Work Helper

The time tracking engine lives entirely in the background service worker. It registers three event listeners — tabs.onActivated, tabs.onUpdated, and windows.onFocusChanged — each routing through a single handleTab() function. On every call, handleTab flushes the elapsed delta for the previous domain into chrome.storage.local as a keyed millisecond count, then resets the active domain and start timestamp for the next session.

The window focus handler is the critical edge case: when the browser loses focus entirely, there is no incoming tab event to trigger a flush. The WINDOW_ID_NONE branch commits the current delta immediately and sets startTime to null, so no phantom time accrues while the user is in another application. The popup reads all keys from storage and displays them sorted by accumulated time.

Reading mode is implemented in the content script as a lightweight DOM overlay. When triggered, the script creates a div with position: fixed, inset: 0, and pointer-events: none — spanning the full viewport without blocking any interaction with the underlying page. The warm background color (rgba(255, 244, 214, 0.35)) softens high-contrast pages while remaining subtle enough not to distort readability.

The popup dispatches a TOGGLE_READER_MODE message to the active tab via chrome.tabs.sendMessage. The content script maintains its own enabled boolean and responds by either appending or removing the overlay element. No state crosses the context boundary — each side owns its own truth.