spinning-square.go

package main

import (
    "github.com/dradtke/allegory"
    "github.com/dradtke/allegory/config"
    "github.com/dradtke/go-allegro/allegro"
    "math"
)

var (
    FULL_ROTATION = float32(2 * math.Pi)
)

type SpinningState struct {
    allegory.BaseState
    Square *allegro.Bitmap
    Angle  float32
}

func (s *SpinningState) InitState() {
    s.Square = allegro.CreateBitmap(100, 100).AsTarget(func() {
        allegro.ClearToColor(allegro.MapRGB(255, 0, 0))
    })
}

func (s *SpinningState) UpdateState() {
    s.Angle += (FULL_ROTATION / 240) // at 60fps, this takes about 4 seconds to do a full rotation
    for s.Angle > FULL_ROTATION {
        s.Angle -= FULL_ROTATION
    }
}

func (s *SpinningState) RenderState(delta float32) {
    dw, dh := config.DisplaySize()
    s.Square.DrawRotated(50, 50, float32(dw/2), float32(dh/2), s.Angle, allegro.FLIP_NONE)
}

func main() {
    allegory.Init(new(SpinningState))
    defer allegory.Cleanup()
    allegory.Loop()
}