okular @0.6.4 makes broken screen when scrolling

[lightoml@…]

Okular 0.6.4 in KDE4.13.3 makes broken screen when scrolling slowly. I attached the screenshot for broken screen. Could you fix the problem?

Thanks!

[lightoml@…]

It is running OSX 10.10 Yosemite

[lightoml@…]

I tested it using external monitor. Strangely there is no problem with the external monitor. It seems to be related to mac monitor. I'm using MBR 15 inch 2013 late

[dsfrancis03@…]

Cc Me!

[dsfrancis03@…]

I'm having exactly the same issue on my Late 2008 15" Macbook Pro, which is also running Yosemite. Here is version information about okular on my Macbook:

$ /Applications/MacPorts/KDE4/okular.app/Contents/MacOS/okular --version 
Qt: 4.8.6
KDE Development Platform: 4.13.3
Okular: 0.19.3

[NicosPavlov]

I could also reproduce the problem, and I think this is due to Okular not handling Retina resolutions properly. Reducing the screen resolution seems to avoid the issue, which is also consistent with the fact that external monitors do not have this issue apparently (see comment:3). Also, changing the zoom value refreshes the screen and suppresses the artifacts.

An issue such as this one should probably be reported upstream.

[dsfrancis03@…]

I'm having this issue on my Macbook, which has an old (non-Retina) display type. I also tried with an external display, but I still had the issue. Hope it goes away on my Macbook as well if it's fixed on Retina display.

[NicosPavlov]

If the issue also appears in non-Retina machines, then my assumption is wrong about the influence on the screen resolution. I noticed however that the problem seems to arise when using the trackpad, but not an external mouse. Also, scrolling by using the cursor also works fine.

Bug reported upstream at: ​https://bugs.kde.org/show_bug.cgi?id=341945

[alessanderbotti@…]

Cc Me!

[alessanderbotti@…]

I'm also affected. I have a non-Retina display and the problem is also present on my external monitor. Moreover, the problem only occurs when using the trackpad, it does not occur when using an external mouse.

[dsfrancis03@…]

Looks like it's an issue with the trackpad. I checked that the issue doesn't appear when I use an external mouse or the scroll bar.

[mkae (Marko Käning)]

Cc Me!

[lightoml@…]

Any update on this issue? This problem is still occured in version 2.3.3.

[lightoml@…]

Is there any news on it?

[xfacter@…]

Cc Me!

[xfacter@…]

I'm also having this issue on Yosemite. It's a shame because Okular seems like the only real Mac alternative to Djview for reading DJVU files. I've found that there are actually more working DJVU viewers for iOS. Are there any ideas yet what the issue is?

[mkae (Marko Käning)]

Replying to xfacter@…:

I'm also having this issue on Yosemite. It's a shame because Okular seems like the only real Mac alternative to Djview for reading DJVU files. I've found that there are actually more working DJVU viewers for iOS. Are there any ideas yet what the issue is?

Can you verify that an external mouse "solves" the issue, as pointed out in comment:11?

[xfacter@…]

Actually, I just tested it with a magic mouse and trackpad on internal and external monitors, and I can confirm that the issue does NOT go away for any combination. In fact, I believe I found the real issue. The issue persists with the magic mouse, but it is far less pronounced. I noticed it only seems to happen at the beginning or end of scrolls when placing or removing my finger from the magic mouse. Then I noticed that if I am very careful to scroll as vertically as possible, the issue goes away or happens very infrequently. Next I tried scrolling very carefully with the trackpad trying to keep it as vertical as possible, and the issue is still bad but less pronounced than normal. Finally, I tried scrolling with both the trackpad and magic mouse with some horizontal component to my scroll direction. The issue becomes very pronounced.

So, I believe the issue is that the rendering pipeline somehow gets confused when the input device attempts to scroll in a direction with some horizontal component, and it apparently has issues with constantly detecting a horizontal component from the trackpad. This only seems to be the case when directly scrolling with hardware -- i.e. click+drag with the mouse is unaffected. So it makes sense that the issue would go away when using a mouse that only scrolls vertically. Please try for yourself if you are able to reproduce the issue.

By the way, while I'm here I might as well ask if anyone else has issues with the "reload on file change" feature constantly trying to reload the document and causing lag, in 2.3.3 on Yosemite? I'll make a new ticket if it's not already been discussed elsewhere.

[xfacter@…]

A quick fix would be to disable diagonal scrolling and only allow vertical/horizontal depending on scroll angle. Is there any other news yet on this issue?

[lightoml@…]

Replying to xfacter@…:

A quick fix would be to disable diagonal scrolling and only allow vertical/horizontal depending on scroll angle. Is there any other news yet on this issue?

How to be disable diagonal scrolling?

[xfacter@…]

Replying to lightoml@…:

How to be disable diagonal scrolling?

Sorry, I meant it would be a quick fix at the code level. I don't think there is an existing setting for this in the program.

[lightoml@…]

Okular is updated. But the problem is still not fixed.

[lightoml@…]

Any news on this issue? There is still the problem.

[NicosPavlov]

The problem has been symptomatically identified, and reported upstream. There is not necessarily the resources in Macports to fix issues directly in the code when upstream does not follow up. I myself do not know the code of okular well enough to identify where this could be tackled.

However, if you happen to have a patch fixing the issue to propose, it would be fully considered.