depopulation for ST

diff --git a/gui/citylist_stats_t.cc b/gui/citylist_stats_t.cc
index 35438b9..2419b6a 100644
--- a/gui/citylist_stats_t.cc
+++ b/gui/citylist_stats_t.cc
@@ -134,7 +134,7 @@ void citylist_stats_t::zeichnen(koord offset)
        sint32 growth = stadt->get_wachstum();

        buf.clear();
-       buf.printf( "%s: ", stadt->get_name() );
+       buf.printf( "%s%s: ", stadt->get_name(), stadt->get_transport_status()?"":" (!)" );
        buf.append( bev, 0 );
        buf.append( " (" );
        buf.append( growth/10.0, 1 );
diff --git a/simcity.cc b/simcity.cc
index ce2b183..1eb7783 100644
--- a/simcity.cc
+++ b/simcity.cc
@@ -1056,6 +1056,9 @@ stadt_t::stadt_t(spieler_t* sp, koord pos, sint32 citizens) :
    check_bau_rathaus(true);

    wachstum = 0;
+   shrink = 0;
+   transport_level = 0;
+   ratio_transported = 0;
    allow_citygrowth = true;
    change_size( citizens );

@@ -1098,6 +1101,10 @@ stadt_t::stadt_t(karte_t* wl, loadsave_t* file) :
    has_low_density = false;

    wachstum = 0;
+   shrink = 0;
+   transport_level = 0;
+   ratio_transported = 0;
+
    stadtinfo_options = 3;

    rdwr(file);
@@ -1437,6 +1444,7 @@ void stadt_t::step(long delta_t)
    }

    while(stadt_t::step_bau_interval < next_bau_step) {
+       step_depopulation();
        calc_growth();
        step_bau();
        next_bau_step -= stadt_t::step_bau_interval;
@@ -1460,7 +1468,51 @@ void stadt_t::step(long delta_t)
    city_history_year[0][HIST_BUILDING] = buildings.get_count();
 }

+/* performs depopulation */
+void stadt_t::step_depopulation()
+{
+   sint64     const(& h1)[MAX_CITY_HISTORY] = city_history_month[1];
+   sint64     const(& h0)[MAX_CITY_HISTORY] = city_history_month[0];
+   ratio_transported                        = (h0[HIST_PAS_TRANSPORTED] + h1[HIST_PAS_TRANSPORTED]) * 10 / ((h0[HIST_PAS_GENERATED] + h1[HIST_PAS_GENERATED]) + 1 ); // transported passengers in 10% steps
+   bool       const   is_shrink_too_high    = (get_wachstum() * -10 >= get_einwohner())?true:false;
+
+   // maybe this town should stay static, also skip depopulation when previous month had no passengers
+   if(  !allow_citygrowth || h1[HIST_PAS_GENERATED] == 0 ) {
+       shrink = 0;
+       return;
+   }

+    // population rewards rising transport level
+    shrink -= (ratio_transported > transport_level && shrink > 0)?1:0;
+
+   // highest level of transported passengers
+   transport_level = (transport_level >= ratio_transported)?transport_level:ratio_transported;
+
+   // city shrinks when expected passenger transport level is higher than reached transport level
+   if ( (transport_level - 1) > ratio_transported ) { // population accepts an underachievement margin
+       shrink += transport_level - ratio_transported - 1;
+   }
+   const int shrink_step = (shrink>>4);
+   DBG_DEBUG("stadt_t::step_depopulation()", "%s: shrink %i; shrink_step %i; transport_level %i; ratio_transported %i; is_shrink_too_high %s", get_name(), shrink, shrink_step, transport_level, ratio_transported, is_shrink_too_high?"true":"false");
+   shrink &= 0x0F;
+   // every shrink_step lowers expected transport level
+   if ( shrink_step > 0 ) {
+       transport_level -= 1;
+       // small chance to bulldoze a public owned building
+       gebaeude_t* const gb = pick_any(buildings);
+       gebaeude_t::typ const typ = gb->get_haustyp();
+       if ( spieler_t::check_owner(gb->get_besitzer(),NULL) && (typ == gebaeude_t::wohnung || typ == gebaeude_t::gewerbe) && !is_shrink_too_high ) {
+           sint32 population_before = get_einwohner();
+           koord gb_koord = gb->get_pos().get_2d();
+           DBG_DEBUG("stadt_t::step_depopulation()", "%s: bulldozed building %s at %i %i %i", get_name(), gb->get_tile()->get_besch()->get_name(), gb->get_pos().x, gb->get_pos().y, gb->get_pos().z);
+           remove_gebaeude_from_stadt(gb);
+           hausbauer_t::remove(welt,welt->get_spieler(1),gb);
+           cbuffer_t buf;
+           buf.printf(translator::translate("The citizens of %s\nare displeased with\nthe public transport.\n%i inhabitants\nemigrated to Mars."), get_name(), population_before - get_einwohner());
+           welt->get_message()->add_message(buf, gb_koord, message_t::city, CITY_KI, IMG_LEER);
+       }
+   }
+}

 /* updates the city history
  * @author prissi
diff --git a/simcity.h b/simcity.h
index 98a9742..a729c48 100644
--- a/simcity.h
+++ b/simcity.h
@@ -155,6 +155,11 @@ private:
     */
    sint32 wachstum;

+   // used for city depopulation
+   sint32 shrink;
+   sint32 transport_level;
+   sint32 ratio_transported;
+
    /**
    * City history
    * @author prissi
@@ -260,6 +265,9 @@ private:
    // calculates the growth rate for next step_bau using all the different indicators
    void calc_growth();

+    /* performs depopulation */
+    void step_depopulation();
+
    /**
     * plant das bauen von Gebaeuden
     * @author Hj. Malthaner
@@ -400,6 +408,9 @@ public:
     */
    void set_name( const char *name );

+   // returns status of transport level (used for depopulation)
+   bool get_transport_status() const { return ((transport_level - 1) < ratio_transported); }
+
    /**
     * gibt einen zufällingen gleichverteilten Punkt innerhalb der
     * Stadtgrenzen zurück