bug#39724: 26.3; Commit 44298ea6aa006ed227e539b02279bd3fc11fd2a6 breaks font display on macOS

["John Wiegley" <johnw@gnu.org>]

I noticed recently that no text was displaying in my Emacs 27 windows. As if
everything were black and black, except that changing the font and background
colors did not help.

It took two days of rebuilding, but I've isolated this as the breaking commit:

commit 44298ea6aa006ed227e539b02279bd3fc11fd2a6
Author: Alan Third <alan@idiocy.org>
Date:   Sat Feb 1 21:17:29 2020 +0000

    Use CGImage instead of NSBitmapImageRep (bug#32932)

    * src/nsterm.m (ns_update_end):
    (ns_clear_frame): Remove forced draws.
    (ns_draw_fringe_bitmap):
    (ns_dumpglyphs_image): No longer need to invert images as the context
    is already flipped.
    ([EmacsView updateFrameSize:]):
    ([EmacsView initFrameFromEmacs:]): Use new function.
    ([EmacsView createDrawingBuffer]): Replaces createDrawingBufferWithRect:.
    ([EmacsView focusOnDrawingBuffer]): Set CGImage context.
    ([EmacsView windowDidChangeBackingProperties:]): Use new function.
    ([EmacsView copyRect:to:]): Copy using CGImages.
    ([EmacsView wantsUpdateLayer]):
    ([EmacsView updateLayer]): New Functions.
    ([EmacsView drawRect:]): We no longer do anything special here for
    Cocoa.
    ([EmacsView windowDidChangeBackingProperties:]): Fix indentation and
    add NSTRACE.

Anything prior to this works as expected. From this commit forward, all
windows are black on black.

-- 
John Wiegley                  GPG fingerprint = 4710 CF98 AF9B 327B B80F
http://newartisans.com                          60E1 46C4 BD1A 7AC1 4BA2