Engine

📖 Summary - 🌆 Screenshots - 🚀 Getting Started - 🛠️ Features - ⚠️ Known Issues - 💬 Contact

Summary

pix_engine is a cross-platform graphics & UI library for simple games, visualizations, digital art, and graphics applications written in Rust, drawing with wgpu and windowing with winit (and soon Web-Assembly!).

The primary goal of this library is to be simple to setup and use for graphics or algorithm exploration and is not meant to be as fully-featured as other, larger graphics libraries.

It is intended to be more than just a toy library, however, and can be used to drive real applications. The Tetanes NES emulator, for example uses pix_engine for rendering, window and event handling.

Some examples of things you can create with pix-engine:

• 2D ray casting of scenes or objects.
• 2D games like Asteroids, Tetris, Pong, or platformers including sound effects, music and UI elements.
• Simple 3D scenes or games.
• Audio playback and capture applications.
• User interfaces for basic applications or configuration.
• Algorithm visualizations for sorting, searching, or particle simulations.
• Image viewing and editing.
• Visual art.

Minimum Supported Rust Version (MSRV)

The current minimum Rust version is 1.67.0.

Screenshots

        

Getting Started

Installing Dependencies

First and foremost you'll need Rust installed! Follow the latest directions at https://www.rust-lang.org/learn/get-started.

Drawing goes through wgpu, which picks Vulkan, Metal, DirectX 12 or OpenGL depending on the platform, so no graphics libraries need installing by hand. Note for Windows: you may need to install Visual Studio C++ Build Tools.

On Linux, audio and gamepad support are built against system libraries:

Ubuntu:

sudo apt-get install libasound2-dev libudev-dev

Fedora:

sudo dnf install alsa-lib-devel systemd-devel

Arch:

sudo pacman -S alsa-lib systemd-libs

Creating Your Application

Creating a visual or interactive application using pix-engine requires implementing only a single method of the PixEngine trait for your application: PixEngine::on_update which gets executed as often as possible. Within that function you'll have access to a mutable PixState object which provides several methods for modifying settings and drawing to the screen.

PixEngine provides additional methods that can be implemented to respond to user events and handle application startup and teardown.

Here's an example application which simply draws a circle following the mouse and renders it white or black depending if the mouse is held down or not:

use pix_engine::prelude::*;

struct MyApp;

impl PixEngine for MyApp {
    // Set up application state and initial settings. `PixState` contains
    // engine specific state and utility methods for actions like getting mouse
    // coordinates, drawing shapes, etc. (Optional)
    fn on_start(&mut self, s: &mut PixState) -> PixResult<()> {
        // Set the background to GRAY and clear the screen.
        s.background(Color::GRAY);

        // Change the font family to NOTO and size to 16 instead of using the
        // defaults.
        s.font_family(Font::NOTO)?;
        s.font_size(16);

        // Returning `Err` instead of `Ok` would indicate initialization failed,
        // and that the application should terminate immediately.
        Ok(())
    }

    // Main update/render loop. Called as often as possible unless
    // `target_frame_rate` was set with a value. (Required)
    fn on_update(&mut self, s: &mut PixState) -> PixResult<()> {
        // Set fill color to black if mouse is pressed, otherwise wite.
        if s.mouse_pressed() {
            s.fill(color!(0));
        } else {
            s.fill(color!(255));
        }

        // Draw a circle with fill color at the mouse position with a radius of
        // 80.
        let m = s.mouse_pos();
        s.circle([m.x(), m.y(), 80])?;

        Ok(())
    }

    // Clean up any state or resources before exiting such as deleting temporary
    // files or saving game state. (Optional)
    fn on_stop(&mut self, s: &mut PixState) -> PixResult<()> {
        Ok(())
    }
}

fn main() -> PixResult<()> {
    let mut engine = Engine::builder()
      .dimensions(800, 600)
      .title("MyApp")
      .show_frame_rate()
      .resizable()
      .build()?;
    let mut app = MyApp;
    engine.run(&mut app)
}

Features

Crate Feature Flags

The following features can be enabled depending on your needs, e.g.:

cargo add pix-engine --features serde

• serde - Adds serde Serialize/Deserialize implementations for all enums/structs.

Errors capture a backtrace through anyhow when the environment variables described in std::backtrace are set, with no feature needed.

PixState

PixState is the global application context for the entire pix-engine lifecycle from setup to teardown. It contains all of the settings and methods required to draw pixels to the screen, manage windows, textures, rendering settings, etc. See Creating Your Application for a brief introduction to the engine lifecycle methods and examples of using PixState.

Drawing

All of the drawing primitives for drawing shapes, text, or UI widgets are all available on the PixState instance. Some methods are only available when the corresponding traits are in scope. Many traits are included by default in the prelude.

Some examples:

// Draw a circle at `(x, y)` coordinates`(0, 0)` with a radius of `80`.
s.circle([0, 0, 80])?;

// Draw a rectangle at `(x, y)` coordinates `(10, 20)` with a width `80` and a
// height of `100`.
s.rect([10, 20, 80, 100])?;

There are also several convenience macros for creating shapes that can be used for drawing, or storing inside a struct:

// Create a triangle with points at `(x, y)` coordinates `(10, 20)`, `(30, 10)`,
// `(20, 25)`.
let t = tri!([10, 20], [30, 10], [20, 25]);

// Create a 3D point at `(x, y, z)` coordinates `(10, 20, 10)`.
let p = point!(10, 20, 10);

// Create a square at point `p` with a width/height of `100`.
let r = square!(p, 100);

Textures

Textures are simple a representation of pixels but have some extra flexibility:

• They can be drawn to separately from the primary canvas being rendered.
• They can be transformed, clipped, or modified.
• They can be blended together and overlayed on each other.

By default, all drawing operations target the primary window canvas. Once drawn, the pixels are static and can only be drawn over. Using textures allows you to create things like draggable elements, popups, animation sprites, etc.

To create a texture:

// Create a texture with a width and height of 256, formatting as RGB with no
// alpha channel. You can also provide `None` as the format which will inherit
// the format of the current window.
let texture_id = s.create_texture(256, 256, PixelFormat::Rgb);

// Draw to the texture. These changes are not visible in the window.
s.set_texture_target(texture_id)?;
s.background(Color::BLACK);
s.text("Hello World!");
s.clear_texture_target();

// Now draw the texture to the current canvas. Specifying `None` as the `src`
// argument means use the entire texture size. The `dst` here is double the
// original texture which has the effect of scaling the texture by 2.
s.texture(texture_id, None, rect!(0, 0, 512, 512))?;

// To clean up unused textures, simply delete them.
s.delete_texture(texture_id)?;

Audio

A limited form of audio support is available, with wider support coming soon. By default, an audio queue is available that you can push samples to:

s.resume_audio(); // Audio queue starts in a `Paused` state.

// Some method generating `f32` samples between 0.0 and 1.0
let samples = generate_audio();
s.enqueue_audio(&samples);

There is also an AudioCallback trait you can implement for doing callback-based audio generation. See the examples/ folder for details. Using this callback you can also do limited audio recording and playback with a microphone.

UI

Overview

pix-engine offers an immediate mode graphical user interface (IMGUI) library which allows for rapid UI development that is performant and simple to setup/iterate on. Some limitations:

• Styling is limited to simple color themes and spacing.
• No animations or graphical effects.
• Limited layout constructs - more complicated layouts require carefully crafted code.
• Limited responsiveness for changes in viewport.

Much of the API design is inspired by Dear ImGui, but note the following differences:

• There are no window rendering utilities or features. Instead, separate native windows can be opened with UI elements rendered within. This approach simplifies window management by leveraging the native window features like minimize, maximize, resizing, etc.

End-User Guide

• Tab/Shift-Tab cycles focus through interactable elements.
• Enter/Return on an active element simulates clicking on it.
• Ctrl+Click (Cmd+Click on macOS) on a slider or drag box to edit the value as text.
  • Pressing Tab/Escape/Return exits editing mode.
• The mouse wheel can scroll elements that are out of view.
• Text Fields:
  • Ctrl+Backspace (Cmd+Backspace on macOS) to delete all content.
  • Alt+Backspace (Option+Backspace on macOS) to delete a single word.
  • Ctrl+X (Cmd+X on macOS) to cut contents to the system clipboard.
  • Ctrl+C (Cmd+C on macOS) to copy contents to the system clipboard.
  • Ctrl+V (Cmd+V on macOS) to paste contents from the system clipboard.

Programmer Notes

• See gui in the examples/ folder to get started.
• The UI is generated in code with UI method calls executed on the PixState instance in the PixState::on_update render loop which is called every frame.
• Elements are rendered in-order from top-left, to bottom-right.
• Unless explicitly changed, each element will position itself below the previous element. Calling PixState::same_line will shift position to the right of the previous element.

Windows

As your application grows, you may find the need to have different views open simultaneously. This can be done by opening up additional windows to render into. Each window has it's own canvas, while sharing the global PixState context settings. The API is very similar to working with textures.

// Create a window with size of 800x600.
let window_id = s
  .window()
  .dimensions(800, 600)
  .title("My Window")
  .position_centered()
  .build()?;

// Draw to the window. These changes are immediately visible in the window.
s.set_window_target(window_id)?;
s.background(Color::BLACK);
s.fill(Color::RED);
s.text("Hello World!");
s.reset_window_target();

// A user can either close the window with the `X` button, `Ctrl-W`, `Alt-F4`,
// etc. or you can close it programatically.
s.close_window(window_id)?;

Note: One thing to consider when creating and managing widnows is that when a window gets closed, its ID becomes invalid. Attempting to draw in an invalid window will return an error. Thus, most window creation will also require removing invalid window IDs from their application:

fn on_window_event(
    &mut self,
    _s: &mut PixState,
    window_id: WindowId,
    event: WindowEvent,
) -> PixResult<()> {
    if event == WindowEvent::Close && self.popup_window == Some(window_id) {
      self.popup_window = None;
    }
    Ok(())
}

Logging

This library uses the log crate. To leverage logging in your application, choose one of the supported logger implementations and initialize it in your main function.

Example using env_logger:

fn main() -> PixResult<()> {
    env_logger::init();

    let mut engine = Engine::builder()
      .dimensions(800, 600)
      .title("MyApp")
      .build()?;
    let mut app = MyApp;
    engine.run(&mut app)
}

Known Issues

See the github issue tracker.

License

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE)
• MIT license (LICENSE-MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

Contact

For issue reporting, please use the github issue tracker. You can also contact me directly at https://lukeworks.tech/contact/.

Credits

This has been a true passion project for several years and I can't thank the open source community enough for the all the amazing content and support.

A special shout out to the following projects which heavily inspired the implementation and evolution of this crate:

• OneLoneCoder and the olcPixelGameEngine.
• The Coding Train and p5js.
• Dear ImGui