`win:style` styles more terminal cells than expected

[fischerling]

We noticed in https://github.com/fischerling/vis-lspc/pull/34 that the highlighting seems off around \t bytes.

This is reproducible by including something like

vis.events.subscribe(vis.events.WIN_HIGHLIGHT, function(win)
    win:style_define(43, 'back:red')
    win:style(43, 2, 2)
end)

in your visrc.lua file and opening a file containing only \t\tx. Instead of highlighting the cell containing x (the third byte in the file) the space after the first \t symbol up to and including the x is styled.

Example Screenshot.

[fischerling]

In view.c the position to sytle is found by iterating all cells on the proper line until we reach the position we want to style with the following while loop:

while (pos < start && col < width)
    pos += line->cells[col++].len;

In our example using a file containing \t\tx and after executing the loop pos will be 2 and col will be 5. However, there are more empty cells (cells with len == 0) following col 5 up until col 9, which we actually want to style.

The bug is fixed by skipping all "empty" cells after we found our starting position.

Briefly tested patch:

diff --git a/view.c b/view.c
index 5fa512b..a60466a 100644
--- a/view.c
+++ b/view.c
@@ -1429,6 +1429,10 @@ void view_style(View *view, enum UiStyle style_id, size_t start, size_t end) {
    while (pos < start && col < width)
        pos += line->cells[col++].len;

+   /* skip empty columns */
+   while (!line->cells[col].len && col < width)
+       col++;
+
    do {
        while (pos <= end && col < width) {
            pos += line->cells[col].len;

[rnpnr]

Hi, this patch seems correct. I have it applied locally and will likely apply it to master soon.

[fischerling]

Hi, this patch seems correct. I have it applied locally and will likely apply it to master soon.

What is the most convenient for you? Should I send it to the mailing list or open a PR here on Github?

[rnpnr]

What is the most convenient for you?

Either or is fine. Maybe more people will look at it if its a Github PR but its hard to say.