getDisplayMedia costs a picker, a permission, and a "Sharing this tab" bar
parked over the projector all night. None of it can be suppressed from the
page — the indicator is a security surface with no API, and the Chromium
switches that hide it were no help here.
The server runs on the machine the screen is plugged into, so it can take the
screenshot itself. server/screen.js drives grim for one region and /shot
returns the finished crop, which means grab() hands back a URL for an <img>
rather than a data URL off a canvas: same synchronous contract, so the
animations are untouched, and no tainting to work around either.
Coordinates line up because a fullscreen page's CSS pixels are the
compositor's logical pixels, which is the space grim's -g takes. The monitor
layout comes from hyprctl, so a projector is measured against itself rather
than the laptop panel, and -s pins the scale to that monitor: it keeps a
mixed-DPI desk deterministic, and it keeps grim native, where resampling costs
440ms against 35ms.
Needs a wlroots compositor and grim on PATH; without them the route reports
501 and the player falls back to getDisplayMedia, probed at load because that
call cannot be reached through an await without losing transient activation.
Also skipped when the page is not on localhost, where the server would be
photographing its own screen rather than the viewer's.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01H9v2Xoa6eoeGYpK6gp95k9
Firefox has no tab capture, so preferCurrentTab is silently dropped and the
operator can only share a window or a screen. Neither maps onto the viewport
the way the crop assumes, so screenshots came out offset by the browser chrome
— and every failure was swallowed by a bare catch, leaving no way to tell why.
Check the shared surface and only crop when the viewport covers it: exact for
Chrome's tab capture, true for a screen while the page is fullscreen. Test that
by dimensions rather than document.fullscreenElement, which F11 leaves null.
Start now requests fullscreen, after getDisplayMedia so the click's transient
activation goes to the fragile call. Reasons surface in a corner notice and the
console, and the check reruns per grab so leaving fullscreen says so.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01H9v2Xoa6eoeGYpK6gp95k9
The frame had exactly one behaviour, started once and run forever. Make
animations a start(context) => stop() lifecycle held in a registry, and
draw a new one on every completed crossfade.
Selection uses a shuffle bag: each animation comes up exactly once per
pass, so they stay evenly used, and a swap at the pass boundary keeps the
same one from running twice in a row. Written for a registry larger than
today's two entries.
The new corners animation parks the frame in a random corner and drops a
screenshot of it into the next of the other three corners every 5s, going
clockwise. The frame's own corner is never a slot, so a still cannot
cover it by construction rather than by clamping. This holds while
FRAME_SCALE stays under 0.5, now noted where that knob lives.
Screenshots need getDisplayMedia: the decks are cross-origin YouTube
iframes, so canvas taints and there is no other way to read the playing
pixels. The prompt has to be requested before start() yields, or the
click's transient activation is gone. Declining, or serving over plain
HTTP where mediaDevices is undefined, leaves the frame parked without
stills instead of failing.
The capture sink is a 1x1 element in the document, like #probe: detached
video elements are never composited and get throttled hard enough to make
every screenshot seconds stale.
startBounce also gains the stop() it always needed — it was leaking its
rAF loop and resize listener, and a queued frame would fight whichever
animation came next.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Tg15tLAuT6NrCE1ZxKVgDB
