QGIS » QGIS Application

Does enabling cache improve this significantly?

I do some tests.
It happened even with shapefile.

If I checked the "use cache render" this don't happened.

It don't happened even if I deselect the "use cache render", but set
the number of features to draw before updating the display to zero (0).

In effect it seem happened only when this settings is set to some number other than zero.

Infact I usually use as settings 3000 or 5000 features because I have postres with
some table very big (1.000.000 features and so on).
And use the 0 setting is unacceptable because it mean wait some minutes before to see something (to full-extent).
I surely prefer set to 5000 features before drawing to have a feedback of progress of display-ing.
But this double redrawing is quite boring.

Now I test better with the use of caching.

Replying to [comment:1 pcav]:

Does enabling cache improve this significantly?

Can't see that happen at all using Trunk on Linux -- with or without rendering cache.

Can you test with Trunk?

I'm able to see what Andrea is saying.

*) With render caching enabled, then the "number of features to be drawn before updating the display" does not work anymore. If you refresh the map the vector will be rendered as if the option is set to "0", so I guess that it would be needed to disabled this option when the render caching is enabled.

*) With the render caching is disabled and you choose something different from "0" in "number of features to be drawn before updating the display" (and you are using a vector with many features, I'm testing myself a 50000 polygons vector) then the problem is evident.

Add another (small) vector and then start enabling/disabling it in the TOC, the big vector is continuously redrawn at each click... very annoying.

In general without render caching enabled (and "number of features to be drawn before updating the display" set to 0), enabling/disabling a vector in a project where there are many others vectors, or a few big ones, it takes really a lot.

I'm on trunk/ubuntu 10,04 and with the render caching enabled, on the contrary, it works really smooth.

It the options enabled by default?

Now I can see even better:

have a look at the following screencast:

http://www.faunalia.pt/downlaods/redrawns.mpeg

the vectors seems to be redrawn TWICE when toggling editing and it is even redrawn when clicking "Ok" or "apply" in QGIS menus.

sorry wrong link

http://www.faunalia.pt/downloads/redrawns.mpeg

Thank you, can see it now.

another useless redraw:

when the identify window is set to be opened docked but it is not (yet) visible: picking the identify tool (or any other one) causes the canvas to be refreshed.

another useless redraw, see #2352

Another huge waste of time:

in a project add a group of layers plus other layers and some kind of overlay. I tested with a bunch of PostGIS layers, some of them grouped and a WMS overlay. When removing the group it seems that the canvas is redrawn as many times as the number of layers in the group being removed.

see also #3427

If I do anything that causes the Identify Results dock to appear, such as clicking on the Identify Features or Select single feature buttons, the entire canvas redraws. Seems like a pointless redraw since the dock, in my case, does not change the canvas dimensions when it opens; it just encroaches on the Layers dock.

If I close the Identify Results dock, there's no redraw, but it happens again if I click on one of those buttons.

(from #5087)

Another useless redraw: Data is redrawn twice if "option/rendering/feature of feature to draw before updating the display " is set to something different than 0. Not good since this option is really nice to let user be patient for huge datasets, he has to be twice more patient ;-)
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