[Vm-dev] [OpenSmalltalk/opensmalltalk-vm] 561d57: Fix issue 651 with VMMaker.oscog-nice.3251

[Nicolas Cellier]

  Branch: refs/heads/Cog
  Home:   https://github.com/OpenSmalltalk/opensmalltalk-vm
  Commit: 561d57da08901d946bda86a5660be16e7c441841
      https://github.com/OpenSmalltalk/opensmalltalk-vm/commit/561d57da08901d946bda86a5660be16e7c441841
  Author: Nicolas Cellier <nicolas.cellier at sirehna.com>
  Date:   2022-08-25 (Thu, 25 Aug 2022)

  Changed paths:
    M src/plugins/BitBltPlugin/BitBltPlugin.c

  Log Message:
  -----------
  Fix issue 651 with VMMaker.oscog-nice.3251

The rgbMul BitBlt operation now work in 1-bit deep forms, and is correctly rounded for any other depth.

Note that the rgbMul might be used for pre-multiplying color channels in some anti-aliasing algorithms.<br>
It's been used in Cuis for font rendering see this thread:

http://forum.world.st/BitBlt-looking-for-rule-blitting-an-alpha-mask-constant-color-td107041.html

http://lists.squeakfoundation.org/pipermail/vm-dev/2009-June/002760.html