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, 116 insertions, 0 deletions

diff --git a/tools/compile-unifont.py b/tools/compile-unifont.py
new file mode 100755
index 0000000000..7004b946d2
--- /dev/null
+++ b/tools/compile-unifont.py
@@ -0,0 +1,116 @@
+#  -*- Mode: python; coding: utf-8; indent-tabs-mode: nil -*- */
+#
+#  This file is part of systemd.
+#
+#  Copyright 2013-2014 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/>.
+
+#
+# Parse a unifont.hex file and produce a compressed binary-format.
+#
+
+from __future__ import print_function
+import re
+import sys
+import fileinput
+import struct
+
+#
+# Write "bits" array as binary output.
+#
+
+def write_bin_entry(entry):
+    l = len(entry)
+    if l != 32 and l != 64:
+        entry = "0" * 64
+        l = 0
+    elif l < 64:
+        entry += "0" * (64 - l)
+
+    sys.stdout.buffer.write(struct.pack('B', int(l / 32)))  # width
+    sys.stdout.buffer.write(struct.pack('B', 0))            # padding
+    sys.stdout.buffer.write(struct.pack('H', 0))            # padding
+    sys.stdout.buffer.write(struct.pack('I', 0))            # padding
+
+    i = 0
+    for j in range(0, 16):
+        for k in range(0, 2):
+            if l <= k * 16 * 2:
+                c = 0
+            else:
+                c = int(entry[i:i+2], 16)
+                i += 2
+
+            sys.stdout.buffer.write(struct.pack('B', c))
+
+def write_bin(bits):
+    sys.stdout.buffer.write(struct.pack('B', 0x44))         # ASCII: 'D'
+    sys.stdout.buffer.write(struct.pack('B', 0x56))         # ASCII: 'V'
+    sys.stdout.buffer.write(struct.pack('B', 0x44))         # ASCII: 'D'
+    sys.stdout.buffer.write(struct.pack('B', 0x48))         # ASCII: 'H'
+    sys.stdout.buffer.write(struct.pack('B', 0x52))         # ASCII: 'R'
+    sys.stdout.buffer.write(struct.pack('B', 0x4d))         # ASCII: 'M'
+    sys.stdout.buffer.write(struct.pack('B', 0x55))         # ASCII: 'U'
+    sys.stdout.buffer.write(struct.pack('B', 0x46))         # ASCII: 'F'
+    sys.stdout.buffer.write(struct.pack('<I', 0))           # compatible-flags
+    sys.stdout.buffer.write(struct.pack('<I', 0))           # incompatible-flags
+    sys.stdout.buffer.write(struct.pack('<I', 32))          # header-size
+    sys.stdout.buffer.write(struct.pack('<H', 8))           # glyph-header-size
+    sys.stdout.buffer.write(struct.pack('<H', 2))           # glyph-stride
+    sys.stdout.buffer.write(struct.pack('<Q', 32))          # glyph-body-size
+
+    # write glyphs
+    for idx in range(len(bits)):
+        write_bin_entry(bits[idx])
+
+#
+# Parse hex file into "bits" array
+#
+
+def parse_hex_line(bits, line):
+    m = re.match(r"^([0-9A-Fa-f]+):([0-9A-Fa-f]+)$", line)
+    if m == None:
+        return
+
+    idx = int(m.group(1), 16)
+    val = m.group(2)
+
+    # insert skipped lines
+    for i in range(len(bits), idx):
+        bits.append("")
+
+    bits.insert(idx, val)
+
+def parse_hex():
+    bits = []
+
+    for line in sys.stdin:
+        if not line:
+            continue
+        if line.startswith("#"):
+            continue
+
+        parse_hex_line(bits, line)
+
+    return bits
+
+#
+# In normal mode we simply read line by line from standard-input and write the
+# binary-file to standard-output.
+#
+
+if __name__ == "__main__":
+    bits = parse_hex()
+    write_bin(bits)