zntg/ui/loop.go

package ui

import (
	"time"

	"opslag.de/schobers/galleg/allegro5"
)

func shouldClose(ev allegro5.Event) bool {
	switch e := ev.(type) {
	case *allegro5.KeyCharEvent:
		switch e.KeyCode {
		case allegro5.KeyEscape:
			return true
		case allegro5.KeyF4:
			if e.Modifiers&allegro5.KeyModAlt == allegro5.KeyModAlt {
				return true
			}
		}
	case *allegro5.DisplayCloseEvent:
		return true
	}
	return false
}

func shouldToggleDebug(ev allegro5.Event) bool {
	switch e := ev.(type) {
	case *allegro5.KeyCharEvent:
		switch e.KeyCode {
		case allegro5.KeyD:
			return e.Modifiers&allegro5.KeyModAlt == allegro5.KeyModAlt
		}
	}
	return false
}

func switchState(ctx Context, curr State, s State) error {
	var err error
	err = curr.Leave(ctx)
	if nil != err {
		return err
	}
	return s.Enter(ctx)
}

func Init() error {
	return allegro5.Init(allegro5.InitAll)
}

func Run(w, h int, title string, s State, f Fonts, opts *allegro5.NewDisplayOptions) error {
	if nil == opts {
		opts = &allegro5.NewDisplayOptions{}
	}
	disp, err := allegro5.NewDisplay(w, h, *opts)
	if nil != err {
		return err
	}
	disp.SetWindowTitle(title)
	defer disp.Destroy()

	evq, err := allegro5.NewEventQueue()
	if nil != err {
		return err
	}
	evq.RegisterDisplay(disp)
	evq.RegisterKeyboard()
	evq.RegisterMouse()
	defer evq.Destroy()

	ctx := newContext(disp, f)

	var state = s
	err = state.Enter(ctx)
	if nil != err {
		return err
	}

	var t = time.Now()
main:
	for nil != state {
		for ev := evq.Get(); ev != nil; ev = evq.Get() {
			if shouldClose(ev) {
				break main
			}
			if shouldToggleDebug(ev) {
				ctx.dbg.enbl = !ctx.dbg.enbl
			}
			err := state.Handle(ctx, ev)
			if nil != err {
				return err
			}
		}
		var now = time.Now()
		var dt = now.Sub(t)
		var s, err = state.Update(ctx, dt)
		if nil != err {
			return err
		}
		t = now
		if s != nil {
			err = switchState(ctx, state, s)
			if nil != err {
				return err
			}
			state = s
		}
		ctx.dbg.resetRainbow()
		err = state.Render(ctx)
		if nil != err {
			return err
		}
		disp.Flip()
		time.Sleep(10 * time.Millisecond)
	}
	err = state.Leave(ctx)
	if nil != err {
		return err
	}

	return nil
}