MeshTools: don't return naked pointer from fullScreenTriangle().

Also make it possible to specify version for which we want it.

src/MeshTools/FullScreenTriangle.cpp

@@ -33,19 +33,19 @@
 
 namespace Magnum { namespace MeshTools {
 
-std::pair<Buffer*, Mesh> fullScreenTriangle() {
+std::pair<std::unique_ptr<Buffer>, Mesh> fullScreenTriangle(Version version) {
     Mesh mesh;
     mesh.setPrimitive(MeshPrimitive::Triangles)
         .setVertexCount(3);
 
-    Buffer* buffer = nullptr;
+    std::unique_ptr<Buffer> buffer;
     #ifndef MAGNUM_TARGET_GLES
-    if(!Context::current()->isVersionSupported(Version::GL300))
+    if(version < Version::GL300)
     #else
-    if(!Context::current()->isVersionSupported(Version::GLES300))
+    if(version < Version::GLES300)
     #endif
     {
-        buffer = new Buffer;
+        buffer.reset(new Buffer);
         constexpr Vector2 triangle[] = {
             Vector2(-1.0,  1.0),
             Vector2(-1.0, -3.0),
@@ -60,4 +60,8 @@ std::pair<Buffer*, Mesh> fullScreenTriangle() {
     return {std::move(buffer), std::move(mesh)};
 }
 
+std::pair<std::unique_ptr<Buffer>, Mesh> fullScreenTriangle() {
+    return fullScreenTriangle(Context::current()->version());
+}
+
 }}

src/MeshTools/FullScreenTriangle.h

@@ -28,6 +28,7 @@
  * @brief Function @ref Magnum::MeshTools::fullScreenTriangle()
  */
 
+#include <memory>
 #include <utility>
 
 #include "Magnum.h"
@@ -49,11 +50,11 @@ computed from them. The vertex positions are, in order:
     \begin{pmatrix} 3 \\ 1 \end{pmatrix}
 @f]
 
-On OpenGL 2.1 and OpenGL ES 2.0 the vertex positions are passed explicitly as
-attribute `0`, contained in the buffer. On OpenGL 3.0+ and OpenGL ES 3.0+ the
-mesh is attribute-less and the vertex positions can be computed using
-`gl_VertexID` builtin shader variable, thus `nullptr` is returned instead of
-vertex buffer.
+Based on @p version parameter, on OpenGL 2.1 and OpenGL ES 2.0 the vertex
+positions are passed explicitly as attribute `0`, contained in the buffer. On
+OpenGL 3.0+ and OpenGL ES 3.0+ the mesh is attribute-less and the vertex
+positions can be computed using `gl_VertexID` builtin shader variable, thus
+`nullptr` is returned instead of vertex buffer.
 
 Computing positions in vertex shader in a portable way might be done like this.
 For OpenGL 2.1 and OpenGL ES 2.0 you then need to bind the location of `position`
@@ -76,11 +77,15 @@ void main() {
     #endif
 }
 @endcode
+*/
+std::pair<std::unique_ptr<Buffer>, Mesh> MAGNUM_MESHTOOLS_EXPORT fullScreenTriangle(Version version);
+
+/**
+@overload
 
-@attention The implementation needs to check OpenGL version, so it expects
-    active context.
+This function implicitly uses current context version.
 */
-std::pair<Buffer*, Mesh> MAGNUM_MESHTOOLS_EXPORT fullScreenTriangle();
+std::pair<std::unique_ptr<Buffer>, Mesh> MAGNUM_MESHTOOLS_EXPORT fullScreenTriangle();
 
 }}