Slideshow presentation sometimes shows blank black screen

[pluby]

While working on "future proofing" the NeoOffice code, I found a bug that started occurring in NeoOffice 3.3: when running a slideshow presentation in Impress, the first slide sometimes displays for a moment and then is replaced by a blank black screen. This bug occurs most commonly when CPU and memory usage by other applications is very low and after the first time a slideshow is run.

From my debugging work, it appears that this is caused by the OpenOffice.org code redrawing the slide background after drawing the slide content. Essentially, OpenOffice.org queues drawing operations for a slide in the incorrect order.

I think that I have fixed this bug by letting the OpenOffice.org painting timer run immediately after dispatching a focus gained or lost event for the slideshow presentation window.

Can anyone install the following test patch and tell us if they still the blank black screen? Note that you may want to start a slideslow presentation a few times before installing the test patch to confirm that your machine is affected by the bug:

Intel:
http://sally.neooffice.org/test/NeoOffice-3.3-Patch-2-Test-8-Intel.dmg

Patrick

[amayze]

I don't see the blank screen bug you describe, but I do have another problem. Using the slide show "Leopardi Operette morali.odp" which was previously posted in the forums I see black slides with blue and yellow areas, but when I run the slide show the blue and yellow areas are black and their rounded corners are coloured instead.

See attached screen shots.

Andy.

[amayze]

Followup to my previous post.

This seems to relate to objects with gradient fills.
See attached demo presentation.

Andy

[pluby]

[pluby]

I think that I have fixed the slideshow gradient drawing bug in the following test patch. Also, I found that the gradient gets clipped when printing the sample document that attached in your last post so I also included a fix for that bug in the test patch.

Can you confirm that gradients in slideshows and printed output are drawn correctly for you?:

Intel:
http://sally.neooffice.org/test/NeoOffice-3.3-Patch-2-Test-9-Intel.dmg

Patrick

[amayze]

I've installed Patch 2 Test 9 and it has fixed the gradient outside the callout problem that I reported and the clipping on print problem that you saw.

There may be a further problem with linear gradients. I've added a slide to my test presentation which shows what I mean. The gradient is smooth for most of the shape and than begins to have parallel black lines through it. This may be an OpenOffice feature of course!

Screen shot attached.

Thanks

Andy

[pluby]

I can reproduce this not only in NeoOffice but also in all versions of OpenOffice.org and LibreOffice so this is definitely an OpenOffice.org bug.

Usually we don't fix OpenOffice.org feature bugs, but the cause of this bug was pretty easy for me to find: the OpenOffice.org engineers did not account for the semi-transparent pixels that are drawn when shapes are drawn with antialiased drawing is enabled. As a result, the semi-transparent pixels that antialiasing draws at the boundary between each color stripes in gradients overlap with the semi-transparent pixels from the adjacent color stripe. This combination of semi-transparent pixels results in the dark lines that you see.

Fortunately, I found a simple solution and I am testing to see if it works in various cases. The problem is that I have so far found to separate chunks of code in OpenOffice.org that draw gradients (one for regular drawing and one for slideshow drawing) and each draws gradients slightly differently.

I will post again when I have more news to report or a test patch for you to try.

Patrick

[amayze]

The problem only seems to show itself in the Slide Show, I've never noticed it anywhere else. As you can see in the other screen shots in this thread, the gradients drawn in the Presentation window when editing the file are fine.

Thanks for looking in to this.

Andy

[pluby]

I think that I have fixed all of the slideshow gradient problems in your sample document in the following test patch. Also, I found several more gradient drawing OpenOffice.org bugs when I printed your sample document or exported it to PDF so I fixed those as well.

Can you confirm that all gradients in your sample document are drawn correctly for you when running a slideshow, printing, or exporting to PDF?:

Intel:
http://sally.neooffice.org/test/NeoOffice-3.3-Patch-2-Test-10-Intel.dmg

Patrick

[amayze]

Patch 2 Test 10 fixes the bugs that I reported and I don't see any problems in the pdfs generated by printing.

If I'm being super picky, there is still a slight problem with the slide show drawing. The bounding line of the callout doesn't quite match the fill area, but this really is nit picking.

I attach a couple of screen shots of parts of the second slide in my test presentation to show it.

Cheers,

Andy

[pluby]

[pluby]

I think that I have found to fix the gradient drawing problem in amayze's last post. The following test patch may still draw a few pixels outside of the gradient's border line, but the number of such pixels should significantly less than before.

Can you confirm that all gradients in your sample document are drawn correctly for you when running a slideshow, printing, or exporting to PDF?:

Intel:
http://sally.neooffice.org/test/NeoOffice-3.3-Patch-2-Test-12-Intel.dmg

Note: this patch does not fix this drawing problem for semi-transparent gradients. For those, this problem requires a separate fix. When I have a fix for semi-transparent gradients, I will post another test patch.

Patrick

[pluby]

I think that I have fixed the drawing problem for semi-transparent gradients in the following test patch.

The tricky thing gradients that have transparency enabled is that the OpenOffice.org code renders gradients by drawing the gradient onto a bitmap image. Since bitmap images consist of square pixels, this conversion causes jagged edges on non-rectangular shapes.

So, to work around the jagged edges in semi-transparent gradients, made a few changes such as drawing to higher resolution bitmap images to reduce the pixel size and, in turn, make the jagged edge less visible.

With the following test patch, I think I have optimized all of the various gradient types that the OpenOffice.org supports. Granted, gradients still don't draw perfectly in all cases, but I believe that these optimizations are a significant improvement over the default OpenOffice.org code's gradient drawing.

Can you confirm that all gradients in your sample document are drawn correctly for you when running a slideshow, printing, or exporting to PDF?:

Intel:
http://sally.neooffice.org/test/NeoOffice-3.3-Patch-2-Test-14-Intel.dmg

If you want to test semi-transparent gradients, right-click or Command-click on a gradient and in the popup menu that appears, select the Area menu item. In the dialog that appears, select the Transparency tab, select one of the options other than "No transparency", and click the OK button.

Patrick

[amayze]

Sorry for delay in replying.

I've installed Patch 2 Test 14 and it all looks much better. I'll take a closer look in the next couple of days and try out some transparent things too.

Thanks.

Andy

[ovvldc]

FYI, I understand that Apache OpenOffice replaced a lot of their drawing code. I don't know if you looked at any of it (I haven't) but I figured it might help if you are stuck with something.