Small app menu for X that launches user defined commands. I created it when I used 9wm. I wanted a lightweight application launcher. This code can be useful to people who wonder how to create X applications without any widget library such as GTK or QT.

gistfile1.c

//      main.c
//      
//      Copyright 2012 Antoine Morin-Paulhus <antoine.morin.paulhus@gmail.com>
//      
//      This program is free software; you can redistribute it and/or modify
//      it under the terms of the GNU General Public License as published by
//      the Free Software Foundation; either version 2 of the License, or
//      (at your option) any later version.
//      
//      This program is distributed in the hope that it will be useful,
//      but WITHOUT ANY WARRANTY; without even the implied warranty of
//      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//      GNU General Public License for more details.
//      
//      You should have received a copy of the GNU General Public License
//      along with this program; if not, write to the Free Software
//      Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
//      MA 02110-1301, USA.

// Goal: allow user to create buttons that
//  launch specific commands defined in ~/.XLauncher
 
//To build with gcc: gcc -Wall `pkg-config --libs --cflags x11` 
 
/*Example ~/.XLauncher file:
#This is a commentary
# "<Label>" "<Command>"
# Label: max lenght: 32 characters
# Command: max lenght: 256 characters
# you must use external scripts to launch longer commands.
"potato""xterm -sb -geometry 300x300-1-1"
"USKB" "setxkbmap us"
"CAKB" "setxkbmap ca"
#use backslash ("\") when next character could 
#be interpreted by the program in a unwanted way.
#	('\','"','#')
#Example:
#"Something""somecommand \"/etc/some\\ file\""

*/

#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <X11/Xlib.h>
#include <X11/keysym.h>


const int BORDER = 1;
const int BORDERCOLOR = 0x111111;
const int BUTTONCOLOR = 0xdddddd;
const int HIGHLIGHTEDCOLOR = 0xaaaaff;
const int TEXTCOLOR = 0x000000;


typedef struct _button
{ 
	char label[32];
	char command[256];
	struct _button *next;
}button;

button * readButtons();
void drawButtons(Display * display,Window win,GC gc,button * firstButton,int highlighted);
void freeButtons(button * first);
void execCommand(char * command);

int main(int ac,char **av)
{
	GC	gc;
	Display	*display;
	int	screen=0;
	Window	win, root;
	unsigned long whitePixel, blackPixel;

	char commandToExecute[512];
	int i=0;
	int clickedButton;
	int numberOfItems=0;
	int xPosition=0, yPosition=0;
		
	if (ac == 3)
	{
		if(strcmp(av[1],"-geometry")==0)
		{
			XParseGeometry(av[2], &xPosition, &yPosition, NULL, NULL);
		}
	}
	
	//We put all the buttons inside a chained list with this function
	button * firstButton = readButtons();
	button * currentButton = firstButton;
	
	/*Button listing + numberOfItems count*/
	puts("Button listing:");
	do
	{
		printf("%s , %s\n",currentButton->label,currentButton->command);
		currentButton = currentButton->next;
		numberOfItems++;
	}while(currentButton != NULL);
	if ((display = XOpenDisplay (NULL)) == NULL) 
	{
		fprintf (stderr, "Can't open Display\n");
		exit (1);
	}
	
	gc = DefaultGC (display, screen);
	screen = DefaultScreen (display);
	root = RootWindow (display, screen);
	whitePixel = WhitePixel (display, screen);
	blackPixel = BlackPixel (display, screen);

	win = XCreateSimpleWindow (display, root, 10, 10, 100, numberOfItems*32,
								2, whitePixel, blackPixel);

	XSelectInput (display, win, ExposureMask | ButtonPressMask);
 
	XStoreName (display, win, "XLauncher");
	XMapWindow (display, win);

	for (;;)
	{
		XEvent ev;
		XEvent previous;		//Previous CLICK (not previous event)
		
		XNextEvent(display,&ev);
		
		switch (ev.type)
		{
			case FocusIn :
			case VisibilityNotify:
			case MapNotify:
			case MotionNotify:
			case Expose :
				drawButtons(display,win,gc,firstButton,-1);
				XMoveWindow(display,win,xPosition,yPosition);
			case ButtonPress:
				if 	(	
						ev.xbutton.button == 1 && 
						ev.xbutton.time-previous.xbutton.time < 700 &&
						ev.xbutton.y <= 32 * numberOfItems &&
						ev.xbutton.x <= 100 &&
						ev.xbutton.x >= 0 &&
						ev.xbutton.y >= 0 &&
						ev.xbutton.y/32 == previous.xbutton.y/32
					)
				{
					//lets find which button was clicked on
					clickedButton = ev.xbutton.y/32;
					currentButton = firstButton;
					drawButtons(display,win,gc,firstButton,clickedButton);
					for(i=0;i<clickedButton;i++)
					{
						currentButton = currentButton->next;
					}
					/*In order for all applications to run happily, we get to 
					  the home folder before executing*/
					sprintf(commandToExecute,"cd %s; %s",getenv("HOME"),currentButton->command);
					execCommand(commandToExecute);
					//lets pause for a while
					sleep(1);
					drawButtons(display,win,gc,firstButton,-1);
				}
				else
				{
					previous = ev;
				}
				break;
			default :
				break;
		}
	}
	freeButtons(firstButton);
	XFreeGC(display,gc);
	XFree(display);
}

void skipLine(FILE * file)
{
	char buffer;
	do
	{
		buffer = fgetc(file);
	}while(buffer != EOF && buffer != '\n');
}
/*Reads a Label or a command and ignores '\*' stops reading after '"'*/
void readString(FILE *file,char *str,int maxLenght)
{
	char buffer;
	int i;
	for(i=0;i<maxLenght;i++)
	{
		buffer=fgetc(file);
		if(buffer == '\\')
		{
			str[i] = fgetc(file);
			i++;
		}
		else if(buffer == '"')
		{
			str[i] = '\0';
			break;
		}
		else
			str[i] = buffer;
	}
}
button * readButtons()
{
	FILE *ButtonFile;
	char buffer;
	char path[512];
	button * firstButton=NULL;
	button * currentButton;

	sprintf(path,"%s%s",getenv("HOME"),"/.XLauncher");
	ButtonFile = fopen(path,"r");
	
	if(ButtonFile == NULL)
	{
		perror("An error occured while loading .XLauncher: ");
		exit(EXIT_FAILURE);
	}
	
	for(;;)
	{
		buffer = fgetc(ButtonFile);
		if (buffer == '"')
		{
			if(firstButton != NULL)
			{
				currentButton->next = malloc(sizeof(button));
				currentButton = currentButton->next;
			}
			else
			{
				currentButton = malloc(sizeof(button));
				firstButton = currentButton;
			}	
			readString(ButtonFile,currentButton->label,32);
			
			//get next '"'
			for(;;)
			{
				buffer = fgetc(ButtonFile);
				if(buffer == '"')
					break;
				if(buffer == EOF)
				{
					puts("Error: Bad formating in file.");
					fclose(ButtonFile);
					exit(EXIT_FAILURE);
				}
			}
			readString(ButtonFile,currentButton->command,256);
		}
		else if(buffer == EOF)
			break;
		else if(buffer == '#')
			skipLine(ButtonFile);
		else if(buffer == '\n');
		else if(buffer != ' ' && buffer != '\t')
			skipLine(ButtonFile);
	}
	
	fclose(ButtonFile);
	return firstButton;
	
}
void drawButtons(Display * display,Window win,GC gc,button * firstButton,int highlighted)
{
	int i=0;
	button * currentButton = firstButton;
	//Lets print all the buttons with a little happy border
	do
	{
		XSetForeground(display, gc, BORDERCOLOR);
		XFillRectangle(display, win, gc, 1, 32*i,100,32);
		
		if(i == highlighted)
		{
			XSetForeground(display, gc,HIGHLIGHTEDCOLOR);
		}
		else
		{
			XSetForeground(display, gc, BUTTONCOLOR);
		}
		XFillRectangle(	display, win, gc,
							BORDER, 32 * i + BORDER,
							100	- 2 * BORDER,32 - 2 * BORDER);
							
		XSetForeground(display, gc, TEXTCOLOR);
		
		XDrawString (	display, win, gc, 10, 32 * i + 16,
						currentButton->label, 
						strlen(currentButton->label));
		i++;
		currentButton = currentButton->next;
	}while(currentButton != NULL);
	
	XFlush(display);
}
void freeButtons(button * first)
{
	button * currentButton;
	button * next;
	currentButton = first;
	
	do
	{
		next = currentButton->next;
		free(currentButton);
		currentButton = next;
	}while(currentButton->next != NULL);
}
void execCommand(char * command)
{
	system(command);
}