image: Introduce programContext (#144)

internal/graphics/draw.go

@@ -55,8 +55,16 @@ func drawTexture(c *opengl.Context, texture opengl.Texture, projectionMatrix *[4
 		return errors.New(fmt.Sprintf("len(quads) must be equal to or less than %d", quadsMaxNum))
 	}
 
-	f := useProgramForTexture(c, glMatrix(projectionMatrix), texture, geo, color)
-	defer f.FinishProgram()
+	p := programContext{
+		program:          programTexture,
+		context:          c,
+		projectionMatrix: glMatrix(projectionMatrix),
+		texture:          texture,
+		geoM:             geo,
+		colorM:           color,
+	}
+	p.begin()
+	defer p.end()
 
 	vertices := vertices[0:0]
 	num := 0

internal/graphics/program.go

@@ -99,38 +99,40 @@ var (
 	lastColorMatrix      []float32
 )
 
-type programFinisher func()
-
-func (p programFinisher) FinishProgram() {
-	p()
+type programContext struct {
+	program          opengl.Program
+	context          *opengl.Context
+	projectionMatrix []float32
+	texture          opengl.Texture
+	geoM             Matrix
+	colorM           Matrix
 }
 
-func useProgramForTexture(c *opengl.Context, projectionMatrix []float32, texture opengl.Texture, geo Matrix, color Matrix) programFinisher {
-	if !lastProgram.Equals(programTexture) {
-		c.UseProgram(programTexture)
+func (p *programContext) begin() {
+	c := p.context
+	if !lastProgram.Equals(p.program) {
+		c.UseProgram(p.program)
 		lastProgram = programTexture
 		lastProjectionMatrix = nil
 		lastModelviewMatrix = nil
 		lastColorMatrix = nil
 	}
-	program := programTexture
-
 	c.BindElementArrayBuffer(indexBufferQuads)
 
-	if !areSameFloat32Array(lastProjectionMatrix, projectionMatrix) {
-		c.UniformFloats(program, "projection_matrix", projectionMatrix)
+	if !areSameFloat32Array(lastProjectionMatrix, p.projectionMatrix) {
+		c.UniformFloats(p.program, "projection_matrix", p.projectionMatrix)
 		if lastProjectionMatrix == nil {
 			lastProjectionMatrix = make([]float32, 16)
 		}
-		copy(lastProjectionMatrix, projectionMatrix)
+		copy(lastProjectionMatrix, p.projectionMatrix)
 	}
 
-	ma := float32(geo.Element(0, 0))
-	mb := float32(geo.Element(0, 1))
-	mc := float32(geo.Element(1, 0))
-	md := float32(geo.Element(1, 1))
-	tx := float32(geo.Element(0, 2))
-	ty := float32(geo.Element(1, 2))
+	ma := float32(p.geoM.Element(0, 0))
+	mb := float32(p.geoM.Element(0, 1))
+	mc := float32(p.geoM.Element(1, 0))
+	md := float32(p.geoM.Element(1, 1))
+	tx := float32(p.geoM.Element(0, 2))
+	ty := float32(p.geoM.Element(1, 2))
 	modelviewMatrix := []float32{
 		ma, mc, 0, 0,
 		mb, md, 0, 0,
@@ -138,19 +140,19 @@ func useProgramForTexture(c *opengl.Context, projectionMatrix []float32, texture
 		tx, ty, 0, 1,
 	}
 	if !areSameFloat32Array(lastModelviewMatrix, modelviewMatrix) {
-		c.UniformFloats(program, "modelview_matrix", modelviewMatrix)
+		c.UniformFloats(p.program, "modelview_matrix", modelviewMatrix)
 		if lastModelviewMatrix == nil {
 			lastModelviewMatrix = make([]float32, 16)
 		}
 		copy(lastModelviewMatrix, modelviewMatrix)
 	}
 
-	c.UniformInt(program, "texture", 0)
+	c.UniformInt(p.program, "texture", 0)
 
 	e := [4][5]float32{}
 	for i := 0; i < 4; i++ {
 		for j := 0; j < 5; j++ {
-			e[i][j] = float32(color.Element(i, j))
+			e[i][j] = float32(p.colorM.Element(i, j))
 		}
 	}
 
@@ -161,7 +163,7 @@ func useProgramForTexture(c *opengl.Context, projectionMatrix []float32, texture
 		e[0][3], e[1][3], e[2][3], e[3][3],
 	}
 	if !areSameFloat32Array(lastColorMatrix, colorMatrix) {
-		c.UniformFloats(program, "color_matrix", colorMatrix)
+		c.UniformFloats(p.program, "color_matrix", colorMatrix)
 		if lastColorMatrix == nil {
 			lastColorMatrix = make([]float32, 16)
 		}
@@ -170,20 +172,21 @@ func useProgramForTexture(c *opengl.Context, projectionMatrix []float32, texture
 	colorMatrixTranslation := []float32{
 		e[0][4], e[1][4], e[2][4], e[3][4],
 	}
-	c.UniformFloats(program, "color_matrix_translation", colorMatrixTranslation)
+	c.UniformFloats(p.program, "color_matrix_translation", colorMatrixTranslation)
 
 	// We don't have to call gl.ActiveTexture here: GL_TEXTURE0 is the default active texture
 	// See also: https://www.opengl.org/sdk/docs/man2/xhtml/glActiveTexture.xml
-	c.BindTexture(texture)
+	c.BindTexture(p.texture)
 
-	c.EnableVertexAttribArray(program, "vertex")
-	c.EnableVertexAttribArray(program, "tex_coord")
+	c.EnableVertexAttribArray(p.program, "vertex")
+	c.EnableVertexAttribArray(p.program, "tex_coord")
 
-	c.VertexAttribPointer(program, "vertex", true, false, int16Size*4, 2, int16Size*0)
-	c.VertexAttribPointer(program, "tex_coord", true, true, int16Size*4, 2, int16Size*2)
-
-	return func() {
-		c.DisableVertexAttribArray(program, "tex_coord")
-		c.DisableVertexAttribArray(program, "vertex")
-	}
+	c.VertexAttribPointer(p.program, "vertex", true, false, int16Size*4, 2, int16Size*0)
+	c.VertexAttribPointer(p.program, "tex_coord", true, true, int16Size*4, 2, int16Size*2)
+}
+
+func (p *programContext) end() {
+	c := p.context
+	c.DisableVertexAttribArray(p.program, "tex_coord")
+	c.DisableVertexAttribArray(p.program, "vertex")
 }