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Fix lines in kitty terminal with text_fg_override_threshold set #197

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merged 3 commits into from
Nov 2, 2023
Merged

Fix lines in kitty terminal with text_fg_override_threshold set #197

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dbe7867
Fix lines in kitty terminal with text_fg_override_threshold set
joveian Oct 30, 2023
0e3d89e
cargo fmt
joveian Oct 30, 2023
414736b
Add comment about kitty's text_fg_override_threshold
joveian Nov 2, 2023
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27 changes: 22 additions & 5 deletions src/cli/hdcanvas.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -75,6 +75,13 @@ impl Canvas {
}
}

// The kitty terminal has a feature text_fg_override_threshold that
// checks the difference in luminosity between text and background and
// changes the text to black or white to make it readable if the
// luminosity difference percentage is below the specified threshold.
// Using block characters for graphics display can trigger this, causing
// black or white lines or blocks, if the color is the same or too close.
// The checkerboard should be ok unless the theshold is set fairly high.
pub fn print(&self, out: &mut dyn Write) -> Result<()> {
for i_div_2 in 0..self.height / 2 {
for j in 0..self.width {
Expand All @@ -85,11 +92,21 @@ impl Canvas {
let p_bottom = self.pixel(2 * i_div_2 + 1, j);

match (p_top, p_bottom) {
(Some(top), Some(bottom)) => write!(
out,
"{}",
self.brush.paint("▀", top.ansi_style().on(bottom))
)?,
(Some(top), Some(bottom)) => {
if top == bottom {
write!(
out,
"{}",
self.brush.paint(" ", top.ansi_style().on(bottom))
)?
} else {
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what about the else path? Isn't that still potentially causing problems if kitty changes colors?

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Potentially, however I think it is only used in the checkerboard, which has a fairly high luminosity difference. I think kitty uses a simple percentage luminosity difference (I want to work on the compare functionality from #21 next and would like to add the value that kitty uses). I set it to 40 which seems high enough to avoid issues with text and the checkerboard still works. Maybe a comment about this potential issue would be appropriate to avoid it being used for something else in the future.

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I just checked and 40 is the highest value of text_fg_override_threshold that the current checkerboard works with, so I guess that would be a potential reason to use the graphics protocol, although I'm not sure if anyone will want to set it higher than that. Does look a bit odd when it triggers.

write!(
out,
"{}",
self.brush.paint("▀", top.ansi_style().on(bottom))
)?
}
}
(Some(top), None) => write!(out, "{}", self.brush.paint("▀", top))?,
(None, Some(bottom)) => write!(out, "{}", self.brush.paint("▄", bottom))?,
(None, None) => write!(out, " ")?,
Expand Down