Add double-buffering support to reduce flicker

* 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

1 files changed, 13 insertions, 0 deletions

diff --git a/doc/lispref/frames.texi b/doc/lispref/frames.texi
index 7736438126c..90f8e3501b2 100644
--- a/doc/lispref/frames.texi
+++ b/doc/lispref/frames.texi
@@ -1539,6 +1539,13 @@ prevent hanging with those window managers.
 If non-@code{nil}, the frame is visible on all virtual desktops on systems
 with virtual desktops.
 
+@vindex inhibit-double-buffering, a frame parameter
+@item inhibit-double-buffering
+If non-@code{nil}, the frame is drawn to the screen without double buffering.
+Emacs normally attempts to use double buffering, where available, to
+reduce flicker.  Set this property if you experience display bugs or
+pine for that retro, flicker-y feeling.
+
 @ignore
 @vindex parent-id, a frame parameter
 @item parent-id
@@ -2210,6 +2217,12 @@ window manager.  This happens below the level at which Emacs can exert
 any control, but Emacs does provide events that you can use to keep
 track of such changes.  @xref{Misc Events}.
 
+@defun x-double-buffered-p &optional frame
+This function returns non-@code{nil} if @var{frame} is currently
+being rendered with double buffering.  @var{frame} defaults to the
+selected frame.
+@end defun
+
 @node Raising and Lowering
 @section Raising and Lowering Frames