Fix a bug where thin strokes be used when the setting was "dark background" or "retina + dark background" even when the background was light because the background color didn't get passed through since we dididn't want to split up ligatures on background color changes. Since the thin strokes setting means the foreground depends on the background, the background color must be passed through and ligatures will be broken if the background color changes within them. Issue 6027

Disable ligatures-across-different-backgrounds when muting is in use (cursor boost and dimming use this). A background color is needed to compute the dimmed value.

Fix a bug where numberOfEquivalentRows was always 0 when minimum contrast is 0, which caused text to have the wrong foreground color.

Add new thin strokes settings to enable it with light backgrounds. People who had Always or Retina are migrated to With Dark Backgrounds or Retina and Dark Backgrounds, respectively. Issue 5910.

Disable the zippy text drawing algorithm for cells that have combining marks or surrogate pairs. CG draws combining marks really badly; core text is slow but much better.

Disable fastpath drawing for box-drawing characters.

This should fix the failing tests.

Issue 5884

Call refresh after changing font size to avoid doing a double redraw at two different scroll positions. Issue 5836

It upsets High Sierra. 

Issue 5811

Scroll to the copy mode cursor when entering copy mode if it's going straight into selecting mode.

Also fix the menu opener to not select the last item.

Draw the default background color behind images. This makes images with alpha<1 areas look nice. It's unfortunate that the "real" background color isn't available since the image y position uses those bits, but this is a good start. Issue 5723.

Add an experimental feature to draw an outline around underline and vertical bar cursors to improve distinction from text. Suggested in issue 4614.

OSC 8 ; url ST Anchor text OSC 8 ; ST

Fix a bug where transitions from ascii to non-ascii weren't properly detected by text drawing helper, causing the first non-ascii character after an ascii character to be drawn with the ascii font.

Use a taller mask when drawing underlines. PragmataPro's underline sits below the bottom of the cell. Issue 5450.

Make the unicode normalization form configurable to None, NFC, NFD, or HFS+. Users who had selected HFS+ are migrated by a computed default profile preference. The new default for everyone else is None. Let's see what breaks besides Inconsolata. Issue 5469.

Add the zippy text drawing algorithm which tries to use the fastpath even for nonascii text. It falls back to core text if a glyph is missing. If ligatures are enabled, zippy won't be used.