I'm using QGIS 1.8. I'd like to customize label features on an existing shapefile using the new label engine and it's "data defined settings" option. I'd like to know what the attribute table field types should be for each of the settings: All 7 font options, all 2 buffer options, and all 6 position options. Should they all be numeric fields, or some text, or both? I want to create these fields in the attribute table correctly so that I can map them to the label field settings. I can't find information on the proper field types anywhere. Thanks for your thoughts.
There is not a complete set of documentation for the data defined labeling features, but here is a breakdown of their values, and how they are used by QGIS's PAL labeling engine in version 1.8:
The following columns can not be data defined unless X and Y are already defined. This is a regression from some features of the older labeling engine (like defining rotation independent from X and Y), but is how the advanced labeling currently works in 1.8.
You could give a try to new EasyCustomLabeling plugin (http://hub.qgis.org/projects/easycustomlabeling) that duplicates a layer and adds those "data defined" labeling fields.. Here are fields definitions types used in that plugin:
QgsField( "LblX", QVariant.Double, "numeric", 10, 2)
Hope it helps