Save style/renderer in the QGIS project file

Question

I have a vector layer in QGIS and using pyqgis I have created two styles/renderers:

style_1 = QgsFeatureRendererV2(...)
style_2 = QgsFeatureRendererV2(...)

vector_layer.setRendererV2(style_1)

One of the styles is assigned to the vector layer and the other one is for later use.

Saving the QGIS project will store style_1 with the layer but the second style will be lost if the project is closed. I would like to store the second style in the QGIS project file, not in a seperate style file.

Using QgsProject.writeEntry(...) I can store numbers, texts and lists in the QGIS project file.

Question:
Is there a corresponding method for storing custom styles/renderers in the QGIS project file?

Answer 1

Interesting question! Although I can't give a direct answer, an alternative approach could be to define a function containing the code for the second style and save this in a macro. This way, when you load the project, the style is available to be added to a layer by running the function from the Python Console.

You can add a macro for your project from the menubar:

Project > Project Properties > Macros

Enable the checkbox and enter your code in a function. E.g.:

def style(layerName):
    vector_layer= QgsMapLayerRegistry.instance().mapLayersByName( layerName )[0]        
    style_2 = QgsFeatureRendererV2(...)
    vector_layer.setRendererV2(style_2)

Click Apply then OK. Then make sure QGIS allows macros to be run by from the menubar:

Settings > Options > General > Project files > Enable macros

And to run the above function from the Python Console, you can type:

style('name of layer')

Don't forget to include single quotation marks as the name of the layer should be a string!