watchfeed.rs

`crates/veilvoice-gui/src/watchfeed.rs`

veilvoice-gui · 412 lines · read the source here · or on GitHub

The device monitor, moved off the thread that paints.

Why this file exists

The monitor used to be polled straight from update, which is the user-interface thread. Asking the operating system which applications hold the microphone is not free, because on Windows it means running reg.exe and on Linux it means walking /proc, and anything that costs tens of milliseconds is several frames.

The shipped v0.1.12 did it the expensive way as well as in the wrong place: two subprocesses per application, 68 of them on the machine this was found on, costing at least 449 ms measured, every two seconds, on the thread that draws. The window froze repeatedly. veilvoice-watch now costs two subprocesses whatever is installed, and this file makes sure the remaining cost never lands on a frame.

Both halves were needed. A cheap scan on the painting thread is still a scan on the painting thread: it would be a stutter rather than a freeze, on a machine slower than the one it was tested on, and it would come back.

One thread for the life of the window

Not one per poll. Spawning a thread every two seconds to do 45 ms of work is most of a thread's lifetime spent being created, and it would put the monitor's own state, which is what makes "started" and "stopped" different from "is using", somewhere it has to be moved back and forth.

So the worker owns the veilvoice_watch::Monitor and keeps it. It polls, sends, sleeps, repeats. The window drains whatever has arrived once a frame and never waits.

It stops when the window does

Nothing tells the thread to exit. When the window closes the receiver is dropped, the next send fails, and the loop ends, which is the whole shutdown protocol and needs no flag, no channel back and no chance of hanging on exit waiting for a sleep to finish.

In plain words

Keeps the microphone and camera monitor running somewhere other than the thread that draws the window.

Asking the operating system which programs are using a device takes long enough to be visible if it happens while the window is being painted. So it happens on its own thread and the window reads whatever has arrived.

If that thread ever stops, the panel says so plainly, because a monitor that has quietly not updated for an hour looks exactly like a machine where nothing is listening.

WHAT THIS FILE CONTAINS

412 lines defining 10 functions (9 public), 2 types and 2 constants. Everything below is read out of the source, so it cannot disagree with the code.

The types it owns.

struct Update line 63 · One look at the machine.
struct WatchFeed line 73 · The window's end of the monitor.

What happens when it runs. These are the ways in: public, and nothing else in this file calls them, so they are what an outside caller reaches first.

WatchFeed::start line 115 · Start watching, on a thread of its own.
reaches idle
WatchFeed::unseen line 199 · Alerts that have arrived and not yet been shown as a notification.
WatchFeed::drain line 207 · Take whatever has arrived.
WatchFeed::active line 252 · What is holding a device right now.
WatchFeed::log line 257 · What has started and stopped, oldest first.
WatchFeed::error line 262 · Why the monitor is not answering, if it is not.
WatchFeed::support line 267 · What this platform can detect at all.
WatchFeed::is_watching line 272 · Whether there is a worker running.

WHAT CALLS WHAT

The functions this file defines, and the calls between them. An edge means the callee's name appears, called, inside the caller's body. This is a syntactic reading, not a type-resolved one.

The same graph as Mermaid source

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flowchart TD
    n_default["WatchFeed::default<br/>line 91"]
    n_idle["WatchFeed::idle<br/>line 99"]
    n_start(["WatchFeed::start<br/>line 115"])
    n_unseen(["WatchFeed::unseen<br/>line 199"])
    n_drain(["WatchFeed::drain<br/>line 207"])
    n_active(["WatchFeed::active<br/>line 252"])
    n_log(["WatchFeed::log<br/>line 257"])
    n_error(["WatchFeed::error<br/>line 262"])
    n_support(["WatchFeed::support<br/>line 267"])
    n_is_watching(["WatchFeed::is_watching<br/>line 272"])
    n_default --> n_idle
    n_start --> n_idle
    click n_default href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L91" "open the source"
    click n_idle href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L99" "open the source"
    click n_start href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L115" "open the source"
    click n_unseen href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L199" "open the source"
    click n_drain href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L207" "open the source"
    click n_active href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L252" "open the source"
    click n_log href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L257" "open the source"
    click n_error href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L262" "open the source"
    click n_support href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L267" "open the source"
    click n_is_watching href "https://github.com/tilas01/veilvoice/blob/main/crates/veilvoice-gui/src/watchfeed.rs#L272" "open the source"
    classDef entry fill:#1f2335,stroke:#7aa2f7,color:#c0caf5
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    classDef api fill:#1f2335,stroke:#7dcfff,color:#c0caf5
    class n_idle api
    classDef helper fill:#1f2335,stroke:#bb9af7,color:#c0caf5
    class n_default helper

This site loads no third-party script, so it cannot run Mermaid; the diagram above is the same nodes and edges drawn by the generator instead. GitHub renders the source below directly.

ITEMS

Item	Line	Documentation
`EVERY` _const	60	How often to look.
`Update` _{pub struct}	63	One look at the machine.
`WatchFeed` _{pub struct}	73	The window's end of the monitor.
`MOST_ALERTS` _const	88	A log that grows without bound is a memory leak with a user interface.
`WatchFeed::default` _fn	91
`WatchFeed::idle` _{pub fn}	99	A feed that watches nothing.
`WatchFeed::start` _{pub fn}	115	Start watching, on a thread of its own.
`WatchFeed::unseen` _{pub fn}	199	Alerts that have arrived and not yet been shown as a notification.
`WatchFeed::drain` _{pub fn}	207	Take whatever has arrived.
`WatchFeed::active` _{pub fn}	252	What is holding a device right now.
`WatchFeed::log` _{pub fn}	257	What has started and stopped, oldest first.
`WatchFeed::error` _{pub fn}	262	Why the monitor is not answering, if it is not.
`WatchFeed::support` _{pub fn}	267	What this platform can detect at all.
`WatchFeed::is_watching` _{pub fn}	272	Whether there is a worker running.