An event is a message to notify an application that something happened
The transformed low-level input is a state (not an event)
The windowing system generates events when the state changes
keydown, keyup, mousedown, mouseup, mousemove are fundamental low-level input events. Basic mouse and keyboard input is described by these 5 events
The windowing system maintains a list of all windows ordered from back to front, the front most window has focus. Events are sent to focused window
The event queue is a buffer between the user and each window
Toolkit should refer to event timestamp, not time when the event was pulled off the queue or handled by the application code
a mousedown followed by a mouseup within a short time and with little movement is a mouse button click
a click followed by another click with a short time is a dblclick
the dragstart event is sent when the mouse button is held down and the mouse moves more than a small amount. Once in the dragging state, each mousemove triggers a drag event. mouseup from dragging state also sends a dragend event
Translated events will have same timestamp as fundamental event that triggered it
e.g. click will have same timestamp as the mouseup
All translated events must be dispatched in deterministic order. Application can assume sequence if listening to multiple events. e.g. a click will come after a mouseup
a mousedown followed by little movement and no mouseup for a long time is a longpress
Event coalescing is an optimization technique where high-frequency events like mousemove (which describe a continuous state) are combined or reduced to avoid overwhelming the system, since not every intermediate movement is important. In contrast, discrete events like mousedown or mouseup are low-frequency and significant, so they must be handled individually. Coalescing improves performance but should be avoided when precise, per-event data is required—such as for capturing exact pointer paths in signatures or drawing.
