From 43f1873709d39405b55f676ef21c42065cc1408d Mon Sep 17 00:00:00 2001
From: Russ Cox <rsc@swtch.com>
Date: Mon, 30 Jul 2018 21:37:37 -0400
Subject: acme: drop trailing spaces during Put of auto-indent window

Auto-indent mode leaves trailing spaces on blank lines
as you type past them, so silently elide them from the
window content as it gets written back to disk.

Another option would be to remove them from the
window entirely during Put, but they're actually nice
to have while editing, and to date Put has never
modified the window content.
---
 src/cmd/acme/exec.c | 41 ++++++++++++++++++++++++++++++++++++++---
 1 file changed, 38 insertions(+), 3 deletions(-)

(limited to 'src/cmd/acme')

diff --git a/src/cmd/acme/exec.c b/src/cmd/acme/exec.c
index 68c5d976..0fc6c16b 100644
--- a/src/cmd/acme/exec.c
+++ b/src/cmd/acme/exec.c
@@ -690,12 +690,44 @@ checksha1(char *name, File *f, Dir *d)
 		f->qidpath = d->qid.path;
 		f->mtime = d->mtime;
 	}
-}	
+}
+
+static uint
+trimspaces(Rune *r, uint *np, int eof)
+{
+	uint i, w, nonspace, n;
+	Rune c;
+
+	nonspace = 0;
+	w = 0;
+	n = *np;	
+	for(i=0; i<n; i++) {
+		c = r[i];
+		if(c == '\n')
+			w = nonspace;
+		r[w++] = c;
+		if(c != ' ' && c != '\t')
+			nonspace = w;
+	}
+	if(nonspace > 0 && nonspace < w) {
+		// Trailing spaces at end of buffer.
+		// Tell caller to reread them with what follows,
+		// so we can determine whether they need trimming.
+		// Unless the trailing spaces are the entire buffer,
+		// in which case let them through to avoid an infinite loop
+		// if an entire buffer fills with spaces.
+		// At EOF, just consume the spaces.
+		if(!eof)
+			*np = n - (w - nonspace);
+		w = nonspace;
+	}
+	return w;
+}
 
 void
 putfile(File *f, int q0, int q1, Rune *namer, int nname)
 {
-	uint n, m;
+	uint n, nn, m;
 	Rune *r;
 	Biobuf *b;
 	char *s, *name;
@@ -750,7 +782,10 @@ putfile(File *f, int q0, int q1, Rune *namer, int nname)
 		if(n > BUFSIZE/UTFmax)
 			n = BUFSIZE/UTFmax;
 		bufread(&f->b, q, r, n);
-		m = snprint(s, BUFSIZE+1, "%.*S", n, r);
+		nn = n;
+		if(w->autoindent)
+			nn = trimspaces(r, &n, q+n==q1);
+		m = snprint(s, BUFSIZE+1, "%.*S", nn, r);
 		sha1((uchar*)s, m, nil, h);
 		if(Bwrite(b, s, m) != m){
 			warning(nil, "can't write file %s: %r\n", name);
-- 
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