* src/composite.c (find_automatic_composition): Limit search
backward in buffers to the first newline.  Fix commentary.

* src/lisp.h (STRING_SET_MULTIBYTE): Make it into a function.

* src/composite.c (Fcomposition_get_gstring):
Prefer `make_multibyte_string` over Fconcat+STRING_SET_MULTIBYTE.

Qunbound is uninterned and can therefore never be EQ to any symbol
with position.

* src/buffer.c (Fbuffer_local_value, buffer_lisp_local_variables)
(buffer_local_variables_1):
* src/bytecode.c (exec_byte_code):
* src/comp.c (compile_function, Fcomp__compile_ctxt_to_file):
* src/composite.c (composition_gstring_cache_clear_font):
* src/data.c (Fboundp, Fsymbol_value, set_internal)
(Fdefault_boundp, Fdefault_value, Fmake_variable_buffer_local):
* src/emacs-module.c (module_global_reference_p):
* src/eval.c (Fdefault_toplevel_value, defvar)
(run_hook_with_args):
* src/fns.c (hash_put, Fmaphash):
* src/font.c (font_put_extra):
* src/frame.c (gui_set_frame_parameters)
(gui_frame_get_and_record_arg, gui_default_parameter)
(gui_figure_window_size):
* src/haikufns.c (get_geometry_from_preferences)
(haiku_create_frame, haiku_create_tip_frame):
* src/haikuterm.c (haiku_draw_text_decoration)
(haiku_default_font_parameter):
* src/json.c (lisp_to_json_nonscalar_1):
* src/keymap.c (access_keymap_1, access_keymap, current_minor_maps):
* src/lread.c (readevalloop, define_symbol):
* src/minibuf.c (read_minibuf, Ftry_completion):
(Fall_completions, Ftest_completion):
* src/pgtkfns.c (pgtk_default_font_parameter, Fx_create_frame)
(x_create_tip_frame):
* src/pgtkselect.c (Fpgtk_own_selection_internal):
* src/print.c (print):
* src/profiler.c (evict_lower_half, record_backtrace):
* src/terminal.c (create_terminal):
* src/textprop.c (set_properties):
* src/w32fns.c (my_create_window, w32_icon)
(w32_default_font_parameter, Fx_create_frame)
(w32_create_tip_frame):
* src/w32term.c (w32_draw_glyph_string):
* src/xdisp.c (handle_single_display_spec)
(cursor_row_fully_visible_p, calc_pixel_width_or_height):
* src/xfns.c (x_default_scroll_bar_color_parameter, x_icon_verify)
(x_icon, x_default_font_parameter, Fx_create_frame)
(x_create_tip_frame):
* src/xselect.c (x_handle_selection_request):
* src/xterm.c (x_draw_glyph_string, x_term_init):
Use BASE_EQ instead of EQ when comparing with Qunbound.

* src/bytecode.c (Fbyte_code):
* src/composite.c (Fclear_composition_cache):
Prefer CALLN to doing it by hand.
* src/fns.c (ccall2): Remove.  All uses replaced by CALLN.

* src/composite.c (composition_compute_stop_pos)
(Ffind_composition_internal): When characters come from a string,
determine whether to compose them from that string's multibyteness,
not from that of the current buffer.  (Bug#53729)

This changeset is based on code originally posted by
Kenichi Handa <handa@gnu.org> as part of discussing bug#20140,
with a few adjustments and changes, mainly to support R2L
text and provide a user option to control the feature.
* src/xdisp.c (compute_stop_pos, next_element_from_buffer)
(composition_reseat_it): Don't allow auto-composing characters
past point when 'composition-break-at-point' is non-nil.
(syms_of_xdisp) <composition-break-at-point>: New boolean variable.
(redisplay_internal, redisplay_window): Disable "just move the
cursor" optimizations when 'composition-break-at-point' is non-nil.
* src/keyboard.c (command_loop_1): Force redisplay when
'composition-break-at-point' is non-nil.

* lisp/cus-start.el (standard): Provide customization form for
'composition-break-at-point'.

* etc/NEWS: Announce the new feature.

The specpdl_ref type is just an alias for ptrdiff_t; the compiled code
remains the same.  All operations on specpdl_ref (arithmetic,
comparison etc) now go through inline functions.

The bulk of the change is almost completely mechanical.  It is done to
prepare for a type-safe representation and subsequent performance
improvement.

* src/lisp.h (specpdl_ref, specpdl_count_to_ref, specpdl_ref_to_count)
(specpdl_ref_eq, specpdl_ref_lt, specpdl_ref_valid_p)
(make_invalid_specpdl_ref, specpdl_ref_add, specpdl_ref_to_ptr): New.
(SPECPDL_INDEX, struct handler, USE_SAFE_ALLOCA, safe_free)
(safe_free_unbind_to):
* src/alloc.c (run_finalizer_function, inhibit_garbage_collection)
(garbage_collect, Fgarbage_collect, which_symbols):
* src/bidi.c (bidi_at_paragraph_end, bidi_find_paragraph_start):
* src/buffer.c (Fkill_buffer, Fset_buffer_major_mode, Fmove_overlay)
(Fdelete_overlay):
* src/bytecode.c (exec_byte_code):
* src/callint.c (Ffuncall_interactively, Fcall_interactively):
* src/callproc.c (Fcall_process, call_process, create_temp_file)
(Fcall_process_region):
* src/charset.c (load_charset_map_from_file):
* src/coding.c (decode_coding_gap, decode_coding_object)
(encode_coding_object, Fread_coding_system):
* src/comp.c (emit_static_object, helper_unbind_n, load_comp_unit):
* src/composite.c (update_compositions, autocmp_chars):
* src/cygw32.c (conv_filename_to_w32_unicode)
(conv_filename_from_w32_unicode):
* src/data.c (notify_variable_watchers):
* src/decompress.c (Fzlib_decompress_region):
* src/dired.c (directory_files_internal, file_name_completion)
(file_attributes):
* src/dispnew.c (Fredisplay):
* src/doc.c (get_doc_string, Fsnarf_documentation):
* src/editfns.c (Fsave_excursion, Fsave_current_buffer)
(Freplace_buffer_contents, Fsubst_char_in_region, Fsave_restriction)
(styled_format):
* src/emacs-module.c (Fmodule_load, funcall_module):
* src/emacs.c (init_cmdargs, Fdump_emacs):
* src/eval.c (call_debugger, do_debug_on_call, FletX, Flet)
(Ffuncall_with_delayed_message, Funwind_protect)
(internal_lisp_condition_case, signal_or_quit)
(load_with_autoload_queue, Feval, grow_specpdl_allocation)
(record_in_backtrace, eval_sub, Ffuncall, apply_lambda)
(funcall_lambda, clear_unwind_protect, set_unwind_protect)
(set_unwind_protect_ptr, unbind_to, Fbacktrace_eval):
* src/fileio.c (Fmake_temp_file_internal, Fcopy_file, Frename_file)
(Finsert_file_contents, write_region, Fdo_auto_save):
* src/fns.c (Fyes_or_no_p, Frequire, hash_table_user_defined_call):
* src/fringe.c (update_window_fringes):
* src/gtkutil.c (xg_dialog_run):
* src/haiku_io.c (c_specpdl_idx_from_cxx):
* src/haiku_support.cc (be_popup_file_dialog):
* src/haiku_support.h (c_specpdl_idx_from_cxx):
* src/haikufns.c (haiku_create_frame, haiku_create_tip_frame)
(haiku_hide_tip, Fx_show_tip, Fhaiku_read_file_name):
* src/haikumenu.c (haiku_popup_dialog, set_frame_menubar):
* src/image.c (slurp_file):
* src/indent.c (line_number_display_width, Fvertical_motion):
* src/insdel.c (signal_before_change, signal_after_change)
(Fcombine_after_change_execute):
* src/intervals.c (get_local_map):
* src/json.c (lisp_to_json_nonscalar_1, Fjson_serialize, Fjson_insert)
(Fjson_parse_string, Fjson_parse_buffer):
* src/keyboard.c (recursive_edit_1, Frecursive_edit, cmd_error)
(Finternal_track_mouse, command_loop_1, read_menu_command)
(safe_run_hooks, read_event_from_main_queue, read_char, timer_check_2)
(menu_item_eval_property, read_key_sequence, read_key_sequence_vs)
(Fsuspend_emacs):
* src/keymap.c (Fcurrent_active_maps, Fdescribe_vector)
(Fhelp__describe_vector):
* src/lread.c (Fload, save_match_data_load, readevalloop)
(Feval_buffer, Feval_region, grow_read_buffer, read_integer, read1):
* src/macros.c (Fexecute_kbd_macro):
* src/menu.c (x_popup_menu_1):
* src/minibuf.c (read_minibuf, set_minibuffer_mode)
(read_minibuf_unwind, Fread_string, Fread_buffer):
* src/nsfns.m (Fx_create_frame, Fx_show_tip):
* src/nsmenu.m (ns_update_menubar, ns_menu_show, ns_popup_dialog):
* src/pdumper.c (Fdump_emacs_portable):
* src/pgtkfns.c (Fx_create_frame, x_create_tip_frame, x_hide_tip)
(Fx_show_tip, Fpgtk_print_frames_dialog, Fx_file_dialog, Fx_select_font):
* src/pgtkmenu.c (set_frame_menubar, create_and_show_popup_menu)
(pgtk_menu_show, create_and_show_dialog, pgtk_dialog_show)
(pgtk_popup_dialog):
* src/pgtkterm.c (pgtk_cr_export_frames):
* src/print.c (PRINTPREPARE, temp_output_buffer_setup)
(Fprin1_to_string, print_vectorlike):
* src/process.c (Fmake_process, create_process, Fmake_pipe_process)
(Fmake_serial_process, connect_network_socket, Fmake_network_process)
(network_interface_info, server_accept_connection)
(wait_reading_process_output, read_process_output, exec_sentinel):
* src/regex-emacs.c (re_match_2_internal):
* src/search.c (looking_at_1, fast_looking_at, search_buffer_re):
* src/sound.c (Fplay_sound_internal):
* src/sysdep.c (system_process_attributes):
* src/term.c (tty_menu_show):
* src/textprop.c (Fnext_single_char_property_change)
(Fprevious_single_char_property_change, add_text_properties_1)
(set_text_properties, set_text_properties_1, Fremove_text_properties)
(Fremove_list_of_text_properties):
* src/thread.c (Fmutex_lock, invoke_thread_function):
* src/undo.c (truncate_undo_list):
* src/w32fns.c (Fx_create_frame, w32_create_tip_frame, w32_hide_tip)
(Fx_show_tip, Fx_file_dialog):
* src/w32font.c (Fx_select_font):
* src/w32menu.c (set_frame_menubar):
* src/window.c (window_list, next_window, window_list_1)
(run_window_configuration_change_hook, Frun_window_scroll_functions)
(run_window_change_functions, set_window_buffer)
(temp_output_buffer_show, window_scroll, scroll_command)
(Fscroll_other_window, Fscroll_other_window_down):
* src/xdisp.c (safe__call, handle_fontified_prop, handle_face_prop)
(handle_single_display_spec, Fbuffer_text_pixel_size)
(message_dolog, with_echo_area_buffer, setup_echo_area_for_printing)
(display_echo_area, set_message, clear_message, echo_area_display)
(gui_consider_frame_title, prepare_menu_bars, update_menu_bar)
(update_tab_bar, update_tool_bar, redisplay_internal)
(redisplay_preserve_echo_area, run_window_scroll_functions)
(redisplay_window, extend_face_to_end_of_line)
(display_count_lines_logically, display_count_lines_visually)
(display_mode_lines, display_mode_line, Fformat_mode_line)
(decode_mode_spec):
* src/xfns.c (Fx_create_frame, x_create_tip_frame, x_hide_tip)
(Fx_show_tip, Fx_file_dialog, Fx_select_font, Fx_print_frames_dialog):
* src/xmenu.c (set_frame_menubar, create_and_show_popup_menu)
(x_menu_show, create_and_show_dialog, x_dialog_show)
(xw_popup_dialog):
* src/xselect.c (x_get_local_selection, x_reply_selection_request)
(x_handle_selection_request, wait_for_property_change):
* src/xterm.c (x_cr_export_frames, x_connection_closed):
Replace ptrdiff_t with specpdl_ref for referencing specpdl and use the
corresponding functions instead of direct arithmetic.