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:tiny-windows-linux-gtk-apps

Writing TINY Desktop Apps in C and GTK3

Jan 15 2022

---

So you finish up your C/C++ backend, and open up the Electron.js

documentation to figure out how to make a quick frontend...

• *NO!!**

You'd better not *dare* write your desktop application in *HTML*.

• *What has this world come to???**


In this tutorial, I will show you how to write a proper GTK3

app, like a **civilized being**, instead of shipping your

"desktop app" as a website in a *web browser*.

Setting Up dev stuff

sudo apt install libgtk-3-dev

Yeah, that's it. Assuming you have a C compiler, you're golden.

Now that everything is set up, let's make a real small test file:

#include <gtk/gtk.h>

int main(int argc, char *argv[]) {
	gtk_init(&argc, &argv);

	GtkWidget *window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
	gtk_window_set_title(GTK_WINDOW(window), "Test Window");
	gtk_window_set_default_size(GTK_WINDOW(window), 300, 300);
	g_signal_connect(window, "delete-event", G_CALLBACK(gtk_main_quit), NULL);
	gtk_widget_show(window);
	
	GtkWidget *label = gtk_label_new("Hello World");
	gtk_widget_set_hexpand(label, TRUE);
	gtk_label_set_justify(GTK_LABEL(label), GTK_JUSTIFY_CENTER);
	gtk_container_add(GTK_CONTAINER(window), label);
	gtk_widget_show(label);
	
	gtk_main();
}

And to compile it:

gcc test.c \`pkg-config --libs gtk+-3.0 --cflags\`

Yay, you've made a *decent* application!

Of course, you aren't going to write your UI in C, only an

[idiot would do that](https://github.com/petabyt/mlinstall/blob/69ea49dbf5e9d9c4e2777729eafde21e7e4a9055/gtk.c#L383). Instead, you want to write it in

some kind of markup language. Lucky for us, GTK has just that.

<?xml version="1.0"?>
<interface>
  <object class="GtkApplicationWindow" id="window">
    <child>
      <object class="GtkLabel">
        <property name="label">This is a test</property>
      </object>
    </child>
  </object>
</interface>

And some loader code:

int main(int argc, char *argv[]) {
	gtk_init(&argc, &argv);

	GtkBuilder *builder = gtk_builder_new();
	gtk_builder_add_from_file(builder, "test.ui", NULL)

	GtkWidget *window = GTK_WIDGET(gtk_builder_get_object(builder, "window"));
	g_signal_connect(window, "delete-event", G_CALLBACK(gtk_main_quit), NULL);
	gtk_window_set_title(GTK_WINDOW(window), "Demo Window");
	gtk_window_set_default_size(GTK_WINDOW(window), 300, 100);

	gtk_widget_show_all(window);
	gtk_main();
	return 0;
}


When it comes to loading this binary in, you have a few options:

1. Load a UI file in with linker trickery

2. Convert the file to a C header with `xxd -i`, and load it in as a string

3. Just load the file in via path

I'm gonna go with xxd.

xxd -i test.ui > test.h

And some loader code:

#include <gtk/gtk.h>
#include "test.h"

static void function(GtkWidget *widget, gpointer data) {
	puts("Hello, World");
}

int main(int argc, char **argv) {
	gtk_init(&argc, &argv);

	GtkBuilder *builder = gtk_builder_new();
	gtk_builder_add_from_string(builder, test_ui, test_ui_len, NULL));

	GtkWidget *window = GTK_WIDGET(gtk_builder_get_object(builder, "window"));
	g_signal_connect(window, "delete-event", G_CALLBACK(gtk_main_quit), NULL);
	gtk_window_set_title(GTK_WINDOW(window), "Demo Window");
	gtk_window_set_default_size(GTK_WINDOW(window), 300, 300);

	GtkWidget *button = GTK_WIDGET(gtk_builder_get_object(builder, "btn"));
	g_signal_connect(button, "clicked", G_CALLBACK(function), NULL);

	gtk_widget_show_all(window);
	gtk_main();
	return 0;
}

The above code creates the same output as the first example.

And now, for my final trick: **Easy cross compilation for Windows.**

CC=x86_64-w64-mingw32
ZIP=win64-gtk-2021.zip

output: test.exe
	-rm -rf output; mkdir output
	cp win32/lib/* output/
	cp test.exe output/

test.exe: win32
	$(CC)-gcc main.c -Iwin32/include win32/lib/* -o test.exe

win32:
	wget -4 https://github.com/petabyt/windows-gtk/raw/master/$(ZIP)
	unzip *.zip
	rm -rf *.zip

No. That's not a joke. You literally just have to install MinGW

(`sudo apt install gcc-mingw-w64-x86-64`), and you can *actually* compile this.

Thanks to some archive scouring and msys2 ripping over at my [windows-gtk](https://github.com/petabyt/windows-gtk) repository,

I figured out how to make GTK cross compilation actually *not* a nightmare.

Here's a simple example you can use to try it out:

[https://code.theres.life/p/gtk-cross](https://code.theres.life/p/gtk-cross)

Good luck, and make sure to have the [GTK3 Docs](https://docs.gtk.org/gtk3/) handy at all times.