Bug report #15213: During rendering WMS-images is removed too early? - QGIS Application - QGIS Issue Tracking

Bug report #15213

During rendering WMS-images is removed too early?

Added by Richard Duivenvoorde over 8 years ago. Updated over 5 years ago.

Status:	Closed
Priority:	Normal
Assignee:	-
Category:	Map Canvas
Affected QGIS version:	master	Regression?:	No
Operating System:		Easy fix?:	No
Pull Request or Patch supplied:	No	Resolution:	end of life
Crashes QGIS or corrupts data:	No	Copied to github as #:	23151

Description

If you have a (not so fast) WMS layer, for example one of the layers from:

http://geoservices.knmi.nl/cgi-bin/RADNL_OPER_R___25PCPRR_L3.cgi?

when you pan or zoom in, the total images is removed before the new (to retrieve) wms image is retrieved.

this results in flickering. Especially when you start using such layers in for example TimeManager.

It would be nice if the 'old image' is at least shown untill the new one is fully(?) received. Even if that means for example if you panned half a mapcanvas that you will not see anything on that half untill the new image comes in.

I had a look into the qgsmaprendererjob.cpp, but could not fully understand where the old image is cleaned up, and how to make this specific for wms.

And as a bonus,... (working with WMS-T (time dimension) layers in combi with TimeManagerplugin): it would be cool if the wms-images could be cached based on the full url. In case of 'moving over time', the extent stays perfectly the same, and only the &TIME= component changes. Making it perfectly suitable to be cached, so playing back or replaying a time-laps could go without resending the GetMap requests?