Information tab in WMS layer properties is unresponsive if a WMS service contains many layers

[andreasneumann]

Issue
When a WMS service contains many layers and the user opens the layer properties, QGIS becomes unresponsive for a while:

• Opening the layer properties takes quite a long time (often several seconds)
• Esp. opening the "Information" tab of the WMS layer takes very long (several seconds, up to a minute)

How to Reproduce

Here is a WMS service with many layers for testing:
https://geo.so.ch/api/wms

You can pick any layer, all have the same "unresponsiveness". e.g. you can pick "ch.so.arp.wanderwege"

QGIS and OS versions

Tested with Master, 3.4 and 3.8 on both Linux and Windows

[elpaso]

@andreasneumann I'm working on it and the main reason for this slowness is that there is a huge amount of HTML that is being constructed but the good new is that there are a few improvements I can make that will make it much faster.

[andreasneumann]

@elpaso Thanks. If you already know what to do to fix this issue, then please go ahead and do it under the general bug fixing effort. Otherwise I would assign our support contract company to have a look at it.
Yes - the HTML in the information tab is - huge - for large WMS services.

[elpaso]

Yes, I already have a patch that definitely fixes the issue but I need to fix some minor cosmetic aspects.