[Oberon] Trying to understand vertical scrolling

[Chris Burrows]

(I originally posted this ten hours ago but it seems to have disappeared.
Apologies if two copies appear on the mailing list)

> -----Original Message-----
> From: Oberon [mailto:oberon-bounces at lists.inf.ethz.ch] On Behalf Of
> Srinivas Nayak
> Sent: Friday, 8 April 2016 3:36 PM
> To: ETH Oberon and related systems
> Subject: [Oberon] Trying to understand vertical scrolling
> 
> Dear All,
> 
> When I MR click on scroll bar of System.Text, I see that instead of
> directly going to the beginning of System.text, it takes several MR
> clicks to reach line number 1 of System.Text
> 

Click MM near the top of the scrollbar to scroll to the beginnng of text.
Click MM near the bottom of the scroll bar to scroll to the end of text.

> I found, in Martin Reiser's book, section 2.4.3, it is written that:
> 
> Then:
> - Clicking the right key scrolls to the beginning OF THE TEXT.
> ...

I'm not sure exactly what he meant either :(

This is how it works:

MR clicking (scroll up) corresponds to ML clicking (scroll down) but in
reverse. i.e. ML clicking scrolls the text so that the line that was next to
the mouse pointer becomes the *first* line of the window.  MR clicking
scrolls the text so that the line that was next to the mouse pointer becomes
the *last* line of the window.  

Hence the number of lines scrolled depends on whether the mouse pointer is
positioned nearer the top or the bottom of the scrollbar when you click the
button. 

If you ML click near the top of the scrollbar, scroll down movement is only
a couple of lines. If you ML click near the bottom of the scroll bar the
scroll down movement is almost the whole screen.

Conversely, if you MR click near the top of the scrollbar, scroll up
movement is almost a whole screen. If you MR click near the bottom of the
scroll bar the scroll up movement is only a couple of lines.

Regards,
Chris

Chris Burrows
CFB Software
http://www.cfbsoftware.com