How Can I Make QGIS Stop Blinking Every Time I Pan?

Question

The way QGIS draws the canvas when panning is quite annoying. If I pan the map even a little bit everything goes blank for a second or two before the layers are drawn. It looks like this happens only when the layer content is supposed to be downloaded (my PostGIS layers are drawn without hurting my eyes), so this might be just a problem with the configuration rather than the code. Does anyone have a solution?

Oh, and the question should be "how can I make QGIS suitable for epileptics?". It's that annoying.

EDIT to pose question for QGIS 2.4 onwards:

This still appears to be an issue in 2.4. There seem to be some helpful setting under Settings > Rendering but these don't help the issue. QGIS just lacks the nice, slippy, smooth feel of other map viewers. Is caching still on the cards?

Answer 1

For anyone who is still having this problem, in QGIS 2.10 you can go to Settings > Options > Rendering, and change the Map update interval to be larger. If QGIS can render all of the layers in less than this amount of time, it will update the whole canvas at once, which gets rid of the blinking. If it cannot update all the layers before this interval passes, it will show a partial update, which causes the blinking. You can view how long a canvas update takes by enabling the debugging flag in the rendering settings.

Answer 2

I'm afraid the answer is: You can stop QGIS from blinking by funding a developer to implement a non-blinking version.

Answer 3

There's an easy "fix" if you're brave enough to change the code source of QGIS:

Open 'qgsmaptoolpan.cpp', and into the corresponding 'canvasMoveEvent' member, add the sentence "mCanvas->refresh();" as follows:

void QgsMapToolPan::canvasMoveEvent( QMouseEvent * e )
{
  if (( e->buttons() & Qt::LeftButton ) )
  {
    mDragging = true;
    // move map and other canvas items
    mCanvas->panAction( e );
    mCanvas->refresh();
  }
}

(QGIS version 1.8 Lisboa)

This will force a continuous refresh on the map while you are panning with the mouse. It could go a bit slower, but it works fine, yeah, a relax for my eyes.

Answer 4

This was fixed in QGIS 3.18, the map redraws are now using existing elements: https://www.qgis.org/en/site/forusers/visualchangelog318/index.html#feature-smarter-map-redraws