message InputEvent

One raw input event, renderer → app.

Field-for-field the shape of canvas::InputEvent, deliberately: the renderer polls one off GLFW and forwards it without interpreting it. What x, y, button and mods mean depends on kind — see InputEventKind in draw_command.hpp, which is the authority for both sides. Keeping the wire struct congruent with the local one is what makes "forward it" a field copy rather than a protocol.

FileDrop arrives here like any other event, but its payload does not fit: the paths are a list, and this struct is fixed-size. The event says a drop happened and where; TakeDroppedPaths says what was in it.