Factor a visitor object out of apply_to_level

3 files changed, 45 insertions, 41 deletions

diff --git a/crawl-ref/source/files.cc b/crawl-ref/source/files.cc
index 82c308de6d..3c8ee8e2ed 100644
--- a/crawl-ref/source/files.cc
+++ b/crawl-ref/source/files.cc
@@ -1901,55 +1901,50 @@ bool is_existing_level(const level_id &level)
     return (Generated_Levels.find(level) != Generated_Levels.end());
 }
 
-// Applies an operation (applicator) after switching to the specified level.
-// If preserve_current is true, will reload the original level after
-// modifying the target level.
-//
-// If the target level has not already been visited by the player, this
-// function will assert.
-bool apply_to_level(const level_id &level, bool preserve_current,
-                    bool (*applicator)())
+// This class provides a way to walk the dungeon with a bit more flexibility
+// than you get with apply_to_all_dungeons.
+level_excursion::level_excursion()
+    : original(level_id::current())
 {
-    ASSERT(is_existing_level(level));
+}
 
-    const level_id original = level_id::current();
-    if (level != original)
+void level_excursion::go_to(const level_id& next)
+{
+    if (level_id::current() != next)
     {
-        if (preserve_current)
-            _save_level(you.your_level, you.level_type, you.where_are_you);
+        _save_level(you.your_level, you.level_type, you.where_are_you);
+        _restore_level(next);
+    }
+}
 
-        you.where_are_you = level.branch;
-        you.your_level = level.dungeon_absdepth();
-        you.level_type = level.level_type;
+level_excursion::~level_excursion()
+{
+    go_to(original);
+}
 
-        // Load the dungeon level...
-        load(DNGN_STONE_STAIRS_DOWN_I, LOAD_VISITOR,
-             LEVEL_DUNGEON, original.absdepth(),
-             original.branch);
-    }
 
-    // Apply the change.
-    const bool result = applicator();
+// Applies an operation (applicator) after switching to the specified level.
+// Will reload the original level after modifying the target level.
+//
+// If the target level has not already been visited by the player, this
+// function will assert.
+bool apply_to_level(const level_id &level, bool (*applicator)())
+{
+    ASSERT(is_existing_level(level));
 
-    if (level != original)
-    {
-        // And save it back.
-        _save_level(you.your_level, you.level_type, you.where_are_you);
+    level_excursion le;
 
-        if (preserve_current)
-            _restore_level(original);
-    }
+    le.go_to(level);
 
-    return (result);
+    return applicator();
 }
 
 bool apply_to_all_dungeons(bool (*applicator)())
 {
-    const level_id original = level_id::current();
+    level_excursion le;
+    level_id original(level_id::current());
 
-    // Apply to current level, then save it out.
     bool success = applicator();
-    _save_level(original.absdepth(), original.level_type, original.branch);
 
     for (int i = 0; i < MAX_LEVELS; ++i)
         for (int j = 0; j < NUM_BRANCHES; ++j)
@@ -1964,12 +1959,12 @@ bool apply_to_all_dungeons(bool (*applicator)())
             if (original == thislevel)
                 continue;
 
-            if (apply_to_level(thislevel, false, applicator))
+            le.go_to(thislevel);
+
+            if (applicator())
                 success = true;
         }
 
-    _restore_level(original);
-
     return (success);
 }
 
diff --git a/crawl-ref/source/files.h b/crawl-ref/source/files.h
index 5c639eeb14..eded735f1b 100644
--- a/crawl-ref/source/files.h
+++ b/crawl-ref/source/files.h
@@ -102,11 +102,20 @@ bool apply_to_all_dungeons(bool (*applicator)());
 
 class level_id;
 
-bool apply_to_level(const level_id &level, bool preserve_current,
-                    bool (*applicator)());
+bool apply_to_level(const level_id &level, bool (*applicator)());
 
 bool is_existing_level(const level_id &level);
 
+class level_excursion
+{
+    level_id original;
+
+public:
+    level_excursion();
+    ~level_excursion();
+
+    void go_to(const level_id &level);
+};
 
 // last updated 12may2000 {dlb}
 /* ***********************************************************************
diff --git a/crawl-ref/source/monstuff.cc b/crawl-ref/source/monstuff.cc
index 3b1aa9e86c..0503db420d 100644
--- a/crawl-ref/source/monstuff.cc
+++ b/crawl-ref/source/monstuff.cc
@@ -829,14 +829,14 @@ void slime_vault_change(bool glass)
     {
         if (glass)
         {
-            apply_to_level(target, true,
+            apply_to_level(target,
                            target == level_id::current() ?
                                _slime_vault_to_glass_onlevel :
                                _slime_vault_to_glass_offlevel);
         }
         else
         {
-            apply_to_level(target, true,
+            apply_to_level(target,
                            target == level_id::current() ?
                                _slime_vault_to_floor_onlevel :
                                _slime_vault_to_floor_offlevel);