terminal: add unifont font-handling

The unifont layer of libsystemd-terminal provides a fallback font for
situations where no system-fonts are available, or if you don't want to
deal with traditional font-formats for some reasons.

The unifont API mmaps a pre-compiled bitmap font that was generated out of
GNU-Unifont font-data. This guarantees, that all users of the font will
share the pages in memory. Furthermore, the layout of the binary file
allows accessing glyph data in O(1) without pre-rendering glyphs etc. That
is, the OS can skip loading pages for glyphs that we never access.

Note that this is currently a test-run and we want to include the binary
file in the GNU-Unifont package. However, until it was considered stable
and accepted by the maintainers, we will ship it as part of systemd. So
far it's only enabled with the experimental --enable-terminal, anyway.

1 files changed, 54 insertions, 0 deletions

diff --git a/src/libsystemd-terminal/unifont-internal.h b/src/libsystemd-terminal/unifont-internal.h
new file mode 100644
index 0000000000..c39512d2c6
--- /dev/null
+++ b/src/libsystemd-terminal/unifont-internal.h
@@ -0,0 +1,54 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright (C) 2014 David Herrmann <dh.herrmann@gmail.com>
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd 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
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#pragma once
+
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include "util.h"
+
+typedef struct unifont unifont;
+typedef struct unifont_glyph unifont_glyph;
+
+/*
+ * Unifont
+ * The unifont API provides a glyph-lookup for bitmap fonts which can be used
+ * as fallback if no system-font is available or if you don't want to deal with
+ * full font renderers.
+ */
+
+struct unifont_glyph {
+        unsigned int width;
+        unsigned int height;
+        unsigned int stride;
+        unsigned int cwidth;
+        const void *data;       /* unaligned! */
+};
+
+int unifont_new(unifont **out);
+unifont *unifont_ref(unifont *u);
+unifont *unifont_unref(unifont *u);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(unifont*, unifont_unref);
+
+unsigned int unifont_get_stride(unifont *u);
+int unifont_lookup(unifont *u, unifont_glyph *out, uint32_t ucs4);