Implement GUI input event system

[pbalduino]

Summary

Implement a unified input event system for GUI applications, abstracting keyboard and mouse events into a common event queue that can be consumed by the compositor and applications.

Background

The GUI needs a unified way to handle input from various devices (keyboard, mouse, future touch). Currently, PS/2 keyboard and mouse drivers generate raw input, but there's no abstraction layer for GUI consumption.

Goals

• Create abstract input event structures
• Implement event queue for GUI
• Integrate with existing PS/2 drivers (#37 keyboard, #143 mouse)
• Provide event dispatch to windows/applications
• Support keyboard focus and mouse grab semantics

Implementation

Input Event Structure

```c enum event_type { EVENT_KEY_PRESS, EVENT_KEY_RELEASE, EVENT_MOUSE_MOTION, EVENT_MOUSE_BUTTON_PRESS, EVENT_MOUSE_BUTTON_RELEASE, EVENT_MOUSE_SCROLL };

struct input_event { uint64_t timestamp; enum event_type type; union { struct { uint32_t keycode; uint32_t modifiers; uint32_t unicode; } key; struct { int32_t x, y; int32_t dx, dy; } motion; struct { uint32_t button; int32_t x, y; } button; struct { int32_t dx, dy; } scroll; }; }; ```

Event Queue

```c #define EVENT_QUEUE_SIZE 256

struct event_queue { struct input_event events[EVENT_QUEUE_SIZE]; size_t head, tail; struct mutex lock; struct semaphore sem; };

int event_queue_push(struct event_queue *q, struct input_event *evt); int event_queue_pop(struct event_queue *q, struct input_event *evt); ```

Timeline

• Phase 1: Event structures and queue (1 week)
• Phase 2: PS/2 driver integration (1 week)
• Phase 3: Event dispatch to compositor (1 week)
• Phase 4: Testing and optimization (3-5 days)

Total: 4-5 weeks

Definition of Done

• [ ] Event structures defined
• [ ] Event queue implemented
• [ ] PS/2 keyboard integrated
• [ ] PS/2 mouse integrated
• [ ] Compositor can receive events
• [ ] Test programs demonstrate functionality

Dependencies

• #143: PS/2 Mouse Driver (CRITICAL BLOCKER)
• #37: PS/2 Keyboard (already complete)

Enables

• Compositor and window manager (all need input events)

See docs/road/road_to_gui.md for complete roadmap.