From 9e6c3a76283bb1045d51b705a798bc5cd25b38a8 Mon Sep 17 00:00:00 2001
From: Robert Osfield <robert@openscenegraph.com>
Date: Thu, 8 May 2008 16:45:59 +0000
Subject: [PATCH] From Melchior Franz, "In KDE I switch desktops with
 Super-Tab, and occasionally I get an excess Tab key report when switching
 back to an OSG application (usually FlightGear :-). Although KDE has consumed
 the Tab, it's sometimes still in the XKeymapEvent's key_vector, and followed
 by a Tab KeyRelease event.

Avoid this artifact by
- asking for a "fresh" keymap (via XQueryKeymap()), rather than
 using the unreliable(?) XKeymapEvent's key_vector, and by
- flushing all key events on focus-in (to avoid the KeyRelease)

After Super-press, Tab-press, Super-release, Tab-release (note
the wrong release order!) I still get an extra Tab event. But
this is not surprising and not exactly wrong either. Also it's
hard to avoid, as we can't see what happened to the keyboard
before we regained focus.

Files changed:
 src/osgViewer/GraphicsWindowX11.cpp
 include/osgViewer/api/X11/GraphicsWindowX11"
---
 include/osgViewer/api/X11/GraphicsWindowX11 |  1 +
 src/osgViewer/GraphicsWindowX11.cpp         | 17 ++++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/include/osgViewer/api/X11/GraphicsWindowX11 b/include/osgViewer/api/X11/GraphicsWindowX11
index c4015af86..6f5436567 100644
--- a/include/osgViewer/api/X11/GraphicsWindowX11
+++ b/include/osgViewer/api/X11/GraphicsWindowX11
@@ -169,6 +169,7 @@ class OSGVIEWER_EXPORT GraphicsWindowX11 : public osgViewer::GraphicsWindow
         void getModifierMap(char* keymap) const;
         int getModifierMask() const;
         void syncLocks();
+        void flushKeyEvents();
         
         bool            _valid;
         Display*        _display;
diff --git a/src/osgViewer/GraphicsWindowX11.cpp b/src/osgViewer/GraphicsWindowX11.cpp
index 513b68214..73d10b550 100644
--- a/src/osgViewer/GraphicsWindowX11.cpp
+++ b/src/osgViewer/GraphicsWindowX11.cpp
@@ -993,6 +993,7 @@ void GraphicsWindowX11::checkEvents()
 
             case FocusIn :
                 osg::notify(osg::INFO)<<"FocusIn event received"<<std::endl;
+                flushKeyEvents();
                 break;
 
             case UnmapNotify :
@@ -1038,12 +1039,15 @@ void GraphicsWindowX11::checkEvents()
                 getModifierMap(modMap);
                 syncLocks();
 
+                char keyMap[32];
+                XQueryKeymap(_eventDisplay, keyMap);
+
                 // release normal (non-modifier) keys
                 for (unsigned int key = 8; key < 256; key++)
                 {
                     bool isModifier = keyMapGetKey(modMap, key);
                     if (isModifier) continue;
-                    bool isPressed = keyMapGetKey(ev.xkeymap.key_vector, key);
+                    bool isPressed = keyMapGetKey(keyMap, key);
                     if (!isPressed) forceKey(key, eventTime, false);
                 }
 
@@ -1052,7 +1056,7 @@ void GraphicsWindowX11::checkEvents()
                 {
                     bool isModifier = keyMapGetKey(modMap, key);
                     if (!isModifier) continue;
-                    bool isPressed = keyMapGetKey(ev.xkeymap.key_vector, key);
+                    bool isPressed = keyMapGetKey(keyMap, key);
                     forceKey(key, eventTime, isPressed);
                 }
 
@@ -1061,7 +1065,7 @@ void GraphicsWindowX11::checkEvents()
                 {
                     bool isModifier = keyMapGetKey(modMap, key);
                     if (isModifier) continue;
-                    bool isPressed = keyMapGetKey(ev.xkeymap.key_vector, key);
+                    bool isPressed = keyMapGetKey(keyMap, key);
                     if (isPressed) forceKey(key, eventTime, true);
                 }
                 break;
@@ -1385,6 +1389,13 @@ void GraphicsWindowX11::rescanModifierMapping()
     }
 }
 
+void GraphicsWindowX11::flushKeyEvents()
+{
+    XEvent e;
+    while (XCheckMaskEvent(_eventDisplay, KeyPressMask|KeyReleaseMask, &e))
+        continue;
+}
+
 // Returns char[32] keymap with bits for every modifier key set.
 void GraphicsWindowX11::getModifierMap(char* keymap) const
 {