vehicle part descriptions: more scrolling fixes, always display if po…

…ssible

limit the maximum amount of scroll based on the size of the w_msg, prevent
accumulation of scroll passed the maximum or minimum amount, and always
display the vehicle part descriptions if the w_msg isn't being used to
display something else.

src/veh_interact.cpp

@@ -287,8 +287,8 @@ void veh_interact::do_main_loop()
         bool redraw = false;
         int dx = 0;
         int dy = 0;
-        if(main_context.get_direction(dx, dy, action)) {
-            move_cursor(dx, dy);
+        if( main_context.get_direction( dx, dy, action ) ) {
+            move_cursor( dx, dy );
         } else if( action == "QUIT" ) {
             finish = true;
         } else if( action == "INSTALL" ) {
@@ -316,10 +316,8 @@ void veh_interact::do_main_loop()
             redraw = do_relabel( msg );
         } else if ( action == "FUEL_LIST_DOWN" ) {
             move_fuel_cursor( 1 );
-            move_cursor( 0, 0 );
         } else if ( action == "FUEL_LIST_UP" ) {
             move_fuel_cursor( -1 );
-            move_cursor( 0, 0 );
         } else if ( action == "DESC_LIST_DOWN" ) {
             move_cursor( 0, 0, 1 );
         } else if ( action == "DESC_LIST_UP" ) {
@@ -344,8 +342,9 @@ void veh_interact::do_main_loop()
             werase( w_msg );
             fold_and_print( w_msg, 0, 1, getmaxx( w_msg ) - 2, c_light_red, msg );
             wrefresh( w_msg );
+        } else {
+            move_cursor( 0, 0 );
         }
-
     }
 }
 

src/vehicle.cpp

@@ -2887,14 +2887,14 @@ int vehicle::print_part_list( const catacurses::window &win, int y1, const int m
 
 /**
  * Prints a list of descriptions for all parts to the screen inside of a boxed window
- * highlighting a selected one.
  * @param win The window to draw in.
  * @param max_y Draw no further than this y-coordinate.
  * @param width The width of the window.
  * @param &p The index of the part being examined.
  * @param start_at Which vehicle part to start printing at.
  */
-void vehicle::print_vparts_descs( const catacurses::window &win, int max_y, int width, int &p, int start_at ) const
+void vehicle::print_vparts_descs( const catacurses::window &win, int max_y, int width, int &p,
+                                  int &start_at ) const
 {
     if( p < 0 || p >= ( int )parts.size() ) {
         return;
@@ -2904,7 +2904,9 @@ void vehicle::print_vparts_descs( const catacurses::window &win, int max_y, int
     std::ostringstream msg;
 
     int lines = 0;
-    start_at = std::max( start_at, 0 );
+    /* never start before the start of the list */
+    /* guess the number of entries that can fit in the window, and don't scroll past that */
+    start_at = std::min( std::max( start_at, 0 ), max_y / 6 );
     if( start_at ) {
            msg << "<color_yellow>" << "<  " << _( "More parts here..." ) << "</color>\n";
            lines += 1;

src/vehicle.h

@@ -581,7 +581,7 @@ class vehicle
 
         // Vehicle parts descriptions - descriptions for all the parts on a single tile
         void print_vparts_descs( const catacurses::window &win, int max_y, int width, int &p,
-                                 int start_at ) const;
+                                 int &start_at ) const;
 
     /**
      *  Operate vehicle controls