Bug report #19546

QGIS 3 slow on macOS at high resolutions

Added by Michal Jurewicz 6 months ago. Updated about 1 month ago.

Affected QGIS version:3.4.2 Regression?:No
Operating System:MacOS High Sierra 10.13.6 Easy fix?:No
Pull Request or Patch supplied:No Resolution:
Crashes QGIS or corrupts data:No


I use QGIS installed via MacPorts. Since QGIS 3.0.0 I noticed that it's very slow and unresponsive. Additionaly all modal windows can't be resized. However in the same time official binaries works fast but has some other problems (huge and misaligned mouse cursor and some others).

Today I made some tests with QGIS 3.2.1 and I confirmed that culprint is QT5.10. When I compiled QGIS with QT5.9 it works fast but has the same problem like official binaries. When recompile it with QT 5.10 it is very slow, size of modal windows are not adjustable but some other UI glithces are fixed.

I don't know if it is more about bugs in QT or QGIS but right now there is no option to have good user experince with QGIS 3 on MacOS.


#1 Updated by Giovanni Manghi 6 months ago

  • Category changed from Unknown to Build/Install

#2 Updated by Michal Jurewicz 5 months ago

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.

#3 Updated by Michal Jurewicz 5 months ago

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 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.

#4 Updated by Giovanni Manghi 5 months ago

  • Subject changed from Problems with QGIS 3 and QT 5.10 on MacOS to QGIS 3 slow on macOS at high resolutions
  • Category changed from Build/Install to OsX UI

#5 Updated by Denis Rouzaud 5 months ago

can anyone confirm that this is really mac specific?
is anyone working on windows with resolution screen?
(will ask on the mailing list)

#6 Updated by Denis Rouzaud 5 months ago

  • Category changed from OsX UI to mac_os_specific

#7 Updated by Michal Jurewicz 5 months ago

I may try it on virtual machine but I don't know how to install QGIS on Windows with QT 5.10 or 5.11. Official installation package is with QT5.9. Is there any documentation how to do it?

#8 Updated by Giovanni Manghi 5 months ago

  • Status changed from Open to Feedback

#9 Updated by Denis Rouzaud 3 months ago

I had a discussion with William Kyngesburye who told me that this should be fixed in Qt 5.12.
Let's see what comes out with QGIS 3.4 next week.

#10 Updated by William Kyngesburye 3 months ago

I finally got Qt 5.11 installed, built QGIS 3.2.3 with that. Tested on a retina Mac with no slow issue. Though that was on macOS Sierra, I haven't upgraded High Sierra, yet. I'll package up an installer so others can test.

#11 Updated by William Kyngesburye 3 months ago

Here is an installer for QGIS 3.2.3 built with Qt 5.11.1.


#12 Updated by Michal Jurewicz 2 months ago

I tried 3.4.1 on High Sierra and Mojave and there is still the same problem with some lag. It feels just a little better but I need to make some test with bigger projects.

#13 Updated by Michal Jurewicz about 1 month ago

Just for your information, QGIS 3.4.2 (QT 5.11.2) is still very unresponsive. Below some screen records with small project. Just panning and zooming the map and closing the project. As you can see it's very slow. I use iMac Pro - it's Retina 5K resolution.


I hope that QT 5.12 is going to fix it.

#14 Updated by Michal Jurewicz about 1 month ago

I have tried QGIS 3.4.2 built and run with QT5.12 and it's more less the same or even slightly worse.

#15 Updated by Giovanni Manghi about 1 month ago

  • Affected QGIS version changed from 3.2.1 to 3.4.2

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