Re: [hackers] [st] Fix cursor move with wide glyphs || Quentin Rameau

[Tim Culverhouse]

On Sun Feb 25, 2024 at 8:13 AM CST, Quentin Rameau wrote:
> Would you have a suggestion about how to handle cursor absolute
> position with text position, maybe we need some addition state?

I would suggest that cursor position control sequences should always operate on
a single-column basis. This is in line with every other terminal that handles
wide characters. It is up to the application running in the emulator to know
where it wants to position the cursor.

For example, the command below should move the cursor into the emoji but the
second `\e[D` should have not *visual* change, but the cursor is actually in the
"first" column of the emoji

  printf " " && sleep 2 && printf "\e[D" && sleep 2 && printf "\e[D" && sleep 2

Just my two cents.

-- 
Tim

Re: [hackers] [st] Fix cursor move with wide glyphs || Quentin Rameau

[Quentin Rameau]

> Hi,

Hola k0ga,

> > st would always move back 1 column,
> > even with wide glyhps (using more than a single column).
> > 
> > The glyph rune is set on its first column,
> > and the other ones are to 0,
> > so loop until we detect the start of the previous glyph.  
> 
> Should this be done in every cursor addressing command?
> What happens if we position the cursor in the middle of a glyph?

That's a preliminary patch to encourage improving the matter,
I suspect there might be some unhandled side-effects in some
perticular cases, when using arbitrary cursor movement
for example, though it's unclear if those should be handled
separately or not.

Would you have a suggestion about how to handle cursor absolute
position with text position, maybe we need some addition state?

Re: [hackers] [st] Fix cursor move with wide glyphs || Quentin Rameau

[Roberto E. Vargas Caballero]

Hi,

On Sun, Feb 25, 2024 at 11:57:03AM +0100, g...@suckless.org wrote:
> st would always move back 1 column,
> even with wide glyhps (using more than a single column).
> 
> The glyph rune is set on its first column,
> and the other ones are to 0,
> so loop until we detect the start of the previous glyph.

Should this be done in every cursor addressing command?
What happens if we position the cursor in the middle of a glyph?

Kind regards,

[hackers] [st] Fix cursor move with wide glyphs || Quentin Rameau

[git]

commit 7473a8d1a57e5f9aba41b953f4e498c35e1c9dc5
Author: Quentin Rameau 
AuthorDate: Sun Feb 25 01:31:31 2024 +0100
Commit: Hiltjo Posthuma 
CommitDate: Sun Feb 25 11:56:43 2024 +0100

Fix cursor move with wide glyphs

st would always move back 1 column,
even with wide glyhps (using more than a single column).

The glyph rune is set on its first column,
and the other ones are to 0,
so loop until we detect the start of the previous glyph.

diff --git a/st.c b/st.c
index 034954d..77c3e8a 100644
--- a/st.c
+++ b/st.c
@@ -86,8 +86,8 @@ enum escape_state {
 
 typedef struct {
Glyph attr; /* current char attributes */
-   int x;
-   int y;
+   int x; /* terminal column */
+   int y; /* terminal row */
char state;
 } TCursor;
 
@@ -2175,12 +2175,16 @@ tstrsequence(uchar c)
 void
 tcontrolcode(uchar ascii)
 {
+   size_t i;
+
switch (ascii) {
case '\t':   /* HT */
tputtab(1);
return;
case '\b':   /* BS */
-   tmoveto(term.c.x-1, term.c.y);
+   for (i = 1; term.c.x && term.line[term.c.y][term.c.x - i].u == 
0; ++i)
+   ;
+   tmoveto(term.c.x - i, term.c.y);
return;
case '\r':   /* CR */
tmoveto(0, term.c.y);