From f309c395fc564de0e2799fa09e3d829ea1c5366a Mon Sep 17 00:00:00 2001
From: Manolo Gouy <Manolo>
Date: Tue, 4 Oct 2011 09:21:47 +0000
Subject: STR#2600 again: under X11, dynamically load the libXrandr shared
 library.

git-svn-id: file:///fltk/svn/fltk/branches/branch-1.3@9123 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
---
 configh.in   |  8 --------
 configure.in | 13 -------------
 src/Fl_x.cxx | 32 +++++++++++++++++++++-----------
 3 files changed, 21 insertions(+), 32 deletions(-)

diff --git a/configh.in b/configh.in
index 1521f46ba..4a806e475 100644
--- a/configh.in
+++ b/configh.in
@@ -83,14 +83,6 @@
 
 #define HAVE_XINERAMA 0
 
-/*
- * HAVE_XRANDR
- *
- * Do we have the Xrandr library to support runtime update of multi-head displays?
- */
-
-#define HAVE_XRANDR 0
-
 /*
  * USE_XFT
  *
diff --git a/configure.in b/configure.in
index e233d2e2a..565561fef 100644
--- a/configure.in
+++ b/configure.in
@@ -997,16 +997,6 @@ case $uname_GUI in
 		LIBS="-lXext $LIBS")
 	fi
 
-	dnl Check for the XRandR extension unless disabled...
-        AC_ARG_ENABLE(xrandr, [  --enable-xrandr         turn on XRandR support [default=yes]])
-
-	if test x$enable_xrandr != xno; then
-	    AC_CHECK_HEADER(X11/extensions/Xrandr.h, AC_DEFINE(HAVE_XRANDR),,
-	        [#include <X11/Xlib.h>])
-	    AC_CHECK_LIB(Xrandr, XRRQueryExtension,
-		LIBS="-lXrandr $LIBS")
-	fi
-
 	dnl Check for overlay visuals...
 	AC_PATH_PROG(XPROP, xprop)
 	AC_CACHE_CHECK(for X overlay visuals, ac_cv_have_overlay,
@@ -1340,9 +1330,6 @@ case $uname_GUI in
 	if test x$enable_xdbe != xno; then
 	    graphics="$graphics+Xdbe"
 	fi
-	if test x$enable_xrandr != xno; then
-	    graphics="$graphics+Xrandr"
-	fi
 	if test x$enable_xinerama != xno; then
 	    graphics="$graphics+Xinerama"
 	fi
diff --git a/src/Fl_x.cxx b/src/Fl_x.cxx
index 5b58a8ca3..3e3e24517 100644
--- a/src/Fl_x.cxx
+++ b/src/Fl_x.cxx
@@ -43,9 +43,13 @@
 #  include <X11/Xlocale.h>
 #  include <X11/Xlib.h>
 #  include <X11/keysym.h>
-#if HAVE_XRANDR
-#include <X11/extensions/Xrandr.h>
-static int randrEventBase = -1;
+#define USE_XRANDR 1 // means attempt to dynamically load libXrandr.so
+#if USE_XRANDR
+#include <dlfcn.h>
+#define RRScreenChangeNotifyMask  (1L << 0) // from X11/extensions/Xrandr.h
+#define RRScreenChangeNotify	0           // from X11/extensions/Xrandr.h
+static void *libxrandr_addr;                // run-time address of libXrandr.so
+static int randrEventBase;                  // base of RandR-defined events
 #endif
 
 static Fl_Xlib_Graphics_Driver fl_xlib_driver;
@@ -642,11 +646,18 @@ void fl_open_display(Display* d) {
 #if !USE_COLORMAP
   Fl::visual(FL_RGB);
 #endif
-#if HAVE_XRANDR
-  int error_base;
-  if (XRRQueryExtension(d, &randrEventBase, &error_base))
-    XRRSelectInput(d, RootWindow(d, fl_screen), RRScreenChangeNotifyMask);
-  else randrEventBase = -1;
+#if USE_XRANDR
+  libxrandr_addr = dlopen("libXrandr.so", RTLD_LAZY);
+  if (libxrandr_addr) {
+    int error_base;
+    typedef Bool (*XRRQueryExtension_type)(Display*, int*, int*);
+    typedef void (*XRRSelectInput_type)(Display*, Window, int);
+    XRRQueryExtension_type XRRQueryExtension_f = (XRRQueryExtension_type)dlsym(libxrandr_addr, "XRRQueryExtension");
+    XRRSelectInput_type XRRSelectInput_f = (XRRSelectInput_type)dlsym(libxrandr_addr, "XRRSelectInput");
+    if (XRRQueryExtension_f && XRRSelectInput_f && XRRQueryExtension_f(d, &randrEventBase, &error_base))
+      XRRSelectInput_f(d, RootWindow(d, fl_screen), RRScreenChangeNotifyMask);
+    else libxrandr_addr = NULL;
+    }
 #endif
 }
 
@@ -932,9 +943,8 @@ int fl_handle(const XEvent& thisevent)
   if ( XFilterEvent((XEvent *)&xevent, 0) )
       return(1);
   
-#if HAVE_XRANDR  
-  if( randrEventBase >= 0 && xevent.type == randrEventBase + RRScreenChangeNotify) {
-    XRRUpdateConfiguration (&xevent);
+#if USE_XRANDR  
+  if( libxrandr_addr && xevent.type == randrEventBase + RRScreenChangeNotify) {
     Fl::call_screen_init();
     fl_init_workarea();
     Fl::handle(FL_SCREEN_CONFIGURATION_CHANGED, NULL);
-- 
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