feat: Initial framework for VKM

[skip ci]

vkm/README.md

@@ -0,0 +1,50 @@
+Virtual keyboard/mouse infrastructure
+=====================================
+
+The virtual keyboard/mouse infrastructure (or VKM), is an API used by an
+application to inject keyboard and mouse events into the OS stack. The advantage
+of using a separate API for this is so that this can be handled in a
+cross-platform manner without having to sprinkle `#ifdef`'s throughout the
+program.
+
+Base API
+========
+
+The API is based around a context, which is an opaque pointer returned by
+`vkm_init`. All subsequent VKM calls will take in this pointer as the first
+argument, and return a signed 32-bit status code. Once done, `vkm_exit` will
+clean up any data structures and close any file descriptors that were opened as
+part of the VKM calls.
+
+VKM can also be configured through the `vkm_config` API call.
+
+Device handling
+===============
+
+`vkm_new_device` is the API to use when creating a new VKM device. While VKM
+will support both keyboard and mouse events from a single device, there may be
+cases where the application needs to separate out keyboard and mouse events into
+different devices. The flags will enable keyboard and/or mouse support.
+
+Note that the supported event codes (on Linux) are fixed, and cannot be updated.
+The keyboard will emulate a standard US keyboard, while the mouse will emulate a
+standard 3 button mouse with a scroll wheel.
+
+Mouse handling
+==============
+
+The mouse is handled as a single API call that passes in dx and dy to move the
+mouse in the relative X and Y axes. VKM will take care of internally translating
+the calls to the appropriate framework. This is handled in `vkm_mouse_move`
+
+The scroll wheel is handled through `vkm_mouse_scroll`. By default, the mouse
+motion uses standard scrolling, but high resolution scrolling may be enabled.
+
+The buttons are handled by `vkm_mouse_click`. The API will send the state,
+depending on the input (pressed or not)
+
+Keyboard handling
+=================
+
+The keyboard is handled through a single call `vkm_keyboard_send`. This sends a
+single key event, with modifiers enabled (Ctrl, Shift, Alt, GUI).