# Render: Go Graphics Library Render is a graphics rendering library for Go. It supports SDL2 and HTML Canvas back-ends enabling its use for both desktop applications (Linux, Mac and Windows) and WebAssembly modules for running in the web browser. ![Screenshot](examples/hello-world/screenshot.png) **Notice:** [github.com/kirsle/render](https://github.com/kirsle/render) is a mirror to the upstream repository at [git.kirsle.net/go/render](https://git.kirsle.net/go/render). Issues and pull requests will be accepted at GitHub. ## Example ```go package main import ( "git.kirsle.net/go/render" "git.kirsle.net/go/render/sdl" ) func main() { mw := sdl.New("Hello World", 320, 240) if err := mw.Setup(); err != nil { panic(err) } // Text that we're gonna draw in the window. text := render.Text{ Text: "Hello, world!", Size: 24, Color: render.SkyBlue, Shadow: render.Blue, FontFilename: "DejaVuSans.ttf", } // Compute the rendered size of the text. rect, _ := mw.ComputeTextRect(text) for { // Blank the window. mw.Clear(render.White) // Poll for events (mouse clicks, keyboard keys, etc.) ev, err := mw.Poll() if err != nil { panic(err) } // Escape key closes the window. if ev.Escape { mw.Teardown() break } // Get the window size. w, h := mw.WindowSize() // Draw the text centered in the window. mw.DrawText(text, render.NewPoint( (int32(w)/2)-(rect.W/2), (int32(h)/2)-(rect.H/2), )) mw.Present() } } ``` See the `examples/` directory for examples. More will come eventually, including some WebAssembly examples. ## Project Status: Alpha This module was written as part of my drawing-based maze game, code named [Project: Doodle](https://www.kirsle.net/doodle). It is currently in **alpha status** and its API may change and be cleaned up in the future. There are a few API cleanup tasks on my to-do list for this project, but they will come later when I have a chance to update the Project: Doodle game accordingly: * I want to replace all `int32` types with normal `int` -- int32 was used initially due to SDL2 but for the Go API I want to abstract this away. ## Drawing Methods (Engine) This package provides some _basic_ primitive drawing methods which are implemented for SDL2 (desktops) and HTML Canvas (WebAssembly). See the render.Engine interface. The drawing methods supported are: * Clear(Color): blank the window and fill it with this color. * DrawPoint(Color, Point): draw a single pixel at a coordinate. * DrawLine(Color, A Point, B Point): draw a line between two points. * DrawRect(Color, Rect): draw a rectangle outline between two points. * DrawBox(Color, Rect): draw a filled rectangle between two points. * DrawText(Text, Point): draw text at a location. * StoreTexture(name string, image.Image): load a Go image.Image object into the engine as a "texture" that can be re-used and pasted on the canvas. * LoadTexture(filename string): load an image from disk into a texture. * Copy(Texturer, src Rect, dst Rect): copy a texture onto the canvas. ## Drawing Types This package defines a handful of types useful for drawing operations. See the godoc for full details. **Note:** all int32 values are to become normal ints at some point in the future, pending refactor in my Project: Doodle game. * Color: an RGBA color holding uint8 values for each channel. * NewRGBA(red, green, blue, alpha uint8) to construct a new color. * Point: holds an X,Y pair of coordinates (int32, to become int at some point) * Rect: holds an X,Y and a W,H value (int32). * Text: holds text and configuration for rendering (color, stroke, shadow, size, etc.) ## Shape Generator Functions The render package includes a few convenience functions for drawing complex shapes. The generator functions return a channel that yields all of the Points that should be drawn to complete the shape. Example: ```go var ( A Point = render.NewPoint(10, 10) B Point = render.NewPoint(15, 20) ) for pt := range render.IterLine(A, B) { engine.DrawPoint(render.Red, pt) } ``` * IterLine(A Point, B Point): draw a line from A to B. * IterRect(A Point, B Point): iterate all the points to draw a rectangle. * IterEllipse(A Point, B Point): draw an elipse fitting inside the rectangle bounded by points A and B. ## License MIT.