[2496621] Fixing view recentering on abyss shifts. Shifts now preserve any scrolling that had occured.

git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@8641 c06c8d41-db1a-0410-9941-cceddc491573

5 files changed, 33 insertions, 3 deletions

diff --git a/crawl-ref/source/abyss.cc b/crawl-ref/source/abyss.cc
index b3081d5379..76ce4be6b9 100644
--- a/crawl-ref/source/abyss.cc
+++ b/crawl-ref/source/abyss.cc
@@ -507,7 +507,7 @@ void area_shift(void)
             delete_cloud( i );
     }
 
-    you.moveto(abyss_center);
+    you.shiftto(abyss_center);
 
     _generate_area(coord_def(MAPGEN_BORDER, MAPGEN_BORDER),
                    coord_def(GXM - MAPGEN_BORDER, GYM - MAPGEN_BORDER), true);
diff --git a/crawl-ref/source/directn.h b/crawl-ref/source/directn.h
index 6d71cfa0b5..c20a3c792d 100644
--- a/crawl-ref/source/directn.h
+++ b/crawl-ref/source/directn.h
@@ -68,6 +68,8 @@ public:
 
     void init_view();
     void set_player_at(const coord_def &c, bool force_centre = false);
+    // Set new location, but preserve scrolling as if the player didn't move.
+    void shift_player_to(const coord_def &c);
 
     coord_def view_centre() const
     {
diff --git a/crawl-ref/source/externs.h b/crawl-ref/source/externs.h
index d5e3f7e8a6..42d6024864 100644
--- a/crawl-ref/source/externs.h
+++ b/crawl-ref/source/externs.h
@@ -978,6 +978,8 @@ public:
 
     // Low-level move the player. Use this instead of changing pos directly.
     void moveto(const coord_def &c);
+    // Move the player during an abyss shift.
+    void shiftto(const coord_def &c);
 
     void reset_prev_move();
 
@@ -1153,6 +1155,8 @@ public:
 
     bool did_escape_death() const;
     void reset_escaped_death();
+protected:
+    void base_moveto(const coord_def &c);
 };
 
 extern player you;
diff --git a/crawl-ref/source/player.cc b/crawl-ref/source/player.cc
index 086782330c..c0dbe2af63 100644
--- a/crawl-ref/source/player.cc
+++ b/crawl-ref/source/player.cc
@@ -7214,13 +7214,12 @@ bool player::is_icy() const
     return (attribute[ATTR_TRANSFORMATION] == TRAN_ICE_BEAST);
 }
 
-void player::moveto(const coord_def &c)
+void player::base_moveto(const coord_def &c)
 {
     ASSERT(!crawl_state.arena);
 
     const bool real_move = (c != pos());
     position = c;
-    crawl_view.set_player_at(c);
 
     if (real_move)
     {
@@ -7233,6 +7232,18 @@ void player::moveto(const coord_def &c)
     }
 }
 
+void player::moveto(const coord_def &c)
+{
+    crawl_view.set_player_at(c);
+    base_moveto(c);
+}
+
+void player::shiftto(const coord_def &c)
+{
+    crawl_view.shift_player_to(c);
+    base_moveto(c);
+}
+
 void player::reset_prev_move()
 {
     prev_move = coord_def(0,0);
diff --git a/crawl-ref/source/view.cc b/crawl-ref/source/view.cc
index b691992e32..d155f10004 100644
--- a/crawl-ref/source/view.cc
+++ b/crawl-ref/source/view.cc
@@ -5693,6 +5693,19 @@ void crawl_view_geometry::init_view()
     set_player_at(you.pos(), true);
 }
 
+void crawl_view_geometry::shift_player_to(const coord_def &c)
+{
+    // Preserve vgrdc offset after moving.
+    const coord_def offset = crawl_view.vgrdc - you.pos();
+    crawl_view.vgrdc = offset + c;
+    last_player_pos = c;
+
+    set_player_at(c);
+    
+    ASSERT(crawl_view.vgrdc == offset + c);
+    ASSERT(last_player_pos == c);
+}
+
 void crawl_view_geometry::set_player_at(const coord_def &c, bool centre)
 {
     if (centre)