Created attachment 139502 [details]
Normal slide view covered with colored speckles
I recently installed LibreOffice 184.108.40.206 (x64) on a new desktop (Dell Inspiron 3668, Windows 10 Pro, Intel Core i5-7400 CPU, integrated Intel graphics 630). Now all of my old presentations show a few instances (maybe 1-3 per long presentation) of slides that are covered with colored multi-pixel rectangular speckles. Sometimes I see this on a normal slide view (see attachment); sometimes it's a thumbnail in the slide pane; and sometimes it's a presentation thumbnail in the Recent Files box. In every case, there's nothing actually wrong with the slide itself: if I open the thumbnail or start a slideshow or sometimes even just change the window size, the speckles disappear. And these aren't flickers: the pattern of colored spots is stable when it appears.
The speckles seem to appear more often on thumbnails than on normal slides, and more often on thumbnails of graphics (maps, lines, text boxes) and videos than on those of photos.
I tried disabling OpenGL rendering, and since then I have not seen any speckles. Could that be the cause? What are the implications of disabling it?
Created attachment 139503 [details]
Recent Files box showing colored speckles on two presentation thumbnails.
Created attachment 139504 [details]
Thumbnail of a video, covered with colored speckles
Created attachment 139505 [details]
Thumbnails of two photos, covered with colored speckles.
That is a weird one, we've seen some graphics pixelation near transparent text boxes on Impress canvas, but with HA (bug 111923) not with OpenGL.
We'll need to see the content of your opengl_device.log (%APPDATA%\LibreOffice\4\Cache); or result of a msinfo32.exe run's System Information -> Components -> Display report to identify the driver for your Intel HD Graphics 630.
Though the Intel HD Graphics 630 has not been a problem device with OpenGL rendering.
Chances are, a driver update would improve things. Latest from Intel is 220.127.116.1101 dated 2017/12/28 ; YMMV but some of the earlier drivers have caused a lot of grief using OpenGL. Do the driver update and retest with OpenGL enabled.
Created attachment 139533 [details]
Intel HD 630 driver info from before and after update (see comment 5)
The Intel driver yesterday, when I first reported the problem, was 18.104.22.16849 (27-Oct-2017). I went through the steps to manually update the driver (download and extract zip file, do Driver Update, select igdlh64.inf), but the result was that the newest driver (22.214.171.12401) was not installed. Instead the new driver is 126.96.36.19901 (21-Dec-2017). I don't understand that, unless the 4901 at the end of each implies that it really is the newest.
I started Impress and enabled OpenGL rendering, and the result was the same: several thumbnails and a couple of slides were covered with speckles, and unless my memory is faulty, it was exactly the same thumbnails and slides as before the driver update, not a random assortment.
In any event, I'm attaching a zip file containing information from before and after the driver update:
System Information.nfo file (result of System Information run)
Installed Drivers (from above, for convenience, because it's a long line)
Driver properties box (after only)
I really appreciate your help in figuring this out.
For what it's worth, I enabled OpenGL rendering in LibreOffice 188.8.131.52 on my laptop (Windows 10 Home, Intel HD 515) and opened the same presentation files. No speckles seen. That proves nothing except maybe that there are no actual problems in the presentation files themselves.
OK, you are now on the latest Intel (15.60 ) 4901 build drivers now. But the earlier (15.60) 4849 should not have caused OpenGL issues with the Intel HD Graphcis 630 chipset, the driver is plenty new enough.
Unfortunately the 184.108.40.206 build is EOL, and there have been additional tweaks to the OpenGL rendering for the 5.4 and latest 6.0 releases. Are you able to test with those?
Otherwise, would be helpful if you could extract a few of the slides into a new test presentation (verify it still causes the issue) and post it here. If we can't duplicate this issue is one-off and not actionable.
 Intel and Microsoft parse the driver numbers differently as described here: https://www.intel.com/content/www/us/en/support/articles/000005654/graphics-drivers.html
I tried 5.4.4, and I tried 220.127.116.11. Neither one fixed my problem. I have shortened one of my presentations to 9 slides and I will post it shortly, along with a screen shot of what I see (4 bad thumbnails and one bad slide). I hope you'll be able to replicate this; otherwise I'll just do without OpenGL.
Created attachment 139537 [details]
Screen shot of presentation showing the speckles
On Impress on my desktop, I see speckles on slide 2 and on the thumbnails of slides 5, 6, 7, and 9.
Created attachment 139538 [details]
Presentation showing the speckles
On LibreOffice on my desktop, I see speckles on slide 2 and on the thumbnails of slides 4 and 5.
Created attachment 139540 [details]
Screen shot of presentation showing the speckles
My view of the presentation in attachment 139538 [details].
Can not reproduce on Intel HD Graphics 620 with Windows 10 (v.4815) driver and OepnGL rendering enabled. Nor when I update to the build v.4901 Driver from Intel (18.104.22.16801).
I have AVI mime configured to play with VLC v.2.2.6 media player. No change if I change system to associate Windows Media Player with .AVI--no visual glitches.
Version: 22.214.171.124 (x64)
Build ID: 64a0f66915f38c6217de274f0aa8e15618924765
CPU threads: 4; OS: Windows 10.0; UI render: GL;
Locale: en-US (en_US); Calc: CL