* src/dispextern.h (struct glyph_string): Remove window member
(block_buffer_flips, unblock_buffer_flips)
(buffer_flipping_blocked_p): Declare.

* src/xterm.h (struct x_display_info): New member supports_xdbe.
(struct x_output): New members draw_desc and need_buffer_flip.
(FRAME_X_DRAWABLE, FRAME_X_RAW_DRAWABLE)
(FRAME_X_DOUBLE_BUFFERED_P)
(FRAME_X_NEED_BUFFER_FLIP): New macros.
(set_up_x_back_buffer, tear_down_x_back_buffer)
(initial_set_up_x_back_buffer): Declare.

* src/xterm.c: Include Xdbe.h.
(x_begin_cr_clip, x_fill_rectangle, x_draw_rectangle)
(x_draw_vertical_window_border, x_update_end)
(x_setup_relief_color, x_draw_relief_rect)
(x_draw_fringe_bitmap, x_shift_glyphs_for_insert)
(x_scroll_run, x_draw_hollow_cursor, x_draw_bar_cursor): Use
FRAME_X_DRAWABLE instead of FRAME_X_WINDOW; rename local
variables appropriately; substitute calls to XClearArea with
x_clear_area, which DTRT for double buffering.
(x_clear_window, x_clear_area): In double-buffering mode, use
rect-drawing X functions instead of XClearWindow and
XClearArea, which always operate on the front buffer.
(show_back_buffer): New function.
(XTframe_up_to_date): Call show_back_buffer when done.
(x_clear_frame, x_clear_frame_area): Remove obsolete calls to
gtk_widget_queue_draw to refresh scroll bars; scroll bars are
now independent X windows.
(handle_one_xevent): Call font_drop_xrender_surfaces when
XftDraw might need regenerating; perform buffer flip when
responding to Expose events; issue front-buffer clearing
commands as stopgap while we wait for redisplay.
Call flush_dirty_back_buffers.
(x_make_frame_visible): Un-bitrot comment; move XSETFRAME
earlier in function.
(x_free_frame_resources): Call tear_down_x_back_buffer when
destroying frame.
(x_term_init): Attempt to initialize double buffer extension.
(x_flip_and_flush): New function.
(x_redisplay_interface): Point to x_flip_and_flush instead of
x_flip directly.
(flush_dirty_back_buffers): New function.
(x_create_terminal): Register buffer_flipping_unblocked_hook.

* src/xftfont.c (xftfont_drop_xrender_surfaces): Use
FRAME_X_DRAWABLE instead of FRAME_X_WINDOW.
(xftfont_draw): Call x_mark_frame_dirty.
(xftfont_drop_xrender_surfaces): New function.
(syms_of_xftfont): Register it.

* src/xfont.c (xfont_draw): Use FRAME_X_DRAWABLE instead of
FRAME_X_WINDOW.

* src/xfns.c: Include Xdbe.h.
(x_set_inhibit_double_buffering, set_up_x_back_buffer)
(Fx_double_buffered_p): New functions.
(x_window): Call initial_set_up_x_back_buffer.
(x_make_gc): Use FRAME_X_DRAWABLE instead of FRAME_X_WINDOW.
(Fx_create_frame): Configure `inhibit-double-buffering'
frame parameter.
(x_create_tip_frame): Call initial_set_up_x_back_buffer.
(x_frame_parm_handlers): Register
x_set_inhibit_double_buffering.
(syms_of_xfns): Register Sx_double_buffered_p.
(x_mark_frame_dirty): Define.

* src/xfaces.c (x_create_gc): Use FRAME_X_DRAWABLE instead of
FRAME_X_WINDOW.

* src/xdisp.c (remember_mouse_glyph, init_glyph_string): Use
FRAME_X_DRAWABLE instead of FRAME_X_WINDOW.
(redisplay_internal): Restart redisplay if a frame is garbaged
during updating; explain why. Block buffer flips
during redisplay.
(redisplay_preserve_echo_area): Block buffer flip during call
to redisplay_internal.
(buffer_flip_blocked_depth): New variable.
(block_buffer_flips, unblock_buffer_flips)
(buffer_flipping_blocked_p): New functions.
(init_glyph_string): Stop setting window member of struct
glyph_string.

* src/w32fns.c (w32_frame_parm_handlers): Add placeholder for
x_set_inhibit_double_buffering.

* src/termhooks.h (struct terminal): Add
buffer_flipping_unblocked_hook.

* src/nsfns.m (ns_frame_parm_handlers): Add placeholder for
x_set_inhibit_double_buffering.

* src/image.c (x_create_bitmap_from_data)
(x_create_bitmap_from_file, x_create_x_image_and_pixmap)
(Create_Pixmap_From_Bitmap_Data)
(x_create_bitmap_from_xpm_data, xpm_load, gs_load): Use
FRAME_X_DRAWABLE instead of FRAME_X_WINDOW; rename local
variables appropriately.

* src/gtkutil.c: Include Xdbe.h.
(xg_get_widget_from_map): Forward declare.
(xg_clear_under_internal_border): Remove obsolete calls to
refresh scroll bars.
(xg_create_frame_widgets): Call initial_set_up_x_back_buffer.
(xg_free_frame_widgets): Call tear_down_x_back_buffer; reset
FRAME_X_DRAWABLE as well as FRAME_X_WINDOW and for the
same reason.
(xg_set_background_color): Set scroll bar background colors.
(xg_finish_scroll_bar_creation): New function with common
logic of xg_create_scroll_bar, xg_create_horizontal_scroll_bar. Force
scroll bars to be real X11 windows.
(xg_create_scroll_bar, xg_create_horizontal_scroll_bar): Call
xg_finish_scroll_bar_creation.
(xg_update_scrollbar_pos, xg_update_horizontal_scrollbar_pos):
Remove obsolete calls to refresh scroll bars; fix comments.

* src/ftxfont.c (ftxfont_get_gcs, ftxfont_draw_bitmap,
(ftxfont_draw_background): Use FRAME_X_DRAWABLE instead of
FRAME_X_WINDOW.

* src/frame.c (frame_parms): Add table entry for new
`inhibit-double-buffering' frame parameter
(syms_of_frame): Register Qinhibit_double_buffering.

* src/font.h (struct font_driver): Add new `flush_frame_caches' hook.
(font_drop_xrender_surfaces): Declare.

* src/font.c (font_drop_xrender_surfaces): New function.

* src/Makefile.in (XDBE_LIBS, XDBE_CFLAGS): Substitute.

* etc/NEWS: Mention use of double buffering

* doc/lispref/frames.texi (Management Parameters): Document
`inhibit-double-buffering' frame parameters.
(Visibility of Frames): Document `x-double-buffered-p'.

* configure.ac: Check for the X double buffer extension

This reverts commit 20038f8ab75dd1551412a43cd58520c483c22921.

I am reverting this change because it was applied without prior discussion
on emacs-devel, and has been found to break the NS port.  It needs more
testing and review before it should be applied here.

* src/dispextern.h (toplevel): Remove 'tip_frame' and 'tip_window' decls.
* src/frame.h (struct frame): New bitfield to indicate tooltip frame.
(FRAME_TOOLTIP_P): New macro.
* src/frame.c (make_frame): Mark new frame as regular frame by default.
(Fframe_list, delete_frame): Redesign to use FRAME_TOOLTIP_P.
(syms_of_frame): Don't DEFSYM 'Qtooltip' but use 'Qtooltip_timer'
and 'Qtooltip_parameters' instead.
* src/gtkutil.h (toplevel): Add 'xg_hide_tip' decl.
* src/gtkutil.c (xg_hide_tip): New function.
(xg_hide_tooltip): Adjust to cancel GTK event loop timeout if needed.
* src/menu.c (Fx_popup_menu): Adjust call to Fx_hide_tip.
* src/nsfns.c (toplevel): Remove 'tip_frame' leftover.
* src/w32fns.c (unwind_create_tip_frame): Remove.
(w32_display_monitor_attributes_list)
(w32_display_monitor_attributes_list_fallback): Use FRAME_TOOLTIP_P.
(toplevel): Remove 'tip_frame', 'tip_window' and 'last_show_tip_args'.
(x_create_tip_frame): Use do_unwind_create_frame.  Mark new frame
as a tooltip frame and record it using appropriate display info.
(x_hide_tooltip): Add frame arg.
(Fx_show_tip): Adjust to avoid globals, store tooltip parameters among
base frame parameters, store tooltip hide timer among tooltip frame
parameters.
(Fx_hide_tip): Add frame arg, hide tooltips on all displays by default.
(syms_of_w32fns): Don't DEFSYM 'Qtip_frame', don't initialize
and GC-protect 'tip_timer', 'tip_frame' and 'last_show_tip_args'.
* src/w32term.c (w32_read_socket): Extract tooltip window id from
per-display data.  Use FRAME_TOOLTIP_P where appropriate.
(x_new_font): Use FRAME_TOOLTIP_P.
(x_free_frame_resources): Reset pointer to tooltip frame.
* src/w32term.h (struct w32_display_info): New member 'w32_tooltip_frame'.
* src/xdisp.c (init_iterator, x_consider_frame_title, prepare_menu_bars):
Use FRAME_TOOLTIP_P.
* src/xfns.c (x_make_monitor_attribute_list)
(Fx_display_monitor_attributes_list): Likewise.
(unwind_create_tip_frame): Remove.
(toplevel): Remove 'tip_frame', 'tip_window' and 'last_show_tip_args'.
(x_create_tip_frame): Use do_unwind_create_frame.  Mark new frame
as a tooltip frame and record it using appropriate display info.
(x_hide_tooltip): Add frame arg.
(Fx_show_tip): Adjust to avoid globals, store tooltip parameters among
base frame parameters, store tooltip hide timer among tooltip frame
parameters.  To hide GTK system tooltip, use timeout hooked into GTK
event loop.
(Fx_hide_tip): Add frame arg, hide tooltips on all displays by default.
(syms_of_xfns): Don't DEFSYM 'Qtip_frame', don't initialize
and GC-protect 'tip_timer', 'tip_frame' and 'last_show_tip_args'.
* src/xterm.c (handle_one_xevent): Extract tooltip window id from
per-display data.  Use FRAME_TOOLTIP_P where appropriate.
(x_new_font, x_set_window_size): Use FRAME_TOOLTIP_P.
(x_free_frame_resources): Reset pointer to tooltip frame.
* src/xterm.h (struct x_display_info): New member 'x_tooltip_frame'.
(struct x_output) [USE_GTK_TOOLTIP]: New member 'ttip_timeout'.

* configure.ac [USE_X_TOOLKIT]: Define X_TOOLKIT_EDITRES if
_XEditResCheckMessages is declared in X11/Xmu/Editres.h and may be
linked with -lXmu.  This should work with any non-ancient Xmu library.
* xfns.c (toplevel): Remove old cruft.
(x_window) [USE_X_TOOLKIT]: Use X_TOOLKIT_EDITRES.
* xterm.c (toplevel): Remove old cruft.
(handle_one_xevent): Use X_TOOLKIT_EDITRES.
* xterm.h (toplevel): Include X11/Xmu/Editres.h if X_TOOLKIT_EDITRES.

* src/xterm.h (struct x_display_info): Add fields to save XRANDR
version number.
* src/xfns.c (x_get_monitor_attributes): Save the version numbers
after querying the X server.
(x_get_monitor_attributes_xrandr): Don't use XRRGetOutputPrimary or
XRRGetScreenResourcesCurrent if the server doesn't support at least
RANDR version 1.3.  Conditionalize the code blocks on compiling
against library version 1.3 or better, rather than feature tests for
each function.
* configure.ac: Stop testing for those two functions.

Work around Bug#22884 by rewording comments and strings to avoid ‘(’
at the start of a line unless it starts a function.  This change
is a short-term hack; in the longer run we plan to fix cc-mode’s
performance for C files that have ‘(’ at the start of a line in a
comment or string.

Run admin/update-copyright.

* configure.ac: If using X11, check for XCB libraries and header.
* src/Makefile.in (XCB_LIBS): Define.
(LIBX_EXTRA): Include it.

* src/xterm.h [USE_XCB]: Include X11/Xlib-xcb.h.
(struct x_display_info) [USE_XCB]: Add an XCB connection handle field.
* src/xterm.c (x_term_init) [USE_XCB]: Initialize the new field.

* src/xterm.c (struct x_error_message_stack): Add new fields for a
callback function and associated data pointer.
(x_error_catcher): If the callback function is set, call it after
saving the error message string.
(x_catch_errors_with_handler): Renamed from x_catch_errors but now
accepts a callback function and data pointer.
(x_catch_errors): Now a wrapper function.
* src/xterm.h (x_special_error_handler): New typedef.
(x_catch_errors_with_handler): Declare.

Both x_had_errors_p and x_check_errors call XSync, so if they're
immediately followed by x_uncatch_errors, its XSync call will be
redundant, resulting in a wasted round trip to the X server.

* src/xterm.c (x_uncatch_errors_after_check): New routine; a copy of
x_uncatch_errors without the XSync call.
(XTmouse_position, x_wm_supports):
* src/xfns.c (x_set_mouse_color):
* src/xmenu.c (Fx_menu_bar_open_internal):
* src/xselect.c (x_own_selection, x_get_foreign_selection):
(Fx_get_atom_name): Call it instead of x_uncatch_errors.
* src/xterm.h (x_uncatch_errors_after_check): Declare.