ -337,7 +337,7 @@ extern wxFont wxGetCCDefaultFont()
     // font which is also used for the icon titles and not the stock default
     // GUI font
     LOGFONT lf;
-    const wxWindow* win = wxTheApp ? wxTheApp->GetTopWindow() : NULL;
+    const wxWindow* win = wxApp::GetMainTopWindow();
     if ( wxSystemParametersInfo
            (
                 SPI_GETICONTITLELOGFONT,

src/msw/window.cpp

@@ -4236,7 +4236,7 @@ bool wxWindowMSW::HandleEndSession(bool endSession, long logOff)
         return false;
 
     // only send once
-    if ( (this != wxTheApp->GetTopWindow()) )
+    if ( this != wxApp::GetMainTopWindow() )
         return false;
 
     wxCloseEvent event(wxEVT_END_SESSION, wxID_ANY);
@@ -4773,10 +4773,11 @@ static wxSize GetWindowDPI(HWND hwnd)
 }
 
 /*extern*/
-int wxGetSystemMetrics(int nIndex, const wxWindow* win)
+int wxGetSystemMetrics(int nIndex, const wxWindow* window)
 {
 #if wxUSE_DYNLIB_CLASS
-    const wxWindow* window = (!win && wxTheApp) ? wxTheApp->GetTopWindow() : win;
+    if ( !window )
+        window = wxApp::GetMainTopWindow();
 
     if ( window )
     {
@@ -4798,14 +4799,14 @@ int wxGetSystemMetrics(int nIndex, const wxWindow* win)
         }
     }
 #else
-    wxUnusedVar(win);
+    wxUnusedVar(window);
 #endif // wxUSE_DYNLIB_CLASS
 
     return ::GetSystemMetrics(nIndex);
 }
 
 /*extern*/
-bool wxSystemParametersInfo(UINT uiAction, UINT uiParam, PVOID pvParam, UINT fWinIni, const wxWindow* win)
+bool wxSystemParametersInfo(UINT uiAction, UINT uiParam, PVOID pvParam, UINT fWinIni, const wxWindow* window)
 {
     // Note that we can't use SystemParametersInfoForDpi() in non-Unicode build
     // because it always works with wide strings and we'd have to check for all
@@ -4813,7 +4814,8 @@ bool wxSystemParametersInfo(UINT uiAction, UINT uiParam, PVOID pvParam, UINT fWi
     // for them, and convert the returned value to ANSI after the call. Instead
     // of doing all this, just don't use it at all in the deprecated ANSI build.
 #if wxUSE_DYNLIB_CLASS && wxUSE_UNICODE
-    const wxWindow* window = (!win && wxTheApp) ? wxTheApp->GetTopWindow() : win;
+    if ( !window )
+        window = wxApp::GetMainTopWindow();
 
     if ( window )
     {
@@ -4838,7 +4840,7 @@ bool wxSystemParametersInfo(UINT uiAction, UINT uiParam, PVOID pvParam, UINT fWi
         }
     }
 #else
-    wxUnusedVar(win);
+    wxUnusedVar(window);
 #endif // wxUSE_DYNLIB_CLASS
 
     return ::SystemParametersInfo(uiAction, uiParam, pvParam, fWinIni) == TRUE;