Adding upstream version 0.0~git20250520.a1d9079+dfsg.

Signed-off-by: Daniel Baumann <daniel@debian.org>

exp/gl/glutil/glutil.go

@@ -0,0 +1,75 @@
+// Copyright 2014 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.
+
+//go:build darwin || linux || windows
+
+package glutil
+
+import (
+	"fmt"
+
+	"golang.org/x/mobile/exp/f32"
+	"golang.org/x/mobile/gl"
+)
+
+// CreateProgram creates, compiles, and links a gl.Program.
+func CreateProgram(glctx gl.Context, vertexSrc, fragmentSrc string) (gl.Program, error) {
+	program := glctx.CreateProgram()
+	if program.Value == 0 {
+		return gl.Program{}, fmt.Errorf("glutil: no programs available")
+	}
+
+	vertexShader, err := loadShader(glctx, gl.VERTEX_SHADER, vertexSrc)
+	if err != nil {
+		return gl.Program{}, err
+	}
+	fragmentShader, err := loadShader(glctx, gl.FRAGMENT_SHADER, fragmentSrc)
+	if err != nil {
+		glctx.DeleteShader(vertexShader)
+		return gl.Program{}, err
+	}
+
+	glctx.AttachShader(program, vertexShader)
+	glctx.AttachShader(program, fragmentShader)
+	glctx.LinkProgram(program)
+
+	// Flag shaders for deletion when program is unlinked.
+	glctx.DeleteShader(vertexShader)
+	glctx.DeleteShader(fragmentShader)
+
+	if glctx.GetProgrami(program, gl.LINK_STATUS) == 0 {
+		defer glctx.DeleteProgram(program)
+		return gl.Program{}, fmt.Errorf("glutil: %s", glctx.GetProgramInfoLog(program))
+	}
+	return program, nil
+}
+
+func loadShader(glctx gl.Context, shaderType gl.Enum, src string) (gl.Shader, error) {
+	shader := glctx.CreateShader(shaderType)
+	if shader.Value == 0 {
+		return gl.Shader{}, fmt.Errorf("glutil: could not create shader (type %v)", shaderType)
+	}
+	glctx.ShaderSource(shader, src)
+	glctx.CompileShader(shader)
+	if glctx.GetShaderi(shader, gl.COMPILE_STATUS) == 0 {
+		defer glctx.DeleteShader(shader)
+		return gl.Shader{}, fmt.Errorf("shader compile: %s", glctx.GetShaderInfoLog(shader))
+	}
+	return shader, nil
+}
+
+// writeAffine writes the contents of an Affine to a 3x3 matrix GL uniform.
+func writeAffine(glctx gl.Context, u gl.Uniform, a *f32.Affine) {
+	var m [9]float32
+	m[0*3+0] = a[0][0]
+	m[0*3+1] = a[1][0]
+	m[0*3+2] = 0
+	m[1*3+0] = a[0][1]
+	m[1*3+1] = a[1][1]
+	m[1*3+2] = 0
+	m[2*3+0] = a[0][2]
+	m[2*3+1] = a[1][2]
+	m[2*3+2] = 1
+	glctx.UniformMatrix3fv(u, m[:])
+}