Subject: [PATCH/RFC v3] diff.tcl: made alignment of tabs in git-gui diff consistent with gitk

From: "Chris Idema via GitGitGadget" <[email-masked]>
Date: Wed, 28 Jan 2026 10:20:39 +0000

From: Chris Idema <[email-masked]>

Tab stop width was not properly rendered in TK regardless of
tab width setting. The + or minus character at start of line made
tabs align incorrectly.

Signed-off-by: Chris Idema <[email-masked]>
---
    diff.tcl: made alignment of tabs in git-gui diff consistent with gitk
    
    cc: Johannes Sixt [email-masked]

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-2179%2FChrisIdema%2Ffix-gitgui-diff-tab-alignment-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-2179/ChrisIdema/fix-gitgui-diff-tab-alignment-v3
Pull-Request: https://github.com/git/git/pull/2179

Range-diff vs v2:

 1:  f2a09c15eb < -:  ---------- diff.tcl: fixed alignment of tabs in git-gui diff by using spaces
 2:  e11aa6d811 ! 1:  18d25b90c4 diff.tcl: call "apply_tab_size 1" to fix alignment instead of spaces.
     @@ Metadata
      Author: Chris Idema <[email-masked]>
      
       ## Commit message ##
     -    diff.tcl: call "apply_tab_size 1" to fix alignment instead of spaces.
     +    diff.tcl: made alignment of tabs in git-gui diff consistent with gitk
     +
     +    Tab stop width was not properly rendered in TK regardless of
     +    tab width setting. The + or minus character at start of line made
     +    tabs align incorrectly.
      
          Signed-off-by: Chris Idema <[email-masked]>
      
       ## git-gui/lib/diff.tcl ##
     -@@ git-gui/lib/diff.tcl: proc apply_tab_size {{firsttab {}}} {
     - 	}
     - }
     - 
     --proc expand_tabs {line {startcol -1}} {
     --	# startcol set to -1, because in preview the lines start with a '+', '-', or ' '
     --	global repo_config
     --
     --	set col $startcol
     --	set out ""
     --
     --	foreach char [split $line ""] {
     --		if {$char eq "\t"} {
     --			set spaces [expr {$repo_config(gui.tabsize) - ($col % $repo_config(gui.tabsize))}]
     --			append out [string repeat " " $spaces]
     --			incr col $spaces
     --		} else {
     --			append out $char
     --			incr col
     --		}
     --	}
     --
     --	return $out
     --}
     --
     - proc clear_diff {} {
     - 	global ui_diff current_diff_path current_diff_header
     - 	global ui_index ui_workdir
      @@ git-gui/lib/diff.tcl: proc read_diff {fd conflict_size cont_info} {
       			}
       		}
       		set mark [$ui_diff index "end - 1 line linestart"]
     --		set line [expand_tabs $line]
      +		apply_tab_size 1
     - 		$ui_diff insert end "$line" $tags
     --
     + 		$ui_diff insert end $line $tags
       		if {[string index $line end] eq "\r"} {
       			$ui_diff tag add d_cr {end - 2c}
     - 		}

 git-gui/lib/diff.tcl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/git-gui/lib/diff.tcl b/git-gui/lib/diff.tcl
index 442737ba4f..7da6e5ccae 100644
--- a/git-gui/lib/diff.tcl
+++ b/git-gui/lib/diff.tcl
@@ -495,6 +495,7 @@ proc read_diff {fd conflict_size cont_info} {
 			}
 		}
 		set mark [$ui_diff index "end - 1 line linestart"]
+		apply_tab_size 1
 		$ui_diff insert end $line $tags
 		if {[string index $line end] eq "\r"} {
 			$ui_diff tag add d_cr {end - 2c}

base-commit: 1faf5b085a171f9ba9a6d7a446e0de16acccb1dc
-- 
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