c++ - XLib application not redrawing unless resized -


so, have application in c++ uses xlib. in it, access date , time using ctime library, , in expose event, create string , put in window, centered. problem that, time updates when resized, instance, seconds not change unless continually resize window. here code:

#include <stdio.h> #include <cstdio> #include <stdlib.h> #include <string.h> #include <x11/xlib.h> #include <ctime>  int main (int argc, char *argv[]) {   display                 *display;   visual                  *visual;   int                     depth;   int                     text_x;   int                     text_y;   xsetwindowattributes    frame_attributes;   window                  frame_window;   xfontstruct             *fontinfo;   xgcvalues               gr_values;   gc                      graphical_context;   xkeyevent               event;   char                    contents[80] = "                                                                               ";   time_t                  rawtime;   struct tm               *timeinfo;   int                     contents_length = strlen(contents);    display = xopendisplay(null);   visual = defaultvisual(display, 0);   depth  = defaultdepth(display, 0);    frame_attributes.background_pixel = xwhitepixel(display, 0);   /* create application window */   frame_window = xcreatewindow(display, xrootwindow(display, 0),       0, 0, 500, 50, 5, depth,       inputoutput, visual, cwbackpixel,       &frame_attributes);   xstorename(display, frame_window, "fly taskbar");   xselectinput(display, frame_window, exposuremask | structurenotifymask);    fontinfo = xloadqueryfont(display, "10x20");   gr_values.font = fontinfo->fid;   gr_values.foreground = xblackpixel(display, 0);   graphical_context = xcreategc(display, frame_window,       gcfont+gcforeground, &gr_values);   xmapwindow(display, frame_window);    while ( 1 ) {     xnextevent(display, (xevent *)&event);     switch ( event.type ) {       case expose:         {           xclearwindow(display, frame_window);           // upkeep of interface usefulness.           window returned_root, returned_parent;           window* top_level_windows;           unsigned int nwin = 0;           xquerytree(               display,               xdefaultrootwindow(display),               &returned_root,               &returned_parent,               &top_level_windows,               &nwin);            time(&rawtime);           timeinfo = localtime(&rawtime);           strftime(contents, 80, "%a %d %b, %t %p", timeinfo);            sprintf(contents, "%s [%d]", contents, nwin);             xwindowattributes window_attributes;           int font_direction, font_ascent, font_descent;           xcharstruct text_structure;           xtextextents(fontinfo, contents, contents_length,               &font_direction, &font_ascent, &font_descent,               &text_structure);           xgetwindowattributes(display, frame_window, &window_attributes);           text_x = (window_attributes.width - text_structure.width) + 5;           text_y = (window_attributes.height -               (text_structure.ascent+text_structure.descent))/2;           xdrawstring(display, frame_window, graphical_context,               text_x, text_y, contents, contents_length);           break;         }       default:         break;     }   }   return 0; }

in case of wondering purpose for, writing window manager (i've gotten far, can open apps, move, , resize them) , tool need debugging purposes. repo here

you need event loop, e.g. calling poll(2) , handle delays. should call xflush or xsync (because xlib buffering requests).

you might consider sending expose event....

and should study source code of xclock


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