Procedure to instruct FLTK to use given X11 connexion (#149)

4 files changed, 17 insertions, 3 deletions

diff --git a/FL/x11.H b/FL/x11.H
index 73af4e7fc..2c98bc39f 100644
--- a/FL/x11.H
+++ b/FL/x11.H
@@ -26,6 +26,11 @@
 
 /** Returns the X11 Display in use */
 extern Display *fl_x11_display();
+/** Have FLTK use a pre-established X11 connexion.
+ This function should be called before FLTK attempts to open its own X11 connexion.
+ \param d the X11 Display* value representing a valid, pre-established X11 connexion
+ */
+extern void fl_x11_use_display(Display *d);
 /** Returns the Window reference for the given Fl_Window, or zero if not \c shown().  */
 extern Window fl_x11_xid(const Fl_Window *win);
 /** Returns the Fl_Window corresponding to the given Window reference.  */
@@ -58,6 +63,7 @@ extern GLXContext fl_x11_glcontext(GLContext rc);
 // constant info about the X server connection:
 extern FL_EXPORT Display *fl_display;
 extern FL_EXPORT Display *fl_x11_display();
+extern FL_EXPORT void fl_x11_use_display(Display *);
 extern FL_EXPORT Window fl_x11_xid(const Fl_Window *win);
 extern FL_EXPORT Fl_Window *fl_x11_find(Window);
 extern FL_EXPORT int fl_screen;
diff --git a/documentation/src/osissues.dox b/documentation/src/osissues.dox
index fa17aec7e..1c8718c62 100644
--- a/documentation/src/osissues.dox
+++ b/documentation/src/osissues.dox
@@ -268,6 +268,10 @@ code will be called before the first \c show() of a window.
 \par
 This may call Fl::abort() if there is an error opening the display.
 
+void fl_x11_use_display(Display *d)
+\par
+Directs FLTK to use a pre-established X11 connexion.
+
 void fl_close_display()
 
 \par
diff --git a/src/Fl_x.cxx b/src/Fl_x.cxx
index 79d0a8fea..07f80cde7 100644
--- a/src/Fl_x.cxx
+++ b/src/Fl_x.cxx
@@ -531,7 +531,8 @@ void Fl_X11_Screen_Driver::disable_im() {
 }
 
 void Fl_X11_Screen_Driver::open_display_platform() {
-  if (fl_display) return;
+  static GC gc = NULL;
+  if (gc) return;
 
   setlocale(LC_CTYPE, "");
   XSetLocaleModifiers("");
@@ -539,7 +540,7 @@ void Fl_X11_Screen_Driver::open_display_platform() {
   XSetIOErrorHandler(io_error_handler);
   XSetErrorHandler(xerror_handler);
 
-  Display *d = XOpenDisplay(0);
+  Display *d = (fl_display ? fl_display : XOpenDisplay(0));
   if (!d) {
     Fl::fatal("Can't open display: %s", XDisplayName(0)); // does not return
     return; // silence static code analyzer
@@ -547,7 +548,7 @@ void Fl_X11_Screen_Driver::open_display_platform() {
 
   open_display_i(d);
   // the unique GC used by all X windows
-  GC gc = XCreateGC(fl_display, RootWindow(fl_display, fl_screen), 0, 0);
+  gc = XCreateGC(fl_display, RootWindow(fl_display, fl_screen), 0, 0);
   Fl_Graphics_Driver::default_driver().gc(gc);
   fl_create_print_window();
 }
diff --git a/src/drivers/X11/Fl_X11_Screen_Driver.cxx b/src/drivers/X11/Fl_X11_Screen_Driver.cxx
index 9e3465f13..7fc7e2b01 100644
--- a/src/drivers/X11/Fl_X11_Screen_Driver.cxx
+++ b/src/drivers/X11/Fl_X11_Screen_Driver.cxx
@@ -80,6 +80,9 @@ void Fl_X11_Screen_Driver::display(const char *d)
   if (d) setenv("DISPLAY", d, 1);
 }
 
+void fl_x11_use_display(Display *d) {
+  fl_display = d;
+}
 
 int Fl_X11_Screen_Driver::XParseGeometry(const char* string, int* x, int* y,
                                          unsigned int* width, unsigned int* height) {