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cairo-xlib

cairo-xlib provides Scala Native bindings for the Cairo X Window System 2D graphics rendering support using XLib.

Overview

The goal of this project is to provide an easy-to-use Scala Native bindings for the Cairo 2D graphics library XLib Surfaces support. Currently, the great majority of XLib related Cairo functions are supported. Also, the cairo_xlib.XlibSurface class extends libcairo.Surface so that this library is perfectly interoperable with libcairo. By using this library as a dependency, you also get Scala Native bindings for XLib. The XLib bindings are not complete, but work is ongoing.

The more "programmer friendly" part of this library is found in the io.github.edadma.cairo_xlib package. That's the only package you need to import from, as seen in the example below. The other package in the library is io.github.edadma.cairo_xlib.extern which provides for interaction with the libcairo and xlib C libraries using Scala Native interoperability elements from the so-call unsafe namespace. There are no public declarations in the io.github.edadma.cairo_xlib package that use unsafe types in their parameter or return types, making it a pure Scala bindings library. Consequently, you never have to worry about memory allocation or type conversions.

Usage

To use this library, libcairo2 (and libx11) needs to be installed:

sudo apt install libcairo2

Include the following in your project/plugins.sbt:

addSbtPlugin("com.codecommit" % "sbt-github-packages" % "0.5.2")

Include the following in your build.sbt:

resolvers += Resolver.githubPackages("edadma")

libraryDependencies += "io.github.edadma" %%% "cairo-xlib" % "0.1.0"

Use the following import statements in your code:

import io.github.edadma.cairo_xlib._
import io.github.edadma.libcairo._
import io.github.edadma.xlib._

Example

This example creates a Window with a simple drawing in it. However, this example also prints all keyboard, mouse and window redraw events, showing how to check for and interpret various X11 events.

import io.github.edadma.cairo_xlib._
import io.github.edadma.libcairo._
import io.github.edadma.xlib._

object Main extends App {

  val sfc = createX11Surface(500, 500)

  eventLoop(sfc)
  destroyX11Surface(sfc)

  def createX11Surface(width: Int, height: Int): XlibSurface = {
    val dsp: Display = openDisplay(null)

    if (dsp.isNull) {
      Console.err.println("can't open display")
      sys.exit(1)
    }

    val screen = dsp.defaultScreen
    val da     = dsp.createSimpleWindow(dsp.defaultRootWindow, 0, 0, width, height, 0, 0, 0)

    dsp.selectInput(
      da,
      ButtonPressMask | ButtonReleaseMask | ButtonMotionMask | PointerMotionMask | KeyPressMask | KeyReleaseMask | ExposureMask)
    dsp.mapWindow(da)

    val sfc = surfaceCreate(dsp, da, dsp.defaultVisual(screen), width, height)

    sfc.setSize(width, height)
    sfc
  }

  def eventLoop(sfc: XlibSurface): Unit = {
    val event = new Event

    while (sfc.getDisplay.nextEvent(event) == Success) {
      event.getType match {
        case `ButtonPress` =>
          println(s"button press: ${event.button.button}, ${event.button.x}, ${event.button.y}, ${event.button.time}")
        case `ButtonRelease` => println(s"button release: ${event.button.button}")
        case `MotionNotify`  => println(s"motion: ${event.motion.state}, ${event.motion.x}, ${event.motion.y}")
        case `KeyPress` =>
          val (keystr, keysym) = event.key.lookupString
          val keysymstr        = keysymToString(keysym)

          println(s"key press: $keystr, $keysym, $keysymstr")

          if (keysym == XK_Return) {
            event.destroy()
            return
          }
        case `KeyRelease` =>
          val (keystr, keysym) = event.key.lookupString
          val keysymstr        = keysymToString(keysym)

          println(s"key release: $keystr, $keysym, $keysymstr")
        case `Expose` =>
          println("redraw")
          drawX11Surface(sfc)
        case e => println(e)
      }
    }

    event.destroy()
  }

  def drawX11Surface(sfc: Surface): Unit = {
    val ctx = sfc.create

    ctx.setSourceRGB(.5, .5, .5)
    ctx.paint()
    ctx.moveTo(20, 20)
    ctx.lineTo(200, 400)
    ctx.lineTo(450, 100)
    ctx.lineTo(20, 20)
    ctx.setSourceRGB(0, 1, 0)
    ctx.fill()
    ctx.destroy()
  }

  def destroyX11Surface(sfc: XlibSurface): Unit = {
    val dsp: Display = openDisplay(null)

    sfc.destroy()
    dsp.closeDisplay
  }

}

Documentation

API documentation is forthcoming, however documentation for Cairo XLib Surfaces is found here, and for the current release of XLib here.

License

ISC