Set data defined text angle without setting x and y coordinate using new style labelling

Question

I have a problem setting angled text labels with the new-style labelling dialog. The situation is this:

I have a shape file which only contains only labelling texts. This is a point layer, and it contains all information needed for the label, like text size, font etc. - while the placement of the label is steered by the cordinates of the geometry of the point, so there are no attributes containing the X and y coordinate. This is legacy data, so I have no choice in the matter - the labels aren't linked to objects in other shapefiles, they're just there by themselves, having originally made up a separate toponym layer.

If I use the old labelling mechanism, I can enter the text angle field in the appropriate place (in my data it's called TextAngle), and the text is displayed at the desired angle. But if I use the new-style labelling dialog, the text angle field in the 'position' section of the 'data defined settings' tab remains greyed out unless I set the fields 'x-coordinate' and 'y-coordinate'. Yet I don't have fields containing x and y coordinates in my data - they are implicit, being the very coordinates my data points occupy. They appear when I get info for the elements as 'derived', but they aren't in the attribute table. If I try and trick the dialog by entering something else in the 'x-coordinate' and 'y-coordinate' fields, I can enter my text angle field, but it has no effect.

Am I missing something? I'd really rather use the new-style labelling, since the buffering is nicer.

Answer 1

In fact, it's very easy to add x-ordinate and y-ordinate columns automatically to the attribute table of a point shapefile: Vector -> Geometry Tools -> Export/Add geometry columns.

Answer 2

Currently it's not possible to rotate new labels without specifying the x/y position. It's one (if not the) major blocker for removing old labeling engine.

You can add explicit x and y attributes using Field Calculator $x and $y operators as a work-around.

Answer 3

I found a python module to do the job. It's called shapefile.py and I found it at

http://code.google.com/p/pyshp/

Using this module, adding the x and y coordinate as attributes was quite straightforward. I wrote a little script called add_xy.py:

#! /bin/python

import sys
import shapefile

sf = shapefile.Reader(sys.argv[1])
fields=sf.fields
shapeRecs = sf.shapeRecords()
fields.append ( ['x-coord', 'F', 19, 11] )
fields.append ( ['y-coord', 'F', 19, 11] )
w = shapefile.Writer(shapefile.POINT)
for f in fields:
w.field (*f)
for r in shapeRecs:
    r.record.extend(r.shape.points[0])
for r in shapeRecs:
    w.point ( *r.shape.points[0] )
for r in shapeRecs:
    w.record ( *r.record )
w.save(sys.argv[2])

I called this like

python add_xy.py input.shp output

Now when I load output.shp into QGIS, I have the additional coordinate fields and I can use the angle defined in the data. Bit of a circuitious route, but it works :)