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List:       mapserver-commits
Subject:    [mapserver-commits] [MapServer/MapServer] ac6053: Allow Expressions to be set for LABEL properties u
From:       Seth G <noreply () github ! com>
Date:       2023-06-22 10:46:35
Message-ID: MapServer/MapServer/push/refs/heads/main/94c1e5-ac6053 () github ! com
[Download RAW message or body]

  Branch: refs/heads/main
  Home:   https://github.com/MapServer/MapServer
  Commit: ac6053904b0a8877ff88b9a0f139f51c8b08269a
      https://github.com/MapServer/MapServer/commit/ac6053904b0a8877ff88b9a0f139f51c8b08269a
  Author: Seth G <sethg@geographika.co.uk>
  Date:   2023-06-22 (Thu, 22 Jun 2023)

  Changed paths:
    M mapfile.c
    M mapscript/python/tests/cases/label_test.py
    M mapscript/swiginc/label.i

  Log Message:
  -----------
  Allow Expressions to be set for LABEL properties using MapScript (#6904)

This pull request allows the new functionality in #6884 of using an expression in a \
LABEL PRIORITY in MapScript.  It takes a similar approach to setting attribute \
bindings for properties, which requires using the appropriate attribute constant such \
as `MS_LABEL_BINDING_PRIORITY`:

```python
label = mapscript.labelObj()
label .setExpressionBinding(mapscript.MS_LABEL_BINDING_PRIORITY, "[MY_ATTRIBUTE] * \
2") ```

This is a little clunky but is at least consistent with setting attribute bindings:

```python
label = mapscript.labelObj()
label.setBinding(mapscript.MS_LABEL_BINDING_COLOR, "NEW_BINDING")
```

While testing this I noticed that the `writeLabel` function used to write Mapfile \
objects ignored expressions. This seems an oversight also for the `LABEL` `SIZE` \
expression. If this approach seems appropriate I can use this for other expression \
bindings.

Something to note is that a property could have an attribute binding **and** an \
expression binding set. In this case the attribute binding currently takes precedence \
when calculating a shape value, so it also takes precedence when writing to a \
Mapfile. 

In theory setting an expression could also set the attribute binding to NULL. This is \
not currently the case for MapScript or when reading a Mapfile twice.


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