Vertical Displacement of line text

[osm@…]

It would be nice to be able to write text along a line with a "vertical" displacement, so that a streetname could be rendered alongside the street. Similar to that for the dy attribute to point textsymbolizer.

<TextSymbolizer name="lcn_ref" face_name="DejaVu Sans Book" size="14" fill="blue" halo_radius="2" placement="line" dy="80"/>

The displacement would probably refer to the distance between the line and text path at right angles to the line, rather than a vertical displacement on the final render. The latter wouldn't work for north-south streets!

Consideration would need to be given to corners in lines, e.g. the displacement given would indicate the gap between the two paths, and would have to be maintained around the corners.

[gravitystorm]

Image showing poor text placement

[gravitystorm]

This was made possible by [493] about five months back, but the text positioning is often sub-optimal, with characters overlapping one another and other positioning artefacts.

For example, see the attached file with three examples of the number 16 written with a dy = '5' on the TextSymbolizer. The first is correct on a straight line, the second exibits excessive spacing between characters, and the third shows characters badly overlapping. <TextSymbolizer name="lcn_ref" face_name="DejaVu Sans Book" size="14" fill="blue" halo_radius="1" placement="line" dy="5" minimum_distance="50"/>

[dave]

New displacement handling style

[dave]

I've changed how displacement is done in the r597, now the same angle of displacement is applied to the whole string, instead of on a per character basis. Example: http://trac.mapnik.org/attachment/ticket/38/fix_1.png

Test and give some feedback :)

[anonymous]

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[springmeyer]

Andy, Have you had a chance to test and comment? Is Dave's r597 working for you?

[springmeyer]

noting here that Ticket #71 requests a related feature - line offsetting (in addition to text offsets)