Created attachment 189543 [details]
1. Open attached PPTX
2. Compare the two slides
The first slide's top shape uses "use background" as a fill but still shows the shape behind it.
The shape is filled with the colour used in Tools > Options > LibreOffice > Application Colours > Document Background.
The same file opened in MS365 will fill the shape with the same colour as the default background.
Note: this is not specific to PPTX. ODP behaves the same, but I attached a PPTX to make it easy to test in MS Office / MS365.
Version: 220.127.116.11.alpha0+ (X86_64) / LibreOffice Community
Build ID: cea165a3ebdb5f2a2b172004ff1b3848f303d78a
CPU threads: 8; OS: Linux 5.15; UI render: default; VCL: gtk3
Locale: en-AU (en_AU.UTF-8); UI: en-US
Already the case in 18.104.22.168, so calling it an implementation error.
Created attachment 189550 [details]
comparison of sample PPTX between LO (left) and MS365 (right)
I think, that is not a problem with the feature "use background" but with the background setting of the master slide. The master slide has set "None" and so "use background" uses "None", which means it becomes transparent.
PowerPoint does not allow setting "None" as fill for a master slide. So the import should set the background of the master page to the background color from the associated theme.
Created attachment 189563 [details]
screenshot comparing using same setting as slide (gradient) to "Use background"
(In reply to Regina Henschel from comment #2)
> I think, that is not a problem with the feature "use background" but with
> the background setting of the master slide. The master slide has set "None"
> and so "use background" uses "None", which means it becomes transparent.
My understanding is that the feature is not supposed to be "use same setting as slide", but instead be "a kind of 'tunnel' that looks through everything all the way to the slide background" (sorry for the lack of a better description :) )
This is best illustrated by using a gradient: if the slide and shape use the same gradient, vs if the shape uses "use background".
> PowerPoint does not allow setting "None" as fill for a master slide. So the
> import should set the background of the master page to the background color
> from the associated theme.
The same is seen with ODP.
Or maybe I misunderstood what you meant?
Samuel, Armin and Michael: copying you in in case you've got some input, given that you all participated in getting that implemented.