make Do reentrant

pixelgl/interface.go

@@ -27,6 +27,8 @@ package pixelgl
 // Also notice, that the functions are passing a Context around. This context contains the most important state variables.
 // Usually, you just pass it as you received it. If you want to pass a changed context to your child (e.g. your a shader),
 // use ctx.With* methods.
+//
+// If possible and makes sense, Do method should be reentrant.
 type Doer interface {
 	Do(sub func(Context))
 }

pixelgl/shader.go

@@ -17,6 +17,7 @@ type UniformFormat map[string]Attr
 
 // Shader is an OpenGL shader program.
 type Shader struct {
+	enabled       bool
 	parent        Doer
 	program       uint32
 	vertexFormat  VertexFormat
@@ -383,6 +384,11 @@ func (s *Shader) SetUniformMat43(purpose AttrPurpose, value mgl32.Mat4x3) (ok bo
 // Do stars using a shader, executes sub, and stops using it.
 func (s *Shader) Do(sub func(Context)) {
 	s.parent.Do(func(ctx Context) {
+		if s.enabled {
+			sub(ctx.WithShader(s))
+			return
+		}
+		s.enabled = true
 		DoNoBlock(func() {
 			gl.UseProgram(s.program)
 		})
@@ -390,5 +396,6 @@ func (s *Shader) Do(sub func(Context)) {
 		DoNoBlock(func() {
 			gl.UseProgram(0)
 		})
+		s.enabled = false
 	})
 }

pixelgl/texture.go

@@ -7,6 +7,7 @@ import (
 
 // Texture is an OpenGL texture.
 type Texture struct {
+	enabled bool
 	parent  Doer
 	tex     uint32
 }
@@ -63,6 +64,11 @@ func (t *Texture) ID() uint32 {
 // Do bind a texture, executes sub, and unbinds the texture.
 func (t *Texture) Do(sub func(Context)) {
 	t.parent.Do(func(ctx Context) {
+		if t.enabled {
+			sub(ctx)
+			return
+		}
+		t.enabled = true
 		DoNoBlock(func() {
 			gl.BindTexture(gl.TEXTURE_2D, t.tex)
 		})
@@ -70,5 +76,6 @@ func (t *Texture) Do(sub func(Context)) {
 		DoNoBlock(func() {
 			gl.BindTexture(gl.TEXTURE_2D, 0)
 		})
+		t.enabled = false
 	})
 }

pixelgl/vertex.go

@@ -69,6 +69,7 @@ const (
 // VertexArray is an OpenGL vertex array object that also holds it's own vertex buffer object.
 // From the user's points of view, VertexArray is an array of vertices that can be drawn.
 type VertexArray struct {
+	enabled bool
 	parent  Doer
 	vao     uint32
 	vbo     uint32
@@ -341,6 +342,11 @@ func (va *VertexArray) SetVertexAttributeVec4(vertex int, purpose AttrPurpose, v
 // Do binds a vertex arrray and it's associated vertex buffer, executes sub, and unbinds the vertex array and it's vertex buffer.
 func (va *VertexArray) Do(sub func(Context)) {
 	va.parent.Do(func(ctx Context) {
+		if va.enabled {
+			sub(ctx)
+			return
+		}
+		va.enabled = true
 		DoNoBlock(func() {
 			gl.BindVertexArray(va.vao)
 			gl.BindBuffer(gl.ARRAY_BUFFER, va.vbo)
@@ -351,5 +357,6 @@ func (va *VertexArray) Do(sub func(Context)) {
 			gl.BindBuffer(gl.ARRAY_BUFFER, 0)
 			gl.BindVertexArray(0)
 		})
+		va.enabled = false
 	})
 }