From 28f1e36e5e8b578846677ad54ef90ebe89d6d87d Mon Sep 17 00:00:00 2001
From: Dmitriy Budashny <dmitriy.budashny@gmail.com>
Date: Tue, 1 Dec 2009 14:08:50 +0200
Subject: Fix for tv which restarts while trying to open a table

Window manager: stumpwm (20090804.git9d6cb388)
Console messages:
Erlang R13B03 (erts-5.7.4) [source] [smp:2:2] [rq:2] [async-threads:0] [hipe] [kernel-poll:false]

Eshell V5.7.4  (abort with ^G)
1> tv:start().
<0.35.0>
2>
=ERROR REPORT==== 1-Dec-2009::13:46:00 ===
Error in process <0.48.0> with exit value: {function_clause,[{lists,nthtail,[6,[]]},{tv_pg_gridfcns,resize_grid,3},{tv_pg,loop,1}]}

Internal error... restarting.
This message appears over and over.
---
 lib/tv/src/tv_pg_gridfcns.erl | 32 +++++++++++++++++++++++++-------
 1 file changed, 25 insertions(+), 7 deletions(-)

(limited to 'lib')

diff --git a/lib/tv/src/tv_pg_gridfcns.erl b/lib/tv/src/tv_pg_gridfcns.erl
index ab88e2864f..3d23c8a69f 100644
--- a/lib/tv/src/tv_pg_gridfcns.erl
+++ b/lib/tv/src/tv_pg_gridfcns.erl
@@ -205,8 +205,8 @@ resize_grid(NewWidth, NewHeight, ProcVars) ->
 	check_nof_cols(ColsShown, (NofColsShown - NofCols), ColFrameIds, ColIds, 
 		       RowIds, NofRows, RowHeight, FgColor, BgColor ),
 
-    clear_fields(lists:nthtail(NofColsShown, NewColIds), 
-		 lists:nthtail(NofRowsShown, NewRowIds)),
+    clear_fields(safe_nthtail(NofColsShown, NewColIds),
+		 safe_nthtail(NofRowsShown, NewRowIds)),
 
     RowsToUpdate = lists:sublist(NewRowIds, NofRowsShown),
 
@@ -279,7 +279,7 @@ resize_grid_column(RealCol, VirtualCol, Xdiff, ProcVars) ->
 
        % Update the ColWidths list.
     TempColWidths = lists:sublist(ColWidths, VirtualCol - 1) ++ 
-	[NewWidthOfCol | lists:nthtail(VirtualCol, ColWidths)],
+	[NewWidthOfCol | safe_nthtail(VirtualCol, ColWidths)],
     
        % Check the other columns, whether a new column has to be created.
     ColsShown    = compute_cols_shown(FirstColShown, TempColWidths, GridWidth, 
@@ -455,8 +455,8 @@ scroll_grid_horizontally(NewFirstColShown, ProcVars) ->
     refresh_visible_rows(RowsToUpdate, NewFirstColShown, NofColsShown, RowDataList, ListAsStr),
 
        % Clear fields currently not visible.
-    clear_fields(lists:nthtail(NofColsShown, NewColIds), 
-		 lists:nthtail(NofRowsShown, NewRowIds)),
+    clear_fields(safe_nthtail(NofColsShown, NewColIds),
+		 safe_nthtail(NofRowsShown, NewRowIds)),
 
     
     NewGridP = GridP#grid_params{nof_cols        = NewNofCols,
@@ -1565,7 +1565,7 @@ update_col_widths(ColsShown, ColWidths, FirstColShown, DefaultColWidth) ->
     if 
 	NecessaryNofVirtualCols > NofVirtualCols ->
 	    TailNo = NofVirtualCols - FirstColShown + 1,   % Always >= 0 !!!
-	    NewColWidths ++ lists:nthtail(TailNo, ColsShown);
+	    NewColWidths ++ safe_nthtail(TailNo, ColsShown);
 	true ->
 	    NewColWidths
     end.
@@ -1653,7 +1653,7 @@ compute_cols_shown(FirstColShown, ColWidths, GridWidth, _NofCols, DefaultColWidt
 			ColWidthsLength < FirstColShown ->
 			    [];
 			true ->
-			    lists:nthtail(FirstColShown - 1, ColWidths)
+			    safe_nthtail(FirstColShown - 1, ColWidths)
 		    end,
     compute_cols_shown(UsedColWidths, GridWidth, DefaultColWidth).
 
@@ -1894,3 +1894,21 @@ extract_ids_for_one_row(N, [ColIds | Tail]) ->
 %%%---------------------------------------------------------------------
 %%% END of functions used to create the grid.
 %%%---------------------------------------------------------------------
+
+
+%%======================================================================
+%% Function:
+%%
+%% Return Value:
+%%
+%% Description:
+%%
+%% Parameters:
+%%======================================================================
+
+
+safe_nthtail(_, []) -> [];
+safe_nthtail(1, [_|T]) -> T;
+safe_nthtail(N, [_|T]) when N > 1 ->
+    safe_nthtail(N - 1, T);
+safe_nthtail(0, L) when is_list(L) -> L.
-- 
cgit v1.2.3