Revert to gl_FragData (future webgl)

internal/graphicsdriver/opengl/context.go

@@ -396,7 +396,7 @@ func (c *context) newShader(shaderType uint32, source string) (shader, error) {
 	return shader(s), nil
 }
 
-func (c *context) newProgram(shaders []shader, attributes, fragData []string) (program, error) {
+func (c *context) newProgram(shaders []shader, attributes []string) (program, error) {
 	p := c.ctx.CreateProgram()
 	if p == 0 {
 		return 0, errors.New("opengl: glCreateProgram failed")
@@ -410,10 +410,6 @@ func (c *context) newProgram(shaders []shader, attributes, fragData []string) (p
 		c.ctx.BindAttribLocation(p, uint32(i), name)
 	}
 
-	for i, name := range fragData {
-		c.ctx.BindFragDataLocation(p, uint32(i), name)
-	}
-
 	c.ctx.LinkProgram(p)
 	if c.ctx.GetProgrami(p, gl.LINK_STATUS) == gl.FALSE {
 		info := c.ctx.GetProgramInfoLog(p)

internal/graphicsdriver/opengl/gl/debug.go

@@ -61,14 +61,6 @@ func (d *DebugContext) BindBuffer(arg0 uint32, arg1 uint32) {
 	}
 }
 
-func (d *DebugContext) BindFragDataLocation(arg0 uint32, arg1 uint32, arg2 string) {
-	d.Context.BindFragDataLocation(arg0, arg1, arg2)
-	fmt.Fprintln(os.Stderr, "BindFragDataLocation")
-	if e := d.Context.GetError(); e != NO_ERROR {
-		panic(fmt.Sprintf("gl: GetError() returned %d at BindFragDataLocation", e))
-	}
-}
-
 func (d *DebugContext) BindFramebuffer(arg0 uint32, arg1 uint32) {
 	d.Context.BindFramebuffer(arg0, arg1)
 	fmt.Fprintln(os.Stderr, "BindFramebuffer")

internal/graphicsdriver/opengl/gl/default_cgo.go

@@ -128,6 +128,10 @@ package gl
 //   typedef void (*fn)(GLuint index);
 //   ((fn)(fnptr))(index);
 // }
+// static void glowDrawBuffers(GLsizei n, const GLenum* bufs) {
+//   typedef void (*fn)(GLsizei n, const GLenum* bufs);
+//   ((fn)(fnptr))(n, bufs);
+// }
 // static void glowDrawElements(uintptr_t fnptr, GLenum mode, GLsizei count, GLenum type, const uintptr_t indices) {
 //   typedef void (*fn)(GLenum mode, GLsizei count, GLenum type, const uintptr_t indices);
 //   ((fn)(fnptr))(mode, count, type, indices);
@@ -351,6 +355,7 @@ type defaultContext struct {
 	gpDeleteVertexArrays       C.uintptr_t
 	gpDisable                  C.uintptr_t
 	gpDisableVertexAttribArray C.uintptr_t
+	gpDrawBuffers              C.uintptr_t
 	gpDrawElements             C.uintptr_t
 	gpEnable                   C.uintptr_t
 	gpEnableVertexAttribArray  C.uintptr_t
@@ -565,6 +570,10 @@ func (c *defaultContext) DisableVertexAttribArray(index uint32) {
 	C.glowDisableVertexAttribArray(c.gpDisableVertexAttribArray, C.GLuint(index))
 }
 
+func (c *defaultContext) DrawBuffers(bufs []uint32) {
+	C.glowDrawBuffers(c.gpDrawBuffers, C.GLsizei(len(bufs)), (*C.GLenum)(unsafe.Pointer(&bufs[0])))
+}
+
 func (c *defaultContext) DrawElements(mode uint32, count int32, xtype uint32, offset int) {
 	C.glowDrawElements(c.gpDrawElements, C.GLenum(mode), C.GLsizei(count), C.GLenum(xtype), C.uintptr_t(offset))
 }
@@ -801,6 +810,7 @@ func (c *defaultContext) LoadFunctions() error {
 	c.gpDeleteVertexArrays = C.uintptr_t(g.get("glDeleteVertexArrays"))
 	c.gpDisable = C.uintptr_t(g.get("glDisable"))
 	c.gpDisableVertexAttribArray = C.uintptr_t(g.get("glDisableVertexAttribArray"))
+	c.gpDrawBuffers = C.uintptr_t(g.get("glDrawBuffers"))
 	c.gpDrawElements = C.uintptr_t(g.get("glDrawElements"))
 	c.gpEnable = C.uintptr_t(g.get("glEnable"))
 	c.gpEnableVertexAttribArray = C.uintptr_t(g.get("glEnableVertexAttribArray"))

internal/graphicsdriver/opengl/gl/default_purego.go

@@ -28,7 +28,6 @@ type defaultContext struct {
 	gpAttachShader             uintptr
 	gpBindAttribLocation       uintptr
 	gpBindBuffer               uintptr
-	gpBindFragDataLocation     uintptr
 	gpBindFramebuffer          uintptr
 	gpBindRenderbuffer         uintptr
 	gpBindTexture              uintptr
@@ -141,12 +140,6 @@ func (c *defaultContext) BindBuffer(target uint32, buffer uint32) {
 	purego.SyscallN(c.gpBindBuffer, uintptr(target), uintptr(buffer))
 }
 
-func (c *defaultContext) BindFragDataLocation(program uint32, index uint32, name string) {
-	cname, free := cStr(name)
-	defer free()
-	purego.SyscallN(c.gpBindFragDataLocation, uintptr(program), uintptr(index), uintptr(unsafe.Pointer(cname)))
-}
-
 func (c *defaultContext) BindFramebuffer(target uint32, framebuffer uint32) {
 	purego.SyscallN(c.gpBindFramebuffer, uintptr(target), uintptr(framebuffer))
 }
@@ -490,7 +483,6 @@ func (c *defaultContext) LoadFunctions() error {
 	c.gpAttachShader = g.get("glAttachShader")
 	c.gpBindAttribLocation = g.get("glBindAttribLocation")
 	c.gpBindBuffer = g.get("glBindBuffer")
-	c.gpBindFragDataLocation = g.get("glBindFragDataLocation")
 	c.gpBindFramebuffer = g.get("glBindFramebuffer")
 	c.gpBindRenderbuffer = g.get("glBindRenderbuffer")
 	c.gpBindTexture = g.get("glBindTexture")

internal/graphicsdriver/opengl/gl/interface.go

@@ -31,7 +31,6 @@ type Context interface {
 	AttachShader(program uint32, shader uint32)
 	BindAttribLocation(program uint32, index uint32, name string)
 	BindBuffer(target uint32, buffer uint32)
-	BindFragDataLocation(program uint32, index uint32, name string)
 	BindFramebuffer(target uint32, framebuffer uint32)
 	BindRenderbuffer(target uint32, renderbuffer uint32)
 	BindTexture(target uint32, texture uint32)

internal/graphicsdriver/opengl/graphics.go

@@ -47,7 +47,6 @@ type Graphics struct {
 
 	uniformVariableNameCache     map[int]string
 	textureVariableNameCache     map[int]string
-	colorBufferVariableNameCache map[int]string
 
 	uniformVars []uniformVariable
 

internal/graphicsdriver/opengl/program.go

@@ -258,18 +258,6 @@ func (g *Graphics) textureVariableName(idx int) string {
 	return name
 }
 
-func (g *Graphics) colorBufferVariableName(idx int) string {
-	if v, ok := g.colorBufferVariableNameCache[idx]; ok {
-		return v
-	}
-	if g.colorBufferVariableNameCache == nil {
-		g.colorBufferVariableNameCache = map[int]string{}
-	}
-	name := fmt.Sprintf("fragColor%d", idx)
-	g.colorBufferVariableNameCache[idx] = name
-	return name
-}
-
 // useProgram uses the program (programTexture).
 func (g *Graphics) useProgram(program program, uniforms []uniformVariable, textures [graphics.ShaderSrcImageCount]textureVariable) error {
 	if g.state.lastProgram != program {

internal/graphicsdriver/opengl/shader.go

@@ -69,11 +69,7 @@ func (s *Shader) compile() error {
 	}
 	defer s.graphics.context.ctx.DeleteShader(uint32(fs))
 
-	colorNames := make([]string, s.ir.ColorsOutCount)
-	for i := range colorNames {
-		colorNames[i] = s.graphics.colorBufferVariableName(i)
-	}
-	p, err := s.graphics.context.newProgram([]shader{vs, fs}, theArrayBufferLayout.names(), colorNames)
+	p, err := s.graphics.context.newProgram([]shader{vs, fs}, theArrayBufferLayout.names())
 	if err != nil {
 		return err
 	}

internal/shaderir/glsl/glsl.go

@@ -229,9 +229,6 @@ func Compile(p *shaderir.Program, version GLSLVersion) (vertexShader, fragmentSh
 				fslines = append(fslines, fmt.Sprintf("in %s;", c.varDecl(p, &t, fmt.Sprintf("V%d", i))))
 			}
 		}
-		for i := 0; i < p.ColorsOutCount; i++ {
-			fslines = append(fslines, fmt.Sprintf("out vec4 fragColor%d;", i))
-		}
 
 		var funcs []*shaderir.Func
 		if p.VertexFunc.Block != nil {
@@ -423,7 +420,7 @@ func (c *compileContext) localVariableName(p *shaderir.Program, topBlock *shader
 		case idx < nv+1:
 			return fmt.Sprintf("V%d", idx-1)
 		default:
-			return fmt.Sprintf("fragColor%d", idx-(nv+1))
+			return fmt.Sprintf("gl_FragData[%d]", idx-(nv+1))
 		}
 	default:
 		return fmt.Sprintf("l%d", idx)