Reactive Graphical Applications

A graphical program is usually an event loop:

while running:
  wait for timer/input events
  update application state
  draw current state
  present frame

The final project should not draw randomly from many places. It should have a clear state model and a rendering pass. Input changes the state. Time advances the state. Rendering reads the state and draws a frame. This sounds like a style preference, but it quickly becomes a correctness issue once projects have menus, animations, moving objects, text, sound, and replay scripts.

A Useful Separation

Device helpers should own scancodes, mouse packets, timer ticks, framebuffer writes, and audio buffers. Application state should own menus, entities, cursors, documents, or song patterns. The renderer should draw that state into pixels. Replay and test code should provide deterministic input timelines.

When those responsibilities are mixed together, every change becomes risky. A keyboard shortcut should not know how a sprite is clipped. A rectangle drawing helper should not know which game level is active. A replay script should not depend on real human typing speed.

Why This Matters

This separation makes projects easier to test, record, debug, and divide among teammates. It also makes final demos more stable. A reactive graphical program should be able to run from live input or from a scripted input trace and produce the same visible behavior.