core: add hidden option EnableVsyncWindowFlag to add the WS_POPUP flag

Goal is to ease testing of Vsync/Tearing

v2:
Properly propagate the WS_POPUP flag

3rdparty/wxwidgets3.0/src/msw/toplevel.cpp

@@ -1111,7 +1111,8 @@ bool wxTopLevelWindowMSW::ShowFullScreen(bool show, long style)
         // affects stretch mode, but most people have 16:9 monitors, so in
         // general the widescreen 16:9 mode is also affected). Let's remove the
         // window style.
-        // newStyle |= WS_POPUP;
+        if (style & WS_POPUP)
+            newStyle |= WS_POPUP;
 
         // change our window style to be compatible with full-screen mode
         ::SetWindowLong(GetHwnd(), GWL_STYLE, newStyle);

pcsx2/gui/AppConfig.cpp

@@ -848,6 +848,7 @@ AppConfig::GSWindowOptions::GSWindowOptions()
 	WindowPos				= wxDefaultPosition;
 	IsMaximized				= false;
 	IsFullscreen			= false;
+	EnableVsyncWindowFlag	= false;
 
 	IsToggleFullscreenOnDoubleClick = true;
 	IsToggleAspectRatioSwitch = false;
@@ -886,6 +887,7 @@ void AppConfig::GSWindowOptions::LoadSave( IniInterface& ini )
 	IniEntry( WindowPos );
 	IniEntry( IsMaximized );
 	IniEntry( IsFullscreen );
+	IniEntry( EnableVsyncWindowFlag );
 
 	IniEntry( IsToggleFullscreenOnDoubleClick );
 	IniEntry( IsToggleAspectRatioSwitch );

pcsx2/gui/AppConfig.h

@@ -218,6 +218,7 @@ public:
 		wxPoint		WindowPos;
 		bool		IsMaximized;
 		bool		IsFullscreen;
+		bool		EnableVsyncWindowFlag;
 
 		bool		IsToggleFullscreenOnDoubleClick;
 		bool		IsToggleAspectRatioSwitch;

pcsx2/gui/FrameForGS.cpp

@@ -491,8 +491,13 @@ bool GSFrame::ShowFullScreen(bool show, bool updateConfig)
 	// also happens on Linux.
 
 	if( !IsShown() ) Show();
-	bool retval = _parent::ShowFullScreen( show );
-	
+
+	uint flags = wxFULLSCREEN_ALL;
+#ifdef _WIN32
+	flags |= g_Conf->GSWindow.EnableVsyncWindowFlag ? WS_POPUP : 0;
+#endif
+	bool retval = _parent::ShowFullScreen( show, flags );
+
 	return retval;
 }