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Subject: Re: lcd_clear_display and lcd_stop_scroll
From: Daniel Stenberg (daniel_at_haxx.se)
Date: 2003-01-15

On Tue, 14 Jan 2003, Kjell Ericson wrote:

> > > I belive it shall clear the display and stop+clear all scrolls.
> >
> > No. If you want that, then stop the scroll and clear the screen.
>
> Well, then I have to modify some kind of menue code. Because when I entered
> a setting menu and made lcd_stop_scroll, a line from the prior menu was
> shown (happened when changing the scroll speed).

Well, that might very well be true and if that was the case I've
re-introduced that problem now.

> I'm not up in Linux right now, so I can't test it. But it was very clear
> (in the simulator) when I added this "ok"/"canceled" thing in the menues.

I can't see it happening. Then again, I see no "ok" or "cancel" either!?!

> The thing is that someone uses lcd_puts_scroll in a menu, and then make a
> sub-call without stopping all scrolls. I could ofcourse make the
> child-function call the lcd_stop_scroll()-function, but then all possible
> child-functions must do this too.

> Of course fixing the faulty caller I'm talking about isn't a totally wrong
> way, but I thought that the functionality of lcd_clear_display() should be to
> totally clear the display (which also means stopping/forgetting all scrolls).
>
> Question: Why do you want to clear the display, but keep any information in
> some kind of scroll?

Because clear_display() (which I think is a rather bad name) clears the frame
buffer. It does not affect scrolling. If I want to disable the scrolling and
thus prevent it from appearing again I should stop the scroll first.

> Isn't the problem here that the lcd_stop_scroll() function is slow in the
> Recorder?

Possibly, but I think that is beyond what we discuss. I talk about a concept
here, more than implementation details. I want to be able to clear the
display without considering if the scroll should be stopped, paused, halted
or anything.

> The code for the Player is very fast :-)

Big surprise! ;-)

> > The recorder screen flickers badly atm.
>
> I agree something must be fixed. Thanks for testing the code in real
> hardware. The simulator didn't give any kind of flickering when I tested.

It sure did. I tested it in the simulator and I saw the flickering. I ficked
the flickering in the simulator and I verified that it looked fine on the
hardware afterwards.

> But something else is also wrong if it is flickering, because if you don't
> have any scroll visible the screen shouldn't be updated (?) if I guess how
> you tested it.

Well, I also made lots of those functions not do unnecessary lcd_update()
calls, which they previosuly did. I just noticed another lcd_update() I can
remove (in menu_run()) when nothing has changed.

> BTW: In what menu/function did it flicker? I like to try it in the
> simulator.

Moving up and down in the dir browser, when it needs to scroll.

But the flicker is gone now. 

-- 
 Daniel Stenberg -- http://rockbox.haxx.se/ -- http://daniel.haxx.se/

Page was last modified "Jan 10 2012" The Rockbox Crew
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