[GIS] In QGIS, how to control the rendering order of objects in a single layer with rule-based symbology

qgisrendering

In QGIS 2.18, I have a symbology of points in a layer based on rules.
I want to control the rendering order of the layer in QGIS, with on top the type with the lower counts.

Intuitively I would expect to observe a rendering order modification by drag-droping the types, but this does not occur. A related question is of no help.

As you can see on the image I have tried using the "control features rendering order" but without success.

How could I do?

Best Answer

Go to Symbol Levels, and there choose the order of rendering. Categories with lower number will be rendered first, and thus will show below categories with higher number.

In the above example, drive oui is below drive NULL, and both are below drive non.

Related Solutions

[GIS] How to control the rendering priority/order of feature layers

The Layer class has methods suspend() and resume(), so you could catch the onUpdateStart event to suspend all but the lowest layer from drawing. Then, in the onUpdateEnd event of the lowest layer you could call resume() for the next layer up, and so on.

Or if you're using FeatureLayers you could trigger each layer's refresh() method in order. Either way would probably be subject to random bugs.

Have you considered looking at the map services to see if any of them are slowing things down? Limiting the amount of data or implementing some kind of clustering might be better than trying to hack the layer refresh process.

[GIS] How to use PyQGIS ( Python QGIS API ) to open/close Update Drawing Order checkbox in QGIS2’s Layers (Legend Interface)

To stop rendering you need to call:

canvas.freeze(True)

then to undo:

canvas.freeze(False)
canvas.refresh()

Best Answer

Related Solutions

[GIS] How to control the rendering priority/order of feature layers

[GIS] How to use PyQGIS ( Python QGIS API ) to open/close Update Drawing Order checkbox in QGIS2’s Layers (Legend Interface)

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