From 8f015537e7c016722dbd7fffee520461fe394f28 Mon Sep 17 00:00:00 2001
From: Mattias Andrée <maandree@kth.se>
Date: Fri, 22 Jul 2022 19:52:07 +0200
Subject: Add default fonts
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Signed-off-by: Mattias Andrée <maandree@kth.se>
---
 Makefile                         |  1 +
 libfonts.h                       | 88 ++++++++++++++++++++++++++++++++++++++++
 libfonts_get_default_font_name.c | 49 ++++++++++++++++++++++
 3 files changed, 138 insertions(+)
 create mode 100644 libfonts_get_default_font_name.c

diff --git a/Makefile b/Makefile
index 97a3499..74bb9e1 100644
--- a/Makefile
+++ b/Makefile
@@ -20,6 +20,7 @@ OBJ =\
 	libfonts_calculate_subpixel_order.o\
 	libfonts_decode_font_description.o\
 	libfonts_encode_font_description.o\
+	libfonts_get_default_font_name.o\
 	libfonts_get_output_dpi.o
 
 HDR =\
diff --git a/libfonts.h b/libfonts.h
index 2d8e94d..5cf2c83 100644
--- a/libfonts.h
+++ b/libfonts.h
@@ -3,6 +3,29 @@
 #define LIBFONTS_H
 
 #include <stdint.h>
+#include <unistd.h>
+
+
+/**
+ * Style-based default fonts
+ */
+enum libfonts_default_font {
+	/**
+	 * A proportional font without serifs
+	 */
+	LIBFONTS_DEFAULT_SANS_SERIF,
+
+	/**
+	 * A proportional font with serifs
+	 */
+	LIBFONTS_DEFAULT_SERIF,
+
+	/**
+	 * A monospace font, which may escape
+	 * the character cell
+	 */
+	LIBFONTS_DEFAULT_MONOSPACE
+};
 
 
 /**
@@ -505,6 +528,71 @@ struct libfonts_font_description {
 };
 
 
+/**
+ * Get the font a default font name aliases to
+ * 
+ * @param   font  The default font
+ * @param   name  Output buffer for the font the default font is an alias
+ *                for; will always be NUL-terminated (unless `size` is 0)
+ * @param   size  Buffer size of `name`
+ * @return        The minimum value required on `size` for a
+ *                complete output to `name`, or -1 on failure
+ * 
+ * @throws  EINVAL  Unrecognised value on `font`
+ */
+ssize_t libfonts_get_default_font(enum libfonts_default_font, char *, size_t);
+/* TODO implement libfonts_get_default_font
+ *
+ * /etc/libfonts/default-fonts.conf
+ *
+ * 	sans-serif = $FONTNAME
+ * 	serif = $FONTNAME
+ * 	monospace = $FONTNAME
+ *
+ * fallback, look in /etc/libfonts/default-fonts/sans-serif/
+ *                   /etc/libfonts/default-fonts/serif/
+ *                   /etc/libfonts/default-fonts/monospace/
+ *
+ * as a last resort look around for some
+ * font that matches the specification as
+ * well as possible
+ */
+
+/**
+ * Get the alias for a default font
+ * 
+ * @param   font   The default font
+ * @param   name   Output buffer for the font name; will always
+ *                 be NUL-terminated (unless `size` is 0)
+ * @param   size   Buffer size of `name`
+ * @param   index  The index of the alias (some default fonts
+ *                 have multiple aliases)
+ * @return         The minimum value required on `size` for a
+ *                 complete output to `name`, 0 if `index` is
+ *                 equal to or greater than the number of
+ *                 aliases, or -1 on failure
+ * 
+ * @throws  EINVAL  Unrecognised value on `font`
+ */
+ssize_t libfonts_get_default_font_name(enum libfonts_default_font, char *, size_t, size_t);
+
+/**
+ * Get a default font a font name represents
+ * 
+ * @param  font   Output parameter for the default font
+ * @param  name   The alias for the default font, optionally
+ *                with style and size information
+ * @param  style  Output parameter for the offset in `name`
+ *                where the style and size information begins;
+ *                will be set to 0 if this information is
+ *                excluded from `name`
+ * @return        1 on successful completion, 0 if `name` is not
+ *                an alias for a default font
+ */
+int libfonts_get_default_font_by_name(enum libfonts_default_font *, const char *, size_t *);
+/* TODO implement libfonts_get_default_font_by_name */
+
+
 /**
  * Encode an X Logical Font Description (XLFD) string
  *
diff --git a/libfonts_get_default_font_name.c b/libfonts_get_default_font_name.c
new file mode 100644
index 0000000..5fe7704
--- /dev/null
+++ b/libfonts_get_default_font_name.c
@@ -0,0 +1,49 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+ssize_t
+libfonts_get_default_font_name(enum libfonts_default_font font, char *name, size_t size, size_t index)
+{
+	const char *alias;
+	size_t len;
+
+	if (font == LIBFONTS_DEFAULT_SANS_SERIF) {
+		if (index == 0)
+			alias = "sans-serif";
+		else if (index == 1)
+			alias = "sans serif";
+		else if (index == 2)
+			alias = "sans";
+		else
+			return 0;
+
+	} else if (font == LIBFONTS_DEFAULT_SERIF) {
+		if (index == 0)
+			alias = "serif";
+		else
+			return 0;
+
+	} else if (font == LIBFONTS_DEFAULT_MONOSPACE) {
+		if (index == 0)
+			alias = "monospace";
+		else if (index == 1)
+			alias = "monospaced";
+		else
+			return 0;
+
+	} else {
+		errno = EINVAL;
+		return -1;
+	}
+
+	len = strlen(alias);
+	if (size) {
+		size -= 1;
+		if (size > len)
+			size = len;
+		memcpy(name, alias, size);
+		name[size] = '\0';
+	}
+	return (ssize_t)len;
+}
-- 
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