Reflow patch: Scrollback buffer contents are lost when clearing screen with `Ctrl+l`

[UtkarshVerma]

This issue is similar to #46 where the scrollback buffer contents are lost when Ctrl+l is pressed.

Here are the patches I have enabled.

#define ALPHA_PATCH 1
#define ANYSIZE_SIMPLE_PATCH 1
#define BLINKING_CURSOR_PATCH 1
#define BOXDRAW_PATCH 1
#define CSI_22_23_PATCH 1
#define DEFAULT_CURSOR_PATCH 1
#define EXTERNALPIPE_PATCH 1
#define FIXKEYBOARDINPUT_PATCH 1
#define LIGATURES_PATCH 1
#define NETWMICON_LEGACY_PATCH 1
#define NEWTERM_PATCH 1
#define REFLOW_PATCH 1
#define SIXEL_PATCH 1
#define SYNC_PATCH 1
#define VERTCENTER_PATCH 1
#define WIDE_GLYPHS_PATCH 1
#define WORKINGDIR_PATCH 1
#define XRESOURCES_PATCH 1
#define XRESOURCES_RELOAD_PATCH 1

Important thing is I have enabled the reflow patch without the scrollback patch.

Steps to reproduce

1. Get the source: https://github.com/UtkarshVerma/st-flexipatch
2. Compile and run st.
3. Run any command to get output.
4. Press Ctrl+l and see that the output is lost from the scrollback history.

Here's a video of the issue: https://github.com/bakkeby/st-flexipatch/assets/31820255/b92ef36a-494c-4f99-ae1c-472f4def1f5f

I have also noticed that while scrolling, the prompt is always shown at the top. Is there any way to avoid this behavior? Is this an intentional feature or is it a bug? https://github.com/bakkeby/st-flexipatch/assets/31820255/6c9bbbdb-007f-4613-a344-7ec0ccba032e

[bakkeby]

I have enabled the reflow patch without the scrollback patch.

Yes that is the intended way.

Both of these issues looks to have been addressed in https://github.com/veltza/st-sx so I'll have a closer look and get back to you.

The history buffer is not cut when you do ctrl+l - presumably it just scrolls all the way down rather than clearing what is in view.

As for the prompt and cursor - it looks like the cursor there is hidden when you start scrolling and it is only revealed again when focus is on the line where the cursor is.

Thanks for reporting.

[veltza]

The code that looks for the last line was accidentally placed inside a conditional compilation block. Move it out of that block and ctrl+l should work.

            #if KEYBOARDSELECT_PATCH
            for (n = term.row-1; n >= 0 && tlinelen(term.line[n]) == 0; n--)
                ;
            #endif // KEYBOARDSELECT_PATCH

[UtkarshVerma]

veltza is right. It works if I move it outside the KEYBOARDSELECT conditional. However, the prompt issue still persists.

https://github.com/bakkeby/st-flexipatch/assets/31820255/1ef449d6-9111-40a3-990b-85a6dbbbfd0e

[veltza]

This should fix both issues. I haven't fully tested it yet though.

diff --git a/st.c b/st.c
index bc1abf7..5932a3f 100644
--- a/st.c
+++ b/st.c
@@ -2227,10 +2227,8 @@ csihandle(void)
            /* vte does this:
            tscrollup(0, term.row-1, term.row, SCROLL_SAVEHIST); */
            /* alacritty does this: */
-           #if KEYBOARDSELECT_PATCH
            for (n = term.row-1; n >= 0 && tlinelen(term.line[n]) == 0; n--)
                ;
-           #endif // KEYBOARDSELECT_PATCH
            #if SIXEL_PATCH
            for (im = term.images; im; im = im->next)
                n = MAX(im->y - term.scr, n);
@@ -3695,11 +3693,9 @@ draw(void)

    #if KEYBOARDSELECT_PATCH && REFLOW_PATCH
    if (!kbds_drawcursor()) {
-   #endif // KEYBOARDSELECT_PATCH
-
-   #if SCROLLBACK_PATCH
+   #elif REFLOW_PATCH || SCROLLBACK_PATCH
    if (term.scr == 0)
-   #endif // SCROLLBACK_PATCH
+   #endif // REFLOW_PATCH || SCROLLBACK_PATCH
    #if LIGATURES_PATCH
    xdrawcursor(cx, term.c.y, term.line[term.c.y][cx],
            term.ocx, term.ocy, term.line[term.ocy][term.ocx],

[UtkarshVerma]

Thanks for the changes, veltzo. I tried them out and they work fine. However, I noticed one minor detail. After clearing the screen, an additional line is appended for the prompt, when scrolling back. Do you have an idea of what this could be?

Here's a video:

https://github.com/bakkeby/st-flexipatch/assets/31820255/3e7001a5-f004-41d8-8edb-2245d3ce5e5b

[UtkarshVerma]

The new prompt line is normal behavior. Please ignore it. Everything works fine.

[bakkeby]

Thanks again for the assist @veltza