docs: Added a page about the preferences

Probably most importantly, it documents where the preferences are stored
on the various supported systems.

docs/index.rst

@@ -29,6 +29,7 @@ Tiled Documentation
    manual/automapping
    manual/export
    manual/keyboard-shortcuts
+   manual/preferences
 
 .. toctree::
    :maxdepth: 2

docs/manual/preferences.rst

@@ -0,0 +1,132 @@
+User Preferences
+================
+
+There are only a few options located in the Preferences, accessible
+though the menu via *Edit > Preferences*. Most other options, like
+whether to draw the grid, what kind snapping to do or the last used
+settings when creating a new map are simply remembered persistently.
+
+The preferences are stored in a system-dependent format and location:
+
++-------------+-----------------------------------------------------------------+
+| **Windows** | Registry key ``HKEY_CURRENT_USER\SOFTWARE\mapeditor.org\Tiled`` |
++-------------+-----------------------------------------------------------------+
+| **macOS**   | ``~/Library/Preferences/org.mapeditor.Tiled.plist``             |
++-------------+-----------------------------------------------------------------+
+| **Linux**   |  ``~/.config/mapeditor.org/tiled.conf``                         |
++-------------+-----------------------------------------------------------------+
+
+
+General
+-------
+
+.. figure:: images/preferences-general.png
+   :alt: General Preferences
+   :scale: 66
+   :align: right
+
+Saving and Loading
+~~~~~~~~~~~~~~~~~~
+
+Include DTD reference in saved maps
+    This option is not enabled by default, since it is of very little
+    use whereas it can in some environments cause problems. Feel free to
+    enable it if it helps with validation for example, but note that the
+    referenced DTD is likely out of date (there is a somewhat more up-to-date
+    XSD file available in the repository).
+
+Reload tileset images when they change
+    This is very useful while working on the tiles or when the tiles
+    might change as a result of a source control system.
+
+Open last files on startup
+    Generally a useful thing to keep enabled.
+
+Use safe writing of files
+    This setting causes files to be written to a temporary file, and
+    when all went well, to be swapped with the target file. This avoids
+    data getting lost due to errors while saving or due to insufficient
+    disk space. Unfortunately, it is known to cause issues when saving
+    files to a Dropbox folder or a network drive, in which case it helps
+    to disable this feature.
+
+Interface
+~~~~~~~~~
+
+Language
+    By default the language tries to match that of the system, but if it
+    picks the wrong one you can change it here.
+
+Grid colour
+    Because black is not always the best color for the grid.
+
+Fine grid divisions
+    The tile grid can be divided further using this setting, which
+    affects the "Snap to Fine Grid" setting in the *View > Snapping*
+    menu.
+
+Object line width
+    Shapes are by default rendered with a 2 pixel wide line, but some
+    people like it thinner or even thicker. On some systems the DPI-based
+    scaling will affect this setting as well.
+
+Hardware accelerated drawing (OpenGL)
+    This enables a rather unoptimized way of rendering the map using
+    OpenGL. It's usually not an improvement and may lead to crashes, but
+    in some scenarios it can make editing more responsive.
+
+.. raw:: html
+
+   <div class="new">New in Tiled 1.1</div>
+
+Mouse wheel zooms by default
+    This option causes the mouse wheel to zoom without the need to hold
+    Control (or Command on macOS). It can be a convenient way to
+    navigate the map, but it can also interfere with panning on a
+    touchpad.
+
+Theme
+-----
+
+On Windows and Linux, the default style used by Tiled is "Tiled Fusion".
+This is a customized version of the "Fusion" style that ships with Qt.
+On macOS, this style can also be used, but because it looks so out of
+place the default is "Native" there.
+
+The "Tiled Fusion" style allows customizing the base color. When
+choosing a dark base color, the text automatically switches to white and
+some other adjustments are made to keep things readable. You can also
+choose a custom selection color.
+
+The "Native" style tries to fit in with the operating system, and is
+available since it is in some cases preferable to the custom style. The
+base color and selection color can't be changed when using this style,
+as they depend on the system.
+
+Updates
+-------
+
+The official macOS builds and the Windows installers of Tiled ship with
+an automatic update check, done by `Sparkle`_ and `WinSparkle`_
+respectively. These solutions also offer to download the new version
+and to upgrade or run the installer afterwards.
+
+You can turn off the update checks or trigger them manually using the
+*Check Now* button.
+
+Plugins
+-------
+
+Here you can choose which plugins are enabled. Currently plugins only
+serve to add support for additional map and/or tileset file formats.
+Some generic plugins are enabled by default, while more specific ones
+need to be manually enabled.
+
+There is no need to restart Tiled when enabling or disabling plugins.
+When a plugin fails to load, try hovering its icon to see if the tool
+tip displays a useful error message.
+
+See :doc:`export` for more information about supported file formats.
+
+.. _Sparkle: https://sparkle-project.org/
+.. _WinSparkle: https://winsparkle.org/