Go inheritance with Interface (Entity) + pixelgl

bounds.go

package main

// Bounds - A bounding (rectangle) box with a x,y origin and width and height
type Bounds struct {
	X      float64
	Y      float64
	Width  float64
	Height float64
	entity Entity
}

chunk.go

//-------------------------------------------------------------
// Part of the world. Handles its part of world pixels.
//=============================================================
package main

import (
	"github.com/faiface/pixel"
	"github.com/faiface/pixel/imdraw"
	_ "github.com/faiface/pixel/pixelgl"
)

//=============================================================
// Chunk Structure
// exmaple:
//         c := &chunk{}
//         c.create(float64(x), float64(y))
//=============================================================
type chunk struct {
	dirty  bool
	model  *imdraw.IMDraw
	bounds Bounds
}

//=============================================================
// Support the Entity interface
//=============================================================
func (c *chunk) hit(x, y float64) bool {
	return false
}

func (c *chunk) explode() {
}

func (c *chunk) getMass() float64 {
	return 1.0
}

func (c *chunk) getType() entityType {
	return entityChunk
}

func (c *chunk) draw(dt float64) {
	if c.dirty {
		c.build()
	}
	c.model.Draw(global.gWin)//global.gWin *pixelgl.Window
}

//=============================================================
// Create a new chunk
//=============================================================
func (c *chunk) create(x, y float64) {
	c.model = imdraw.New(nil)
	c.dirty = true
	c.bounds = Bounds{
		X:      x,
		Y:      y,
		Width:  wPixelsPerChunk,
		Height: wPixelsPerChunk,
		entity: Entity(c),
	}
}

//=============================================================
// Rebuild/Build the chunk.
//=============================================================
func (c *chunk) build() {
	model := imdraw.New(nil)
	for x := c.bounds.X; x < c.bounds.X+c.bounds.Width; x++ {
		for y := c.bounds.Y; y < c.bounds.Y+c.bounds.Height; y++ {
			p := global.gWorld.pixels[int(float64(global.gWorld.width)*x+y)]
			if p == 0 {
				continue
			}

			model.Color = pixel.RGB(
				float64(p>>24&0xFF)/255.0,
				float64(p>>16&0xFF)/255.0,
				float64(p>>8&0xFF)/255.0,
			).Mul(pixel.Alpha(float64(p&0xFF) / 255.0))

			model.Push(
				pixel.V(float64(x*wPixelSize), float64(y*wPixelSize)),
				pixel.V(float64(x*wPixelSize+wPixelSize), float64(y*wPixelSize+wPixelSize)),
			)
			model.Rectangle(0)
		}
	}
	c.model = model
	c.dirty = false
}

constants.go

package main

const (
	wPixelsPerChunk     = 64
	wPixelSize          = 1
)

interfaces.go

package main

type Entity interface {
	hit(x, y float64) bool
	explode()
	getMass() float64
	getType() entityType //iota
	draw(dt float64)
}