--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libadventure/adventure/trace_hud.c	Wed Oct 14 10:29:53 2020 +0200
@@ -0,0 +1,113 @@
+/*
+ * trace_hud.c -- on screen hud
+ *
+ * Copyright (c) 2020 David Demelier <markand@malikania.fr>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <assert.h>
+#include <stdio.h>
+#include <string.h>
+
+#include <core/label.h>
+#include <core/font.h>
+#include <core/theme.h>
+#include <core/trace.h>
+
+#include "trace_hud.h"
+
+#define LINES_MAX       (4)
+#define THEME(t)        ((t) ? (t) : theme_default())
+
+static struct {
+	char lines[LINES_MAX + 1][TRACE_LINE_MAX];
+	unsigned int elapsed;
+} data;
+
+struct trace_hud trace_hud = {
+	.timeout = TRACE_HUD_TIMEOUT_DEFAULT
+};
+
+void
+trace_hud_handler(const char *str)
+{
+	assert(str);
+
+	/* 1.Try to find an empty line. */
+	for (size_t i = 0; i < LINES_MAX; ++i) {
+		if (data.lines[i][0] == '\0') {
+			snprintf(data.lines[i], sizeof (data.lines[i]), "%s", str);
+			return;
+		}
+	}
+
+	/* 2. All lines are full, put in last one and move other. */
+	memmove(&data.lines[0], &data.lines[1], sizeof (data.lines[0]) * LINES_MAX - 1);
+	snprintf(data.lines[LINES_MAX - 1], sizeof (data.lines[0]), "%s", str);
+
+	/* 3. Reset elapsed time now. */
+	data.elapsed = 0;
+}
+
+void
+trace_hud_update(unsigned int ticks)
+{
+	data.elapsed += ticks;
+
+	/*
+	 * We have an empty line in the data.lines at LINES_MAX, so we simply so
+	 * to move the whole array.
+	 *
+	 * [0] = "abc"
+	 * [1] = "def"
+	 * [2] = "xyz"
+	 * [3] = "zef"
+	 * [n] = "ldkf"
+	 * [LINES_MAX + 1] = "\0"
+	 */
+	if (data.elapsed >= trace_hud.timeout) {
+		data.elapsed = 0;
+		memmove(&data.lines[0], &data.lines[1], sizeof (data.lines[0]) * LINES_MAX);
+	}
+}
+
+void
+trace_hud_draw(void)
+{
+	struct theme *th;
+	int x, y;
+
+	th = THEME(trace_hud.theme);
+	x = th->padding;
+	y = th->padding;
+
+	for (int i = 0; i < LINES_MAX && data.lines[i][0]; ++i) {
+		label_draw(&(struct label) {
+			.x = x,
+			.y = y,
+			.text = data.lines[i],
+			.theme = th,
+			.flags = LABEL_NO_HCENTER
+		});
+
+		y += font_height(th->fonts[THEME_FONT_INTERFACE]);
+		y += th->padding;
+	}
+}
+
+void
+trace_hud_clear(void)
+{
+	memset(&data, 0, sizeof (data));
+}