Add user preference for Bridges' "G" key (show_hints)

I missed this in my previous addition of preferences for UI controls
(4227ac1fd5dc25c247e7526526079b85e1890766) because it wasn't documented.
Now it is documented and it has a preference.

I've phrased it as showing possible bridge locations, which doesn't
really make clear that "possible" relates only to the locations of
islands and not to anything already placed.  Improvements welcome!

2 files changed, 37 insertions, 3 deletions

diff --git a/bridges.c b/bridges.c
index 6bf0cf6..0cbe779 100644
--- a/bridges.c
+++ b/bridges.c
@@ -2132,13 +2132,37 @@ static game_ui *new_ui(const game_state *state)
 {
     game_ui *ui = snew(game_ui);
     ui_cancel_drag(ui);
-    ui->cur_x = state->islands[0].x;
-    ui->cur_y = state->islands[0].y;
+    if (state != NULL) {
+        ui->cur_x = state->islands[0].x;
+        ui->cur_y = state->islands[0].y;
+    }
     ui->cur_visible = getenv_bool("PUZZLES_SHOW_CURSOR", false);
     ui->show_hints = false;
     return ui;
 }
 
+static config_item *get_prefs(game_ui *ui)
+{
+    config_item *ret;
+
+    ret = snewn(2, config_item);
+
+    ret[0].name = "Show possible bridge locations";
+    ret[0].kw = "show-hints";
+    ret[0].type = C_BOOLEAN;
+    ret[0].u.boolean.bval = ui->show_hints;
+
+    ret[1].name = NULL;
+    ret[1].type = C_END;
+
+    return ret;
+}
+
+static void set_prefs(game_ui *ui, const config_item *cfg)
+{
+    ui->show_hints = cfg[0].u.boolean.bval;
+}
+
 static void free_ui(game_ui *ui)
 {
     sfree(ui);
@@ -3288,7 +3312,7 @@ const struct game thegame = {
     free_game,
     true, solve_game,
     true, game_can_format_as_text_now, game_text_format,
-    NULL, NULL, /* get_prefs, set_prefs */
+    get_prefs, set_prefs,
     new_ui,
     free_ui,
     NULL, /* encode_ui */
diff --git a/puzzles.but b/puzzles.but
index c427d7b..5e86283 100644
--- a/puzzles.but
+++ b/puzzles.but
@@ -2316,6 +2316,9 @@ By pressing a number key, you can jump to the nearest island with that
 number.  Letters \q{a}, ..., \q{f} count as 10, ..., 15 and \q{0} as
 16.
 
+The \q{G} key will draw a grey line between each pair of islands that
+could be connected with a bridge or non-bridge but are currently not.
+
 Violations of the puzzle rules will be marked in red:
 
 \b An island with too many bridges will be highlighted in red.
@@ -2387,6 +2390,13 @@ tightly-packed islands.
 
 }
 
+\H{bridges-prefs} \I{preferences, for Bridges}Bridges user preferences
+
+On platforms that support user preferences, the \q{Preferences} option
+on the \q{Game} menu will let you configure whether possible bridge
+locations are shown.  Unlike the \q{G} key, this will persist between
+games.
+
 
 \C{unequal} \i{Unequal}