GNOME Bugzilla – Bug 782928
Blank transition from an animated wallpapers
Last modified: 2021-07-05 13:45:11 UTC
It appears the transition tag is broken for background xml format. The code below as example: <background> <starttime> <year>2017</year> <month>06</month> <day>20</day> <hour>07</hour> <minute>00</minute> <second>00</second> </starttime> <!-- This animation will start at 7 AM. --> <!-- We start with dawn at 7 AM. It will remain up for 2 hours. --> <static> <duration>50.0</duration> <file> <!-- Wide 16:10 --> <size width="1920" height="1200">/usr/share/backgrounds/f26/default-animated/tv-wide/f26-00-dawn.png</size> <!-- Wide 16:9 --> <size width="1920" height="1200">/usr/share/backgrounds/f26/default-animated/wide/f26-00-dawn.png</size> <!-- Standard 4:3 --> <size width="2048" height="1536">/usr/share/backgrounds/f26/default-animated/standard/f26-00-dawn.png</size> <!-- Normalish 5:4 --> <size width="1280" height="1024">/usr/share/backgrounds/f26/default-animated/normalish/f26-00-dawn.png</size> </file> </static> <!-- Dawn ended and starts to transition to day at 9 AM. The transition lasts for 2 hours, ending at 11 AM. --> <transition> <duration>10.0</duration> <from> <size width="1920" height="1200">/usr/share/backgrounds/f26/default-animated/tv-wide/f26-00-dawn.png</size> <size width="1920" height="1080">/usr/share/backgrounds/f26/default-animated/wide/f26-00-dawn.png</size> <size width="2048" height="1536">/usr/share/backgrounds/f26/default-animated/standard/f26-00-dawn.png</size> <size width="1280" height="1024">/usr/share/backgrounds/f26/default-animated/normalish/f26-00-dawn.png</size> </from> <to> <size width="1920" height="1200">/usr/share/backgrounds/f26/default-animated/tv-wide/f26-01-day.png</size> <size width="1920" height="1080">/usr/share/backgrounds/f26/default-animated/wide/f26-01-day.png</size> <size width="2048" height="1536">/usr/share/backgrounds/f26/default-animated/standard/f26-01-day.png</size> <size width="1280" height="1024">/usr/share/backgrounds/f26/default-animated/normalish/f26-01-day.png</size> </to> </transition> Somehow, the starting image from the transition display a blank instead as demonstrated by the screencast below: https://luya.fedorapeople.org/videos/Screencast%20from%2020-05-17%2010:32:45%20PM.webm The transitioin previously worked smoothly until recently.
What makes you think that this is a problem with the parser? I'm asking because mutter/gnome-shell are responsible for displaying the background, but parsing the XML description of animated backgrounds is implemented in libgnome-desktop ... (FWIW, GNOME's default background uses an animation, and I never noticed any "holes" - I noticed that your duration values don't match the comments at all, but I suspect that you changed them for testing purposes.)
(In reply to Florian Müllner from comment #1) > What makes you think that this is a problem with the parser? I'm asking > because mutter/gnome-shell are responsible for displaying the background, > but parsing the XML description of animated backgrounds is implemented in > libgnome-desktop ... That was a guess as I did not know how to exactly identify the cause of possible issue. Taking the example from a modified /usr/share/gnome-background-properties/f26-animated.xml for testing purpose <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE wallpapers SYSTEM "gnome-wp-list.dtd"> <wallpapers> <wallpaper deleted="false"> <name>Fedora 26 Animated</name> <filename>/usr/share/backgrounds/f26/default-animated/f26-fast.xml</filename> <options>stretched</options> <shade_type>solid</shade_type> <pcolor>#ffffff</pcolor> <scolor>#000000</scolor> </wallpaper> </wallpapers> Where f26-fast.xml is the content for transition. Attachement will be included on the following post. The file from <from> tag should display properly but show a blank instead. > > (FWIW, GNOME's default background uses an animation, and I never noticed any > "holes" - I noticed that your duration values don't match the comments at > all, but I suspect that you changed them for testing purposes.) Yes, that was for testing purpose. The actual content is on /usr/shares/backgrounds/f26/default-animated/f26.xml if you installed f26-backgrounds-26.2.2. https://apps.fedoraproject.org/packages/f26-backgrounds
Created attachment 352324 [details] testing xml from /usr/share/backgrounds/f26/default-animated to illustrate the issue
So I've been debugging this a bit, and I've been able to narrow down the problem. The transition loads just fine, but https://git.gnome.org//browse/gnome-shell/tree/js/ui/background.js#n372 gives an unexpected result for ]0,1[ (that is, only 0 and 1 work correctly). It's not immediately clear to me what's going wrong, but the issues appears to be in the mutter/cogl layer rather than gnome-desktop or gnome-shell.
(In reply to Florian Müllner from comment #4) > It's not immediately clear to me what's going wrong, but the issues appears > to be in the mutter/cogl layer rather than gnome-desktop or gnome-shell. Thanks for debugging. I linked the related downstream report to this page https://bugzilla.redhat.com/show_bug.cgi?id=1450260
GNOME is going to shut down bugzilla.gnome.org in favor of gitlab.gnome.org. As part of that, we are mass-closing older open tickets in bugzilla.gnome.org which have not seen updates for a longer time (resources are unfortunately quite limited so not every ticket can get handled). If you can still reproduce the situation described in this ticket in a recent and supported software version, then please follow https://wiki.gnome.org/GettingInTouch/BugReportingGuidelines and create a new ticket at https://gitlab.gnome.org/GNOME/mutter/-/issues/ Thank you for your understanding and your help.