From c85c5dedb11d104e45b74e460ac48b1aa075b218 Mon Sep 17 00:00:00 2001
From: Marvin Blum <marvin@marvinblum.de>
Date: Fri, 6 May 2016 12:27:33 +0200
Subject: [PATCH] Added GL initializsation, added clear buffer and clear color
 options.

---
 ToDo.md                 |  1 +
 game.go                 | 90 +++++++++++++++++++++++++++++++++++++++--
 gl_util.go              | 15 +++++++
 util.go => math_util.go |  0
 tex.go                  |  7 ++--
 5 files changed, 106 insertions(+), 7 deletions(-)
 create mode 100644 gl_util.go
 rename util.go => math_util.go (100%)

diff --git a/ToDo.md b/ToDo.md
index 9db4b59..25311e6 100644
--- a/ToDo.md
+++ b/ToDo.md
@@ -2,3 +2,4 @@
 
 * cleanup resources
 * more logging
+* limit FPS
diff --git a/game.go b/game.go
index 7615ec3..e84d78e 100644
--- a/game.go
+++ b/game.go
@@ -5,6 +5,7 @@ import (
 	"github.com/go-gl/glfw/v3.1/glfw"
 	"log"
 	"math"
+	"runtime"
 	"time"
 )
 
@@ -20,6 +21,7 @@ type RunOptions struct {
 	Title       string
 	Width       uint32
 	Height      uint32
+	ClearColor  Vec4
 	ExitOnClose bool
 }
 
@@ -28,14 +30,29 @@ type Game interface {
 }
 
 var (
-	running = true
+	running     = true
+	clearColor  = Vec4{}
+	clearBuffer []uint32
 )
 
+func init() {
+	// GL functions must be called from main thread.
+	log.Print("Locking OS thread")
+	runtime.LockOSThread()
+}
+
 // Creates a new window with given options and starts the game.
 // The game struct must implement the Game interface.
 // If options is nil, the default options will be used.
 // This function will panic on error.
 func Run(game Game, options *RunOptions) {
+	// init GL
+	log.Print("Initializing GL")
+
+	if err := gl.Init(); err != nil {
+		panic("Error initializing GL: " + err.Error())
+	}
+
 	// init glfw
 	log.Print("Initializing GLFW")
 
@@ -52,9 +69,15 @@ func Run(game Game, options *RunOptions) {
 	title := default_title
 	exitOnClose := default_exit_on_close
 
-	if options != nil {
+	if options != nil && options.Width > 0 {
 		width = options.Width
+	}
+
+	if options != nil && options.Height > 0 {
 		height = options.Height
+	}
+
+	if options != nil {
 		title = options.Title
 		exitOnClose = options.ExitOnClose
 	}
@@ -65,11 +88,22 @@ func Run(game Game, options *RunOptions) {
 		panic("Error creating GLFW window: " + err.Error())
 	}
 
+	wnd.MakeContextCurrent()
+
 	// init go-game
 	log.Print("Initializing goga")
-	wnd.MakeContextCurrent()
 	initGoga()
 
+	if options != nil && options.Width > 0 && options.Height > 0 {
+		SetViewport(0, 0, int32(options.Width), int32(options.Height))
+	} else {
+		SetViewport(0, 0, int32(default_width), int32(default_height))
+	}
+
+	if options != nil {
+		clearColor = options.ClearColor
+	}
+
 	// start and loop
 	log.Print("Starting main loop")
 	delta := time.Duration(0)
@@ -82,6 +116,12 @@ func Run(game Game, options *RunOptions) {
 		}
 
 		start := time.Now()
+		glfw.PollEvents()
+		gl.ClearColor(float32(clearColor.X), float32(clearColor.Y), float32(clearColor.Z), float32(clearColor.W))
+
+		for _, buffer := range clearBuffer {
+			gl.Clear(buffer)
+		}
 
 		if !math.IsInf(deltaSec, 0) && !math.IsInf(deltaSec, -1) {
 			updateSystems(deltaSec)
@@ -90,7 +130,6 @@ func Run(game Game, options *RunOptions) {
 		delta = time.Since(start)
 		deltaSec = delta.Seconds()
 		wnd.SwapBuffers()
-		glfw.PollEvents()
 	}
 }
 
@@ -100,7 +139,47 @@ func Stop() {
 	running = false
 }
 
+// Adds color buffer to list of buffers to be cleared.
+// If parameter is false, it will be removed.
+func ClearColorBuffer(do bool) {
+	removeClearBuffer(gl.COLOR_BUFFER_BIT)
+
+	if do {
+		clearBuffer = append(clearBuffer, gl.COLOR_BUFFER_BIT)
+	}
+}
+
+// Adds depth buffer to list of buffers to be cleared.
+// If parameter is false, it will be removed.
+func ClearDepthBuffer(do bool) {
+	removeClearBuffer(gl.DEPTH_BUFFER_BIT)
+
+	if do {
+		clearBuffer = append(clearBuffer, gl.DEPTH_BUFFER_BIT)
+	}
+}
+
+// Sets GL viewport.
+func SetViewport(x, y, width, height int32) {
+	gl.Viewport(x, y, width, height)
+}
+
+// Sets GL clear color.
+func SetClearColor(r, g, b, a float64) {
+	clearColor = Vec4{r, g, b, a}
+}
+
+func removeClearBuffer(buffer uint32) {
+	for i, buffer := range clearBuffer {
+		if buffer == buffer {
+			clearBuffer = append(clearBuffer[:i], clearBuffer[i+1:]...)
+			return
+		}
+	}
+}
+
 func initGoga() {
+	ClearColorBuffer(true)
 	AddLoader(&PngLoader{gl.LINEAR, false})
 }
 
@@ -118,4 +197,7 @@ func cleanup() {
 	for _, system := range systems {
 		system.Cleanup()
 	}
+
+	// cleanup resources
+	log.Print("TODO: cleanup resources")
 }
diff --git a/gl_util.go b/gl_util.go
new file mode 100644
index 0000000..86461b6
--- /dev/null
+++ b/gl_util.go
@@ -0,0 +1,15 @@
+package goga
+
+import (
+	"github.com/go-gl/gl/v4.5-core/gl"
+	"log"
+)
+
+// Checks for GL errors and prints to log if one occured.
+func CheckGLError() {
+	error := gl.GetError()
+
+	if error != 0 {
+		log.Print(error)
+	}
+}
diff --git a/util.go b/math_util.go
similarity index 100%
rename from util.go
rename to math_util.go
diff --git a/tex.go b/tex.go
index 4e82f5c..dccefb5 100644
--- a/tex.go
+++ b/tex.go
@@ -7,9 +7,10 @@ import (
 
 // Texture object.
 type Tex struct {
-	name          string
-	path          string
-	ext           string
+	name string
+	path string
+	ext  string
+
 	id            uint32
 	target        uint32
 	activeTexture uint32