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

[Pavel Tsekov <ptsekov gmx net>]

Hello Grigory,

On Wed, 29 Nov 2006, Grigory Trenin wrote:

> 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.

I can confirm the problem.

> 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.

I am not convinced of that yet - see below. It's more likely
that the navigation code messes the value of 'startpoint'.

> '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.

This is not true - 'currentpoint' points to the first byte of
the currently disaplyed help contents, while 'startpoint'
points to the start of the current link/topic. 'startpoint'
gets messed after one returns back from following a link.


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

I won't apply this patch yet. I want to investigate further.