XLib Event Loop - My code entry point??

I'm working on a terminal/monitoring program that displays serial input stream using standard lib fopen() in a window. I used a file viewing program as the basis for my Xlib program. I have modifed it get its input from the serial port, instead of a file. Everything works fine, but now I need read lines of serial I/O continiously into a circular buffer and output it directly to a Region of the window until told to stop. It really nothing more than a terminal window.

For this discussion, I'm just focused on how do I keep reading serial input while the processing has moved into the event loop. The function call display_lines() does all of the work copying and clearing regions, and scrolling lines of data up or down in the window.

if (theEvent.xexpose.count == 0) display_lines();
break;

Q: Do I need to fork() a child process? If so, and where:confused:.

I've been looking for code eamples, but haven't found any so far. I looked at xterm source, but it was to complicated to follow.:confused:

Hope someone can guide me in the right direction. This is pure XLib programming. I will be glad to post code and expand on this more if needed.

jw

Yes, more code would help.

1 Attachment(s)

Xlib Event Loop - My code snippet

Okay, I give up on code tagging. I don't know what the deal is...? I had everything laid out correctly in this message and it won't let me submit.:mad:

Code:

My code....

It should be that simple... Oh well, just see the file.:cool:

So, why did that work? I guess the code tag don't like my code!!

Here is the code placed inside code tags.

Code:

/*-------------------------------------------------------------*/ /* File: xjwmon_2-1.c * * Program to view serial output from /dev/ttyS? port. */ /*-------------------------------------------------------------*/ #include <stdio.h> #include <string.h> #include <X11/Xlib.h> #include <X11/Xutil.h> #include <X11/keysym.h> #include "xwins.h" #include "app_glob.c" #define LEFT_MARGIN 4 /* Leave a 4-pixel margin */ /* Maximum length of string generated by a keypress */ #define MAX_MAPPING 10 /* Menu styles */ #define MENUBAR_STYLE 0 #define PULLDOWN_STYLE 1 #define SCROLL_UP 0 #define SCROLL_DOWN 1 #define MAXCHARS 250 /* Maximum length of a line */ typedef struct D_LINE /* Holds info on each line */ { struct D_LINE *prev; /* Pointer to previous line */ struct D_LINE *next; /* Pointer to next line */ char *line; /* Null-terminated line */ short length; /* Number of characters in line*/ short lbearing;/* Left and right edges of */ short rbearing;/* rectangle covered by line */ short height; /* Height of text string */ } D_LINE; typedef struct D_LBUF /* Info on entire buffer */ { D_LINE *lines; /* First line in buffer */ D_LINE *lstart; /* First line in window */ GC gc; /* GC used to display text */ Region rexp; /* Current exposed region */ XFontStruct *fstruct;/* Info on current font */ int font; /* Currently selected font */ int weight; /* weight and */ int size; /* size */ unsigned dwidth; /* Width of text display area */ unsigned dheight; /* Height of text display area */ long count; /* How many lines in buffer */ } D_LBUF; static D_LBUF fbuf = { NULL,NULL, None, None, None, 0, 0, 0, 0, 0, 0}; static int zero=0, one=1, two=2, three=3, four=4; static GC invertGC; /* GC used for highlighting */ static int PullDownOn = 0, full_update = 0; static Window pulldown_id; static unsigned quit_width, quit_height; /* Information necessary to construct X11R3 font names */ static char *fontname[] = { "courier", "helvetica", "new century schoolbook", "times" }; static char *weight[] = { "medium", "bold" }; static char *size[] = {"100", "120", "140", "180", "240"}; char *quit_label = "Quit"; /* File to be opened */ char *port_name; static FILE *fp; /* Function prototypes */ void initapp(/* int, char **, int, int, unsigned, unsigned */); static int disp_menu(/* caddr_t */); static int quit_action(/* caddr_t */); static void process_event(); static void hilite_button(/* XWIN * */); static int font_select(/* caddr_t */); static int wt_select(/* caddr_t */); static int size_select(/* caddr_t */); static void open_port(/* char *portname */); static void apply_font(); static void read_lines(); /* read input */ static void display_lines(); static void scroll_lines(/* int direction, int numlines */); /* Windows in the application */ Window dWin; XWIN *menubar, *PullDown[3]; /*-------------------------------------------------------------*/ main(argc, argv) int argc; char **argv; { XWIN *QuitButton, *which_xwin; XGCValues xgcv; int i, yp, xp1, xp2; /* char buf[MAXCHARS] */; /* FILE *fp; */ xwin_init(); initapp(argc, argv, 20, 20, 500, 400); /* Get file name from command line */ for (i = 1; i < argc; i += 2) { if(strcmp("-port", argv[i]) == 0) { port_name = argv[i+1]; break; } } if(i >= argc) { fprintf(stderr, "Need: xjwmon -port </dev/ttyS?>\n"); exit(1); } /* Create the "Quit" button */ quit_width = XTextWidth(theFontStruct, quit_label, strlen(quit_label)) + 4; quit_height = theFontStruct->max_bounds.ascent + theFontStruct->max_bounds.descent + 4; QuitButton = MakeXButton(2, 3, quit_width, quit_height, 1, theFGpix, theBGpix, theMain, quit_label, quit_action, NULL); /* Create a menu bar */ menubar = MakeXMenu(quit_width+16, 1, 1, theFGpix, theBGpix, theMain, MENUBAR_STYLE, "Font", disp_menu, (caddr_t)&zero, "Weight", disp_menu, (caddr_t)&one, "Size", disp_menu, (caddr_t)&two, NULL); yp = quit_height + 10; xp1 = quit_width+16 + XTextWidth(theFontStruct, "Font", strlen("Font")) + 8; xp2 = xp1 + XTextWidth(theFontStruct, "Weight", strlen("Weight")) + 8; /* Create the pull-down menus */ PullDown[0] = MakeXMenu(0, yp, 1, theFGpix, theBGpix, theMain, PULLDOWN_STYLE, "Courier", font_select, (caddr_t)&zero, "Helvetica", font_select, (caddr_t)&one, "New Century Schoolbook", font_select, (caddr_t)&two, "Times", font_select, (caddr_t)&three, NULL); PullDown[1] = MakeXMenu(xp1, yp, 1, theFGpix, theBGpix, theMain, PULLDOWN_STYLE, "Medium", wt_select, (caddr_t)&zero, "Bold", wt_select, (caddr_t)&one, NULL); PullDown[2] = MakeXMenu(xp2, yp, 1, theFGpix, theBGpix, theMain, PULLDOWN_STYLE, " 10pt", size_select, (caddr_t)&zero, " 12pt", size_select, (caddr_t)&one, " 14pt", size_select, (caddr_t)&two, " 18pt", size_select, (caddr_t)&three, " 24pt", size_select, (caddr_t)&four, NULL); /* Set up a GC to display text */ fbuf.gc = XCreateGC(theDisplay, theMain, 0, 0); XCopyGC(theDisplay, theGC, GCForeground | GCBackground | GCFont, fbuf.gc); /* Set up a GC to hilight the buttons */ invertGC = XCreateGC(theDisplay, theMain, 0, 0); XCopyGC(theDisplay, theGC, GCForeground | GCBackground, invertGC); XSetFunction(theDisplay, invertGC, GXinvert); XSetPlaneMask(theDisplay, invertGC, theFGpix^theBGpix); /* Add ButtonRelease to the event selection of the main * window so that we can detect when the user releases * the button without selecting any menu item. */ AddNewEvent(theMain, ButtonReleaseMask|StructureNotifyMask); /* Create and map a window that serves as the file display area */ dWin = XCreateSimpleWindow(theDisplay, theMain, 1, quit_height+8, 500, 400, 1, theFGpix, theBGpix); XSelectInput(theDisplay, dWin, ExposureMask | ButtonPressMask | OwnerGrabButtonMask| ButtonReleaseMask | StructureNotifyMask | KeyPressMask); XMapRaised(theDisplay, dWin); /* JW's Notes: * * */ /* open the serial port using standard I/O. */ open_port(port_name); read_lines(); fbuf.lstart = fbuf.lines; /* loads .lstart with the first line in the buffer. */ printf("assign fbuf.lstart = fbuf.lines....\n\n"); apply_font(); /* printf("apply_font() completed....\n\n"); */ fbuf.rexp = XCreateRegion(); printf("initialize fbuf.rexp = XCreateRegion() complete....\n\n"); /* Event handling loop--keep processing events until done */ printf("start processing events in event loop....\n\n"); while (!AppDone) process_event(); /* Close connection to display and exit */ XCloseDisplay(theDisplay); fclose(fp); exit(0); } /*-------------------------------------------------------------*/ /* p r o c e s s _ e v e n t * * Retrieve an event and process it... */ static void process_event() { XWIN *which_xwin; /* Get the next event from Xlib */ XNextEvent(theDisplay, &theEvent); /* If main window is resized, we must resize dWin */ if(theEvent.xany.window == theMain && theEvent.type == ConfigureNotify) { XResizeWindow(theDisplay, dWin, theEvent.xconfigure.width, theEvent.xconfigure.height - quit_height - 8); } /* Handle events for the dWin, the text display window */ if(theEvent.xany.window == dWin) { switch (theEvent.type) { case Expose: { /* Accumulate exposed areas in a region */ XRectangle r; r.x = theEvent.xexpose.x; r.y = theEvent.xexpose.y; r.width = theEvent.xexpose.width; r.height = theEvent.xexpose.height; XUnionRectWithRegion(&r, fbuf.rexp, fbuf.rexp); if(fbuf.dwidth == 0 || fbuf.dheight == 0) { Window rid; int junk; /* Get dimensions of this window */ XGetGeometry(theDisplay, theMain, &rid, &junk, &junk, &fbuf.dwidth, &fbuf.dheight, &junk, &junk); fbuf.dheight -= (quit_height+8); } if(theEvent.xexpose.count == 0) display_lines(); break; }/* close brace for case Expose: */ case KeyPress: { char xlat[MAX_MAPPING]; KeySym key; int count; /* Translate keycode into keysym and string */ count = XLookupString(&theEvent, xlat, MAX_MAPPING, &key, None); /* Up and Down arrows */ if(key == XK_Up) scroll_lines(SCROLL_DOWN, 1); if(key == XK_Down) scroll_lines(SCROLL_UP, 1); /* Is it Ctrl-D or Ctrl-U? */ if(theEvent.xkey.state & ControlMask) { if(key == XK_l) /* Refresh display */ XClearArea(theDisplay, dWin, 0,0,0,0,True); printf("screen refreshed...\n"); if(key == XK_u) scroll_lines(SCROLL_DOWN, fbuf.dheight/fbuf.lstart->height-1); if(key == XK_d) scroll_lines(SCROLL_UP, fbuf.dheight/fbuf.lstart->height-1); } /* close brace for if(theEvent.xkey.state & ControlMask) */ } /* close brace for case: KeyPress */ break; case ConfigureNotify: fbuf.dwidth = theEvent.xconfigure.width; fbuf.dheight = theEvent.xconfigure.height; XClearArea(theEvent.xany.display, dWin, 0, 0, 0, 0, True); break; } /* close brace for switch() */ } /* close brace for if(theEvent.xany.window == dWin) */ /************** Process events for other windows *************/ /* Next, retrieve the XWIN data from Xlib using the * context manager routine XFindContext */ if(XFindContext(theDisplay, theEvent.xany.window, xwin_context, (caddr_t *) &which_xwin) == 0) { /* Call the event handler of this XWIN structure */ if (*(which_xwin->event_handler) != NULL) (*(which_xwin->event_handler))(which_xwin); } /* Handle EnterNotify and LeaveNotify events for the buttons */ if(theEvent.type == EnterNotify || theEvent.type == LeaveNotify) hilite_button(which_xwin); if(PullDownOn && theEvent.type == ButtonRelease) PullDownOn = 0; } /*-------------------------------------------------------------*/ static int disp_menu(data) caddr_t data; { XWIN *which_xwin; int menu_number; /* Display the PullDown menu and process events until a * choice is made */ menu_number = * ((int *) data); pulldown_id = PullDown[menu_number]->xid; XMapRaised(theDisplay, pulldown_id); PullDownOn = 1; while(PullDownOn) process_event(); /* Unmap the pull-down menu window */ XUnmapWindow(theDisplay, pulldown_id); return 1; } /*-------------------------------------------------------------*/ /* q u i t _ a c t i o n * * This routine is called when a ButtonPress event occurs in * the quit window. */ static int quit_action(data) caddr_t data; { /* Set the done flag */ AppDone = 1; return 1; } /*-------------------------------------------------------------*/ /* h i l i t e _ b u t t o n * * Highlight a button window by inverting it */ static void hilite_button(p_xwin) XWIN *p_xwin; { int i, go_on = 0; /* Check if window's parent is one of the pull-down menus */ for(i = 0; i < 3; i++) { if(p_xwin->parent == PullDown[i]->xid) { go_on = 1; break; } } if (!go_on) return; /* Invert a rectangle large enough so that the button window * gets highlighted */ XFillRectangle(theDisplay, p_xwin->xid, invertGC, 0, 0, 1024, 1024); XFlush(theDisplay); } /*-------------------------------------------------------------*/ /* f o n t _ s e l e c t * * Process a font selection * */ static int font_select(data) caddr_t data; { int font = *((int *)data); PullDownOn = 0; if(font != fbuf.font) { fbuf.font = font; apply_font(); /* Clear the display window so that text is displayed again */ XClearArea(theDisplay, dWin, 0, 0, 0, 0, True); } return 1; } /*-------------------------------------------------------------*/ /* w t _ s e l e c t * * Font weight changed. * */ static int wt_select(data) caddr_t data; { int weight = *((int *)data); PullDownOn = 0; if(weight != fbuf.weight) { fbuf.weight = weight; apply_font(); /* Clear the display window so that text is displayed again */ XClearArea(theDisplay, dWin, 0, 0, 0, 0, True); } return 1; } /*-------------------------------------------------------------*/ /* s i z e _ s e l e c t * * New size font selected * */ static int size_select(data) caddr_t data; { int size = *((int *)data); PullDownOn = 0; if(size != fbuf.size) { fbuf.size = size; apply_font(); /* Clear the display window so that text is displayed again */ XClearArea(theDisplay, dWin, 0, 0, 0, 0, True); } return 1; } /*-------------------------------------------------------------*/ /* o p e n s e r i a l p o r t * * JW's Notes: * 1) Open the serial port instead of a file using C libaray * standard I/O. */ static void open_port(portname) char *portname; { /* Open the serial port in "r" (read mode) using standard I/O. */ if((fp = fopen(portname, "r")) == NULL) { fprintf(stderr, "Cannot open: %s\n", portname); exit(1); } } /*-------------------------------------------------------------*/ /* r e a d s e r i a l i n p u t * * JW's Notes: */ static void read_lines() { D_LINE *p_l = NULL, *p_l_prev = NULL; char buf[MAXCHARS]; /* Read each line and store in linked list of D_LINE structs */ while(((fgets(buf, MAXCHARS, fp)) != NULL) && fbuf.count <= 10) { if((p_l = (D_LINE *) calloc(1, sizeof(D_LINE))) != NULL) { if(fbuf.lines == NULL) { fbuf.lines = p_l; printf("read the first line fbuf.lines...\n\n"); } else { p_l_prev->next = p_l; p_l->prev = p_l_prev; printf("read additional lines... p_l_prev-> = p_l\n\n"); } } else { /* Allocation failed...*/ fprintf(stderr, "Failed to allocate memory for\ line data structure...\n"); exit(1); } p_l->length = strlen(buf) - 1; /* Exclude newline */ buf[p_l->length] = '\0'; if((p_l->line = malloc(p_l->length+1)) == NULL) { fprintf(stderr, "Failed to allocate memory for\ line:\n%s\n", buf); exit(1); } strcpy(p_l->line, buf); p_l_prev = p_l; fbuf.count++; printf("This is line %d\n", fbuf.count); } /* end of while loop */ } /*-------------------------------------------------------------*/ /* a p p l y _ f o n t * * Set up a new font for use. Also compute screen areas * occupied by each line. */ static void apply_font() { D_LINE *p_l; int dir, ascent, descent; char fname[120]; /* Room for font's name */ XCharStruct cinfo; int font = fbuf.font, wt = fbuf.weight, sz = fbuf.size; /* Construct font's name */ sprintf(fname, "*adobe-%s-%s-r*%s*", fontname[font], weight[wt], size[sz]); printf("Font = %s\n", fname); /* Free the font, if necessary */ if(fbuf.fstruct != NULL && fbuf.fstruct != theFontStruct) XFreeFont(theDisplay, fbuf.fstruct); /* Load the new font */ if ((fbuf.fstruct = XLoadQueryFont(theDisplay, fname)) == NULL) { fprintf(stderr, "%s: display %s cannot load font %s\n", theAppName, DisplayString(theDisplay), fname); /* Set fbuf.fstruct to our default font */ fbuf.fstruct = theFontStruct; } /* Compute bounding box of each line in the buffer */ for(p_l = fbuf.lines; p_l != NULL; p_l = p_l->next) { XTextExtents(fbuf.fstruct, p_l->line, p_l->length, &dir, &ascent, &descent, &cinfo); p_l->lbearing = cinfo.lbearing; p_l->rbearing = cinfo.rbearing; p_l->height = ascent + descent; } /* Set the font in the GC */ XSetFont(theDisplay, fbuf.gc, fbuf.fstruct->fid); } /*-------------------------------------------------------------*/ /* d i s p l a y _ l i n e s * * Displays the lines in the text window */ static void display_lines() { int xpos = 0; int ypos = 0, width; D_LINE *p_l; /* If a full update is needed, alter the exposed region */ if(full_update) { XRectangle r; r.x = r.y = 0; r.width = fbuf.dwidth; r.height = fbuf.dheight; XUnionRectWithRegion(&r, fbuf.rexp, fbuf.rexp); full_update = False; } /* Set the accumulated exposed regions as the clip mask */ XSetRegion(theDisplay, fbuf.gc, fbuf.rexp); /* Display the lines starting with the first one. Draw * a string ONLY if it falls in the exposed region. */ for(p_l = fbuf.lstart; p_l != NULL && ypos < fbuf.dheight; p_l = p_l->next) { xpos = LEFT_MARGIN - p_l->lbearing; ypos += p_l->height; if(XRectInRegion(fbuf.rexp, xpos, ypos - p_l->height, p_l->lbearing + p_l->rbearing, p_l->height) != RectangleOut) { /* Yes. String's rectangle is partially in region. Draw it */ XDrawImageString(theDisplay, dWin, fbuf.gc, xpos, ypos, p_l->line, p_l->length); } } /* Destroy current region and create a new "empty" one */ XDestroyRegion(fbuf.rexp); fbuf.rexp = XCreateRegion(); /* s c r o l l _ l i n e s * * Scroll the text display by a specified amount. */ static void scroll_lines(direction, numlines) int direction; int numlines; { int i, ysrc, yclr, numpix = 0; D_LINE *p_l; /* Figure out how many pixels to scroll */ switch(direction) { case SCROLL_UP: for(i = 0, p_l = fbuf.lstart; i < numlines && p_l->next != NULL; i++, p_l = p_l->next) numpix += p_l->height; ysrc = numpix; yclr = fbuf.dheight - numpix; break; case SCROLL_DOWN: for(i = 0, p_l = fbuf.lstart; i < numlines && p_l->prev != NULL; i++, p_l = p_l->prev) numpix += p_l->height; ysrc = 0; yclr = 0; break; } if(numpix == 0) { /* No need to scroll */ XBell(theDisplay, 0); return; } /* Adjust first line to display */ fbuf.lstart = p_l; /* Copy area */ XSetClipMask(theDisplay, fbuf.gc, None); XCopyArea(theDisplay, dWin, dWin, fbuf.gc, 0, ysrc, fbuf.dwidth, fbuf.dheight - numpix, 0, numpix - ysrc); /* Clear new rectangle so that it is redrawn */ XClearArea(theDisplay, dWin, 0, yclr, fbuf.dwidth, numpix, True); }

Jim

> if((fp = fopen(portname, "r")) == NULL)
>...
> while(((fgets(buf, MAXCHARS, fp)) != NULL) && fbuf.count <= 10)
I would change these to be open() and if ( read() ... ) (note: use of if, not while)

By having a file descriptor instead of a FILE*, you can then make use of select.

With this, your event loop would look something like this.

Code:

while (!AppDone) { fd_set rd; FD_CLR(&rd); FD_SET(serialfd,&rd); if ( select(serialfd+1,&rd,NULL,NULL,NULL) > 0 ) { read_lines(); } process_event(); }

It's important that read_lines() performs only a single read() call to extract what data is present. If you make more than one call, then it will almost certainly block.

A further consequence of using read() as opposed to fgets() is that \n is no longer a delimiter. You will need to deal with line fragments within read_lines().

Many thanks! I'll try it out. The original source was using open() to read an entire file into memory. I switched to fopen() for testing and stuck with it. As I remember, I saw something about excessive system calls and performance issues using open() and read(). This was in the HOWTO-serial programming doc (old stuff).

Salem,

Can you explain and "blocking" a little more. Is it a general term in C programming, or is it event programming term? I have read about it many times but I'm not totally clear on when it occurs. I assume it is like a wait state in the event loop. I will certainly read up on it again.