wxGLCanvas is a class for displaying OpenGL graphics. It is always used in conjunction with wxGLContext as the context can only be made current (i.e. active for the OpenGL commands) when it is associated to a wxGLCanvas.
More precisely, you first need to create a wxGLCanvas window and then create an instance of a wxGLContext that is initialized with this wxGLCanvas and then later use either setCurrent/2 with the instance of the wxGLContext or wxGLContext:setCurrent/2 with the instance of the wxGLCanvas (which might be not the same as was used for the creation of the context) to bind the OpenGL state that is represented by the rendering context to the canvas, and then finally call swapBuffers/1 to swap the buffers of the OpenGL canvas and thus show your current output.
Please note that wxGLContext always uses physical pixels, even on the platforms where wxWindow uses logical pixels, affected by the coordinate scaling, on high DPI displays. Thus, if you want to set the OpenGL view port to the size of entire window, you must multiply the result returned by wxWindow:getClientSize/1 by wxWindow:getContentScaleFactor/1 before passing it to glViewport(). Same considerations apply to other OpenGL functions and other coordinates, notably those retrieved from wxMouseEvent in the event handlers.
Notice that versions of wxWidgets previous to 2.9 used to implicitly create a wxGLContext inside wxGLCanvas itself. This is still supported in the current version but is deprecated now and will be removed in the future, please update your code to create the rendering contexts explicitly.
To set up the attributes for the canvas (number of bits for the depth buffer, number of bits for the stencil buffer and so on) you pass them in the constructor using a wxGLAttributes (not implemented in wx) instance. You can still use the way before 3.1.0 (setting up the correct values of the attribList parameter) but it's discouraged.
Note: On those platforms which use a configure script (e.g. Linux and macOS) OpenGL support is automatically enabled if the relative headers and libraries are found. To switch it on under the other platforms (e.g. Windows), you need to edit the setup.h file and set wxUSE_GLCANVAS to 1 and then also pass USE_OPENGL=1 to the make utility. You may also need to add opengl32.lib (and glu32.lib for old OpenGL versions) to the list of the libraries your program is linked with.
See: wxGLContext, wxGLAttributes (not implemented in wx), wxGLContextAttrs (not implemented in wx)
wxWidgets docs: wxGLCanvas
new(Parent) -> wxGLCanvas()
new(Parent, Options :: [Option]) -> wxGLCanvas()
This constructor is still available only for compatibility reasons.
Please use the constructor with wxGLAttributes (not implemented in wx) instead.
If attribList is not specified, wxGLAttributes::PlatformDefaults() (not implemented in wx) is used, plus some other attributes (see below).
setCurrent(This, Context) -> boolean()
Makes the OpenGL state that is represented by the OpenGL rendering context context current, i.e.
it will be used by all subsequent OpenGL calls.
This is equivalent to wxGLContext:setCurrent/2 called with this window as parameter.
Note: This function may only be called when the window is shown on screen, in particular it can't usually be called from the constructor as the window isn't yet shown at this moment.
Return: false if an error occurred.
swapBuffers(This) -> boolean()
Swaps the double-buffer of this window, making the back-buffer the front-buffer and vice versa, so that the output of the previous OpenGL commands is displayed on the window.
Return: false if an error occurred.
destroy(This :: wxGLCanvas()) -> ok
Destroys the object.