Merge pull request #45 from mapycz/line-offset-info

more detailed info about offsetting lines

Author: springmeyer

_posts/blog/2015-07-11-3.0-cartographer.md

@@ -42,9 +42,17 @@ For PostGIS datasources with polygons that follow the left-hand rule instead, if
 
 The existing `line-offset` in the stylesheet will need to be inverted.
 
-### Text offsetting from lines
+### Offsetting from lines
+Direction of all offsets from lines is inverted. These properties have to be changed to achieve compatibility between 2.2 and 3.0:
 
-Handling of text offset from lines has changed. To get consistent behavior between 2.2 and 3.0, use `vertical-alignment: middle`. This may require adjustments to the `text-dy` value.
+* `TextSymbolizer` with line placement
+  * swap `top` and `bottom` values in `vertical-alignment`
+  * multiple `dy` by -1
+  * Take care of `vertical-alignment` and `dy` in `Layout` and `Placement` nodes.
+* `LineSymbolizer`, `LinePatternSymbolizer`, `MarkersSymbolizer` with line placement
+  * multiple `offset` by -1
+
+Special attention should be taken to `TextSymbolizer` when `dy` is not zero and `vertical-alignment` is not set. In such situation `vertical-alignment="middle"` needs to be set to get consistent behavior between 2.2 and 3.0.
 
 ### Harfbuzz support