commit 43f1873709d39405b55f676ef21c42065cc1408d
from: Russ Cox <rsc@swtch.com>
date: Fri Feb 01 18:20:46 2019 UTC

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.

commit - 2607cc565ee3d5facb8949e9acfed35c8ae300c9
commit + 43f1873709d39405b55f676ef21c42065cc1408d
blob - 68c5d9769104ff055b0de019884778a8de944b40
blob + 0fc6c16b4e33aabe25b80028cd30cbe807d279a9
--- src/cmd/acme/exec.c
+++ 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 nnam
 		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);