LinuxCollections.com How To Video - Introduction to GUI Development

File: README.txt
Files used in examples/video:
mountoptiso.sh,
build, hello.c,
buildx, hellox.c,
buildgtk, helloworldgtk.c,
buildwayland, hellowayland.c, xdg-shell-protocol.c

Introduction to GUI Development
(the Graphical User Interface)

To begin with, we are going to start with a very basic C program, to lay the groundwork for
development, and cover some very basic "getting started" foundational items.

We will be using our Debian USB Developer Collection from LinuxCollections.com
All references will be on the Debian system and using the apt system (apt-get) to
install development tools, libraries, and header files.

We will indicate command line text by ending with "[Enter]"
Script code will be separated with ################## lines
Source code will be separated the /*********************/ lines

To start with, we use a new hard drive, install Debian 12.7.0 with ALL Desktop environments
(so we are able to test/work with different Window Managers/Desktop Environments)

Then we copy all the ISO files from the USB to the /opt/iso location, and as super user (root),
we mount all these iso files and add them to the sources.list for apt, so we have access
to ALL packages. The specific steps would be as follows:
1) su/password, run as root
2) cd /opt
3) mkdir iso
4) cd iso
5) cp /media/[user]/USB_Boot/boot/iso/*.iso . (THIS WILL TAKE AWHILE!)
6) cp /home/[user]/code/mountoptiso.sh .
7) ./mountoptiso.sh

So one of the reasons for these details are to help people new to Linux to
understand what is needed to do development work. So where to start?

The Debian wiki has a Building Tutorial, so let's start there...

For reference, this is the site that covers modifying Debian source
https://wiki.debian.org/BuildingTutorial

As outlined there, the very first set of packages to be installed are listed.
Even if we aren't going to modify Debian packages, let's get these installed
so we have a good base for doing development work.

For required build tools, etc., make sure to install essentials, e.g.:

apt-get install build-essential fakeroot devscripts[Enter]

At this point, we can actually build (compile) source code and create
working programs. Let's do that with the basic Hello World! program.

See the build script and hello.c
#################################################################
#!/bin/bash

#build script

echo "Begin..."

gcc -o helloworld hello.c

if [ $? -eq 0 ]; then
echo "Hello built!"
else
echo "gcc compile failed with exit code $?"
fi

#################################################################
/***************************************************************/
/*********************************************************************************************
* hello.c
********************************************************************************************/
#include
#include

void main(void)
{
printf("Hello World!\n");
}
/***************************************************************/

For the XLib / X-Window example (buildx, hellox.c) you will
need the X11 XLib headers and libraries. The Debian package is
"libx11-dev" - to install:

apt-get install libx11-dev[Enter]

The buildx script looks like this:
#################################################################
#!/bin/bash

#buildx script

echo "Begin..."

#apt-get install libx11-dev

gcc -o helloworldx hellox.c
#gcc -o helloworldx hellox.c -lX11

if [ $? -eq 0 ]; then
echo "Hello built!"
else
echo "gcc compile failed with exit code $?"
fi

#################################################################

As noted in the comments, this package is required

We won't be including the source code due to the increasing length,
so you have to reference the file directly - hellox.c

For the GTK example (buildgtk, helloworldgtk.c) you will
need the pkgconf (Package Configuration), and the GTK-4 headers
and libraries. The Debian packages are "pkgconf" and "libgtk-4-dev"
To install:

apt-get install pkgconf[Enter]
apt-get install libgtk-4-dev[Enter]

The buildgtk script looks like this:
#################################################################
#!/bin/bash

#buildgtk script

echo "Begin..."

#apt-get install pkgconf
#apt-get install libgtk-4-dev

gcc $(pkg-config --cflags gtk4) -o helloworldgtk helloworldgtk.c $(pkg-config --libs gtk4)

if [ $? -eq 0 ]; then
echo "Hello built!"
else
echo "gcc compile failed with exit code $?"
fi

#################################################################

For the wayland example (buildwayland, hellowayland.c) you will
need the wayland headers and libraries. The Debian package is
"libwayland-dev"
To install:

apt-get install libwayland-dev[Enter]

The buildwayland script looks like this:

#################################################################
#!/bin/bash

#buildwayland script

echo "Begin..."

#apt-get install libwayland-dev

gcc -o hellowayland hellowayland.c xdg-shell-protocol.c -ggdb3 -lm -lwayland-client `pkg-config --cflags --libs pangocairo` `pkg-config --cflags --libs cairo`

#to build with full debug information add in -ggdb3
#gcc -o hellowayland hellowayland.c xdg-shell-protocol.c -ggdb3 -lm -lwayland-client `pkg-config --cflags --libs pangocairo` `pkg-config --cflags --libs cairo`

if [ $? -eq 0 ]; then
echo "Hello built!"
else
echo "gcc compile failed with exit code $?"
fi

#################################################################

As one final note, we introduce valgrind, which is a development tool that can find memory leaks.
It is too involved to go into here, but we want your to be aware of it. Refer to valgrind
documentation and examples to learn about it. Note in these 4 examples, the high-level ones
(GTK/Wayland) have memory leaks, even though there is code to clean things up on exit.

apt-get install valgrind[Enter]