[PATCH] Fix scrolling right in the TUI (Re: [RFC 8.3 0/3] Some style fixes)

[Pedro Alves <palves@redhat.com>]

On 03/13/2019 03:44 PM, Eli Zaretskii wrote:
>> Date: Tue, 12 Mar 2019 17:08:33 +0000 (UTC)
>> From: "Hannes Domani via gdb-patches" <gdb-patches@sourceware.org>
>>
>> In copy_source_line() it checks if (column < first_col), and because of the ++column directly
>> before, it basically starts with 1 instead of 0.
>>
>> Attached is a patch that fixes most of 2) and 3), but I ignored the handling of escaped
>> characters, because I just don't have them in any of my sources.
> I can confirm that this patch fixes the problems with horizontal
> scrolling, with or without TAB characters in the sources.  I think we
> should push it.

I agree.  Hannes, I've written a git commit log entry, as well
as a ChangeLog entry for you.  Please double-check whether
I didn't make some mistake.

I've made one change in the patch, here:

On 03/12/2019 05:08 PM, Hannes Domani via gdb-patches wrote:
> +      if (column <= first_col || column > first_col + line_width)
> +	{
> +	  if (c == '\t')
> +	    {
> +	      int j, max_tab_len = tui_tab_width;
> +
> +	      --column;
> +	      for (j = column % max_tab_len;
> +		   j < max_tab_len && column < first_col + line_width;
> +		   column++, j++)
> +		if (column >= first_col)
> +		  result.push_back (' ');
> +	    }
> +	  continue;
> +	}

instead of duplicating that code, I'd put it in a lambda
and use it in both places.

Tromey, WDYT?  Would you prefer the version without the lambda?

From 3b88b2cebb2d8697fbbcf957e587440ee2a4968c Mon Sep 17 00:00:00 2001
From: Hannes Domani <ssbssa@yahoo.de>
Date: Thu, 14 Mar 2019 20:46:27 +0000
Subject: [PATCH] Fix scrolling right in the TUI

This commit fixes two issues in scrolling right in the TUI:

#1 - Scrolling right with the arrow keys, the first keypress doesn't
do anything.  The problem is that copy_source_line() checks if
(column < first_col), and because of the ++column directly before, it
basically starts with 1 instead of 0.

#2 - Scrolling right handles TABS and escaped characters as single
characters, which just looks weird.  The problem is that there's a
spot that misses handling TABS.

gdb/ChangeLog:
yyyy-mm-dd  Hannes Domani  <ssbssa@yahoo.de>

	* tui/tui-source.c (copy_source_line): Fix handling of 'column'.
	Handle tabs.
---
 gdb/tui/tui-source.c | 30 ++++++++++++++++++++----------
 1 file changed, 20 insertions(+), 10 deletions(-)

diff --git a/gdb/tui/tui-source.c b/gdb/tui/tui-source.c
index 7cc3c00069..1fa0e986e0 100644
--- a/gdb/tui/tui-source.c
+++ b/gdb/tui/tui-source.c
@@ -71,10 +71,27 @@ copy_source_line (const char **ptr, int line_no, int first_col,
 
       ++lineptr;
       ++column;
+
+      auto process_tab = [&] ()
+	{
+	  int max_tab_len = tui_tab_width;
+
+	  --column;
+	  for (int j = column % max_tab_len;
+	       j < max_tab_len && column < first_col + line_width;
+	       column++, j++)
+	    if (column >= first_col)
+	      result.push_back (' ');
+	};
+
       /* We have to process all the text in order to pick up all the
 	 escapes.  */
-      if (column < first_col || column > first_col + line_width)
-	continue;
+      if (column <= first_col || column > first_col + line_width)
+	{
+	  if (c == '\t')
+	    process_tab ();
+	  continue;
+	}
 
       if (c == '\n' || c == '\r' || c == '\0')
 	{
@@ -91,14 +108,7 @@ copy_source_line (const char **ptr, int line_no, int first_col,
 	  result.push_back ('?');
 	}
       else if (c == '\t')
-	{
-	  int j, max_tab_len = tui_tab_width;
-
-	  for (j = column - ((column / max_tab_len) * max_tab_len);
-	       j < max_tab_len && column < first_col + line_width;
-	       column++, j++)
-	    result.push_back (' ');
-	}
+	process_tab ();
       else
 	result.push_back (c);
     }
-- 
2.14.4