GL: create the buffer passed to setBuffer() if it's not already.

doc/changelog.dox

@@ -579,6 +579,11 @@ See also:
     @fn_gl{GetString} returning a @cpp nullptr @ce
 -   @ref GL::Texture::imageSize() was present on WebGL 2 by mistake (see
     [mosra/magnum#365](https://github.com/mosra/magnum/pull/365))
+-   @ref GL::BufferTexture::setBuffer() now creates the passed buffer if not
+    already (and if it was not created by @fn_gl{CreateBuffers}). Before that,
+    passing a freshly created @ref GL::Buffer to it was causing
+    @ref GL::Renderer::Error::InvalidOperation on systems without
+    @gl_extension{ARB,direct_state_access}.
 
 @subsection changelog-latest-docs Documentation
 

src/Magnum/GL/Buffer.cpp

@@ -210,7 +210,7 @@ void Buffer::setTargetHintImplementationSwiftShader(const TargetHint hint) {
 }
 #endif
 
-inline void Buffer::createIfNotAlready() {
+void Buffer::createIfNotAlready() {
     if(_flags & ObjectFlag::Created) return;
 
     /* glGen*() does not create the object, just reserves the name. Some

src/Magnum/GL/Buffer.h

@@ -221,8 +221,6 @@ by OpenGL in order to preserve the data. If running on OpenGL ES or extension
 functions do nothing.
  */
 class MAGNUM_GL_EXPORT Buffer: public AbstractObject {
-    friend Implementation::BufferState;
-
     public:
         /**
          * @brief Buffer target
@@ -1155,6 +1153,11 @@ class MAGNUM_GL_EXPORT Buffer: public AbstractObject {
         void bindInternal(TargetHint target) { bindInternal(target, this); }
 
     private:
+        friend Implementation::BufferState;
+        #if !defined(MAGNUM_TARGET_GLES2) && !defined(MAGNUM_TARGET_WEBGL)
+        friend BufferTexture; /* calls createIfNotAlready() */
+        #endif
+
         static void bindInternal(TargetHint hint, Buffer* buffer);
         TargetHint MAGNUM_GL_LOCAL bindSomewhereInternal(TargetHint hint);
 

src/Magnum/GL/BufferTexture.cpp

@@ -79,11 +79,13 @@ Int BufferTexture::size() {
 }
 
 BufferTexture& BufferTexture::setBuffer(const BufferTextureFormat internalFormat, Buffer& buffer) {
+    buffer.createIfNotAlready();
     (this->*Context::current().state().texture->setBufferImplementation)(internalFormat, buffer);
     return *this;
 }
 
 BufferTexture& BufferTexture::setBuffer(const BufferTextureFormat internalFormat, Buffer& buffer, const GLintptr offset, const GLsizeiptr size) {
+    buffer.createIfNotAlready();
     (this->*Context::current().state().texture->setBufferRangeImplementation)(internalFormat, buffer, offset, size);
     return *this;
 }