In addition to lots of bug fixes, here are the major changes in this release:

General

• Updated OpenGL headers to the latest API from The Khronos Group Inc.
• Added SDL_GetWindowSizeInPixels() to get the window size in pixels, which may differ from the window coordinate size for windows with high-DPI support
• Added simulated vsync synchronization for the software renderer
• Added the mouse position to SDL_MouseWheelEvent
• Added SDL_ResetHints() to reset all hints to their default values
• Added SDL_GetJoystickGUIDInfo() to get device information encoded in a joystick GUID
• Added the hint SDL_HINT_JOYSTICK_HIDAPI_XBOX_360 to control whether the HIDAPI driver for XBox 360 controllers should be used
• Added the hint SDL_HINT_JOYSTICK_HIDAPI_XBOX_360_PLAYER_LED to control whether the player LEDs should be lit to indicate which player is associated with an Xbox 360 controller
• Added the hint SDL_HINT_JOYSTICK_HIDAPI_XBOX_360_WIRELESS to control whether the HIDAPI driver for XBox 360 wireless controllers should be used
• Added the hint SDL_HINT_JOYSTICK_HIDAPI_XBOX_ONE to control whether the HIDAPI driver for XBox One controllers should be used
• Added the hint SDL_HINT_JOYSTICK_HIDAPI_XBOX_ONE_HOME_LED to control the brightness of the XBox One guide button LED
• Added support for PS3 controllers to the HIDAPI driver, enabled by default on macOS, controlled by the SDL_HINT_JOYSTICK_HIDAPI_PS3 hint
• Added support for Nintendo Wii controllers to the HIDAPI driver, not enabled by default, controlled by the SDL_HINT_JOYSTICK_HIDAPI_WII hint
• Added the hint SDL_HINT_JOYSTICK_HIDAPI_WII_PLAYER_LED to control whether the player LED should be lit on the Nintendo Wii controllers
• Added the hint SDL_HINT_JOYSTICK_HIDAPI_VERTICAL_JOY_CONS to control whether Nintendo Switch Joy-Con controllers will be in vertical mode when using the HIDAPI driver
• Added access to the individual left and right gyro sensors of the combined Joy-Cons controller
• Added a microsecond timestamp to SDL_SensorEvent and SDL_ControllerSensorEvent, when the hardware provides that information
• Added SDL_SensorGetDataWithTimestamp() and SDL_GameControllerGetSensorDataWithTimestamp() to retrieve the last sensor data with the associated microsecond timestamp
• Added the hint SDL_HINT_HIDAPI_IGNORE_DEVICES to have the SDL HID API ignore specific devices
• SDL_GetRevision() now includes more information about the SDL build, including the git commit hash if available

Windows:

• Added the hint SDL_HINT_MOUSE_RELATIVE_SYSTEM_SCALE to control whether the system mouse acceleration curve is used for relative mouse motion

Linux:

• Added SDL_SetPrimarySelectionText(), SDL_GetPrimarySelectionText(), and SDL_HasPrimarySelectionText() to interact with the X11 primary selection clipboard
• Added the hint SDL_HINT_VIDEO_WAYLAND_EMULATE_MOUSE_WARP to control whether mouse pointer warp emulation is enabled under Wayland