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[PR #6853] Refactor the renderer color calculations #26795

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opened 2026-01-31 09:18:12 +00:00 by claunia · 0 comments
claunia commented 2026-01-31 09:18:12 +00:00
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Original Pull Request: https://github.com/microsoft/terminal/pull/6853

State: closed
Merged: Yes

This is a refactoring of the renderer color calculations to simplify the
implementation, and to make it easier to support additional
color-altering rendition attributes in the future (e.g. faint and
conceal).

References

  • This is a followup to PRs #3817 and #6809, which introduced additional
    complexity in the color calculations, and which suggested the need for
    refactoring.

Detailed Description of the Pull Request / Additional comments

When we added support for DECSCNM, that required the foreground and
background color lookup methods to be able to return the opposite of
what was requested when the reversed mode was set. That made those
methods unnecessarily complicated, and I thought we could simplify them
considerably just by combining the calculations into a single method
that derived both colors at the same time.

And since both conhost and Windows Terminal needed to perform the same
calculations, it also made sense to move that functionality into the
TextAttribute class, where it could easily be shared.

In general this way of doing things is a bit more efficient. However, it
does result in some unnecessary work when only one of the colors is
required, as is the case for the gridline painter. So to make that less
of an issue, I've reordered the gridline code a bit so it at least
avoids looking up the colors when no gridlines are needed.

Validation Steps Performed

Because of the API changes, quite a lot of the unit tests had to be
updated. For example instead of verifying colors with two separate calls
to LookupForegroundColor and LookupBackgroundColor, that's now
achieved with a single LookupAttributeColors call, comparing against a
pair of values. The specifics of the tests haven't changed though, and
they're all still working as expected.

I've also manually confirmed that the various color sequences and
rendition attributes are rendering correctly with the new refactoring.

**Original Pull Request:** https://github.com/microsoft/terminal/pull/6853 **State:** closed **Merged:** Yes --- This is a refactoring of the renderer color calculations to simplify the implementation, and to make it easier to support additional color-altering rendition attributes in the future (e.g. _faint_ and _conceal_). ## References * This is a followup to PRs #3817 and #6809, which introduced additional complexity in the color calculations, and which suggested the need for refactoring. ## Detailed Description of the Pull Request / Additional comments When we added support for `DECSCNM`, that required the foreground and background color lookup methods to be able to return the opposite of what was requested when the reversed mode was set. That made those methods unnecessarily complicated, and I thought we could simplify them considerably just by combining the calculations into a single method that derived both colors at the same time. And since both conhost and Windows Terminal needed to perform the same calculations, it also made sense to move that functionality into the `TextAttribute` class, where it could easily be shared. In general this way of doing things is a bit more efficient. However, it does result in some unnecessary work when only one of the colors is required, as is the case for the gridline painter. So to make that less of an issue, I've reordered the gridline code a bit so it at least avoids looking up the colors when no gridlines are needed. ## Validation Steps Performed Because of the API changes, quite a lot of the unit tests had to be updated. For example instead of verifying colors with two separate calls to `LookupForegroundColor` and `LookupBackgroundColor`, that's now achieved with a single `LookupAttributeColors` call, comparing against a pair of values. The specifics of the tests haven't changed though, and they're all still working as expected. I've also manually confirmed that the various color sequences and rendition attributes are rendering correctly with the new refactoring.
claunia added the pull-request label 2026-01-31 09:18:12 +00:00
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