[Libreoffice-bugs] [Bug 139296] Text font size changes when scrolling document with a mouse

[bugzilla-daemon at bugs.documentfoundation.org]

https://bugs.documentfoundation.org/show_bug.cgi?id=139296

--- Comment #5 from spokanemagneto at gmail.com ---
(In reply to V Stuart Foote from comment #4)
> What you show is screen tearing, extending horizontally across entire lines
> of text as the document canvas is redrawn with scrolling (by mouse, touch
> pad, or cursor arrows).
> 
> It has nothing to do with font metrics and the rendering of the fonts.
> Likewise it probably has nothing to do with your mouse hardware & drivers
> (the scroll size is not read from your mouse settings, rather from LO
> program settings).
> 
> Skia rendering is enabled by default with the Windows builds. You must
> explicitly disable it to revert to "default" GDI based rendering by CPU
> (with optional CPU controlled Hardware Acceleration).
> 
> We need to know if the tearing continues when you eliminate Skia and switch
> to GDI rendering.
> 
> Also, we need to know your graphics hardware, so before disabling Skia--with
> Vulkan rendering enabled--copy the contents of the Skia.log from
> %APPDATA%\LibreOFfice\4\cache\skia.log  and if present the opengl_device.log


Ah, the term tearing explains it perfectly. Why I didn't think of that term, I
don't know. I found another possible bug in that when I checked for updates, it
would tell me I am current--but I found out that there was a newer version
(7.0.4.2), so I updated, but that did not fix the problem. I also tried running
it as an administrator (even though I only have one account, an administrator
account), but that did not fix the problem either. 

I thought I was onto something when I deselected the Math baseline alignment
under Tools>Options>LO Writer>Formatting Aids, but this morning I checked and
the checkbox was once again selected--and the tearing problem was back, even
though I had pressed Apply and OK the evening before.

The %APPDATA%\LO\4\cache\skia.log file that you requested only contained these
two lines of text:

RenderMethod: raster
Compiler: Clang

There was on opengl_device.log file.

After the change to deselect Skia, which I had done before without it fixing
the problem, the %APPDATA%\...\skia.log file contained the following:

DriverVersion: 20.19.15.5107
DriverDate: 11-15-2019
DeviceID: PCI\VEN_8086&DEV_22B1&SUBSYS_10C01043&REV_21
AdapterVendorID: 0x8086
AdapterDeviceID: 0x22b1
AdapterSubsysID: 0x10c01043
DeviceKey:
System\CurrentControlSet\Control\Video\{BCDC4E8B-D8FD-11EA-918F-B232891AD31F}\0000
DeviceString: Intel(R) HD Graphics

The dramatic difference in file size makes me think I might have messed up when
I copied the file before the skia change (perhaps LO has to be open at the
time, and I cannot remember if I had opened it before I hunted for the files
you requested. 

So, I made the change from Skia to using the hardware accelerator, and the Math
baseline alignment checkbox is again selected, and I it still fails. I did
notice another clue, and that is that if I turn off the Toggle Automatic Spell
Checking, then turn it right back on, the tearing text goes away without having
to scroll the page up or down passed the torn text and then back again.

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