Qgis3 port is very slow and unresponsive

[Malauch]

Since qgis3 port verions 3.0 I noticed that it is very unresponsive. I even created the ticket in the past: #56169 However, official binaries works fast. Today I found the time to make some experiments and try to compile qgis3 port with qt59. Now I can confirm that this is a culprint for slowing down of qgis3 port. Additionaly qt59 fixes other problem with no option to resize modal windows: #56911. Naturally it also introduce some new bugs like huge mouse cursors (for addint new features and etc.).

For now running qgis3 port with qt59 is only workaround to make it usable for serious work. Therefore It would be nice to have convienient option to +qt59 variant. Please add this variant to the port.

To Install qgis3 port with qt59 I had to manually edited two ports definition:

1. Uninstall all ports and macports files.
2. To qgis3 port I added these lines: changeset:312eec49096c92819071c3e87bea0ef9a562eed8/macports-ports
3. I also had to Install older version of py-pyqt5 port. I installed 5.9.2 version. The recent version just install qt5 port which makes conflict with qt59.

[Veence (Vincent)]

I’m going to do this if you request it, but I’m a bit surprised, because the QGis3 I run on my computer has been linked with Qt 5.10 and seems to work normally. Well, I agree modal windows cannot be resized, but it hasn't really bugged me until now. However, what do you think work slow? Do you have any specific example to support this?

[Malauch]

It's easiest to spot the difference in speed when adding very quickly new points to point layer. With QT 5.9 all points shows immediately on canvas, with QT 5.10 it's shows with a lot of lag. Naturally it's just a test to show a problem, not a real task. However when editing medium or large project that lag is visible and very annoying when panning the canvas, zoom in, zoom out. Sometimes when panning, some part of map is blank for 1-2 seconds (all layers are local files with vectors).

I'm curious about how it works with QT 5.11 but it's not on a macports yet.

[Veence (Vincent)]

Ok. A qt59 is feasible, but some other packages need to be updated as well, such as qca-qt and most importantly py36-qt5 which currently has no option to build on a backward version of Qt.

[dmarteau (David Marteau)]

The problem has been reported upstream: ​https://issues.qgis.org/issues/19546

Please, take care that full Qt5.11 supports for qgis3 is a work in progress (see ​https://github.com/qgis/QGIS/pull/7513) and should not be ready before Qgis 3.4 .

[Malauch]

Today I installed recent master with QT 5.11.1 and it's even worst. QGIS became extremly slow in every action on canvas, opening new windows and etc. Addtional mouse cursors are to big (the same problem like with QT 5.9) but modal windows are resizeable again.

By the way I installed QGIS master by manual modifying qgis3 port to download recent master from github. It installed without any problem.

[Veence (Vincent)]

I’m just turning back from vacations.

I’ll try QGis with Qt 5.11 today.

I get from your message that you downloaded and installed the master version from GitHub. Does it have all the problems you reported, or does it work fine? In which case we could change the official Portfile to make it refer to the master version.

[Malauch]

Sorry, I just didn't write it clearly enough. I have installed recent QGIS3 master with QT 5.11.1 via Macports. QGIS have compiled and installed without any errors. However general performance is even worst then with QT 5.10.1. Every action on map canvas is very laggy, all windows are drawing incredibly slow and etc. Bug with to big mouse cursor has returned. Only improvemnt is that modal windows are resizeable again.

[Veence (Vincent)]

Does the 3.2.2 version I committed correct that?

[Malauch]

I installed QGIS 3.2.2 (it was installed with QT 5.11.1) and it is still broken (very slow). QGIS3 on QT 5.11.1 it's even slower then ArcGIS Pro. :)

[Veence (Vincent)]

I’m a bit nonplussed. I tried various things, including digitizing a point vector layer, with QGis 3.2.2 and really I didn't notice any slowness. The points appear almost immediately, the scrolling is fluid. Also, I don’t seem to have any problem with the cursor size. What seems also weird to me is that you’re the only one to report this. It would probably be worth checking if other people experience the same sluggishness.

[Malauch]

I have made additional test and now I know everything. It's all about buggy high resolution support in QGIS3. It's not even about Retina multiplier but high resolution as general. General slowness is proportional to resolution. When display resolution is below lower then 1600x1000 then there is no visible lag. Higher resolution are making QGIS laggy. Higher then 2560x1440 and it's more and more unsuable. Full 5K 5120x2880 is just unusable.

Only me report this bug, probably because there is no many people which uses QGIS3 installed via MacPorts on high resolution screens. Official installation package is still on QGIS 5.9.6 and works ok.

[Veence (Vincent)]

Ah, excellent. That explains why I didn't get any sign of lag (I’m using it on a MacBook Air without even Retina display). Perfect. So I assume this has to do with the graphics performance in Qt?

I’m closing this bug because it seems to be unrelated to MacPorts itself, but please continue to comment. Did you report this upstream?

[Malauch]

I just copied my comment to bug report on official QGIS bug tracker.

[Malauch]

Just for information, there is crowdfunding campaign to fix that bug and many other which are related to QGIS3 on MacOS. ​http://blog.qgis.org/2018/09/12/macosx-specific-bug-fixing-campaign/

[Veence (Vincent)]

Thanks for that information! I’ll relay it in my magazine. Since the guy seems to be French, that’s gonna be all benefit for him.