Let’s see how this is achieved. Boomla files have a file type property, which is simply a pointer (path) to another file. Let’s call this other file an app. These pointers form a chain, the file’s type chain. When the background image is to be shown, the type chain will be searched for this image. Thus, you can override the original background image of an app by simply creating a new file with the same name. Uploading it via the contextmenu makes it super user-friendly, but you could as well override it manually.
Developer note: changes to the runtime
To make overriding any part of an app possible, application files must be stored directly in the app file. The files
.Request/.Style are stored as grandchildren, thus overriding only the
.Inline/.Style file is impossible without also overriding the
.Inline file. To solve the issue, both files were moved under the app itself with different names:
The original files are deprecated. All websites hosted on Boomla will be auto-migrated in the coming days.