From 9f08ee7af9056dfcf244d8d1c4619a17558fd11d Mon Sep 17 00:00:00 2001
From: Leonard Hecker <lhecker@microsoft.com>
Date: Fri, 29 Mar 2024 15:46:51 +0100
Subject: [PATCH] Buffer Restore: Fix turning off intense/faint (#16970)
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This takes care of an edge case in regards to SGR 22: It turns off
both intense and faint attributes which means that we may need to
turn on one of the two if only one of them turned off.

Additionally, this removes the mapping for `BottomGridline` which
has no real VT equivalent anyway.

## Validation Steps Performed
* Turn session restore on
* In pwsh write:
  ```pwsh
  "`e[1;2mboth`e[0;1mintense`e[m`n`e[1;2mboth`e[0;2mfaint`e[m"
  ```
* Close the app and open the `buffer_*.txt` file next to settings.json
* It contains... ✅
  ```
  ␛[1m␛[2mboth␛[22;1mintense␛[22m
  ␛[1m␛[2mboth␛[22;2mfaint␛[22m
  ```
---
 src/buffer/out/textBuffer.cpp | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/src/buffer/out/textBuffer.cpp b/src/buffer/out/textBuffer.cpp
index 62371474adc..40cfc6b17ad 100644
--- a/src/buffer/out/textBuffer.cpp
+++ b/src/buffer/out/textBuffer.cpp
@@ -2557,7 +2557,32 @@ void TextBuffer::Serialize(const wchar_t* destination) const
 
             if (previousAttr != attr)
             {
-                const auto attrDelta = attr ^ previousAttr;
+                auto attrDelta = attr ^ previousAttr;
+
+                // There's no escape sequence that only turns off either bold/intense or dim/faint. SGR 22 turns off both.
+                // This results in two issues in our generic "Mapping" code below. Assuming, both Intense and Faint were on...
+                // * ...and either turned off, it would emit SGR 22 which turns both attributes off = Wrong.
+                // * ...and both are now off, it would emit SGR 22 twice.
+                //
+                // This extra branch takes care of both issues. If both attributes turned off it'll emit a single \x1b[22m,
+                // if faint turned off \x1b[22;1m (intense is still on), and \x1b[22;2m if intense turned off (vice versa).
+                if (WI_AreAllFlagsSet(previousAttr, CharacterAttributes::Intense | CharacterAttributes::Faint) &&
+                    WI_IsAnyFlagSet(attrDelta, CharacterAttributes::Intense | CharacterAttributes::Faint))
+                {
+                    wchar_t buf[8] = L"\x1b[22m";
+                    size_t len = 5;
+
+                    if (WI_IsAnyFlagSet(attr, CharacterAttributes::Intense | CharacterAttributes::Faint))
+                    {
+                        buf[4] = L';';
+                        buf[5] = WI_IsAnyFlagSet(attr, CharacterAttributes::Intense) ? L'1' : L'2';
+                        buf[6] = L'm';
+                        len = 7;
+                    }
+
+                    buffer.append(&buf[0], len);
+                    WI_ClearAllFlags(attrDelta, CharacterAttributes::Intense | CharacterAttributes::Faint);
+                }
 
                 {
                     struct Mapping
@@ -2574,7 +2599,6 @@ void TextBuffer::Serialize(const wchar_t* destination) const
                         { CharacterAttributes::Faint, { 22, 2 } },
                         { CharacterAttributes::TopGridline, { 55, 53 } },
                         { CharacterAttributes::ReverseVideo, { 27, 7 } },
-                        { CharacterAttributes::BottomGridline, { 24, 4 } },
                     };
                     for (const auto& mapping : mappings)
                     {