github.com/c-darwin/mobile@v0.0.0-20160313183840-ff625c46f7c9/exp/gl/glutil/glutil.go (about)

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