An FLTK Window
This tutorial will show you how to open an FLTK window. We will
build on the project from the previous tutorial so please complete it
first if you haven't already.
Before we start, please first download a proper FLTK library according to the
vesion of VS you use (fltk-lib-2008, fltk-lib-2010,
fltk-lib-2012, fltk-lib-2017 ).
If you are using VS 2017 in a Windows 10 machine, download
Lets get started.
- Add a Window Class
- Modify Main
- Add Include and Library Paths
- Project Settings
- Build and Run the Program
Step 1: Add a Window Class
We need to add a class to project which will control our FLTK
window. We begin by adding two new files to the project. We
want to add a new source file or C++
File (.cpp) in VS called
MyWindow.cpp and a new header
file or Header File(.h) in
MyWindow.h. These files
can be added just like main.cpp was in
the previous tutorial.
We now need to add the code for this class. First the header file
class MyWindow : public Fl_Window
MyWindow(int width, int height, const char*
Lets look at this for a second. It defines a class called
MyWindow which is derived from
the FLTK base window class
Fl_Window. The file Fl_Window.h was included to get the
definition of this class. Notice how the Fl directory is
prepended to this file. All FLTK files should be prepended with
Fl when they are included. Our window class has only a
constructor (which takes three arguments) and a destructor. The
underlying FLTK window class is going to do all the rest for us.
The code for the source file MyWindow.cpp
contains the implementations
of the constructor and destructor.
MyWindow::MyWindow(int width, int height, const char* title) : Fl_Window(width, height, title)
The constructor just passes its arguments to the constructor of the
base class, the FLTK class Fl_window.
The destructor doesn't do
anything yet but we'll need it later so we might as well make it now.
Step 2: Modify Main
Now that we have a window class we need to modify our main function to
make use of it. Here's the updated contents of main.cpp.
int main(int argc, char** args)
MyWindow myWindow(400, 400, "CS447 Tutorial");
This new version of main creates an instance of our window class
with a size of 400x400 pixels and a title of "CS447 Tutorial".
FLTK windows are not visible until they are shown. This allows
you to create a window, set various attributes and then display the
window. If it was visible initially the user might see the
attributes of the window changing as you initialized them. So to
make our window visible we call its show()
method. This is one of the many method MyWindow inherited from the base
Now we tell our window to show itself we have only one step
remaining. We must tell the FLTK system to start processing
events. FLTK is an event driven system, meaning it responds to
user inputs. FLTK will not do anything until we tell it to start
the event processing loop. We do this my calling Fl::run() which was included from
the file Fl.h.
Step 3: Add Include and Library Paths
We've now got all the code we need and we almost ready to build our
project but first we must tell VS where to find the FLTK files that
we are using. We must tell it where to find the header files
that we've included in our project, such as Fl.h. It also need to know
where to find the FLTK library that we've built for you.
Choose Project -> Properties
from the VS menus and you should get the dialog to the
right. In the left hand pane go to Configuration Properties -> C/C++ ->General,
then choose Additional Include Directories.
Suppose you've placed a copy of all FLTK in E:\code\fltk.
So select this folder as shown in the dialog.
We now need to tell VS where to find the pre-built fltk
libraries. Similarly, choose Project -> Properties from the VS menus and you should get the dialog to the
right. In the left hand pane go to Configuration Properties -> Linker ->General,
then choose Additional Libary Directories.
Input E:\code\fltk\lib, supposing you placed a copy of FLTK there.
Step 4: Project Settings
Now that VS knows where to find the FLTK library we need to tell it
which libraries we're interested in.
Similarly, choose Project -> Properties from the VS menus and you should get the dialog to the
right. In the left hand pane go to Configuration Properties -> Linker ->Input,
then choose Additional Dependencies.
Input fltkdlld.lib, which is the FLTK debug dll library file that this project uses.
We now show the setting for the FLTK library. The FLTK library uses a
version of the C runtime from a dll (dynamically linked library). We need to make sure our project's settings match FLTK.
Go to the Project Property page in the same way as Step 3, and choose C/C++ -> Code Generation from the left hand pane and set the Runtime
Library to Multi-threaded
Debug DLL (/MDd).
VS needs to know where to find the FLTK dll files.
Go to the Project Property page in the same way as Step 3, and choose Debugging
from the left hand pane. Suppose you placed a copy of FLTK at E:\Course\fltk. So set the Working Directory as E:\Course\fltk\lib which contains the FLTK dll files.
Step 5: Build and Run the Program
We build our program just like before. Choose Build -> Build Solution.
Your project should build with no errors (you can safely ignore the
warnings). If you have some errors see where they are and find
the difference between your code and the code supplied with this
tutorial. Fix the errors and try again.
One its built you can run it via Debug
-> Start Without Debugging. You should get a gray
window like this one. What's that? All this for a gray
window? Don't worry we'll actually start doing something with our
window in the next tutorial.
Source code for this tutorial.
Go to the programming tutorials page.