From 1c187597e6b7b0bfbc7f8d73a4bc95354c69835c Mon Sep 17 00:00:00 2001
From: Hajime Hoshi <hajimehoshi@hajimehoshi.com>
Date: Sun, 4 May 2014 03:29:45 +0900
Subject: [PATCH] Add some comments

---
 graphics/opengl/context.go             | 9 ++++-----
 graphics/opengl/shader/draw_texture.go | 1 +
 graphics/opengl/shader/program.go      | 8 +++++---
 3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/graphics/opengl/context.go b/graphics/opengl/context.go
index 44df7a2fb..6a671384a 100644
--- a/graphics/opengl/context.go
+++ b/graphics/opengl/context.go
@@ -1,15 +1,14 @@
 package opengl
 
-import (
-	"github.com/hajimehoshi/go-ebiten/graphics"
-	"github.com/hajimehoshi/go-ebiten/graphics/matrix"
-)
-
 // #cgo LDFLAGS: -framework OpenGL
 //
 // #include <stdlib.h>
 // #include <OpenGL/gl.h>
 import "C"
+import (
+	"github.com/hajimehoshi/go-ebiten/graphics"
+	"github.com/hajimehoshi/go-ebiten/graphics/matrix"
+)
 
 func enableAlphaBlending() {
 	C.glEnable(C.GL_TEXTURE_2D)
diff --git a/graphics/opengl/shader/draw_texture.go b/graphics/opengl/shader/draw_texture.go
index bf9252114..536dfd8f9 100644
--- a/graphics/opengl/shader/draw_texture.go
+++ b/graphics/opengl/shader/draw_texture.go
@@ -25,6 +25,7 @@ func DrawTexture(native NativeTexture, projectionMatrix [16]float32,
 	if len(quads) == 0 {
 		return
 	}
+	// TODO: Check performance
 	shaderProgram := use(projectionMatrix, geometryMatrix, colorMatrix)
 	defer C.glUseProgram(0)
 
diff --git a/graphics/opengl/shader/program.go b/graphics/opengl/shader/program.go
index 2890752cc..be15a9370 100644
--- a/graphics/opengl/shader/program.go
+++ b/graphics/opengl/shader/program.go
@@ -85,7 +85,8 @@ func getLocation(program C.GLuint, name string, qvType qualifierVariableType) C.
 	locationName := C.CString(name)
 	defer C.free(unsafe.Pointer(locationName))
 
-	location := C.GLint(-1)
+	const invalidLocation = -1
+	location := C.GLint(invalidLocation)
 
 	switch qvType {
 	case qualifierVariableTypeAttribute:
@@ -95,7 +96,7 @@ func getLocation(program C.GLuint, name string, qvType qualifierVariableType) C.
 	default:
 		panic("no reach")
 	}
-	if location == -1 {
+	if location == invalidLocation {
 		panic("glGetUniformLocation failed")
 	}
 	shaderLocationCache[qvType][name] = location
@@ -112,7 +113,8 @@ func getUniformLocation(program C.GLuint, name string) C.GLint {
 }
 
 func use(projectionMatrix [16]float32,
-	geometryMatrix matrix.Geometry, colorMatrix matrix.Color) C.GLuint {
+	geometryMatrix matrix.Geometry,
+	colorMatrix matrix.Color) C.GLuint {
 	programId := programRegular
 	if !colorMatrix.IsIdentity() {
 		programId = programColorMatrix