[9fans] Page problems

[9fans] Page problems

[Gregory Pavelcak]

I've seen one posting about page since the recent changes,
so I waited. I'm starting to wonder if I'm alone seeing problems.

I've been using page mainly to review a paper I've been
working on, but I've also had these problems while reading
pdfs and plan 9 docs. Usually, page starts with a blank page.
If I advance a page, then go back, I can see page 1. Then,
usually after a few pages of reading, a page will show up
with a black bottom quarter, and the mouse button menus
start to linger around after they've been used, though I can
still open new menus and use them.

This is using drawterm-osx. I've reverted to the old binary,
so it's not a big deal to me. Just thought I'd throw it out there.

Greg

Re: [9fans] Page problems

[erik quanstrom]

> I've been using page mainly to review a paper I've been
> working on, but I've also had these problems while reading
> pdfs and plan 9 docs. Usually, page starts with a blank page.
> If I advance a page, then go back, I can see page 1. Then,
> usually after a few pages of reading, a page will show up
> with a black bottom quarter, and the mouse button menus
> start to linger around after they've been used, though I can
> still open new menus and use them.
>
> This is using drawterm-osx. I've reverted to the old binary,
> so it's not a big deal to me. Just thought I'd throw it out there.

the cachedpage() handling appears to be new.  perhaps that's
the rub.  this doesn't cause trouble on my linux drawterm.
so there might be a quirk with osx drawterm.

i can't test a real terminal at the moment.

- erik

Re: [9fans] Page problems

[Martin Neubauer]

As I said, it is weekend and I've got a little time at my hands to look
into this. The problem is indeed with the cacheing. A quick fix is this
change to /sys/src/cmd/page/view.c:

136,138c136
<       if(im == nil)
<               wexits(0);
<       if(resizing)
---
>       if(im && resizing)

I'm about to submit a patch with that for the powers that be. I haven't
extensively tested the diff, but it is as unobtrusive as I could wish for.

	Martin

Re: [9fans] Page problems

[Martin Neubauer]

I haven't read the mail properly. The diff is only aimed at my problem. I
didn't experience Greg's symptoms, but I doubt I affected those.

	Martin

Re: [9fans] Page problems

[erik quanstrom]

> As I said, it is weekend and I've got a little time at my hands to look
> into this. The problem is indeed with the cacheing. A quick fix is this
> change to /sys/src/cmd/page/view.c:
>
> 136,138c136
> <       if(im == nil)
> <               wexits(0);
> <       if(resizing)
> ---
>>       if(im && resizing)
>
> I'm about to submit a patch with that for the powers that be. I haven't
> extensively tested the diff, but it is as unobtrusive as I could wish for.
>
> 	Martin

in order for im to return nil, this test has to be true

	if((page < 0 || page >= doc->npage) && !doc->fwdonly)
		return nil;

i think the question is, why is page out of range and what's it's value?

- erik

Re: [9fans] Page problems

[Martin Neubauer]

* erik quanstrom (quanstro@quanstro.net) wrote:
> in order for im to return nil, this test has to be true
>
> 	if((page < 0 || page >= doc->npage) && !doc->fwdonly)
> 		return nil;
>
> i think the question is, why is page out of range and what's it's value?
>
> - erik

That happens at startup with the -i option. Somewhere in main is a call of
initgfx(nil, 0, nil, nil, 0) in that case. This leads to doc->npage being 0
which puts any value of page out of range in this case. Essentially it's
something of a timing issue. Page wants to display an image and looks for it
in the cache. At that point the cache is empty because page gets the data
via the plumber and the event loop hasn't yet started to process plumbing
messages. At least that's as far as I have understood what's going on. And
it probably isn't the cause for Greg's problem (which I couldn't reproduce).

	Martin

Re: [9fans] Page problems

[erik quanstrom]

> * erik quanstrom (quanstro@quanstro.net) wrote:
>> in order for im to return nil, this test has to be true
>>
>> 	if((page < 0 || page >= doc->npage) && !doc->fwdonly)
>> 		return nil;
>>
>> i think the question is, why is page out of range and what's it's value?
>>
>> - erik
>
> That happens at startup with the -i option. Somewhere in main is a call of
> initgfx(nil, 0, nil, nil, 0) in that case. This leads to doc->npage being 0
> which puts any value of page out of range in this case. Essentially it's
> something of a timing issue. Page wants to display an image and looks for it
> in the cache. At that point the cache is empty because page gets the data
> via the plumber and the event loop hasn't yet started to process plumbing
> messages. At least that's as far as I have understood what's going on. And
> it probably isn't the cause for Greg's problem (which I couldn't reproduce).
>
> 	Martin

if this is a timing issue, then that should be addressed.  if your diagnosis is
correct, then if pagecache would slept until the event loop were running,
that would fix the timing problem.

maybe something like

int	eventdawn;		/* set after event loop is fired up */

Image*
cachedpage(Document *doc, int angle, int page)
{
	static int lastpage = -1;
	static int rabusy;
	Image *im;
	int ra;

+	while(eventdawn == 0)
+		sleep(1);

Re: [9fans] Page problems

[Martin Neubauer]

* erik quanstrom (quanstro@quanstro.net) wrote:
> if this is a timing issue, then that should be addressed.  if your diagnosis is
> correct, then if pagecache would slept until the event loop were running,
> that would fix the timing problem.
>
> maybe something like
>
> int	eventdawn;		/* set after event loop is fired up */
>
> Image*
> cachedpage(Document *doc, int angle, int page)
> {
> 	static int lastpage = -1;
> 	static int rabusy;
> 	Image *im;
> 	int ra;
>
> +	while(eventdawn == 0)
> +		sleep(1);

I'm afraid in this instance this wouldn't help. The control flow is smething
like main -> viewer -> { showpage -> cachedpage ; event loop }. Maybe
the following would better:

void
viewer(Document *dd)
{
	.
	.
	.

	midmenu.item = miditems;
	midmenu.gen = 0;
	midmenu.lasthit = Next;

<	showpage(page, &menu);
---
>	if(doc->npage > 0)
>		showpage(page, &menu);
	esetcursor(nil);

	Martin