On 13 May 2015 at 23:22, Nicolai Hess <[email protected]> wrote: > > > 2015-05-08 22:28 GMT+02:00 Igor Stasenko <[email protected]>: > >> >> >> On 8 May 2015 at 22:20, Nicolai Hess <[email protected]> wrote: >> >>> >>> >>> 2015-05-08 21:42 GMT+02:00 Igor Stasenko <[email protected]>: >>> >>>> >>>> >>>> On 8 May 2015 at 21:32, Igor Stasenko <[email protected]> wrote: >>>> >>>>> >>>>> >>>>> On 8 May 2015 at 00:43, Nicolai Hess <[email protected]> wrote: >>>>> >>>>>> >>>>>> Some testers needed! >>>>>> >>>>>> I can not reproduce the BitBlt bug and I would like to get this >>>>>> right, so that surface pattern >>>>>> paints use the correct form dimension. >>>>>> >>>>>> Be sure, my fried, the bug is there, sitting in VM. >>>>> Bitblt implementation prereads a pixel from bitmap *before* checking >>>>> the loop bounds, meaning that it reads at least a single byte beyond the >>>>> actual contents of the bitmap. >>>>> It is not harmful in cases when bitmap is allocated in object memory >>>>> since VM memory design actually guarantees, that there are at least >>>>> certain >>>>> amount of bytes in form of breathing space always available, so reading >>>>> single word past any allocated object is not hurts.. >>>>> But not in case, when bitmap residing in external heap.. because >>>>> reading beyond allocated space might cause segmentation fault.. and it >>>>> was, >>>>> until i figured what was causing it and where the bug is. >>>>> >>>> >>> This mean it can happen every time we read form data from a surface >>> plugin - it is not only an issue for athens/cairo. >>> >>> Right, this is not cairo-only issue.. It just manifested itself when i >> was started using external surfaces allocated by cairo with bitblt. >> Which was causing occasional, irregular crashes time to time and i was >> quite lucky finding the cause of it. >> > > > Any chance you remember what triggers this error? What code did you use, > simple drawings or more advanced > use of athens. Image patterns, gradient patterns. > Or at least, what platform mac/win/linux? > > I tried different vm/image versions but only on windows so far. > > There were some changes on some bitblt functions, maybe the bug does not > exist anymore? > > the easiest way to reproduce it would be: - allocate a new surface of such dimensions, that its buffer size will be aligned with 4k page boundary (a smallest one would be 1x1024, or 1024x1, since one pixel is 4 bytes) - try to blit this surface with bitblt - crash
(sure it happens not always, since often there could be another memory page allocated for other purposes with read access granted, but if you continuously do that, you will inevitable face the crash) > > nicolai > > >> >> >>> I will take a look at bitblt implementation. >>> >>> Thank you ! >>> >>> >>>> >>>>> >>>> The workaround, that i introduced was simply to tell Cairo to allocate >>>> surface 1 row taller and then use smaller height in bitblt operations, so >>>> it can never use the last row.. >>>> that, of course, going in conflict of using cairo for a patterns to >>>> fill things with bitmaps, which relying on surface's dimensions and using >>>> all its pixels.. >>>> :( >>>> >>>> hmm.. >>>> >>>>> >>>>> >>>>>> Prefered test setup: >>>>>> a (fresh) pharo image >>>>>> load bleeding edge from Bloc (because with bloc the whole (morphic) >>>>>> world is drawn with athens). >>>>>> change to watery theme ( because it makes some heavy use of form >>>>>> fills) >>>>>> verify that vertical scrollbars have this artifact (blank lines). >>>>>> load the attached code (this code reverts igors change for the 1 >>>>>> pixel extra height. >>>>>> >>>>>> please report back >>>>>> what platform windows/linux/mac 32/64 bit >>>>>> what pharo vm and image version. >>>>>> >>>>>> For me >>>>>> Windows 7 32 bit >>>>>> Win32 built on Apr 9 2015 21:05:04 Compiler: 4.6.2 >>>>>> Latest update: #50039 >>>>>> >>>>>> -> no segfault >>>>>> >>>>>> thanks in advance >>>>>> >>>>>> >>>>>> 2015-03-13 21:22 GMT+01:00 stepharo <[email protected]>: >>>>>> >>>>>>> I do not know. May be igor is reading this mailing-list but I doubt. >>>>>>> >>>>>>> >>>>>>> 2015-01-27 21:46 GMT+01:00 Nicolai Hess <[email protected]>: >>>>>>> >>>>>>> Anyone knows what this BitBlt bug is or was? >>>>>>>> 12818 <https://pharo.fogbugz.com/default.asp?12818> Last row >>>>>>>> missing >>>>>>>> 13236 <https://pharo.fogbugz.com/default.asp?13236> Fix 1 extra >>>>>>>> height for Cairo surface >>>>>>>> >>>>>>>> Because with the fix in 13236, it is not (easily) possible to make >>>>>>>> a repeating (vertical) pattern paint with 1 pixel height: >>>>>>>> 14813 <https://pharo.fogbugz.com/default.asp?14813> Wrong size >>>>>>>> for Athens surface pattern paint from a Form >>>>>>>> >>>>>>>> >>>>>>>> nicolai >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>> BUMP >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>> >>>>> >>>>> >>>>> -- >>>>> Best regards, >>>>> Igor Stasenko. >>>>> >>>> >>>> >>>> >>>> -- >>>> Best regards, >>>> Igor Stasenko. >>>> >>> >>> >> >> >> -- >> Best regards, >> Igor Stasenko. >> > > -- Best regards, Igor Stasenko.
