MapnikViewer.md

+The Mapnik Viewer is a GUI tool for rendering and viewing maps based on Mapnik XML mapfiles.
+
+It's available in the `demo/viewer` folder of your mapnik source code. It is not compiled by default, but can be built separately after installing Mapnik.
+
+----
+[[/images/mapnik_viewer.png]]
+----
+
+## Requirements
+
+ * A working Mapnik installation
+ * A Mapnik XML file to view
+ * Qt4 including dev files (for example, see [Qt/Mac Open Source Edition](http://trolltech.com/developer/downloads/qt/mac))
+ * Qmake
+
+## Building
+
+NOTE: these instructions assume you are using Mapnik >= 2.1. Mapnik 2.1 source code includes a `viewer.pro` file that will leverage the `mapnik-config` to get the proper build settings from your Mapnik install.
+
+Run Qmake to generate a makefile:
+
+```sh
+cd ./demo/viewer
+qmake -makefile
+```
+
+On Mac OSX the above command may generate an XCode project. To generate a normal Makefile do:
+
+```sh
+qmake -spec macx-g++
+```
+
+Finally, run Make to build the *viewer.app* or *viewer.exe*
+
+```sh
+make
+```
+
+On OS X, if a viewer.xcodeproj was built then open the project in Apple's XCode environment and hit "build and run"
+
+## Usage
+
+Double click on the resulting application (viewer.app on Mac OS)
+
+ * You can then load map files from the file menu (make sure you have absolute paths set to datasources).
+ * Hit the *Home* button to zoom to the data extent.
+ * The rest should be obvious.
+
+You can also load your XML files when launching the viewer from a terminal:
+
+```sh
+# On linux this would look like:
+./viewer /path/to/your.xml
+# On mac this would look like:
+./viewer.app/Contents/MacOS/viewer /path/to/your.xml
+# or
+open -a viewer
+```
+
+or
+
+```sh
+    # ./viewer your.xml -1,50,1,52
+```
+
+## Register plugins directory
+Plugin directory is default to /usr/local/lib/mapnik/input/  
+To override it: create a viewer.ini file for example:
+
+```ini
+[mapnik]
+plugins_dir=/usr/lib/mapnik/3.0/input/ 
+```