1// Copyright 2014 The Go Authors. All rights reserved.
2// Use of this source code is governed by a BSD-style
3// license that can be found in the LICENSE file.
4
5//go:build darwin || linux || windows
6// +build darwin linux windows
7
8package glutil // import "golang.org/x/mobile/exp/gl/glutil"
9
10import (
11	"fmt"
12
13	"golang.org/x/mobile/exp/f32"
14	"golang.org/x/mobile/gl"
15)
16
17// CreateProgram creates, compiles, and links a gl.Program.
18func CreateProgram(glctx gl.Context, vertexSrc, fragmentSrc string) (gl.Program, error) {
19	program := glctx.CreateProgram()
20	if program.Value == 0 {
21		return gl.Program{}, fmt.Errorf("glutil: no programs available")
22	}
23
24	vertexShader, err := loadShader(glctx, gl.VERTEX_SHADER, vertexSrc)
25	if err != nil {
26		return gl.Program{}, err
27	}
28	fragmentShader, err := loadShader(glctx, gl.FRAGMENT_SHADER, fragmentSrc)
29	if err != nil {
30		glctx.DeleteShader(vertexShader)
31		return gl.Program{}, err
32	}
33
34	glctx.AttachShader(program, vertexShader)
35	glctx.AttachShader(program, fragmentShader)
36	glctx.LinkProgram(program)
37
38	// Flag shaders for deletion when program is unlinked.
39	glctx.DeleteShader(vertexShader)
40	glctx.DeleteShader(fragmentShader)
41
42	if glctx.GetProgrami(program, gl.LINK_STATUS) == 0 {
43		defer glctx.DeleteProgram(program)
44		return gl.Program{}, fmt.Errorf("glutil: %s", glctx.GetProgramInfoLog(program))
45	}
46	return program, nil
47}
48
49func loadShader(glctx gl.Context, shaderType gl.Enum, src string) (gl.Shader, error) {
50	shader := glctx.CreateShader(shaderType)
51	if shader.Value == 0 {
52		return gl.Shader{}, fmt.Errorf("glutil: could not create shader (type %v)", shaderType)
53	}
54	glctx.ShaderSource(shader, src)
55	glctx.CompileShader(shader)
56	if glctx.GetShaderi(shader, gl.COMPILE_STATUS) == 0 {
57		defer glctx.DeleteShader(shader)
58		return gl.Shader{}, fmt.Errorf("shader compile: %s", glctx.GetShaderInfoLog(shader))
59	}
60	return shader, nil
61}
62
63// writeAffine writes the contents of an Affine to a 3x3 matrix GL uniform.
64func writeAffine(glctx gl.Context, u gl.Uniform, a *f32.Affine) {
65	var m [9]float32
66	m[0*3+0] = a[0][0]
67	m[0*3+1] = a[1][0]
68	m[0*3+2] = 0
69	m[1*3+0] = a[0][1]
70	m[1*3+1] = a[1][1]
71	m[1*3+2] = 0
72	m[2*3+0] = a[0][2]
73	m[2*3+1] = a[1][2]
74	m[2*3+2] = 1
75	glctx.UniformMatrix3fv(u, m[:])
76}
77