[PATCH] Help Viewer - incorrect behaviour of <up> arrrow key

[Grigory Trenin <gtrenin gmail com>]

Hello all,

While browsing MC's help, I've noticed a strange behaviour of <up> arrow
key. After I visit some topic and return back (using <right> arrow key),
the behaviour of <up> arrow key weirdly changes: instead of selecting
the previous link, it jumps to the top of the window!

Here is a detailed description how to reproduce it:

1) Open the Help Contents (press <F1>, <Tab>, <Enter>)
2) Navigate some lines forward (press <End> or <PageDown> several times)
3) Enter the selected topic (press <Enter>)
4) Return back (press <right arrow>)
5) Move to the top of Contents (press <Home>)
6) Now try navigating the Contents using the <up> and <down> arrow keys.
 (for example, press <down arrow> for 5 times, then press <up arrow>).
You will notice that when you press <up arrow> key the selection
jumps to the top of window.


The problem is in the help_handle_key() function:
 case KEY_UP:
 case ALT ('\t'):
     /* select previous link */
     new_item = select_prev_link (startpoint, selected_item);

The 'startpoint' variable should be a pointer to the first byte
displayed in the Help window. But here it has a wrong value - that's
the problem. That's why select_prev_link() cannot find the link and
returns NULL, and the selection moves to the first link in the window.

I tried to find out what's wrong with the 'startpoint' variable.
I came to the conclusion that 'startpoint' is used here erroneously
instead of 'currentpoint' variable.
'currentpoint' always contains a pointer to the first byte displayed,
and it should be used here. And by the way, 'startpoint' variable
seems to be totally useless.

So in my patch I replaced 'startpoint' with 'currentpoint' and
removed the 'startpoint' variable completely.


Regards,
 Grigory Trenin

--- help.c.orig	2006-11-29 18:06:27.000000000 +0300
+++ help.c	2006-11-29 18:09:20.000000000 +0300
@@ -72,7 +72,7 @@
 static const char *main_node;	/* The main node */
 static const char *last_shown = NULL;	/* Last byte shown in a screen */
 static int end_of_node = 0;	/* Flag: the last character of the node shown? */
-static const char *currentpoint, *startpoint;
+static const char *currentpoint;
 static const char *selected_item;
 
 /* The widget variables */
@@ -489,7 +489,7 @@
     event->y -= 2;
 
     if (event->buttons & GPM_B_RIGHT){
-	currentpoint = startpoint = history [history_ptr].page;
+	currentpoint = history [history_ptr].page;
 	selected_item = history [history_ptr].link;
 	history_ptr--;
 	if (history_ptr < 0)
@@ -527,7 +527,7 @@
 	history_ptr = (history_ptr+1) % HISTORY_SIZE;
 	history [history_ptr].page = currentpoint;
 	history [history_ptr].link = current_area->link_name;
-	currentpoint = startpoint = help_follow_link (currentpoint, current_area->link_name);
+	currentpoint = help_follow_link (currentpoint, current_area->link_name);
 	selected_item = NULL;
     } else{
 	if (event->y < 0)
@@ -561,7 +561,7 @@
     if (p == NULL)
 	return;
 
-    currentpoint = startpoint = p + 1;
+    currentpoint = p + 1;
     selected_item = NULL;
     help_callback (h, DLG_DRAW, 0);
 }
@@ -582,7 +582,7 @@
     history[history_ptr].page = currentpoint;
     history[history_ptr].link = selected_item;
 
-    currentpoint = startpoint = new_item + 1;
+    currentpoint = new_item + 1;
     selected_item = NULL;
     help_callback (h, DLG_DRAW, 0);
 }
@@ -595,7 +595,7 @@
 static void prev_node_cmd (void *vp)
 {
     Dlg_head *h = vp;
-    currentpoint = startpoint = history [history_ptr].page;
+    currentpoint = history [history_ptr].page;
     selected_item = history [history_ptr].link;
     history_ptr--;
     if (history_ptr < 0)
@@ -672,14 +672,14 @@
 	    if (history_ptr < 0)
 		history_ptr = HISTORY_SIZE-1;
 	    
-	    currentpoint = startpoint = history [history_ptr].page;
+	    currentpoint = history [history_ptr].page;
 	    selected_item   = history [history_ptr].link;
 #endif
 	} else {
 	    history_ptr = (history_ptr+1) % HISTORY_SIZE;
 	    history [history_ptr].page = currentpoint;
 	    history [history_ptr].link = selected_item;
-	    currentpoint = startpoint = help_follow_link (currentpoint, selected_item) + 1;
+	    currentpoint = help_follow_link (currentpoint, selected_item) + 1;
 	}
 	selected_item = NULL;
 	break;
@@ -704,7 +704,7 @@
     case KEY_UP:
     case ALT ('\t'):
 	/* select previous link */
-	new_item = select_prev_link (startpoint, selected_item);
+	new_item = select_prev_link (currentpoint, selected_item);
 	selected_item = new_item;
 	if (selected_item < currentpoint || selected_item >= last_shown){
 	    if (c == KEY_UP)
@@ -835,7 +835,7 @@
 		    DLG_TRYUP | DLG_CENTER | DLG_WANT_TAB);
 
     selected_item = search_string_node (main_node, STRING_LINK_START) - 1;
-    currentpoint = startpoint = main_node + 1;
+    currentpoint = main_node + 1;
 
     for (history_ptr = HISTORY_SIZE; history_ptr;) {
 	history_ptr--;