Oficial fixes to make Gnuplot work with wxWidgets 3.0.

Can be removed with Gnuplot update to version 5.0 or later.

https://github.com/gnuplot/gnuplot/commit/a275a85b335fb358cea09d7e64204caca3193e1a

https://github.com/gnuplot/gnuplot/commit/632f86b64659b9ad14bfae1c850ce268f0d39352

--- gnuplot-4.6.0/src/wxterminal/wxt_gui.h

+++ gnuplot-4.6.0/src/wxterminal/wxt_gui.h

@@ -203,6 +203,8 @@

  * ====================================================================*/

 #ifdef WXT_MULTITHREADED

+#include <X11/Xlib.h>	/* Magic fix for linking against wxgtk3.0 */

+

 /* thread class, where the gui loop runs.

  * Not needed with Windows, where the main loop

  * already processes the gui messages */

@@ -234,6 +236,10 @@

 class wxtApp : public wxApp

 {

 public:

+#ifdef WXT_MULTITHREADED 

+	/* Magic fix needed by wxgtk3.0 */

+	wxtApp() : wxApp() { XInitThreads(); } 

+#endif 

 	/* This one is called just after wxWidgets initialization */

 	bool OnInit();

 	/* cleanup on exit */

--- gnuplot-4.6.0/src/wxterminal/wxt_gui.cpp

+++ gnuplot-4.6.0/src/wxterminal/wxt_gui.cpp

@@ -2493,6 +2498,20 @@

 /* refresh the plot by (re)processing the plot commands list */

 void wxtPanel::wxt_cairo_refresh()

 {

+	/* This check may prevent the assert+die behavior seen with wxgtk3.0 */

+	/* Symptom:

+	  ./src/gtk/dcclient.cpp(2043): assert "m_window" failed in DoGetSize(): GetSize() doesn't work without window [in thread 7fb21f386700]

+	  Call stack:

+	  [00] wxOnAssert(char const*, int, char const*, char const*, wchar_t const*)

+	  [01] wxClientDCImpl::DoGetSize(int*, int*) const

+	  [02] wxBufferedDC::UnMask()                  

+	  wxwidgets documentation to the contrary, panel->IsShownOnScreen() is unreliable

+	 */

+	if (!wxt_current_window) {

+		FPRINTF((stderr,"wxt_cairo_refresh called before window exists\n"));

+		return;

+	}

+

 	/* Clear background. */

 	gp_cairo_solid_background(&plot);