Bug report #18322

Zooming in causes canvas to go blank

Added by Patrick Dunford almost 6 years ago. Updated almost 6 years ago.

Category:Map Canvas
Affected QGIS version:3.0.0 Regression?:No
Operating System:Debian 9.3 Easy fix?:No
Pull Request or Patch supplied:No Resolution:
Crashes QGIS or corrupts data:No Copied to github as #:26212


I just started using a project in Qgis 3 and it has some raster images loaded in the background. Quite often when I zoom in, the canvas goes completely blank and never redraws. This behaviour has never been seen in 2.18

Screenshot_2018-03-06_03-03-54.png (48.4 KB) Patrick Dunford, 2018-03-05 03:04 PM


#1 Updated by Giovanni Manghi almost 6 years ago

  • Status changed from Open to Feedback

Please attach sample project with sample data, as of course this is not a issue that shows in general.

#2 Updated by Patrick Dunford almost 6 years ago

That's not easy to do as it is a large project with hundreds of raster images.

I can describe what is happening and state that none of the following versions have this problem: 2.14.22, 2.18.17 or 2.99 build 313ec55.

Basically I can have my project open, and all the hundreds of rasters are turned off. They are not being displayed on the canvas. The only layers displayed on the canvas are vector layers.

I started to see this happening as soon as I displayed one single raster layer but after a lot of testing I started seeing it happening even with none of them displayed.

Basically you just drag the canvas, zoom, etc, whatever until a magical moment happens where it blanks the canvas as preparation for redrawing and never redraws, instead all you see is a continuously moving progress bar that never stops.

It's like it somehow ran out of or leaked all the resources and there are none left, or however one would describe it.

Doesn't look like any out of memory problem. It doesn't crash on any of the VMs for the older versions, those VMs typically have around 8 GB allocated memory. On my 24 GB PC the memory is nowhere near all used up, no swap or anything.

I just left it sitting there and came back 2 hours later and it's still hung. But even in this state you can still save the project and quit normally, you just can't do anything else.

#3 Updated by Patrick Dunford almost 6 years ago

https://my.pcloud.com/publink/show?code=kZAfT57Z0doVKojjEQ4dvJQfYAmsOQpolq4k is currently uploading, needs another hour or so.

Was retested under 3.1 build 871132e on Devuan 2.0

#4 Updated by Patrick Dunford almost 6 years ago

Download the Root folder
Project file called 18322 TEST PROJECT
see attached screenshot

#5 Updated by Giovanni Manghi almost 6 years ago

  • Status changed from Feedback to Open

#6 Updated by Patrick Dunford almost 6 years ago

Just FTR this doesn't just happen with big projects. I have a project at the moment with 10 vector layers and about a hundred rasters, after a few days of work it's just frozen up. It just happens a lot faster with a big project, that's all.

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