SDL_GL_GetDrawableSize was introduced after 2.0.0, so we need to check for that version before we call this method. Fixes MethodNotFounException on vanilla libsdl2-2.0.0 on linux.
When HiDPI is enabled, the size of the OpenGL surface (specified in
pixels) may no longer correspond to the size of the window (specified
in points). Width, Height, ClientSize and ClientRectangle return the
size of the OpenGL surface in device-dependent pixel coordinates
(origin: top-left pixel of the surface). Bounds and Size return the
size of the window in device-independent point coordinates (origin:
desktop).
MouseMove no longer leaves the window borders when the cursor is
invisible. MouseButtonUp events are now reported even when they occur
outside the window. This aligns SDL2 behavior with the native drivers.
Added IDisposable interface to all classes holding native data that must be freed. OpenTK.Toolkit.Init() now returns an IDisposable instance that can be used to cleanup all native data held by OpenTK. This is useful when re-initializing OpenTK (possibly in a new AppDomain), as is the case in the Example browser.
This resolves the issue where different layouts would return different
keys when pressing the same physical key. A new API must be introduced
for text input.
The SDL surface is no longer needed and will cause a memory leak if not
freed. Additionally, the decoded BitmapData should not be unlocked until
after updating the window icon, as it may be moved by the GC otherwise.
SDL2 suffers many of the issues we encountered when implementing
OpenTK.Platform.Windows. Workarounds are now in place to make
WindowState changes behave reasonably.
This is a new platform that can be used then sdl2 is installed on the target system. SDL2 is commercially supported by Valve and provides better support for MacOS compared to our current implementation (Cocoa vs Carbon). It will also help us introduce faster support for new platforms. Existing platforms remain as a fallback and will be automatically used if sdl2 is not installed.
Please note that this is still a work in progress. The new mouse and keyboard API is not supported yet. Due to limitations of sdl2, multiple mice/keyboards are also not supported.
