Temporary repo, the lib/render package from Doodle showing SDL2 and HTML Canvas implementations.
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3 years ago
package canvas
import (
// Engine implements a rendering engine targeting an HTML canvas for
// WebAssembly targets.
type Engine struct {
canvas Canvas
startTime time.Time
width int
height int
ticks uint32
// Private fields.
events *events.State
running bool
textures map[string]*Texture // cached texture PNG images
// Event channel. WASM subscribes to events asynchronously using the
// JavaScript APIs, whereas SDL2 polls the event queue which orders them
// all up for processing. This channel will order and queue the events.
queue chan Event
// New creates the Canvas Engine.
func New(canvasID string) (*Engine, error) {
canvas := GetCanvas(canvasID)
engine := &Engine{
canvas: canvas,
startTime: time.Now(),
events: events.New(),
width: canvas.ClientW(),
height: canvas.ClientH(),
queue: make(chan Event, 1024),
textures: map[string]*Texture{},
return engine, nil
// WindowSize returns the size of the canvas window.
func (e *Engine) WindowSize() (w, h int) {
// Good time to recompute it first?
var (
window = js.Global().Get("window")
width = window.Get("innerWidth").Int()
height = window.Get("innerHeight").Int()
e.canvas.Value.Set("width", width)
e.canvas.Value.Set("height", height)
return e.canvas.ClientW(), e.canvas.ClientH()
// GetTicks returns the number of milliseconds since the engine started.
func (e *Engine) GetTicks() uint32 {
ms := time.Since(e.startTime) * time.Millisecond
return uint32(ms)
func (e *Engine) Setup() error {
return nil
func (e *Engine) Present() error {
return nil
// Delay for a moment.
func (e *Engine) Delay(delay uint32) {
time.Sleep(time.Duration(delay) * time.Millisecond)
// Teardown tasks.
func (e *Engine) Teardown() {}
func (e *Engine) Loop() error {
return nil