From 1bd7e81fb04314d7f373454a944fab9bc189e904 Mon Sep 17 00:00:00 2001
From: Consolatis <35009135+Consolatis@users.noreply.github.com>
Date: Sat, 16 Mar 2024 19:03:06 +0100
Subject: [PATCH] treewide: properly clear the buffer

Before this patch, the OSD would repeat the last buffer
content in case the new buffer content would be empty.

This was mostly happening for the `title` OSD field that is intended
to be empty when it matches the app_id / WM_CLASS of the application.
Due to only buffer.len being reset but its internal allocations being
untouched, buffer.buf would still carry the old data.

This patch fixes it by also overwriting the first byte in the buffer
allocation with '\0' via the new `buf_clear()` function.

Do the same for buf_expand_shell_variables() although that one should
have been fine before as it always writes new data to the buffer.
---
 src/common/buf.c | 2 +-
 src/osd.c        | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/common/buf.c b/src/common/buf.c
index f6667418..f6bde97f 100644
--- a/src/common/buf.c
+++ b/src/common/buf.c
@@ -52,7 +52,7 @@ buf_expand_shell_variables(struct buf *s)
 	for (int i = 0 ; i < s->len ; i++) {
 		if (s->buf[i] == '$' && isvalid(s->buf[i+1])) {
 			/* expand environment variable */
-			environment_variable.len = 0;
+			buf_clear(&environment_variable);
 			buf_add(&environment_variable, s->buf + i + 1);
 			char *p = environment_variable.buf;
 			while (isvalid(*p)) {
diff --git a/src/osd.c b/src/osd.c
index caefe66d..2ed45713 100644
--- a/src/osd.c
+++ b/src/osd.c
@@ -286,7 +286,7 @@ render_osd(struct server *server, cairo_t *cairo, int w, int h,
 		int nr_fields = wl_list_length(&rc.window_switcher.fields);
 		struct window_switcher_field *field;
 		wl_list_for_each(field, &rc.window_switcher.fields, link) {
-			buf.len = 0;
+			buf_clear(&buf);
 			cairo_move_to(cairo, x, y
 				+ theme->osd_window_switcher_item_padding_y
 				+ theme->osd_window_switcher_item_active_border_width);