The preview picture, shown once it exists and has loaded — a missing card or a failed request draws
nothing, so the card never shows a broken image. A picture that has to load slides open as it arrives;
one the browser already has is simply there.
A screenshot service answers while it is still rendering with a placeholder picture (mShots
does). The caller says what width it asked for (expectedWidth); a loaded picture of another width
is the placeholder, so it stays hidden and the request repeats every PREVIEW_POLL_MS until the
shot arrives. The polling stops with the card.
The preview picture, shown once it exists and has loaded — a missing card or a failed request draws nothing, so the card never shows a broken image. A picture that has to load slides open as it arrives; one the browser already has is simply there.
A screenshot service answers while it is still rendering with a placeholder picture (mShots does). The caller says what width it asked for (
expectedWidth); a loaded picture of another width is the placeholder, so it stays hidden and the request repeats every PREVIEW_POLL_MS until the shot arrives. The polling stops with the card.