Compile fails, shows up with file not found error

[RichCat6]

I tried compiling this from the source code, but I can't compile it because whenever I try to run the make command, I get this error:
g++ -I"/home/cadendurden/smooth/classes/backends/xlib"/../../../include -fvisibility=hidden -fPIC -pthread -DSMOOTH_DLL -c backendxlib.cpp -o backendxlib.o
backendxlib.cpp:11:10: fatal error: gtk/gtk.h: No such file or directory
11 | #include <gtk/gtk.h>
| ^~~~~~~~~~~

System Specs If Needed:
System Name: Dell Latitude D630
RAM: 2GB DDR2
WiFi Card: Broadcom BCM4311
Operating System: Debian Sid (Originally Debian 12 Bookworm)

[enzo1982]

You will need to install GTK 3 development packages in order to build smooth.

Additionally, you will need the following development packages:

• libbz2
• libcurl
• libfribidi
• libjpeg
• libxml2

There are some other dependencies, but those should already be included as dependencies of GTK 3.