altos/draw: Add ao_text_width

Computes the total advance of the given string, not the width of the
resulting ink.

Signed-off-by: Keith Packard <[email protected]>

Author: keith-packard

src/draw/ao_draw.h

@@ -103,6 +103,14 @@ struct ao_glyph_metrics {
 	int8_t	advance;
 };
 
+struct ao_text_metrics {
+	int16_t	width;
+	int16_t	height;
+	int16_t	x_off;
+	int16_t	y_off;
+	int16_t	advance;
+};
+
 struct ao_font {
 	const uint8_t	*bytes;
 	const uint16_t	*pos;
@@ -169,6 +177,10 @@ ao_text(struct ao_bitmap	*dst,
 	uint32_t		fill,
 	uint8_t			rop);
 
+int16_t
+ao_text_width(const struct ao_font	*font,
+	      const char		*string);
+
 void
 ao_logo_poly(struct ao_bitmap		*dst,
 	     const struct ao_transform	*transform,

src/draw/ao_text_width.c

@@ -0,0 +1,40 @@
+/*
+ * Copyright © 2024 Keith Packard <[email protected]>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ */
+
+#include <ao_draw.h>
+#include <ao_draw_int.h>
+#include "ao_font.h"
+#include <string.h>
+#include <stdio.h>
+
+int16_t
+ao_text_width(const struct ao_font	*font,
+	      const char		*string)
+{
+	char		c;
+	int16_t		x = 0;
+
+	while ((c = *string++)) {
+		if (font->metrics) {
+			x += font->metrics[(uint8_t) c].advance;
+		} else {
+			x += font->max_width;
+		}
+	}
+	return x;
+}