The button next to the currently playing playlist item acts as a close window button in order to allow closing app without leaving fullscreen. It should use the theme "window-close" icon to better show what it does.
In case of local files the "filename" variable holds the string that is later assigned to the filename property (no difference which is used), but when playing URIs only filename property holds the string. Passing an undefined value to the label caused an error in this case and prevented playback of URIs.
Ship custom gtk4glsink plugin as part of API insead of normal gstreamer plugin. This avoids gstreamer plugin registry conflicts with gtk3 plugin and allows more customization.
A signal telling that "something somewhere changed" that is emitted multiple times per second (when bitrate changes). Not useful at all and a disaster performance-wise.
Not useful anymore since the player does 1s interval by default and now supports changing seek mode without stopping playback (unlike config which worked only when stopped).
Notify signal is a little problematic here as we already post a signal from player while jumping between APP and API contexts. Limit and disable it where not needed.
The "clapper_src" directory name was unusual. This was done to make it work as a widget for other apps. Now that this functionality got removed it can be named simply "src" as recommended by guidelines.
Clapper build scripts were updated to GTK 4.0.0 some time ago. Most distros either received GTK 4.0 from start or an update to it. No point in having a special workarounds to support 3.99.X versions.
This seemed like a good idea when the app still used GTK3, but GTK4 already has a built-in video widget. Maintaning this single functionality would be hard and I cannot promise a stable API anyway. The app main and only purpose will be a video player from now on.
Fast seeks are always a little off from requested time. When seeking to chapter position, do it by using a normal seek and restore user selected fast seeks afterwards.
