From d53eefbf59d2e45c4d7c45207469d34f2ed8d967 Mon Sep 17 00:00:00 2001
From: faiface <faiface@ksp.sk>
Date: Wed, 30 Nov 2016 17:41:48 +0100
Subject: [PATCH] shader uniforms

---
 pixelgl/shader.go | 28 ++++++++++++++++++++++++----
 pixelgl/vertex.go | 10 ++++++++--
 2 files changed, 32 insertions(+), 6 deletions(-)

diff --git a/pixelgl/shader.go b/pixelgl/shader.go
index 134f4c4..858894a 100644
--- a/pixelgl/shader.go
+++ b/pixelgl/shader.go
@@ -7,18 +7,29 @@ import (
 	"github.com/pkg/errors"
 )
 
+// UniformFormat defines names, purposes and types of uniform variables inside a shader.
+//
+// Example:
+//
+//   UniformFormat{"transform": {Transform, Mat3}, "camera": {Camera, Mat3}}
+type UniformFormat map[string]Attr
+
 // Shader is an OpenGL shader program.
 type Shader struct {
-	parent  Doer
-	program uint32
+	parent   Doer
+	format   UniformFormat
+	program  uint32
+	uniforms map[Attr]int32
 }
 
 // NewShader creates a new shader program from the specified vertex shader and fragment shader sources.
 //
 // Note that vertexShader and fragmentShader parameters must contain the source code, they're not filenames.
-func NewShader(parent Doer, vertexShader, fragmentShader string) (*Shader, error) {
+func NewShader(parent Doer, format UniformFormat, vertexShader, fragmentShader string) (*Shader, error) {
 	shader := &Shader{
-		parent: parent,
+		parent:   parent,
+		format:   format,
+		uniforms: make(map[Attr]int32),
 	}
 
 	var err, glerr error
@@ -87,6 +98,15 @@ func NewShader(parent Doer, vertexShader, fragmentShader string) (*Shader, error
 			gl.DeleteShader(vshader)
 			gl.DeleteShader(fshader)
 
+			// uniforms
+			for uname, utype := range format {
+				ulocation := gl.GetUniformLocation(shader.program, gl.Str(uname+"\x00"))
+				if ulocation == -1 {
+					return fmt.Errorf("shader does not contain uniform '%s'", uname)
+				}
+				shader.uniforms[utype] = ulocation
+			}
+
 			return nil
 		})
 	})
diff --git a/pixelgl/vertex.go b/pixelgl/vertex.go
index 30e8277..9cd4a59 100644
--- a/pixelgl/vertex.go
+++ b/pixelgl/vertex.go
@@ -12,6 +12,8 @@ import (
 // Example:
 //
 //   VertexFormat{{Position, Vec2}, {Color, Vec4}, {TexCoord, Vec2}, {Visible, Bool}}
+//
+// Note: vertex array currently doesn't support matrices in vertex format.
 type VertexFormat []Attr
 
 // Size calculates the total size of a single vertex in this vertex format (sum of the sizes of all vertex attributes).
@@ -226,12 +228,15 @@ func (va *VertexArray) SetVertex(vertex int, data unsafe.Pointer) {
 
 // SetVertexAttribute sets the value of the specified vertex attribute of the specified vertex.
 // Argument data must point to a slice/array containing the new attribute data.
-func (va *VertexArray) SetVertexAttribute(vertex int, attr Attr, data unsafe.Pointer) {
+//
+// This function returns false if the specified attribute does not exist. Note that the function panics
+// if the vertex is out of range.
+func (va *VertexArray) SetVertexAttribute(vertex int, attr Attr, data unsafe.Pointer) (ok bool) {
 	if vertex < 0 || vertex >= va.count {
 		panic("set vertex attribute error: invalid vertex index")
 	}
 	if _, ok := va.attrs[attr]; !ok {
-		return // ignore non-existing attributes
+		return false
 	}
 	DoNoBlock(func() {
 		gl.BindBuffer(gl.ARRAY_BUFFER, va.vbo)
@@ -245,6 +250,7 @@ func (va *VertexArray) SetVertexAttribute(vertex int, attr Attr, data unsafe.Poi
 			panic(errors.Wrap(err, "set attribute vertex error"))
 		}
 	})
+	return true
 }
 
 // Do binds a vertex arrray and it's associated vertex buffer, executes sub, and unbinds the vertex array and it's vertex buffer.