Xlib - XNextEvent never sees an event

[oggie]

---

This is actually for mips embedded linux. If I'm posting to the wrong place, I aplogize....

I'm trying to code a simple x application, but when I call the XNextEvent() method, I never get any events from the keyboard.

Now, the application is threaded, but all the X stuff is done in the same thread. Code is C.

ok.

Here's the initialization:

g_display = XOpenDisplay(":0.0");
    if (g_display == NULL) {
 	EVODRV_log_post( IDERR(ERRCODE_FAILURE_DURING_INIT), "init_Xlib::cannot connect X server") ;
	return FALSE;
    }
    screen_num = DefaultScreen(g_display);
    g_display_width = DisplayWidth(g_display, screen_num);
    g_display_height = DisplayHeight(g_display, screen_num);
    /* find bit depth */
    g_vis = DefaultVisual (g_display, screen_num);
    g_win = XCreateSimpleWindow(g_display, RootWindow(g_display, screen_num),
                            0, 0, g_display_width, g_display_height, 0,555,1221672);
    XMapWindow(g_display, g_win);
    XFlush(g_display);
    create_gc(g_display, g_win, 0);	
    XSelectInput(g_display, g_win, KeyPressMask | KeyReleaseMask | ButtonPressMask | StructureNotifyMask | ExposureMask);
    XMapWindow(g_display, g_win);
    oriImg = XGetImage(g_display,g_win,0,0,g_display_width,g_display_height,AllPlanes,ZPixmap);
oPlane.oPixmap.format = PIX_32_8888;
    oPlane.oPlaneInfo.format = GFX_PLANE_FORMAT_RGBA;
    /* allocate the offline buffer */
    g_memSize = oriImg->width * oriImg->height * oriImg->bits_per_pixel/8;
    oPlane.oPixmap.pixbuf = (char *) mem_alloc (g_memSize);
   /* Clear the double buffer */
    memset(oPlane.oPixmap.pixbuf, 0, g_memSize);
    /* create offline screen buffer */
    g_img = XCreateImage (g_display,g_vis, oriImg->depth,oriImg->format,oriImg->xoffset,(
	char *) oPlane.oPixmap.pixbuf,oriImg->width,oriImg->height,oriImg->bitmap_pad, oriImg->bytes_per_line);
/* Fill the rest of the pixmap structure */
    oPlane.oPixmap.width = oriImg->width;
    oPlane.oPixmap.height = oriImg->height;
    oPlane.oPixmap.pitch = oriImg->width * oriImg->bits_per_pixel/8;

    /* Store any other required information */
    oDisplayInfo.res_width = oriImg->width;
    oDisplayInfo.res_height = oriImg->height;

    oPlane.oPlaneInfo.flags = GFX_PLANE_FLAG_DRAWABLE;
    oPlane.oPlaneInfo.type = GFX_PLANE_ONSCREEN_GRAPHICS;
    oPlane.oPlaneInfo.width = oriImg->width;
    oPlane.oPlaneInfo.height = oriImg->height;
    oPlane.oPlaneInfo.view.width = oPlane.oPlaneInfo.width;
    oPlane.oPlaneInfo.view.height = oPlane.oPlaneInfo.height;
    oPlane.oPlaneInfo.drawprims = get_gfx_draw_functions_for(&(oPlane.oPixmap));

    /* Fill in the draw context */
    oDrawCtx.pixmap = &(oPlane.oPixmap);
    oPlane.oPlaneInfo.drawprims->init_gdc(&oDrawCtx, NULL);
    oPlane.oPlaneInfo.drawprims->set_color(&oDrawCtx, 0);
    oPlane.oPlaneInfo.drawprims->set_alpha_rule(&oDrawCtx, SRC);
    XUnlockDisplay(g_display);

You can sell I have the masks for key press in the XSelectEvent() call.

Then, the event handling portion:

if (XEventsQueued(g_display, QueuedAfterReading) > 0)
	{
		XNextEvent(g_display, &report);
		switch (report.type) 
		{
	   		case KeyPress:
                                  fprintf( stderr, "Key Press Event\n");
		  		 /* Respond to buttonpress, probably depending on
		   		 * which window is reported in report.xbutton.window */
	   		break;
	   		case KeyRelease:
                                  fprintf( stderr, "Key Release Event\n");
		  		 /* Respond to buttonpress, probably depending on
		   		 * which window is reported in report.xbutton.window */
	   		break;
			default:
	   			fprintf( stderr, "Event being thrown away\n");
			   /* All *Notify events except ConfigureNotify will
			    * be thrown away; they are not needed by most
			    * applications but are sent because ConfigureNotify
			    * can’t be selected independently */
	   		break;
		}

No matter what I do, I never see the events. Am I missing something? Is there anything else I can do?

[Javasnob]

Please place your code in [code] sections next time!

I'll critique your code now...

You should probably pass NULL instead of ":0.0"...it's more general.
g_display = XOpenDisplay(":0.0");
if (g_display == NULL) {
	EVODRV_log_post( IDERR(ERRCODE_FAILURE_DURING_INIT), "init_Xlib::cannot connect X server") ;
	return FALSE;
}
screen_num = DefaultScreen(g_display);
g_display_width = DisplayWidth(g_display, screen_num);
g_display_height = DisplayHeight(g_display, screen_num);
/* find bit depth */
g_vis = DefaultVisual (g_display, screen_num);
g_win = XCreateSimpleWindow(g_display, RootWindow(g_display, screen_num),
		0, 0, g_display_width, g_display_height, 0,555,1221672);
XMapWindow(g_display, g_win);
You don't need this here because XNextEvent flushes the queue
XFlush(g_display);
create_gc(g_display, g_win, 0);
XSelectInput(g_display, g_win, KeyPressMask | KeyReleaseMask | ButtonPressMask | StructureNotifyMask | ExposureMask);
 You already mapped it! (This won't cause an error though)
XMapWindow(g_display, g_win);
oriImg = XGetImage(g_display,g_win,0,0,g_display_width,g_di splay_height,AllPlanes,ZPixmap);
oPlane.oPixmap.format = PIX_32_8888;
oPlane.oPlaneInfo.format = GFX_PLANE_FORMAT_RGBA;
/* allocate the offline buffer */
g_memSize = oriImg->width * oriImg->height * oriImg->bits_per_pixel/8;
oPlane.oPixmap.pixbuf = (char *) mem_alloc (g_memSize);
/* Clear the double buffer */
memset(oPlane.oPixmap.pixbuf, 0, g_memSize);
/* create offline screen buffer */
g_img = XCreateImage (g_display,g_vis, oriImg->depth,oriImg->format,oriImg->xoffset,(
			char *) oPlane.oPixmap.pixbuf,oriImg->width,oriImg->height,oriImg->bitmap_pad, oriImg->bytes_per_line);
/* Fill the rest of the pixmap structure */
oPlane.oPixmap.width = oriImg->width;
oPlane.oPixmap.height = oriImg->height;
oPlane.oPixmap.pitch = oriImg->width * oriImg->bits_per_pixel/8;

/* Store any other required information */
oDisplayInfo.res_width = oriImg->width;
oDisplayInfo.res_height = oriImg->height;

oPlane.oPlaneInfo.flags = GFX_PLANE_FLAG_DRAWABLE;
oPlane.oPlaneInfo.type = GFX_PLANE_ONSCREEN_GRAPHICS;
oPlane.oPlaneInfo.width = oriImg->width;
oPlane.oPlaneInfo.height = oriImg->height;
oPlane.oPlaneInfo.view.width = oPlane.oPlaneInfo.width;
oPlane.oPlaneInfo.view.height = oPlane.oPlaneInfo.height;
oPlane.oPlaneInfo.drawprims = get_gfx_draw_functions_for(&(oPlane.oPixmap));

/* Fill in the draw context */
oDrawCtx.pixmap = &(oPlane.oPixmap);
oPlane.oPlaneInfo.drawprims->init_gdc(&oDrawCtx, NULL);
oPlane.oPlaneInfo.drawprims->set_color(&oDrawCtx, 0);
oPlane.oPlaneInfo.drawprims->set_alpha_rule(&oDrawCtx, SRC);
XUnlockDisplay(g_display);

I'd use XPending in a while loop, inside of an infinite while loop
if (XEventsQueued(g_display, QueuedAfterReading) > 0)
{
	XNextEvent(g_display, &report);
	switch (report.type)
	{
		case KeyPress:
			fprintf( stderr, "Key Press Event\n");
			/* Respond to buttonpress, probably depending on
			 * which window is reported in report.xbutton.window */
			break;
		case KeyRelease:
			fprintf( stderr, "Key Release Event\n");
			/* Respond to buttonpress, probably depending on
			 * which window is reported in report.xbutton.window */
			break;
		default:
			fprintf( stderr, "Event being thrown away\n");
			/* All *Notify events except ConfigureNotify will
			 * be thrown away; they are not needed by most
			 * applications but are sent because ConfigureNotify
			 * can¿t be selected independently */
			break;
	}
}

I hope this helps!

[oggie]

Thanks for the reply. I edited the post to wrap the code with the tags. Kind of late, but oh well.

I tried using NULL when I did the XOpenDisplay, but the application would crash. Not sure why, but maybe the MIPS platform doesn't like it.....

Nice nickname... javasnob... I'm a java guy as well, and prefer it over c/c++.