ferusgfx is a rendering engine made for the Ferus web engine, made with the concept of "display lists" in mind.
It uses OpenGL as its primary backend, but there are plans to add Vulkan support later on.

ferusgfx can be installed directly from Nimble. It requires a recent Nim version (>=2.0).

# nimble install ferusgfx

ferusgfx's main object is a Scene. It essentially acts as the rendering context and contains a tree full of Drawable objects (or types descending from Drawable).

The tree is not meant to be edited manually, rather, you should use DisplayList(s) to manipulate the scene tree and perform actions like adding drawables, removing them, etc.

And as expected, Drawables are not redrawn each frame unless they are marked as needing a redraw (or you call fullDamage on the scene).

ferusgfx is primarily meant for applications that show a lot of text and images. It can be used for a plethora of things, ranging from a PDF reader, an image viewer, a web engine (duh) and other things. Here is what it currently does.

• Render stuff for you, providing a neat little API that ensures you don't need to have a headache fighting with lower level APIs (it itself is an abstraction over boxy).
• Provide a camera with smooth scrolling support.

• Fetch fonts from the system instead of making the programmer manually specify them.
• Vulkan rendering (not coming soon!)

A more fleshed out example can be seen in tests/example_compositor.nim.
windy is used here but ferusgfx is window-library-agnostic so anything can be used here. The example compositor has support for both GLFW and Windy that can be enabled/disabled via -d:compositorUseWindy.

import ferusgfx, windy, opengl

const
  WIDTH = 1280
  HEIGHT = 720

# create our window
let window = newWindow("ferusgfx barebones compositor", ivec2(WIDTH, HEIGHT))
window.makeContextCurrent()

# load OpenGL
loadExtensions()

var scene = newScene(WIDTH, HEIGHT)

# hooking up windy events to ferusgfx's internal ones
window.onResize = proc() =
  scene.onResize((w: window.size.x.int, h: window.size.y.int))

window.onScroll = proc() =
  # ferusgfx sends this info to the camera, which applies some math to scroll the view
  # each frame a little bit, making it pretty smooth. It also uses it for some rudimentary culling logic.
  scene.onScroll(
    vec2(window.scrollDelta.x, window.scrollDelta.y)
  )

scene.fontManager.load("Default", "/path/to/your/font.font_extension")

var displayList = newDisplayList(addr scene) # pass a pointer to the scene
displayList.add(
  newTextNode(
    "This is a very barebones example of what ferusgfx can do.",
    vec2(100f, 300f),
    scene.fontManager
  )
)

displayList.add(
  newImageNode(
    "/path/to/your/image.image_extension",
    vec2(100f, 800f)
  )
)

displayList.commit() # commit our changes, the scene tree will be mutated by the display list accordingly.

while not window.closeRequested:
  # tell the scene to draw itself
  scene.draw()
  
  # windy stuff
  window.swapBuffers()
  pollEvents()