Window flickering problem in XWin multiwindow mode
S.J. Luo
sjaluo@gmail.com
Tue Apr 26 03:53:56 GMT 2022
Hi,
I have some EDA tools running on a Linux machine and display on my Windows
PC using xorg-server-21.1.3 XWin multiwindow mode
Sometimes the application window flickers forever for an unknown reason.
The problem became more severe after my PC upgrade to Windows10.
Googling the problem, I did not find such issue reported.
I decided to take advantage of open source nature and solve it by myself.
After re-compiling and debugging, I found a calling loop triggered.
Here I eliminate the detail of the cause. I may write later if someone requires.
Knowing the root cause, I am now able to demonstrate the issue with a small
test case as well as a patch that works for me. Both are attached below.
SL
The test case:
==============
/* Compile : gcc -o flicker2 flicker2.c -lX11 */
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void SetMax(Display *dpy, Window win, int val)
{
XEvent xev;
Atom wm_state = XInternAtom(dpy, "_NET_WM_STATE", False);
Atom max_horz = XInternAtom(dpy, "_NET_WM_STATE_MAXIMIZED_HORZ", False);
Atom max_vert = XInternAtom(dpy, "_NET_WM_STATE_MAXIMIZED_VERT", False);
memset(&xev, 0, sizeof(xev));
xev.type = ClientMessage;
xev.xclient.window = win;
xev.xclient.message_type = wm_state;
xev.xclient.format = 32;
xev.xclient.data.l[0] = val; // _NET_WM_STATE_ADD or _NET_WM_STATE_REMOVE
xev.xclient.data.l[1] = max_horz;
xev.xclient.data.l[2] = max_vert;
XSendEvent(dpy, DefaultRootWindow(dpy), False,
SubstructureNotifyMask, &xev);
}
int main(void) {
Display *display;
Window win;
XEvent X;
int screen;
if (!(display = XOpenDisplay(NULL)))
exit(1);
screen = DefaultScreen(display);
win = XCreateSimpleWindow(display, RootWindow(display, screen), 10,
10, 100, 100, 0,
BlackPixel(display, screen),
WhitePixel(display, screen));
XMapWindow(display, win);
SetMax(display, win, 1);
SetMax(display, win, 0);
XSelectInput(display, win, KeyPressMask | StructureNotifyMask);
while (1) {
XNextEvent(display, &X);
}
XCloseDisplay(display);
return 0;
}
==============
and the patch I have applied
=======================
--- a/hw/xwin/winmultiwindowwm.c
+++ b/hw/xwin/winmultiwindowwm.c
@@ -153,6 +153,9 @@ static void
static WMMsgNodePtr PopMessage(WMMsgQueuePtr pQueue, WMInfoPtr pWMInfo);
+static Bool
+ HaveMessage(WMMsgQueuePtr pQueue, UINT msg, xcb_window_t iWindow);
+
static Bool
InitQueue(WMMsgQueuePtr pQueue);
@@ -319,7 +322,6 @@ PopMessage(WMMsgQueuePtr pQueue, WMInfoPtr pWMInfo)
return pNode;
}
-#if 0
/*
* HaveMessage -
*/
@@ -331,12 +333,11 @@ HaveMessage(WMMsgQueuePtr pQueue, UINT msg,
xcb_window_t iWindow)
for (pNode = pQueue->pHead; pNode != NULL; pNode = pNode->pNext) {
if (pNode->msg.msg == msg && pNode->msg.iWindow == iWindow)
- return True;
+ return TRUE;
}
- return False;
+ return FALSE;
}
-#endif
/*
* InitQueue - Initialize the Window Manager message queue
@@ -1173,7 +1174,9 @@ winMultiWindowWMProc(void *pArg)
break;
case WM_WM_CHANGE_STATE:
- UpdateState(pWMInfo, pNode->msg.iWindow, pNode->msg.dwID);
+ if(!HaveMessage(&pWMInfo->wmMsgQueue, pNode->msg.msg,
pNode->msg.iWindow))
+ UpdateState(pWMInfo, pNode->msg.iWindow, pNode->msg.dwID);
+
break;
default:
=======================
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