Open Radar

 
Summary:
Terminal.app window becomes partially transparent when glyphs from the U+1F300 page are rendered.  It also may cause the Inspector window's scroll frame-rate to droop or become unresponsive due to rendering lag.

Steps to Reproduce:
Open a window in Terminal.app.  Position it on top of some other window which is not filled with a solid color.
Pick window settings with a black background (e.g. the Homebrew preset).
Run this print statement to fill the terminal with, for instance, U+1F310:
python -c 'print u"\U0001F310"*8000'

Expected Results:
Dark window with alpha-blended Emoji glyphs rendered on top.

Actual Results:
Terminal.app window is transparent in the regions where the Emoji glyphs' backgrounds were painted.  Observed behavior is consistent with a Source Copy raster operation being used instead of Source Over.

If you bump the print statement up from 8000 to 80000 copies of the character, then pressing command-I to bring up the inspector and scrolling up and down results in lag.

Regression:
Observed in Terminal.app Version 2.2.2 (303)

Notes:
Don't ask why I tried this.