Keyboard Controls

Learning Objectives Analyze the differences between key-down, key-up, and key-press events in an event-driven system. Implement a stateful input manager using a hash map (or dictionary) to track multiple simultaneous key presses. Design and code logic for handling key combinations, including modifier keys like Ctrl, Shift, and Alt. Differentiate between event-driven input and state polling, and determine the appropriate use case for each. Implement input buffering to handle rapid sequences of key presses for complex commands. Prevent default system behaviors associated with specific key combinations (e.g., Ctrl+S) within an application. Ever wondered how video games allow for smooth diagonal movement or how software like Photoshop uses complex shortcuts like Ctrl+Alt+Shift+E...

TermDefinitionExample Event-Driven ProgrammingA programming paradigm where the flow of the program is determined by events such as user actions (mouse clicks, key presses), sensor outputs, or messages from other programs.An application's code doesn't run top-to-bottom, but instead has 'listeners' that wait for a 'keyDown' event. When the user presses a key, the corresponding listener function is executed. Key State PollingThe process of actively checking the current state of a key (up or down) at regular intervals, typically once per frame in a game loop, rather than waiting for an event to be fired.Inside a game loop that runs 60 times per second: `if (is_key_pressed('W')) { player.move_forward(); }`. This is checked every frame, regardless of when...

Stateful Input Tracking Pattern 1. Initialize a hash map for key states. 2. On `keyDown`, set `keyStates[key] = true`. 3. On `keyUp`, set `keyStates[key] = false`. 4. In the main loop, read from the hash map to determine actions. Use this pattern for continuous actions that depend on multiple keys being held down simultaneously, like smooth character movement in games. It decouples the input events from the application logic (e.g., physics update). Key Combination (Shortcut) Pattern In the `keyDown` event handler: `if (event.ctrlKey && event.key === 's') { action(); event.preventDefault(); }` Use this for discrete, one-time actions triggered by a specific combination. Always check for modifier keys first, then the primary key. Use `preventDefault()` to stop...