When LH Web Application prints the iOS startup images, it asks for the image through its lh_web_application_return_ios_startup_id filter. For a signed-in member on a front-end page, this plugin answers with an image tagged with one of their groups. Everyone else, and members with no suitable tagged image, get the site’s default from Settings, Web Application.
How the image is chosen
- Images tagged with any of the member’s groups (the 500 most recent).
- Images smaller than 640 pixels on their short side are left out, as are images LH Image CDN will not serve, such as protected attachments, since iOS needs a crop at the exact screen size.
- Portrait images rank first, then large ones: those WordPress has scaled down, or at least 2436 pixels on the long side.
- Among the top-ranked images, the one tagged with the most of the member’s own groups wins, and between equals the newest. Team mates therefore usually share a photo, and it moves on as newer photos of their groups are tagged.
iOS takes the startup image when the app is added to the home screen, so a member gets their own image only if they install the app while signed in, and keeps it until they reinstall.
Caching and filters
- The choice is kept in the object cache for a day per member and site. All choices are dropped when an image’s group tags change, an image is deleted, or anyone joins or leaves a group.
lh_bgt_startup_image_candidatesfilters the tied top-ranked attachment IDs for a user, newest first; the first is used.lh_bgt_startup_image_idfilters the final choice (0 falls back to the site default), with the user ID and the default attachment ID.
