emacs-doom/patches

EMACS NS ACCESSIBILITY PATCHES
================================
author: Martin Sukany <martin@sukany.cz>

This directory contains two independent patch sets for the Emacs NS
(Cocoa) port:

  A. Standalone Zoom patch (0000)
  B. VoiceOver accessibility patch series (0001-0008)

Each can be applied independently.  They do not depend on each other.


PATCH A: ZOOM CURSOR TRACKING (0000)
-------------------------------------

  0000 ns: integrate with macOS Zoom for cursor tracking

A minimal patch that informs macOS Zoom of the text cursor position
after every physical cursor redraw.  When Zoom is enabled (System
Settings -> Accessibility -> Zoom -> Follow keyboard focus), the
zoomed viewport automatically tracks the Emacs insertion point.

Files modified:
  src/nsterm.h  (+4 lines: lastZoomCursorRect ivar)
  src/nsterm.m  (+66 lines: cursor store + UAZoomChangeFocus)
  etc/NEWS      (+8 lines)

Implementation:
  ns_draw_window_cursor stores the cursor rect in
  view->lastZoomCursorRect and calls UAZoomChangeFocus() with
  CG-space coordinates.  A fallback call in ns_update_end ensures
  Zoom tracks the cursor even after window switches (C-x o) where
  the physical cursor may not be redrawn.

  Coordinate conversion: EmacsView pixels (AppKit, flipped) ->
  NSWindow -> NSScreen -> CGRect with y-flip for CoreGraphics
  top-left origin.

  No user option is needed: UAZoomEnabled() returns false when Zoom
  is not active, so the overhead is a single function call per
  redisplay cycle.


PATCH B: VOICEOVER ACCESSIBILITY (0001-0008)
----------------------------------------------

  0001 ns: add accessibility base classes and text extraction
  0002 ns: implement buffer accessibility element (core protocol)
  0003 ns: add buffer notification dispatch and mode-line element
  0004 ns: add interactive span elements for Tab navigation
  0005 ns: integrate accessibility with EmacsView and redisplay
  0006 doc: add VoiceOver accessibility section to macOS appendix
  0007 ns: announce overlay completion candidates for VoiceOver
  0008 ns: announce child frame completion candidates for VoiceOver

Files modified:
  src/nsterm.h       (~120 lines: class declarations, ivars)
  src/nsterm.m       (~3400 lines: implementation)
  doc/emacs/macos.texi  (~50 lines: documentation)
  etc/NEWS           (~8 lines)

This patch series adds comprehensive VoiceOver accessibility support
to the NS port.  Before this patch, Emacs exposed only a minimal,
largely broken accessibility interface: EmacsView identified itself
as a generic NSAccessibilityGroup with no text content, no cursor
tracking, and no notifications.


ARCHITECTURE
------------

  Virtual element tree above EmacsView:

    EmacsAccessibilityElement (base)
      +-- EmacsAccessibilityBuffer     (AXTextArea; one per window)
      +-- EmacsAccessibilityModeLine   (AXStaticText; mode line)
      +-- EmacsAccessibilityInteractiveSpan  (AXButton/Link; Tab nav)

  Each buffer element maintains a text cache with visible-run mapping
  (O(log n) index lookup) and a precomputed line index (O(log L) line
  queries).  Notifications are posted asynchronously via dispatch_async
  to prevent VoiceOver deadlocks.

  Full details in the commit messages of each patch.


PERFORMANCE
-----------

  ns-accessibility-enabled (DEFVAR_BOOL, default nil):
    Set automatically at startup when macOS Zoom or an assistive
    technology (VoiceOver, Switch Control) is detected.
    When nil, no virtual elements are built, no notifications are
    posted, and ns_draw_window_cursor skips the cursor rect store.
    Zero overhead for users who do not use assistive technology.

  When enabled:
    - Text cache rebuilds only on BUF_MODIFF change (not per-keystroke)
    - Index lookups are O(log n) via binary search on visible runs
    - Line queries are O(log L) via precomputed lineStartOffsets
    - Interactive span scan runs only when dirty flag is set
    - No character cap: full buffer exposed, but cache is lazy


THREADING MODEL
---------------

  Main thread: all Lisp calls, buffer mutations, notification posting.
  AX thread: VoiceOver queries dispatch_sync to main thread.
  Async notifications: dispatch_async prevents deadlock (same pattern
  as WebKit's AXObjectCacheMac).


KNOWN LIMITATIONS
-----------------

  - Mode line: CHAR_GLYPH only (icon fonts produce incomplete text)
  - Overlay face matching: string containment ("current", "selected")
  - GNUstep excluded (#ifdef NS_IMPL_COCOA)
  - No multi-frame coordination
  - Child frame childFrameLastCandidate (per-view ivar, freed in dealloc)


TESTING
-------

  See TESTING.txt for the full test matrix and results.


-- end of README --