From bdf65ac8f0b6c7f1a06d2a906bd065658493ce5f Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Konstantin=20Ka=CC=88fer?= Date: Mon, 12 Sep 2011 11:05:49 +0200 Subject: [PATCH] add documentation about symbolizer instances --- CHANGELOG.md | 5 +++++ README.md | 13 ++++++++++++- 2 files changed, 17 insertions(+), 1 deletion(-) diff --git a/CHANGELOG.md b/CHANGELOG.md index a943137..1c6c0bd 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -1,5 +1,10 @@ ## Changelog +### 0.3.0 (NOT YET RELEASED) + +* Add "name/" prefix for creating multiple instances of a symbolizer in the same + attachment + ### 0.2.3 * Fixes many bugs diff --git a/README.md b/README.md index e31f1da..cbda390 100644 --- a/README.md +++ b/README.md @@ -52,7 +52,7 @@ Cascadenik MML </Layer> </Map> -## Attachments +## Attachments and Instances _new_ In CSS, a certain object can only have one instance of a property. A `
` has a specific border width and color, rules that match better than others (#id instead of .class) override previous definitions. `carto.js` acts the same way normally for the sake of familiarity and organization, but Mapnik itself is more powerful. @@ -73,6 +73,17 @@ Attachments are optional: if you don't define them, carto.js does overriding of This brings us to another _incompatibility_: `line-inline` and `line-outline` have been removed from the language, because attachments are capable of the same trick. +While attachments allow creating implicit "layers" with the same data, using **instances** allows you to create multiple symbolizers in the same style/layer: + + #roads { + casing/line-width: 6; + casing/line-color: #333; + line-width: 4; + line-color: #666; + } + +This makes Mapnik first draw the line of color #333 with a width of 6, and then immediately afterwards, it draws the same line again with width 4 and color #666. Contrast that to attachments: Mapnik would first draw all casings before proceeding to the actual lines. + ## text-name _incompatibility_