According to https://www.freedesktop.org/software/appstream/docs/chap-Metadata.html#sect-Metadata-GenericComponent "The <image/> tag may have the following properties: ... height ..." If the width/height attribute is omitted, no screenshots are shown in the rightmost Discover pane.
Can you provide an example so I can reproduce?
Ok, when looking for examples I noticed this is probably not related to the width/height attribute. One non-working example is poedit. The appdata contains: <screenshots> <screenshot type="default"> <image type="source">https://upload.wikimedia.org/wikipedia/commons/c/c2/Poedit_1.8.1_en.png</image> </screenshot> </screenshots> When I click on the poedit entry, wireshark tells me a connection to upload.wikimedia.org is established, and it transfers e few 100 bytes in each direction. The URL is correct, the screenshot is ~62kByte. Pragha-music-player (working): <screenshot type="default"> <image type="source">http://pragha-music-player.github.io/images/Pragha-Xfce-HIG.png</image> </screenshot>
Ok, found a different possible cause - all non-working apps have exactly *one* screenshot, multiple screenshots work.
Which platform are you testing on? I don't have poedit neither on archlinux or ubuntu.
Git commit 3297fe6026edebb8db72bb179289bee844c26ae3 by Antonio Larrosa. Committed on 02/11/2016 at 11:40. Pushed by antlarr into branch 'Plasma/5.8'. Make screenshots visible when there's only one screenshot too Summary: Applications with only one screenshot also deserve to have it visible. FIXED-IN: 5.8.4 Test Plan: Open any application that only has one screenshot (e.g. poedit). No screenshot is shown until this patch is applied. Reviewers: davidedmundson, apol Reviewed By: davidedmundson, apol Differential Revision: https://phabricator.kde.org/D3223 M +1 -1 discover/qml/ApplicationScreenshots.qml http://commits.kde.org/discover/3297fe6026edebb8db72bb179289bee844c26ae3