FlashGuard

Holds the light of a picture to a flash limit, whatever asked for the light.

WCAG 2.2 calls one flash a pair of opposing changes in relative luminance of at least 0.10, where the darker of the two states is below 0.80. A red flash is the same pattern in saturated red. This guard watches one light value that the caller supplies each frame, and not the flashes a drawing asks for, because feedback, a palette change, a transition and a shader can all flash without asking. The built-in surface supplies the light its drawings are told to give and scales them by allowance. It does not read the composed frame back.

Call limit once a frame with the light the picture is about to show. It answers the light the picture may show, which is never above the light asked for. The caller scales by the ratio of the two, so a held frame is dimmer rather than dropped, and the picture keeps moving.

The policy is the project's own and is stricter than WCAG's: at most mostPerSecond flashes in any rolling second, no area exception, and no saturated red flashing at all.