From 6de0216ace8e54ec823458b2cd0df3b6438a0e1f Mon Sep 17 00:00:00 2001
From: John Tsiombikas <nuclear@member.fsf.org>
Date: Sat, 31 Mar 2012 13:34:32 +0000
Subject: [PATCH] added an option (GLUT_SKIP_STALE_MOTION_EVENTS) to ignore
 all but the last MotionNotify event in the queue.

git-svn-id: svn+ssh://svn.code.sf.net/p/freeglut/code/trunk/freeglut/freeglut@1218 7f0cb862-5218-0410-a997-914c9d46530a
---
 include/GL/freeglut_ext.h |    2 ++
 src/fg_init.c             |    3 ++-
 src/fg_internal.h         |    2 ++
 src/fg_state.c            |    7 +++++++
 src/x11/fg_main_x11.c     |   15 +++++++++++++++
 5 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/include/GL/freeglut_ext.h b/include/GL/freeglut_ext.h
index 0a91166..0fda0e2 100644
--- a/include/GL/freeglut_ext.h
+++ b/include/GL/freeglut_ext.h
@@ -83,6 +83,8 @@
 
 #define  GLUT_FULL_SCREEN                   0x01FF
 
+#define  GLUT_SKIP_STALE_MOTION_EVENTS      0x0204
+
 /*
  * New tokens for glutInitDisplayMode.
  * Only one GLUT_AUXn bit may be used at a time.
diff --git a/src/fg_init.c b/src/fg_init.c
index bf55602..d564e83 100644
--- a/src/fg_init.c
+++ b/src/fg_init.c
@@ -85,6 +85,7 @@ SFG_State fgState = { { -1, -1, GL_FALSE },  /* Position */
                       0,                      /* MouseWheelTicks */
                       1,                      /* AuxiliaryBufferNumber */
                       4,                      /* SampleNumber */
+                      GL_FALSE,               /* SkipStaleMotion */
                       1,                      /* OpenGL context MajorVersion */
                       0,                      /* OpenGL context MinorVersion */
                       0,                      /* OpenGL ContextFlags */
@@ -682,4 +683,4 @@ void FGAPIENTRY glutInitWarningFunc( void (* vfgWarning) ( const char *fmt, va_l
     fgState.WarningFunc = vfgWarning;
 }
 
-/*** END OF FILE ***/
\ No newline at end of file
+/*** END OF FILE ***/
diff --git a/src/fg_internal.h b/src/fg_internal.h
index 7e0f30c..2119d1a 100644
--- a/src/fg_internal.h
+++ b/src/fg_internal.h
@@ -314,6 +314,8 @@ struct tagSFG_State
     int              AuxiliaryBufferNumber;  /* Number of auxiliary buffers */
     int              SampleNumber;         /*  Number of samples per pixel  */
 
+    GLboolean        SkipStaleMotion;      /* skip stale motion events */
+
     int              MajorVersion;         /* Major OpenGL context version  */
     int              MinorVersion;         /* Minor OpenGL context version  */
     int              ContextFlags;         /* OpenGL context flags          */
diff --git a/src/fg_state.c b/src/fg_state.c
index 208b5e2..734a57c 100644
--- a/src/fg_state.c
+++ b/src/fg_state.c
@@ -111,6 +111,10 @@ void FGAPIENTRY glutSetOption( GLenum eWhat, int value )
       fgState.SampleNumber = value;
       break;
 
+    case GLUT_SKIP_STALE_MOTION_EVENTS:
+      fgState.SkipStaleMotion = value;
+      break;
+
     default:
         fgWarning( "glutSetOption(): missing enum handle %d", eWhat );
         break;
@@ -198,6 +202,9 @@ int FGAPIENTRY glutGet( GLenum eWhat )
     case GLUT_MULTISAMPLE:
       return fgState.SampleNumber;
 
+    case GLUT_SKIP_STALE_MOTION_EVENTS:
+      return fgState.SkipStaleMotion;
+
     default:
         return fgPlatformGlutGet ( eWhat );
         break;
diff --git a/src/x11/fg_main_x11.c b/src/x11/fg_main_x11.c
index e72db37..3ecb811 100644
--- a/src/x11/fg_main_x11.c
+++ b/src/x11/fg_main_x11.c
@@ -55,6 +55,9 @@
 #    define MIN(a,b) (((a)<(b)) ? (a) : (b))
 #endif
 
+/* used in the event handling code to match and discard stale mouse motion events */
+static Bool match_motion(Display *dpy, XEvent *xev, XPointer arg);
+
 /*
  * TODO BEFORE THE STABLE RELEASE:
  *
@@ -788,6 +791,13 @@ void fgPlatformProcessSingleEvent ( void )
 
         case MotionNotify:
         {
+            /* if GLUT_SKIP_STALE_MOTION_EVENTS is true, then discard all but
+             * the last motion event from the queue
+             */
+            if(fgState.SkipStaleMotion) {
+                while(XCheckIfEvent(fgDisplay.pDisplay.Display, &event, match_motion, 0));
+            }
+
             GETWINDOW( xmotion );
             GETMOUSE( xmotion );
 
@@ -1077,6 +1087,11 @@ void fgPlatformProcessSingleEvent ( void )
 }
 
 
+static Bool match_motion(Display *dpy, XEvent *xev, XPointer arg)
+{
+    return xev->type == MotionNotify;
+}
+
 void fgPlatformMainLoopPreliminaryWork ( void )
 {
 }
-- 
1.7.10.4