I have been building small "proof of principle" programs to learn about GTK3, and now that GTK4 has limited availability, I have been attempting to learn about this version as well. In attempting to migrate to GTK4, I took a program I wrote for GTK3 that displays two progress bars with different attributes using CSS providers and rebuilt it under GTK4. When I ran the GTK4 version of the program, the CSS overrides in the program are ignored unless I introduce the CSS provider context to the display level for one of the progress bars. But that then results in having both progress bars exhibiting the same behavior instead of having unique behavior for each progress bar. Just as a further test, I added CSS providers and context for a label widget and that override worked. So some CSS overrides in GTK4 work as before, but some do not. It is as though some CSS provider overrides are ignored at the display level. Reviewing documentation about priorities (e.g. GTK_STYLE_PROVIDER_PRIORITY_APPLICATION) and testing out various priority constants did not make a difference.
Displaying the content of the code would be too long in this narrative, so I have uploaded the GTK3 and GTK4 versions of the code to my Github repositories along with a "pdf" file visually illustrating the different behavior between GTK3 and GTK4. If you want to review and test out the code yourself, the link is:
https://github.com/cschuls/GTK4_Mystery
I would suppose that widget-specific CSS customization could be added at the display level with an "id#" attribute, but that seems like that would just be adding unnecessary complexity when this practice works fine with GTK3. Thanks in advance for any answers and suggestions.
Additional comment.
Experimenting with various scenarios, I came up with a work-around that provides the desired result of having distinct style properties applied to each progress bar widget. For those widgets, I added their respective CSS provider data to the display style context instead of attempting to add the CSS provider to each widget's context. If you wish to view this work-around, I added a "work-around" folder with the source code to my Github repository.
This provides a decent solution to this problem, but it does not answer my underlying question as to why the CSS provider information for each progress bar widget is not enacted upon during the application's execution; whereas, CSS provider information associated with widgets such as labels and buttons do behave as they did with GTK3. If anyone can answer my core question, I would be very happy.
Regards,
Craig
