Re: Problems with Opaque Window Moving

I wrote:
> When I use the "Opaque Window Moving" option, I get a very slow
> update on the screen, resulting in several seconds of lag before
> the moved window settles in the final position. There are also
> large ugly artefacts on the screen during this slow motion.
>[...]
> However when I tried fluxbox in an Xnest window, the problem
> disappeared completely. So opaque window moving works in Xnest,
> but not in the root window.

The part about Xnest turned out to be untrue -- the problem became
noticeable in Xnest too when I added a custom background and more
windows (the reason I tried Xnest was for testing the git version
of fluxbox without affecting my main screen).

I played around a bit with the source code today, and I think I have
found a quick-and-dirty solution. I don't know if this solution breaks
anything else, since I am not familiar with the internal machinery of
fluxbox. But it solves the problem for me, and the patch is very
simple: When a window is in motion, FluxboxWindow::motionNotifyEvent()
ignores the current event if the next event is also a MotionNotify
event. This causes the lag to disappear completely. The artefacts are
still there (i.e. LSD-like tracers) but they are not as disturbing as
before since the whole system feels more responsive.

My patch is attached below.



-- 
Bjorn Danielsson  <[email protected]>

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diff --git a/src/Window.cc b/src/Window.cc
index 4b4d1dc..614e483 100644
--- a/src/Window.cc
+++ b/src/Window.cc
@@ -2417,12 +2417,29 @@ void FluxboxWindow::buttonReleaseEvent(XButtonEvent &re) {
 
 }
 
+static Bool peekNextEvent(Display *, XEvent *e, char *args) {
+    XEvent **e1 = (XEvent**) args;
+    if (*e1 == NULL) {
+        *e1 = e;
+    }
+    return False;
+}
 
 void FluxboxWindow::motionNotifyEvent(XMotionEvent &me) {
     if (isMoving() && me.window == parent()) {
         me.window = frame().window().window();
     }
 
+    if (isMoving()) {
+        // return immediately if the next queued event is also a motion event
+        XEvent dummy;
+        XEvent *e = NULL;
+        XCheckIfEvent(display, &dummy, peekNextEvent, (char*) &e);
+        if (e != NULL && e->type == MotionNotify) {
+            return;
+        }
+    }
+
     bool inside_titlebar = frame().insideTitlebar( me.window );
 
     if (Fluxbox::instance()->getIgnoreBorder() && m_attaching_tab == 0