# Custom texture with pixel values filled programmatically
#
# At creation, the texture is composed of `width` by `height` (rounded down)
# transparent pixels. The pixels value can be set using `[]=`.
#
# ~~~
# # Build a texture with 4 colors
# var tex = new CustomTexture(2.0, 2.0)
# tex[0, 0] = [1.0, 0.0, 0.0] # Red
# tex[0, 1] = [0.0, 1.0, 0.0] # Green
# tex[1, 0] = [0.0, 0.0, 1.0] # Blue
# tex[1, 1] = [1.0, 1.0, 1.0, 0.5] # Transparent white
# tex.load
# ~~~
class CustomTexture
	super RootTexture

	redef var width
	redef var height

	private var cpixels = new CByteArray(4*width.to_i*height.to_i) is lazy

	# Set the `color` of the pixel at `x`, `y` (from the top-left corner)
	#
	# The argument `color` should be an array of up to 4 floats (RGBA).
	# If `color` has less than 4 items, the missing items are replaced by 1.0.
	#
	# Require: `x < width.to_i and y < height.to_i`
	fun []=(x, y: Int, color: Array[Float])
	do
		assert x < width.to_i and y < height.to_i else print_error "{class_name}::[] out of bounds"

		# Simple conversion from [0.0..1.0] to [0..255]
		var bytes = [for c in color do (c*255.0).round.to_i.clamp(0, 255).to_bytes.last]
		while bytes.length < 4 do bytes.add 255

		var offset = 4*(x + y*width.to_i)
		for i in [0..4[ do cpixels[offset+i] = bytes[i].to_b

		loaded = false
	end

	# Overwrite all pixels with `color`, return `self`
	#
	# The argument `color` should be an array of up to 4 floats (RGBA).
	# If `color` has less than 4 items, the missing items are replaced by 1.0.
	fun fill(color: Array[Float]): SELF
	do
		# Simple conversion from [0.0..1.0] to [0..255]
		var bytes = [for c in color do (c*255.0).round.to_i.clamp(0, 255).to_bytes.last]
		while bytes.length < 4 do bytes.add 255

		var i = 0
		for x in [0..width.to_i[ do
			for y in [0..height.to_i[ do
				for j in [0..4[ do cpixels[i+j] = bytes[j].to_b
				i += 4
			end
		end

		loaded = false
		return self
	end

	redef fun load(force)
	do
		force = force or else false
		if loaded and not force then return

		if force and glIsTexture(gl_texture) then
			# Was already loaded, free the previous GL name
			glDeleteTextures([gl_texture])
		end
		gl_texture = -1

		# Round down the desired dimension
		var width = width.to_i
		var height = height.to_i
		self.width = width.to_f
		self.height = height.to_f

		load_from_pixels(cpixels.native_array, width, height, gl_RGBA)

		loaded = true
	end
end