README.md: Add FAQ with known issues

README.md

@@ -24,6 +24,73 @@ Building from source
 
 See the file [HACKING](HACKING.md) for more details on building from source.
 
+FAQ
+---
+
+**Where can I find my coordinates to put in the configuration file?**
+
+There are multiple web sites that provide coordinates for map locations, for
+example clicking anywhere on Google Maps will bring up a box with the
+coordinates. Remember that longitudes in the western hemisphere (e.g. the
+Americas) must be provided to Redshift as negative numbers.
+
+**Why doesn't Redshift work on my Chromebook/Raspberry Pi?**
+
+Certain video drivers do not support adjustable gamma ramps. In some cases
+Redshift will fail with an error message, but other drivers silently ignore
+adjustments to the gamma ramp.
+
+**Why doesn't Redshift change the backlight when I use the brightness option?**
+
+Redshift has a brightness adjustment setting but it does not work the way most
+people might expect. In fact it is a fake brightness adjustment obtained by
+manipulating the gamma ramps which means that it does not reduce the backlight
+of the screen. Preferable only use it if your normal backlight adjustment is
+too coarse-grained.
+
+**Why doesn't Redshift work on Wayland (e.g. Fedora 25)?**
+
+The Wayland protocol does not support Redshift. There is currently no way for
+Redshift adjust the color temperature in Wayland.
+
+**Why doesn't Redshift work on Ubuntu with Mir enabled?**
+
+Mir does not support Redshift.
+
+**The redness effect is applied during the day instead of at night. Why?**
+
+This usually happens to users in America when the longitude has been set in the
+configuration file to a positive number. Longitudes in the western hemisphere
+should be provided as negative numbers (e.g. New York City is at approximately
+latitude/longitude 41, -74).
+
+**Why does the redness effect occasionally switch off for a few seconds?**
+
+Redshift uses the gamma ramps of the graphics driver to apply the redness
+effect but Redshift cannot block other applications from also changing the
+gamma ramps. Some applications (particularly games and video players) will
+reset the gamma ramps. After a few seconds Redshift will kick in again. There
+is no way for Redshift to prevent this from happening.
+
+**Why does the redness effect continuously flicker?**
+
+You may have multiple instances of Redshift running simultaneously. Make sure
+that only one instance is running for the display where you are seeing the
+flicker.
+
+**Why doesn't Redshift change the color of the mouse cursor?**
+
+Mouse cursors are usually handled separately by the graphics hardware and is
+not affected by gamma ramps. Some graphics drivers can be configured to use
+software cursors instead.
+
+**I have an issue with Redshift but it was not mentioned in this FAQ. What
+do I do?**
+
+Please go to [the issue tracker](https://github.com/jonls/redshift/issues) and
+check if your issue has already been reported. If not, please open a new issue
+describing you problem.
+
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