Add overmap_loc_text and some better comments

- Adds a new overmap_loc_text widget variable, showing overmap coords
- Add overmap_location_desc to custom sidebar
- Documentation

data/json/ui/overmap.json

@@ -8,5 +8,13 @@
     "width": 0,
     "height": 7,
     "flags": [ "W_LABEL_NONE" ]
+  },
+  {
+    "id": "overmap_location_desc",
+    "type": "widget",
+    "label": "Location",
+    "var": "overmap_loc_text",
+    "style": "text",
+    "flags": [ "W_LABEL_NONE" ]
   }
 ]

data/json/ui/sidebar.json

@@ -18,6 +18,7 @@
       "weapon_style_layout",
       "place_date_time_layout",
       "overmap_full_width",
+      "overmap_location_desc",
       "light_moon_wind_temp_layout",
       "vehicle_azimuth_cruise_fuel_layout",
       "vital_numbers_layout",

doc/SIDEBAR_MOD.md

@@ -552,6 +552,7 @@ Some vars refer to text descriptors. These must use style "text". Examples:
 | `moon_phase_text`     | Phase of the moon - "New moon", "Waxing gibbous", "Full moon" etc.
 | `move_mode_letter`    | Movement mode - "W": walking, "R": running, "C": crouching, "P": prone
 | `move_mode_text`      | Movement mode - "walking", "running", "crouching", "prone"
+| `overmap_loc_text`    | Overmap coordinates, same as shown in the lower corner of overmap screen
 | `overmap_text`        | Colored text rendering of the local overmap; may define "width" and "height"
 | `pain_text`           | "Mild pain", "Distracting pain", "Intense pain", etc.
 | `place_text`          | Location place name

src/widget.cpp

@@ -141,6 +141,8 @@ std::string enum_to_string<widget_var>( widget_var data )
             return "move_mode_text";
         case widget_var::pain_text:
             return "pain_text";
+        case widget_var::overmap_loc_text:
+            return "overmap_loc_text";
         case widget_var::overmap_text:
             return "overmap_text";
         case widget_var::place_text:
@@ -517,6 +519,7 @@ bool widget::uses_text_function()
         case widget_var::move_mode_letter:
         case widget_var::move_mode_text:
         case widget_var::pain_text:
+        case widget_var::overmap_loc_text:
         case widget_var::overmap_text:
         case widget_var::place_text:
         case widget_var::power_text:
@@ -544,10 +547,15 @@ bool widget::uses_text_function()
 std::string widget::color_text_function_string( const avatar &ava, unsigned int max_width )
 {
     std::string ret;
-    bool apply_color = true;
+    // Most text variables have both a string and a color.
+    // The string and color in `desc` will be converted to colorized text with markup.
     std::pair<std::string, nc_color> desc;
-    // Give a default color (some widget_vars do not define one)
+    // Set a default color
     desc.second = c_light_gray;
+    // By default, colorize the string in desc.first with the color in desc.second.
+    bool apply_color = true;
+    // Some helper display:: functions do their own internal colorization of the string.
+    // For those, desc.first is the already-colorized string, and apply_color is set to false.
     switch( _var ) {
         case widget_var::activity_text:
             desc = display::activity_text_color( ava );
@@ -592,6 +600,9 @@ std::string widget::color_text_function_string( const avatar &ava, unsigned int
         case widget_var::pain_text:
             desc = display::pain_text_color( ava );
             break;
+        case widget_var::overmap_loc_text:
+            desc.first = display::overmap_position_text( ava.global_omt_location() );
+            break;
         case widget_var::overmap_text:
             desc.first = display::colorized_overmap_text( ava, _width == 0 ? max_width : _width, _height );
             apply_color = false;

src/widget.h

@@ -59,6 +59,7 @@ enum class widget_var : int {
     moon_phase_text,// Current phase of the moon
     move_mode_letter, // Movement mode, color letter (W/R/C/P)
     move_mode_text, // Movement mode, color text (walking/running/crouching/prone)
+    overmap_loc_text,// Local overmap position, pseudo latitude/longitude with Z-level
     overmap_text,   // Local overmap and mission marker, multi-line color string
     pain_text,      // Pain description text, color string
     place_text,     // Place name in world where character is