30 Module Documentation. 31 Class Documentation code itself, special comments in the code, and additional documentation files. 2 – FLTK Basics. This chapter teaches you the basics of compiling programs that use FLTK. Writing Your First FLTK Program. All programs must include the file. class Fl. Class Hierarchy. Fl. Include Files. #include. Description. The Fl class is the FLTK global (static) class containing state information and global.
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This library aims to make it easy for users to build native apps that work portably across platforms. I’m also very interested in the user interface renaissance in the programming community, whether the various kinds of functional reactive programming, meta-object protocol UIs, or something like React.
The hope is that a low-cost, hassle-free way of getting a UI up and running without having to deal with browser, authentication, and compilation issues will make it more fun to play around with these great ideas using Haskell. Even in this era of web interfaces, it is still useful to be able to make native apps.
They are usually faster and have fewer security issues. These are all great projects and produce really nice UIs, but they all fail at least one of criterion listed under the Goals section below. To my knowledge, as of the last quarter ofno other package in the Haskell ecosystem meets all those constraints.
fltk(3) – Linux man page
The documentation for this package still applies because the theme mostly just re-draws widgets to look a little nicer so the fundamentals of the API are not touched. This section attempts to briefly highlight some possible dealbreakers users might want to know about before proceeding. To be clear, building and deploying portable static application binaries works well on all platforms which is why documentatioon library is considered usable. And most of these issues are being aggressively addressed but in the interests of full disclosure The good news is that this is a known issue.
The bundled way is by far the easiest on all platforms. It is completely self-contained, you don’t documentatiob any sudo access to your system. The reason is that it’s been quite a while the FLTK documentaiton cut an official release but the development branch is actually quite stable and has acquired a lot of useful features including Docmuentation and SVG support which are exposed via these bindings.
Since we are temporarily using stable releases please don’t install FLTK with your package manager. Pick the Stack installer that matches your distribution and install according to the instructions.
If git is not installed, download the latest version of the fltkhs-hello-world application skeleton from here. You will be greeted by an incredibly boring little window with a button that says “Hello world”. If you click it, it will change to “Goodbye world”.
You will be greeted by an incredibly boring little window with a button that says “Hello world”, if you click it, it will change to “Goodbye world. Downloading and following the default instructions for the standard Windows installer should be enough. If the install succeeded stack should on the PATH.
fltk(3): fast light tool kit – Linux man page
To test run ‘cmd. It is a far superior environment to the command prompt. To open the MSYS2 shell do:. Please see the Demos section of this document for examples of apps that show off more complex uses of the API. While the ‘fltkhs-hello-world’ application is mostly stand-alone the MSYS2 environment bundled with stack seems to require 3 runtime DLLs. The DLLs are bundled with stack so it’s easy to zip them up with the executable and deploy.
The required DLLs are: Copy over the DLLs. They are usually located in ‘. Any Windows 10 user should now be able to extract ‘fltkhs-hello-world. Pick the Stack installer that matches your distribution and install according the instructions. Please make sure to only download version FLTK 1. It should build and install smoothly with the standard:. If you didn’t install FLTK from source, you can use the ‘fltk-config’ tool to ensure that version 1.
You will also need the makeautoconfand autoheader tools to build the Haskell bindings. The reason we install from source is that some package managers seem to be behind on versions as of this writing Ubuntu Some package managers put the libraries and headers in nonstandard places, so it is best to build from source. If you click it, it will change to “Goodbye world. The brew package for the current stable release of FLTK is broken. Fortunately installing from source is pretty quick and painless.
While the ‘fltkhs-hello-world’ application can mostly stand alone, the MSYS2 environment bundled with stack seems to require 3 runtime DLLs. The DLLs are bundled with stackso you can zip them up with the executable and deploy.
They are split into two sets: The READMEs in the repos have installation instructions, but they assume that you have successfully installed FLTK and the ‘fltkhs-hello-world’ app see platform specific instructions above. By this point, I assume that you have successfully installed hello world see above or one of the demo packages.
Though it is a simple app, it shows the basics of widget creation and callbacks. Other demo packages show more complicated usage of the API.
Since the API is a low-level binding, code using it takes on the imperative style of the underlying toolkit. Fortunately, it should look pretty familiar to those who have used object-oriented GUI toolkits before. This package also comes with a utility fltkhs-fluidtohs that takes a user interface generated using the Fluid GUI builder that ships with FLTK and generates Haskell code.
Now the user can drag and drop widgets into place instead of having to calculate coordinates and sizes by hand. Additionally, arbitrary Haskell code can be inserted into Fluid interfaces, allowing the user to do most of the callback wiring directly from Fluid. The recently minted ‘CallStack’ implicit parameter is used to get a trace of the function that made the offending call along with a file name and line number. For example, in the following code:. The resulting stack trace will look something like:.
Notice, however, that the trace stops there. It does not tell you getLabel was invoked from buttonCb. For a more detailed trace, the CallStack implicit parameter needs to be passed to each function in the chain like:.
This approach makes Haddock very unhappy and the generated documentation is frequently unhelpful. For instance, I urge newcomers to this library not to look at Graphics. The purpose of this guide is to point you in a more useful direction. Each widget has its own module, all of which are listed below under the Widgets heading. The Haskell functions that bind to the instance methods of an FLTK class are listed under the Functions heading in that widget’s module. It’s worth remembering that these type signatures associated with the functions listed under the Functions heading are not the real ones but are artifically generated because they are much more helpful to users.
For instance, the actual type of activate exposes all the type level arithmetic required so it can be used by subclasses of Widget but is unhelpful as a reference compared to the artificial type under Functions heading of Graphics.
Unfortunately to see this more helpful type signature the poor reader has to navigate to the corresponding widget’s module, find the Functions header and scroll down to the desired function.
Haddock, unfortunately, does not support anchors that link to a named point in the page. I’m very open to ideas on how to make this easier.
Carrying on the previous example from the Widget Creation section, the methods on a Ref Window widget are documented in Graphics. Each function takes the Ref Window reference as its first argument followed by whatever else it needs and delegates it appropriately.
It is hoped that until the documentation becomes more self-sustaining the user can use these heuristics and the type signatures along with the official FLTK documentation to “guess” what the binding functions do.
Documentation – Fast Light Toolkit (FLTK)
Every widget module in the API has a Hierarchy heading that shows all its parents. The design of the API makes all the parent functions transparently available to that widget. This is also the reason why the actual type signatures are so complicated requiring the manual generation of artificial type signatures.
For instance, the Functions section under Graphics. Window shows that a Ref Window can be passed to getModal to check if the window is modal, but it can also be passed to children in Graphics. Group which counts up the number of widgets inside the Window and getX in Graphics. Widget which returns the X coordinate of the Window’ s flltk hand corner.
This means that the Haskell user has complete control of the look and feel as well as the event loop. The sky is the limit! Unlike callbacks, they can be set only on object instantiation. An example of this is Documnetation. Widget which, since it is a base class for most widgets and doesn’t have much functionality of its own, only allows custom construction using widgetCustom.
This constructor takes a CustomWidgetFuncs datatype which is a record of functions which tells a Graphics. Widget how to handle events and draw, resize and display itself.
Window can be used a motivating example. Its custom constructor windowCustomin fact, takes two records: Widget parent class, and also a CustomWindowFuncs documnetation which allows you to override flusha method on the Window class which doxumentation the window how to force a redraw.
Every widget that supports customizing also provides a default function record that can be passed to the constructor. Widget provides defaultCustomWidgetFuncs and Graphics. In the demo mentioned above, the singleWindowCustom documenation is given defaultCustomWidgetFuncs but with an overridden drawCustom.
Another case where customization comes up a lot is when using Graphics. Table which is a low-level table widget that needs doxumentation be told, for example, how to draw its cells. Hopefully the demos just mentioned and others included with this library show that, even though customizing is limited, it is possible to do a lot. For instance, you can provide a custom implementation of handle on Graphics. This comes in handy when the custom function is just setting up variables or logging and you want the underlying implementation to take over at some point.