Re: Question about display engine

[Ergus]

On Sun, Oct 13, 2019 at 07:06:18PM +0300, Eli Zaretskii wrote:
> > Date: Sun, 13 Oct 2019 17:40:52 +0200
> > From: Ergus <address@hidden>
> > Cc: address@hidden, address@hidden
> >
> > #0  0x000055cb1453ac98 in redisplay_windows (window=0x55cb15e3bfb5) at 
> > ../../src/xdisp.c:16126
> > #1  0x000055cb1453ac6d in redisplay_windows (window=0x55cb163ffc55) at 
> > ../../src/xdisp.c:16120
> > #2  0x000055cb1455b35d in redisplay_internal () at ../../src/xdisp.c:15596
> > #3  0x000055cb145fff3f in read_char (commandflag=1, map=0x55cb16838f93, 
> > prev_event=0x0, used_mouse_menu=0x7ffc1a89f4eb, end_time=0x0) at 
> > ../../src/keyboard.c:2473
> > #4  0x000055cb1460278a in read_key_sequence
> >     (keybuf=<optimized out>, prompt=0x0, dont_downcase_last=<optimized out>, 
> > can_return_switch_frame=true, fix_current_buffer=true, prevent_redisplay=<optimized out>)
> >     at ../../src/keyboard.c:9527
> > #5  0x000055cb14603e2c in command_loop_1 () at ../../src/lisp.h:1032
> > #6  0x000055cb1466af87 in internal_condition_case
> >     (bfun=bfun@entry=0x55cb14603c30 <command_loop_1>, handlers=handlers@entry=0x90, 
> > hfun=hfun@entry=0x55cb145fadc0 <cmd_error>) at ../../src/eval.c:1355
> > #7  0x000055cb145f5b94 in command_loop_2 (ignore=ignore@entry=0x0) at 
> > ../../src/lisp.h:1032
> > #8  0x000055cb1466aee1 in internal_catch (tag=tag@entry=0xd4a0, 
> > func=func@entry=0x55cb145f5b70 <command_loop_2>, arg=arg@entry=0x0) at 
> > ../../src/eval.c:1116
> > #9  0x000055cb145f5b3b in command_loop () at ../../src/lisp.h:1032
> > #10 0x000055cb145fa9d6 in recursive_edit_1 () at ../../src/keyboard.c:714
> > #11 0x000055cb145fad02 in Frecursive_edit () at ../../src/keyboard.c:786
> > #12 0x000055cb1451c957 in main (argc=18, argv=<optimized out>) at 
> > ../../src/emacs.c:2055
> >
> > After some other tests I just did; I found that:
> >
> > #0 seems to be the root of the loop. redisplay_windows never ends (inf
> >  loop) and I can't understand why. But at least this explains why in gui
> >  it works but not in tui, because there is the WINDOWP test.
>
> The WINDOWP test has nothing to do with GUI vs TTY, it tests whether
> w->contents is a window or a buffer.
>
> > What I can't understand is how the code can be in #1 that should always
> > filtered by the WINDOWP condition in tui right?
>
> No, see above.
>
> This function is a simple depth-first tree traversal of the window
> tree, starting from the root window of a frame.  Each leaf of the
> window tree has a buffer in its w->contents pointer, while
> intermediate nodes of the tree have windows in that pointer.
>
> > In any case the inf loop is there, but the recursions levels does not
> > grow... so after the first time it enters in #1, it goes in the other
> > branch if the if.
>
> If it goes to the other branch, it should descend the tree via the
> w->next pointer, and eventually get to a leaf node.
>
> Could it be that redisplay_window_0, or some function it calls,
> signals an error, which is caught by internal_condition_case_1?  What
> happens if you put a breakpoint in signal_or_quit, does it get called
> from redisplay_window or some other function called by
> redisplay_windows?

Yes, actually:

#0  0x00005597732a0380 in signal_or_quit (error_symbol=0x2cd0, 
data=0x559775ee2633, keyboard_quit=false) at ../../src/eval.c:1586
#1  0x000055977314c308 in Fsignal (error_symbol=<optimized out>, 
error_symbol@entry=0x2cd0, data=<optimized out>) at ../../src/eval.c:1568
#2  0x000055977314c4c9 in xsignal (data=<optimized out>, error_symbol=0x2cd0) 
at ../../src/lisp.h:4139
#3  0x000055977314c4c9 in xsignal2 (error_symbol=error_symbol@entry=0x2cd0, 
arg1=<optimized out>, arg2=<optimized out>) at ../../src/eval.c:1713
#4  0x000055977314b76e in args_out_of_range (a1=<optimized out>, a2=<optimized 
out>) at ../../src/lisp.h:1032
#5  0x000055977314e97b in validate_interval_range (object=0x559775cee0d5, 
begin=0x7fff35ec34b8, end=0x7fff35ec34b8, force=<optimized out>) at 
../../src/textprop.c:158
#6  0x00005597732f4050 in Ftext_properties_at (position=<optimized out>, 
object=<optimized out>) at ../../src/textprop.c:572
#7  0x00005597732f40bc in Fget_text_property (position=<optimized out>, prop=0x5d30, 
object=<optimized out>) at ../../src/textprop.c:592
#8  0x00005597731f8eec in face_at_buffer_position
   (w=0x5597758e7620, pos=0, endptr=endptr@entry=0x7fff35ec3650, limit=100, 
mouse=mouse@entry=false, base_face_id=1, attr_filter=LFACE_EXTEND_INDEX)
   at ../../src/xfaces.c:6090
#9  0x000055977316ab25 in face_at_pos (it=0x7fff35ec3710, 
attr_filter=LFACE_EXTEND_INDEX) at ../../src/xdisp.c:4167
#10 0x000055977317083d in extend_face_to_end_of_line (it=0x7fff35ec3710) at 
../../src/xdisp.c:21584
#11 0x0000559773185891 in display_mode_line (w=w@entry=0x5597758e7620, 
face_id=<optimized out>, format=0x7efd5d2d9ed3) at ../../src/xdisp.c:24990
#12 0x0000559773185afe in display_mode_lines (w=w@entry=0x5597758e7620) at 
../../src/lisp.h:730
#13 0x000055977319ebbc in redisplay_window (window=0x5597758e7625, 
just_this_one_p=<optimized out>) at ../../src/xdisp.c:18803
#14 0x00005597731a327b in redisplay_window_0 
(window=window@entry=0x5597758e7625) at ../../src/xdisp.c:16146
#15 0x000055977329f014 in internal_condition_case_1
   (bfun=bfun@entry=0x5597731a3250 <redisplay_window_0>, arg=arg@entry=0x5597758e7625, 
handlers=<optimized out>, hfun=hfun@entry=0x559773165800 <redisplay_window_error>) at 
../../src/eval.c:1379
#16 0x000055977316ec98 in redisplay_windows (window=0x5597758e7625) at 
../../src/xdisp.c:16126
#17 0x000055977316ec6d in redisplay_windows (window=0x5597758e7415) at 
../../src/xdisp.c:16120
#18 0x000055977318f35d in redisplay_internal () at ../../src/xdisp.c:15596
#19 0x0000559773233f3f in read_char (commandflag=1, map=0x559775ee36d3, 
prev_event=0x0, used_mouse_menu=0x7fff35ec8cbb, end_time=0x0) at 
../../src/keyboard.c:2473
#20 0x000055977323678a in read_key_sequence
   (keybuf=<optimized out>, prompt=0x0, dont_downcase_last=<optimized out>, 
can_return_switch_frame=true, fix_current_buffer=true, prevent_redisplay=<optimized out>)
   at ../../src/keyboard.c:9527
#21 0x0000559773237e2c in command_loop_1 () at ../../src/lisp.h:1032
#22 0x000055977329ef87 in internal_condition_case
   (bfun=bfun@entry=0x559773237c30 <command_loop_1>, handlers=handlers@entry=0x90, 
hfun=hfun@entry=0x55977322edc0 <cmd_error>) at ../../src/eval.c:1355
#23 0x0000559773229b94 in command_loop_2 (ignore=ignore@entry=0x0) at 
../../src/lisp.h:1032
#24 0x000055977329eee1 in internal_catch (tag=tag@entry=0xd4a0, 
func=func@entry=0x559773229b70 <command_loop_2>, arg=arg@entry=0x0) at 
../../src/eval.c:1116
#25 0x0000559773229b3b in command_loop () at ../../src/lisp.h:1032
#26 0x000055977322e9d6 in recursive_edit_1 () at ../../src/keyboard.c:714
#27 0x000055977322ed02 in Frecursive_edit () at ../../src/keyboard.c:786
#28 0x0000559773150957 in main (argc=18, argv=<optimized out>) at 
#../../src/emacs.c:2055

This makes more sense now.