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ui: disable clearing almost everywhere

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Avoid clearing the screen in most situations. NOT_VALID should be
equivalent to CLEAR unless some external force messed up the terminal,
for these situations <c-l> and :mode will still clear the screen.

Also eliminate some obsolete code in screen.c, that dealt with that in
vim drawing window 1 can mess up window 2, but this never happens in
nvim.

But what about slow terminals? There is two common meanings in which
a terminal is said to be "slow":

Most commonly (and in the sense of vim:s nottyfast) it means low
bandwidth for sending bytes from nvim to the terminal. If the screen is
very similar before and after the update_screen(CLEAR) this change
should reduce bandwidth. If the screen is quite different, but there is
no new regions of contiguous whitespace, clearing doesn't reduce
bandwidth significantly. If the new screen contains a lot of whitespace,
it will depend of if vsplits are used or not: as long as there is no
vsplits, ce is used to cheaply clear the rest of the line, so
full-screen clear is not needed to reduce bandwith. However a left
vsplit currently needs to be padded with whitespace all the way to the
separator. It is possible ec (clear N chars) can be used to reduce
bandwidth here if this is a problem. (All of this assumes that one
doesn't set Normal guibg=... on a non-BCE terminal, if you do you are
doomed regardless of this change).

Slow can also mean that drawing pixels on the screen is slow. E-ink
screens is a recent example. Avoiding clearing and redrawing the
unchanged part of the screen will always improve performance in these
cases.
This commit is contained in:
Björn Linse
2018-10-20 23:43:47 +02:00
parent 565bbd1485
commit e598811e76
18 changed files with 119 additions and 185 deletions
Download Patch File Download Diff File Expand all files Collapse all files

29
src/nvim/ex_docmd.c
View File

@@ -208,8 +208,8 @@ void do_exmode(int improved)
return;
save_msg_scroll = msg_scroll;
++RedrawingDisabled; /* don't redisplay the window */
++no_wait_return; /* don't wait for return */
RedrawingDisabled++; // don't redisplay the window
no_wait_return++; // don't wait for return
MSG(_("Entering Ex mode. Type \"visual\" to go to Normal mode."));
while (exmode_active) {
@@ -253,10 +253,11 @@ void do_exmode(int improved)
}
}
--RedrawingDisabled;
--no_wait_return;
update_screen(CLEAR);
need_wait_return = FALSE;
RedrawingDisabled--;
no_wait_return--;
redraw_all_later(NOT_VALID);
update_screen(NOT_VALID);
need_wait_return = false;
msg_scroll = save_msg_scroll;
}
@@ -6857,7 +6858,8 @@ static void ex_tabs(exarg_T *eap)
static void ex_mode(exarg_T *eap)
{
if (*eap->arg == NUL) {
ui_refresh();
must_redraw = CLEAR;
ex_redraw(eap);
} else {
EMSG(_(e_screenmode));
}
@@ -6963,7 +6965,7 @@ do_exedit(
no_wait_return = 0;
need_wait_return = FALSE;
msg_scroll = 0;
must_redraw = CLEAR;
redraw_all_later(NOT_VALID);
normal_enter(false, true);
@@ -7782,11 +7784,14 @@ static void ex_redraw(exarg_T *eap)
p_lz = FALSE;
validate_cursor();
update_topline();
update_screen(eap->forceit ? CLEAR :
VIsual_active ? INVERTED :
0);
if (need_maketitle)
if (eap->forceit) {
redraw_all_later(NOT_VALID);
}
update_screen(eap->forceit ? NOT_VALID
: VIsual_active ? INVERTED : 0);
if (need_maketitle) {
maketitle();
}
RedrawingDisabled = r;
p_lz = p;