Use QGLFunctions to fix OpenGL calls

src/backdrop.cpp

@@ -2,6 +2,8 @@
 
 Backdrop::Backdrop()
 {
+    initializeGLFunctions();
+
     shader.addShaderFromSourceFile(QGLShader::Vertex, ":/gl/quad.vert");
     shader.addShaderFromSourceFile(QGLShader::Fragment, ":/gl/quad.frag");
     shader.link();

src/backdrop.h

@@ -1,10 +1,11 @@
 #ifndef BACKDROP_H
 #define BACKDROP_H
 
+#include <QtOpenGL/QGLFunctions>
 #include <QtOpenGL/QGLShaderProgram>
 #include <QtOpenGL/QGLBuffer>
 
-class Backdrop
+class Backdrop : protected QGLFunctions
 {
 public:
     Backdrop();

src/canvas.cpp

@@ -49,6 +49,8 @@ void Canvas::clear_status()
 
 void Canvas::initializeGL()
 {
+    initializeGLFunctions();
+
     mesh_shader.addShaderFromSourceFile(QGLShader::Vertex, ":/gl/mesh.vert");
     mesh_shader.addShaderFromSourceFile(QGLShader::Fragment, ":/gl/mesh.frag");
     mesh_shader.link();

src/canvas.h

@@ -3,6 +3,7 @@
 
 #include <QWidget>
 #include <QtOpenGL/QGLWidget>
+#include <QtOpenGL/QGLFunctions>
 #include <QtOpenGL/QGLShaderProgram>
 #include <QMatrix4x4>
 
@@ -10,7 +11,7 @@ class GLMesh;
 class Mesh;
 class Backdrop;
 
-class Canvas : public QGLWidget
+class Canvas : public QGLWidget, protected QGLFunctions
 {
     Q_OBJECT
 

src/glmesh.cpp

@@ -4,6 +4,8 @@
 GLMesh::GLMesh(const Mesh* const mesh)
     : vertices(QGLBuffer::VertexBuffer), indices(QGLBuffer::IndexBuffer)
 {
+    initializeGLFunctions();
+
     vertices.create();
     indices.create();
 

src/glmesh.h

@@ -2,10 +2,11 @@
 #define GLMESH_H
 
 #include <QtOpenGL/QGLBuffer>
+#include <QtOpenGL/QGLFunctions>
 
 class Mesh;
 
-class GLMesh
+class GLMesh : protected QGLFunctions
 {
 public:
     GLMesh(const Mesh* const mesh);