[Vm-dev] Latest VM "tears" screen

Eliot Miranda eliot.miranda at gmail.com
Mon Oct 1 20:20:41 UTC 2018

Hi Alistair,

> On Oct 1, 2018, at 12:15 PM, Alistair Grant <akgrant0710 at gmail.com> wrote:
> Hi Everyone,
> I've just rebuilt my vmmaker squeak image and found that dragging
> windows around "tears" the windows underneath, as shown in the
> attached image.  Bringing the damaged window to the front causes the
> contents to be redrawn correctly.
> I also saw this when building a pharo vm a couple of days ago.  It
> causes tests in PNGReadWriterTest class to fail (#test2BitReversed,
> #test4BitReversed and #test8BitReversed from memory).
> I'm guessing the change was made in the last 6 weeks or so.
> If no one recognises this I'll start looking at it in a few days (I hope).

See the changes in my latest commit.  I am trying to fix a serious bug in copyBits, namely reading the word past the last word in a bitmap in certain cases (ie a case where preload is true but the trailing word is not used).  I know my changes are correct for deep bitmaps but they’re clearly broken for depths 8 and less.

Please post test cases here.  I need to look using the simulator to try and figure things out.  I am currently looking at the #test2BitReversed, #test4BitReversed and #test8BitReversed cases to try and figure out what’s wrong.

> Thanks,
> Alistair
> $ sqlinux.201809301616/squeak --version
> 5.0-201809301616  Sun Sep 30 16:24:40 UTC 2018 gcc 4.8 [Production
> Spur 64-bit VM]
> CoInterpreter VMMaker.oscog-eem.2437 uuid:
> 0e97c106-dd0b-437b-b1aa-e15257288c3f Sep 30 2018
> StackToRegisterMappingCogit VMMaker.oscog-eem.2432 uuid:
> 7b14d114-0e04-4e46-b8a7-4b5e6d87f5fe Sep 30 2018
> VM: 201809301616 https://github.com/OpenSmalltalk/opensmalltalk-vm.git
> Date: Sun Sep 30 09:16:55 2018 CommitHash: 057c592
> Plugins: 201809301616 https://github.com/OpenSmalltalk/opensmalltalk-vm.git
> Linux travis-job-0b521285-dae6-496e-a96c-06870f88a3a5
> 4.4.0-101-generic #124~14.04.1-Ubuntu SMP Fri Nov 10 19:05:36 UTC 2017
> x86_64 x86_64 x86_64 GNU/Linux
> plugin path: sqlinux.201809301616/lib/squeak/5.0-201809301616
> [default: /home/alistair/vmmaker/opensmalltalk-vm/image20181001/sqlinux.201809301616/lib/squeak/5.0-201809301616/]
> OS: Ubuntu 16.04
> <Screenshot from 2018-10-01 21-05-33.png>

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