Graphics.UI.Font.Load

Motivation

The goal of this library is to provide a simple way of giving an application access to a font that isn't available system-wide allowing you to bundle fonts with your executable ensuring uniform look-and-feel across platforms. It has been tested on Windows 10, Arch Linux and OSX Sierra

Quick Start

While this package ships with a fully working demo the basic usage is lost in all of the GUI code. And frankly the demo takes a while to build and pulls in a GUI library dependency so it's not worth it unless you really want to convince yourself the library works. To get started with the minimum fuss thrill at the screenshot, take my word for it and do the following:

• Add your fonts to the Cabal file's data-files stanza (completely optional, you can load fonts from anywhere on the file system but highly recommended for portability):

data-files:
    fonts/*.ttf

• Add the load-font dependency:

  executable myAwesomeApp
  ...
    build-depends:
      ...
      , load-font
      ...
  ...

• Somewhere in your app code before you use the font :

 import Paths_myAwesomeApp
 ...
 myAwesomeFunction = do
   ...
   fontPath <- getDataFileName "fonts/my-awesome-font.ttf"
   loadFont fontPath
   ...

The API

loadFont :: FilePath -> IO (Either String ())

Make a font located at some FilePath available to your application. The font is automatically cleared from the font database with the process exits.

On Linux this uses FcConfigAppFontAddFile under the hood and so assumes X11/Xft are available. It should work fine on modern Linux systems but will break with old Xlib legacy fonts.

Currently the error case just returns a pretty uninformative message because underlying calls on Linux and Windows which are out of my control only return 0 or 1 in case of failure or success. Given this it would make more sense that the return type should be 'Maybe ()' but 'Either String ()' has two advantages 1. It makes errors easier to collect when batch loading 2. OSX has a much nicer error which I plan to expose in the future

unloadFont :: FilePath -> IO ()

Remove a private font located at FilePath from the application.

For the most part you shouldn't need this function because private fonts are automatically unloaded when the process exits but it's available in case you're doing something more exotic like switching between two versions of the same font.

On Windows and OSX this works as you would expect. But on Linux the only available function is FcConfigAppFontClear which ignores the FilePath and removes all private fonts. This adheres violently to the Principle Of Greatest Surprise and in the future I will transparently reload the other fonts but for now, caveat computer.