Updated docs to reflect changes to the GUI

Documentation/Manuals/Native/gui.md

@@ -16,7 +16,7 @@ You will almost certainly be interested in `GUIElement`, and are unlikely to nee
 When creating a custom GUI element you will need to override the @ref BansheeEngine::GUIElement "GUIElement" type. The minimum set of methods you need to implement for your custom elements are:
  - @ref BansheeEngine::GUIElement::_getOptimalSize "_getOptimalSize()" - Return the optimal size of your GUI element. This is used for controlling the size of the element in a layout (if it's not fixed). For example if your element was displaying a texture 64x64 in size, then the optimal size should probably return 64x64. If you element is displaying text you can use @ref BansheeEngine::GUIHelper "GUIHelper" to help you calculate the bounds of the text. If displaying something else then it's up to you to determine what constitutes an optimal size.
  - @ref BansheeEngine::GUIElement::_getNumRenderElements() "_getNumRenderElements()" - Return the number of separate elements that your GUIElement consists of. Each element has its own mesh, material and texture. In most cases there is only one element.
- - @ref BansheeEngine::GUIElement::_getNumQuads() "_getNumQuads()" - Returns the number of quads for the mesh of the render element at the specified index (e.g. one quad if the GUI element displays just one texture). This allows external systems to know how big of a buffer to allocate for the element's mesh.
+ - @ref BansheeEngine::GUIElement::_getMeshSize() "_getMeshSize()" - Returns the number of vertices and indices for the mesh of the render element at the specified index (e.g. one quad (4 vertices, 6 indices) if the GUI element displays just one texture). This allows external systems to know how big of a buffer to allocate for the element's mesh.
  - @ref BansheeEngine::GUIElement::_fillBuffer() "_fillBuffer()" - This is the meat of the `GUIElement` override. It allows you to fill a buffer with vertices, uv coordinates and indices for a mesh for the specified render element. This allows you to fully control the look of your GUI element by providing customized geometry.
  - @ref BansheeEngine::GUIElement::_getMaterial() "_getMaterial()" - Here you should return a material that will be applied to the mesh output in the previous method. You can choose from a few pre-built material types and provide a texture and a color. 
  - @ref BansheeEngine::GUIElement::updateRenderElementsInternal() "updateRenderElementsInternal()" - Called whenever the element's size or style changes. In this method you should rebuild the element's mesh. (While you could build the mesh in `_fillBuffer` it is inefficient as `_fillBuffer` will get called much more often than `updateRenderElementsInternal` due to mesh batching).