You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: texture.go
    path of file: ./repos/gdlv/vendor/golang.org/x/exp/shiny/driver/gldriver
    
    the code of the file until where you have to start completion: // Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package gldriver

import (
	"encoding/binary"
	"image"
	"image/color"
	"image/draw"

	"golang.org/x/exp/shiny/screen"
	"golang.org/x/mobile/gl"
)

type textureImpl struct {
	w    *windowImpl
	id   gl.Texture
	fb   gl.Framebuffer
	size image.Point
}

func (t *textureImpl) Size() image.Point       { retur
    
func (t *textureImpl) Fill(dr image.Rectangle, src color.Color, op draw.Op) {
	minX := float64(dr.Min.X)
	minY := float64(dr.Min.Y)
	maxX := float64(dr.Max.X)
	maxY := float64(dr.Max.Y)
	mvp := calcMVP(
		t.size.X, t.size.Y,
		minX, minY,
		maxX, minY,
		minX, maxY,
	)

	glctx := t.w.glctx

	t.w.glctxMu.Lock()
	defer t.w.glctxMu.Unlock()

	create := t.fb.Value == 0
	if create {
		t.fb = glctx.CreateFramebuffer()
	}
	glctx.BindFramebuffer(gl.FRAMEBUFFER, t.fb)
	if create {
		glctx.FramebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, t.id, 0)
	}

	glctx.Viewport(0, 0, t.size.X, t.size.Y)
	doFill(t.w.s, t.w.glctx, mvp, src, op)

	// We can't restore the GL state (i.e. bind the back buffer, also known as
	// gl.Framebuffer{Value: 0}) right away, since we don't necessarily know
	// the right viewport size yet. It is valid to call textureImpl.Fill before
	// we've gotten our first size.Event. We bind it lazily instead.
	t.w.backBufferBound = false
}