makepad-event-action_skill

Overview

This skill provides focused guidance for Makepad event and action handling in widgets and apps. It explains how to detect hits, respond to mouse/keyboard/touch events, create and emit actions, and capture child widget actions so parents can react. Use it to implement robust input, lifecycle, timer, and inter-widget communication patterns in Makepad-based Rust UI code.

How this skill works

The skill inspects the Event enum and Hit enum to determine how input and lifecycle events should be matched to widget areas using event.hits(cx, area). It shows how widgets emit actions with cx.action(...) and how parents capture those actions with cx.capture_actions(...) or by iterating an ActionsBuf. It also covers timers, next-frame callbacks, and thread-safe posting via Cx::post_action().

When to use it

• Implementing widget input handling (mouse, touch, keyboard)
• Coordinating child-to-parent communication via actions
• Managing lifecycle events (startup, pause, resume)
• Scheduling timers and frame callbacks
• Handling async results or background threads that must notify the UI

Best practices

• Use event.hits(cx, area) to limit work to relevant widgets and avoid false positives
• Keep actions small, typed enums (derive DefaultNone for a None variant) to simplify pattern matching
• Capture child actions with cx.capture_actions() and check with helper methods (e.g., button.clicked(&actions))
• Use Cx::post_action() for thread-safe notifications from background threads
• Prefer explicit matching of Event variants (Timer, NextFrame) using stored ids to avoid cross-talk

Example use cases

• A clickable button: detect FingerDown/FingerUp hits and emit ButtonAction::Clicked via cx.action
• Text input: capture TextInput/TextCopy events and use TextInputRef helpers to extract changes
• Parent container: call cx.capture_actions() around child handle_event calls and react to ButtonAction::Clicked to update state
• Timers: start a timer with cx.start_timer(duration) and match Event::Timer(timer_event) to perform periodic updates
• Async load: spawn a background task and call Cx::post_action(MyAction::DataLoaded(data)) to deliver results to the main thread