Add hidden escape sequence

This adds support for the `hidden` escape sequence `\e[8m`, which will
render the text as invisible.

This has also raised a few questions about the rendering of foreground
and background colors and their interaction with the different escape
sequences. Previously, Alacritty has oriented itself after URxvt, which
has some strange and unexpected behavior.

The new implementation of color inversion is modeled after XTerm, which
has a consistent pattern of always inverting the foreground and
background colors. This should hopefully lead to less confusion for the
user and a more consistent behavior.

A full matrix showcasing the new way Alacritty inverses text can be
found here:
https://i.imgur.com/d1XavG7.png

This fixes #1454 and fixes #1455.

CHANGELOG.md

@@ -8,11 +8,13 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Added
 
+- Implement the `hidden` escape sequence (`echo -e "\e[8mTEST"`)
 - Add support for macOS systemwide dark mode
 - Set the environment variable `COLORTERM="truecolor"` to advertise 24-bit color support
 
 ### Changed
 
+- Inverse/Selection color is now modelled after XTerm/VTE instead of URxvt to improve consistency
 - First click on unfocused Alacritty windows is no longer ignored on platforms other than macOS
 
 ## Version 0.2.0

scripts/fg-bg.sh

@@ -1,14 +1,53 @@
 #!/bin/bash
 
-printf "Fg=Black,     Bg=Background          \e[30;49mTEST\e[m\n"
+printf "Fg=Black  Bg=Black           \e[30;40mTEST\e[m\n"
-printf "Fg=Black,     Bg=Black               \e[30;40mTEST\e[m\n"
+printf "Fg=Black  Bg=White           \e[30;107mTEST\e[m\n"
-printf "Fg=Foreground,Bg=Background          \e[39;49mTEST\e[m\n"
+printf "Fg=Black  Bg=Red             \e[30;41mTEST\e[m\n"
-printf "Fg=Foreground,Bg=Black               \e[39;40mTEST\e[m\n"
+printf "Fg=Black  Bg=BG              \e[30;49mTEST\e[m\n"
-printf "Fg=Foreground,Bg=White               \e[39;47mTEST\e[m\n"
+printf "Fg=White  Bg=Black           \e[97;40mTEST\e[m\n"
-printf "Fg=White,     Bg=Foreground          \e[37;39mTEST\e[m\n"
+printf "Fg=White  Bg=White           \e[97;107mTEST\e[m\n"
-printf "Fg=Black,     Bg=Background, Inverse \e[7;30;49mTEST\e[m\n"
+printf "Fg=White  Bg=Red             \e[97;41mTEST\e[m\n"
-printf "Fg=Black,     Bg=Black,      Inverse \e[7;30;40mTEST\e[m\n"
+printf "Fg=White  Bg=BG              \e[97;49mTEST\e[m\n"
-printf "Fg=Foreground,Bg=Background, Inverse \e[7;39;49mTEST\e[m\n"
+printf "Fg=Red    Bg=Black           \e[31;40mTEST\e[m\n"
-printf "Fg=Foreground,Bg=Black,      Inverse \e[7;39;40mTEST\e[m\n"
+printf "Fg=Red    Bg=White           \e[31;107mTEST\e[m\n"
-printf "Fg=Foreground,Bg=White,      Inverse \e[7;39;47mTEST\e[m\n"
+printf "Fg=Red    Bg=Red             \e[31;41mTEST\e[m\n"
-printf "Fg=White,     Bg=Foreground, Inverse \e[7;37;39mTEST\e[m\n"
+printf "Fg=Red    Bg=BG              \e[31;49mTEST\e[m\n"
+printf "\n"
+printf "Fg=Black  Bg=Black  Inverse  \e[7;30;40mTEST\e[m\n"
+printf "Fg=Black  Bg=White  Inverse  \e[7;30;107mTEST\e[m\n"
+printf "Fg=Black  Bg=Red    Inverse  \e[7;30;41mTEST\e[m\n"
+printf "Fg=Black  Bg=BG     Inverse  \e[7;30;49mTEST\e[m\n"
+printf "Fg=White  Bg=Black  Inverse  \e[7;97;40mTEST\e[m\n"
+printf "Fg=White  Bg=White  Inverse  \e[7;97;107mTEST\e[m\n"
+printf "Fg=White  Bg=Red    Inverse  \e[7;97;41mTEST\e[m\n"
+printf "Fg=White  Bg=BG     Inverse  \e[7;97;49mTEST\e[m\n"
+printf "Fg=Red    Bg=Black  Inverse  \e[7;31;40mTEST\e[m\n"
+printf "Fg=Red    Bg=White  Inverse  \e[7;31;107mTEST\e[m\n"
+printf "Fg=Red    Bg=Red    Inverse  \e[7;31;41mTEST\e[m\n"
+printf "Fg=Red    Bg=BG     Inverse  \e[7;31;49mTEST\e[m\n"
+printf "\n"
+printf "Fg=Black  Bg=Black  Hidden   \e[8;30;40mTEST\e[m\n"
+printf "Fg=Black  Bg=White  Hidden   \e[8;30;107mTEST\e[m\n"
+printf "Fg=Black  Bg=Red    Hidden   \e[8;30;41mTEST\e[m\n"
+printf "Fg=Black  Bg=BG     Hidden   \e[8;30;49mTEST\e[m\n"
+printf "Fg=White  Bg=Black  Hidden   \e[8;97;40mTEST\e[m\n"
+printf "Fg=White  Bg=White  Hidden   \e[8;97;107mTEST\e[m\n"
+printf "Fg=White  Bg=Red    Hidden   \e[8;97;41mTEST\e[m\n"
+printf "Fg=White  Bg=BG     Hidden   \e[8;97;49mTEST\e[m\n"
+printf "Fg=Red    Bg=Black  Hidden   \e[8;31;40mTEST\e[m\n"
+printf "Fg=Red    Bg=White  Hidden   \e[8;31;107mTEST\e[m\n"
+printf "Fg=Red    Bg=Red    Hidden   \e[8;31;41mTEST\e[m\n"
+printf "Fg=Red    Bg=BG     Hidden   \e[8;31;49mTEST\e[m\n"
+printf "\n"
+printf "Fg=Black  Bg=Black  Hid+Inv  \e[7;8;30;40mTEST\e[m\n"
+printf "Fg=Black  Bg=White  Hid+Inv  \e[7;8;30;107mTEST\e[m\n"
+printf "Fg=Black  Bg=Red    Hid+Inv  \e[7;8;30;41mTEST\e[m\n"
+printf "Fg=Black  Bg=BG     Hid+Inv  \e[7;8;30;49mTEST\e[m\n"
+printf "Fg=White  Bg=Black  Hid+Inv  \e[7;8;97;40mTEST\e[m\n"
+printf "Fg=White  Bg=White  Hid+Inv  \e[7;8;97;107mTEST\e[m\n"
+printf "Fg=White  Bg=Red    Hid+Inv  \e[7;8;97;41mTEST\e[m\n"
+printf "Fg=White  Bg=BG     Hid+Inv  \e[7;8;97;49mTEST\e[m\n"
+printf "Fg=Red    Bg=Black  Hid+Inv  \e[7;8;31;40mTEST\e[m\n"
+printf "Fg=Red    Bg=White  Hid+Inv  \e[7;8;31;107mTEST\e[m\n"
+printf "Fg=Red    Bg=Red    Hid+Inv  \e[7;8;31;41mTEST\e[m\n"
+printf "Fg=Red    Bg=BG     Hid+Inv  \e[7;8;31;49mTEST\e[m\n"

src/renderer/mod.rs

@@ -835,12 +835,17 @@ impl<'a> RenderApi<'a> {
                 glyph_cache.font_key
             };
 
-            let glyph_key = GlyphKey {
+            let mut glyph_key = GlyphKey {
                 font_key,
                 size: glyph_cache.font_size,
                 c: cell.c
             };
 
+            // Don't render text of HIDDEN cells
+            if cell.flags.contains(cell::Flags::HIDDEN) {
+                glyph_key.c = ' ';
+            }
+
             // Add cell to batch
             {
                 let glyph = glyph_cache.get(glyph_key, self);

src/term/cell.rs

@@ -18,15 +18,16 @@ use index::Column;
 bitflags! {
     #[derive(Serialize, Deserialize)]
     pub struct Flags: u32 {
-        const INVERSE           = 0b0000_0001;
+        const INVERSE           = 0b0_0000_0001;
-        const BOLD              = 0b0000_0010;
+        const BOLD              = 0b0_0000_0010;
-        const ITALIC            = 0b0000_0100;
+        const ITALIC            = 0b0_0000_0100;
-        const UNDERLINE         = 0b0000_1000;
+        const UNDERLINE         = 0b0_0000_1000;
-        const WRAPLINE          = 0b0001_0000;
+        const WRAPLINE          = 0b0_0001_0000;
-        const WIDE_CHAR         = 0b0010_0000;
+        const WIDE_CHAR         = 0b0_0010_0000;
-        const WIDE_CHAR_SPACER  = 0b0100_0000;
+        const WIDE_CHAR_SPACER  = 0b0_0100_0000;
-        const DIM               = 0b1000_0000;
+        const DIM               = 0b0_1000_0000;
-        const DIM_BOLD          = 0b1000_0010;
+        const DIM_BOLD          = 0b0_1000_0010;
+        const HIDDEN            = 0b1_0000_0000;
     }
 }
 

src/term/mod.rs

@@ -14,9 +14,8 @@
 //
 //! Exports the `Term` type which is a high-level API for the Grid
 use std::ops::{Range, Index, IndexMut};
-use std::ptr;
+use std::{ptr, io, mem};
 use std::cmp::{min, max};
-use std::io;
 use std::time::{Duration, Instant};
 
 use arraydeque::ArrayDeque;
@@ -424,26 +423,15 @@ impl<'a> Iterator for RenderableCellsIter<'a> {
             };
 
             // Apply inversion and lookup RGB values
-            let mut bg_alpha = 1.0;
+            let mut fg_rgb = self.compute_fg_rgb(cell.fg, &cell);
-            let fg_rgb;
+            let mut bg_rgb = self.compute_bg_rgb(cell.bg);
-            let bg_rgb;
 
-            let invert = selected ^ cell.inverse();
+            let bg_alpha = if selected ^ cell.inverse() {
-
+                mem::swap(&mut fg_rgb, &mut bg_rgb);
-            if invert {
+                self.compute_bg_alpha(cell.fg)
-                if cell.fg == cell.bg {
-                    bg_rgb = self.colors[NamedColor::Foreground];
-                    fg_rgb = self.colors[NamedColor::Background];
-                    bg_alpha = 1.0
             } else {
-                    bg_rgb = self.compute_fg_rgb(cell.fg, &cell);
+                self.compute_bg_alpha(cell.bg)
-                    fg_rgb = self.compute_bg_rgb(cell.bg);
+            };
-                }
-            } else {
-                fg_rgb = self.compute_fg_rgb(cell.fg, &cell);
-                bg_rgb = self.compute_bg_rgb(cell.bg);
-                bg_alpha = self.compute_bg_alpha(cell.bg);
-            }
 
             return Some(RenderableCell {
                 line: cell.line,
@@ -1877,6 +1865,8 @@ impl ansi::Handler for Term {
             Attr::CancelItalic => self.cursor.template.flags.remove(cell::Flags::ITALIC),
             Attr::Underscore => self.cursor.template.flags.insert(cell::Flags::UNDERLINE),
             Attr::CancelUnderline => self.cursor.template.flags.remove(cell::Flags::UNDERLINE),
+            Attr::Hidden => self.cursor.template.flags.insert(cell::Flags::HIDDEN),
+            Attr::CancelHidden => self.cursor.template.flags.remove(cell::Flags::HIDDEN),
             _ => {
                 debug!("Term got unhandled attr: {:?}", attr);
             }