From 7cdec9ef4be675ddde317a21aa5bbc78c23950c6 Mon Sep 17 00:00:00 2001
From: Rishabh Dave <address@hidden>
Date: Sat, 10 Dec 2016 17:49:53 +0530
Subject: [PATCH] help: stay in same place when window size changes

For horizontally resizing, nano will only roughly stay in the same
place.

Signed-off-by: Rishabh Dave <address@hidden>
---
 src/help.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/src/help.c b/src/help.c
index 9245805..e4309ca 100644
--- a/src/help.c
+++ b/src/help.c
@@ -44,6 +44,33 @@ char *tempfilename = NULL;
 	/* Name of the safe temporary file that we will use for wrapping
 	 * and writing the help text. */
 
+bool first_time;
+	/* For making the line at the center to be the current line. Needs
+	 * to be done only when redisplaying the help text for the first
+	 * time. */
+
+/* Return the maximum length at which help text is wrapped. */
+int max_wrapping_len()
+{
+    int max = 0;
+    int len;
+    const char *ptr = beg_of_intro;
+
+    while (strlen(ptr) > 0) {
+	len = help_line_len(ptr);
+
+	if (max < len)
+	    max = len;
+
+	if (*ptr == '\n')
+	    ++ptr;
+
+	ptr += len;
+    }
+
+    return max;
+}
+
 /* Writes the hard wrapped help text in the temp file and displays it. */
 void display_the_help_text(bool redisplaying)
 {
@@ -51,12 +78,26 @@ void display_the_help_text(bool redisplaying)
     const char *ptr = beg_of_intro;
 	/* The current line of the help text. */
     FILE *fp = fopen(tempfilename, "w+b");
+    size_t saved_current_lineno = openfile->current->lineno;
+	/* For staying at, or at least, close to the current position. */
+    static int last_wrap_len = 0;
+
+    /* If window size has changed and there is for no need for rewrapping,
+     * only refresh the window contents. */
+    if (redisplaying && (COLS > 76 || last_wrap_len == max_wrapping_len())) {
+	total_refresh();
+
+	fclose(fp);
+	return;
+    }
 
     if (fp == NULL) {
 	statusline(ALERT, _("Error writing temp file: %s"), strerror(errno));
 	return;
     }
 
+    last_wrap_len = max_wrapping_len();
+
     /* Wrap and copy the rest of the help_text into the temporary file. */
     while (strlen(ptr) > 0) {
 	line_size = help_line_len(ptr);
@@ -83,6 +124,23 @@ void display_the_help_text(bool redisplaying)
 	open_buffer(tempfilename, FALSE);
 
     display_buffer();
+
+    if (redisplaying) {
+	if (first_time) {
+	    /* Current line must be one at the center for proper scrolling
+	     * of text while rewrapping. */
+	    saved_current_lineno += 10;
+	    first_time = FALSE;
+	}
+
+	while (openfile->current->lineno < saved_current_lineno) {
+	    /* do_down only if we can. */
+	    if (openfile->current->lineno + 9 > openfile->filebot->lineno)
+		break;
+	    else
+		do_down(TRUE);
+	}
+    }
 }
 
 /* Our main help-viewer function. */
@@ -106,6 +164,7 @@ void do_help(void)
 	 * if any, by the user at the prompt. */
 
     inhelp = TRUE;
+    first_time = TRUE;
 
     blank_statusbar();
 
-- 
2.7.4