Bug report #14172

QGIS freezes after canvas refresh when using graduated style with many classes

Added by Sebastian Dietrich about 8 years ago. Updated about 7 years ago.

Category:Map Legend
Affected QGIS version:master Regression?:No
Operating System: Easy fix?:No
Pull Request or Patch supplied:No Resolution:not reproducable
Crashes QGIS or corrupts data:No Copied to github as #:22174


We have some layers that make use of the graduated style with many classes (a few hundred). After upgrading from 2.10 to 2.12.0 the projects containing those layers started to misbehave:
A short time (around one second) after the canvas has been updated by a pan or zoom operation, QGIS freezes for a few seconds. The length of the freeze is proportional to the number of classes in the graduated style, regardless of whether the layer is visible. It happens even if the layer is empty.

I attach a sample project. To reproduce:
  • Open the sample project
  • Select the panning maptool
  • Zoom using the mouse-wheel
  • Immediately start panning by pressing the left mouse-button and continually moving the mouse

Note that QGIS freezes during the last step for a few seconds (depending on your hardware).

FreezeGraduatedStyle.qgs - Sample project to reproduce the bug (2.2 MB) Sebastian Dietrich, 2016-01-26 06:45 AM

Related issues

Related to QGIS Application - Bug report #13078: Size of legend items Closed 2015-07-06


#1 Updated by Sebastian Dietrich about 8 years ago

  • Priority changed from Normal to High

Bisected the bug to 8776449a148e8b5422a73de45e5a364d1a7e5d5d, part of PR 2245, addressing #13078.

#2 Updated by Giovanni Manghi about 7 years ago

  • Priority changed from High to Normal
  • Status changed from Open to Feedback
  • Category changed from Symbology to Map Legend


while I can see some kind of lag (not very long to tell the truth, and no freeze) on 2.18.2 I really cannot appreciate the implications as the attached project does have any data (well it has, point?crs=EPSG:4326&memoryid={c97b4801-9e29-4621-998a-1f38d50a422f} but there are no features), so I cannot also say if previously behaved in a different way.

Can you add more data/details? How this impacts real life work?

#3 Updated by Giovanni Manghi about 7 years ago

  • Resolution set to not reproducable
  • Status changed from Feedback to Closed

Closing for lack of feedback.

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