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, 128 insertions, 0 deletions

diff --git a/src/libsystemd-terminal/test-unifont.c b/src/libsystemd-terminal/test-unifont.c
new file mode 100644
index 0000000000..2c415941fb
--- /dev/null
+++ b/src/libsystemd-terminal/test-unifont.c
@@ -0,0 +1,128 @@
+/*-*- 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/>.
+***/
+
+/*
+ * Test Unifont Helper
+ * This tries opening the binary unifont glyph-array and renders some glyphs.
+ * The glyphs are then compared to hard-coded glyphs.
+ */
+
+#include <errno.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "macro.h"
+#include "unifont-def.h"
+#include "unifont-internal.h"
+#include "util.h"
+
+static void render(char *w, const unifont_glyph *g) {
+        unsigned int i, j;
+        const uint8_t *d = g->data;
+
+        for (j = 0; j < 16; ++j) {
+                for (i = 0; i < 8 * g->cwidth; ++i) {
+                        if (d[i / 8] & (1 << (7 - i % 8)))
+                                *w++ = '#';
+                        else
+                                *w++ = ' ';
+                }
+                *w++ = '\n';
+                d += g->stride;
+        }
+
+        *w++ = 0;
+}
+
+static void test_unifont(void) {
+        char buf[4096];
+        unifont_glyph g;
+        unifont *u;
+
+        assert_se(unifont_new(&u) >= 0);
+
+        /* lookup invalid font */
+        assert_se(unifont_lookup(u, &g, 0xffffffffU) < 0);
+
+        /* lookup and render 'A' */
+        assert_se(unifont_lookup(u, &g, 'A') >= 0);
+        assert_se(g.width == 8);
+        assert_se(g.height == 16);
+        assert_se(g.stride >= 1);
+        assert_se(g.cwidth == 1);
+        assert_se(g.data != NULL);
+        render(buf, &g);
+        assert_se(!strcmp(buf,
+                          "        \n"
+                          "        \n"
+                          "        \n"
+                          "        \n"
+                          "   ##   \n"
+                          "  #  #  \n"
+                          "  #  #  \n"
+                          " #    # \n"
+                          " #    # \n"
+                          " ###### \n"
+                          " #    # \n"
+                          " #    # \n"
+                          " #    # \n"
+                          " #    # \n"
+                          "        \n"
+                          "        \n"
+                          ));
+
+        /* lookup and render '什' */
+        assert_se(unifont_lookup(u, &g, 0x4ec0) >= 0);
+        assert_se(g.width == 16);
+        assert_se(g.height == 16);
+        assert_se(g.stride >= 2);
+        assert_se(g.cwidth == 2);
+        assert_se(g.data != NULL);
+        render(buf, &g);
+        assert_se(!strcmp(buf,
+                          "    #     #     \n"
+                          "    #     #     \n"
+                          "    #     #     \n"
+                          "   #      #     \n"
+                          "   #      #     \n"
+                          "  ##      #     \n"
+                          "  ## ########## \n"
+                          " # #      #     \n"
+                          "#  #      #     \n"
+                          "   #      #     \n"
+                          "   #      #     \n"
+                          "   #      #     \n"
+                          "   #      #     \n"
+                          "   #      #     \n"
+                          "   #      #     \n"
+                          "   #      #     \n"
+                          ));
+
+        unifont_unref(u);
+}
+
+int main(int argc, char **argv) {
+        if (access(UNIFONT_PATH, F_OK))
+                return 77;
+
+        test_unifont();
+
+        return 0;
+}