## Summary of the Pull Request
- Height adjustment of a glyph is now restricted to itself in the DX
renderer instead of applying to the entire run
- ConPTY compensates for drawing the right half of a fullwidth
character. The entire render base has this behavior restored now as
well.
## PR Checklist
* [x] Closes#2191
* [x] I work here
* [x] Tests added/passed
* [x] No doc
* [x] Am core contributor.
## Detailed Description of the Pull Request / Additional comments
Two issues:
1. On the DirectX renderer side, when confronted with shrinking a glyph,
the correction code would apply the shrunken size to the entire run, not
just the potentially individual glyph that needed to be reduced in size.
Unfortunately while adjusting the horizontal X width can be done for
each glyph in a run, the vertical Y height has to be adjusted for an
entire run. So the solution here was to split the individual glyph
needing shrinking out of the run into its own run so it can be shrunk.
2. On the ConPTY side, there was a long standing TODO that was never
completed to deal with a request to draw only the right half of a
two-column character. This meant that when encountering a request for
the right half only, we would transmit the entire full character to be
drawn, left and right halves, struck over the right half position. Now
we correct the cursor back a position (if space) and draw it out so the
right half is struck over where we believe the right half should be (and
the left half is updated as well as a consequence, which should be OK.)
The reason this happens right now is because despite VIM only updating
two cells in the buffer, the differential drawing calculation in the
ConPTY is very simplistic and intersects only rectangles. This means
from the top left most character drawn down to the row/col cursor count
indicator in vim's modeline are redrawn with each character typed. This
catches the line below the edited line in the typing and refreshes it.
But incorrectly.
We need to address making ConPTY smarter about what it draws
incrementally as it's clearly way too chatty. But I plan to do that with
some of the structures I will be creating to solve #778.
## Validation Steps Performed
- Ran the scenario listed in #2191 in vim in the Terminal
- Added unit tests similar to examples given around glyph/text mapping
in runs from Microsoft community page
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