Document "Best S+P" in the User Guide.

doc/CMakeLists.txt

@@ -67,6 +67,7 @@ set (UG_IMGS
   images/Astronomical_data.png
   images/auto-seq.png
   images/band-settings.png
+  images/Best_S+P.png
   images/colors.png
   images/config-menu.png
   images/decode-menu.png

doc/user_guide/en/tutorial-example4.adoc

@@ -1,4 +1,8 @@
-// Status=review
+FT4 is designed for contesting, particularly on the HF bands.
+Compared with FT8 it is 3.5 dB less sensitive and requires 1.6 times
+the bandwidth, but it offers the potential for twice the QSO rate.
+FT4 is not recommended for everyday use.
+
 .Main Window:
 - Select *FT4* on the *Mode* menu.
 - Double-click on *Erase* to clear both text windows.
@@ -39,11 +43,32 @@ Rx frequency to that of the selected message and leaving Tx frequency
 unchanged.  To change both Rx and Tx frequencies, hold *Ctrl* down
 when double-clicking.
 
-TIP: To avoid QRM from competing callers, it is frequently desirable
-to answer a CQ on a different frequency from that of the CQing
-station.  The same is true when you tail-end another QSO.  Choose a Tx
-frequency that appears to be not in use.  You might want to check the
-box *Hold Tx Freq*.
+.Best S+P Button
+
+The FT4 user interface includes a new button labeled *Best S+P*.
+
+image::Best_S+P.png[align="center"]
+
+Clicking *Best S+P* during an Rx cycle arms the program to examine all
+CQ messages decoded at the end of the Rx sequence.  The program will
+select the best potential QSO partner (from a contesting perspective),
+and treat it as if you had double-clicked on that line of decoded
+text. Here "best potential QSO partner" means "New Multiplier" (1st
+priority) or "New Call on Band" (2nd priority).  "New Multiplier" is
+currently interpreted to mean "New DXCC"; a more broadly defined
+multiplier category (for the ARRL RTTY Roundup rules) will be
+implemented in due course.  We may provide additional priority
+rankings, for example “New Grid on Band” (useful for North American
+VHF contests), sorting by signal strength, etc.
+
+*Best S+P* is a useful feature only if you have defined what "best" is
+supposed to mean.  This is done by configuring suitable options on the
+*Settings | Colors* tab.  Selection and ordering of color-highlighting
+options determines what potential QSO partners will be chosen by the
+"Best S+P" feature.  Optimum choices will be different for different
+contests.  In a contest using RTTY Roundup rules we recommend
+activating *My Call in message*, *New DXCC*, *New Call on Band*, *CQ
+in message* and *Transmitted message*, reading from top to bottom.
 
 TIP: Keyboard shortcuts *Shift+F11* and *Shift+F12* provide an easy
 way to move your FT4 Tx frequency down or up in 90 Hz steps.