[Qgis-developer] Labeling of starts and ends of a line

[Andreas Neumann]

Hi,

Sounds interesting to me. Cartographers would love it! Esp. the dragging 
along a line. Sounds like something for QGIS 2.1.

The other thing that bothers me a lot is the efficient (performant) 
labeling of banana-shaped polygons ... this would be kind if it could 
still be fixed in QGIS 2.0. But I'd be also patient and wait for 2.1 ;-)

Thanks a lot,
Andreas

On 3/5/13 9:16 PM, Larry Shaffer wrote:
> Hi,
>
> I have an idea concerning this that was originally cooked up for an 
> approach to doing multi-line curved labels [0]. I refer to them as 
> 'label anchors,' which would be for line and polygon features (though 
> they could be handy for point features). The concept is roughly like so:
>
> * An anchor point is sent into PAL that constrains where a single 
> label candidate is generated. The point could be data defined or a 
> reference to a calculate-able point, e.g. midpoint, beginning/end, 
> leftmost/rightmost, nearest point on on line relative to off-line 
> point, point furthest from extent center, etc..
>
> * With data defined anchors, a map tool could be made that allows the 
> user to visualize and dynamically move the anchor along a line or even 
> place the anchor off the line (e.g., over a nearby related feature, 
> like a building-to-street relationship). This would allow data defined 
> curved labels to work like moving text along a path in an illustration 
> program, and allow for precise control over label placement along a 
> line without forcing full pinning of the label.
>
> * Additional options could be weighting the above/below line labeling 
> option (for off-line anchors), and quadrant and offset placement of 
> the label relative to anchor.
>
> There may be other advantages to sending controllable label anchor 
> points into PAL. This is different than data defined x/y, which 
> totally skips chosen placement algorithms and essentially treats the 
> feature geometry as a point. Right now it is just conceptual, and I'd 
> like to hear some feedback.
>
> Regards,
>
> Larry
>
> [0] http://hub.qgis.org/issues/4442
>
>
> On Tue, Mar 5, 2013 at 12:24 PM, Andreas Neumann <a.neumann at carto.net 
> <mailto:a.neumann at carto.net>> wrote:
>
>     Hi,
>
>     So this sounds like its not happening any time soon. Definitely
>     after QGIS 2.0
>
>     In this case I will do a helper layer and restrict that line using
>     linear referencing. My data is in Postgis and I can use its linear
>     referencing functions.
>
>     For the long run I would want to get rid of that helper layer and
>     find a QGIS only solution.
>
>     Thanks for your reply!
>
>     Andreas
>
>     On 3/5/13 8:13 PM, Martin Dobias wrote:
>
>         Hi Andreas
>
>         On Tue, Mar 5, 2013 at 2:20 PM, Andreas Neumann
>         <a.neumann at carto.net <mailto:a.neumann at carto.net>> wrote:
>
>             Hi,
>
>             Maybe Larry, Martin or Marco can answer this:
>
>             I am looking for the possibility to label a line at the
>             start or end (plus a
>             given offset from start/end). As far as I know this is not
>             yet possible now?
>             Does PAL support this and is it a matter of exposing this
>             option in the GUI
>             or is this not yet supported at all?
>
>         That's not supported as far as I know. It would be handy to have a
>         functionality in PAL that would allow us to constrain where
>         the label
>         candidates should be created and how they should be
>         prioritized. That
>         would also allow us to decide where to put labels for point
>         features
>         and which positions are preferred.
>
>         Martin
>
>
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