Support Unicode symbols in VESA modes

sys/msdos/font.h

@@ -0,0 +1,53 @@
+/* Maintain a data structure describing a monospaced bitmap font */
+
+#ifndef FONT_H
+#define FONT_H
+
+#include "integer.h"
+
+/*
+ * The file format is Linux PSF, version 2. Version 1 is not supported.
+ * Actual Linux fonts are restricted to 256 or 512 glyphs; for NetHack, the
+ * font can have any number of glyphs. The Unicode map is expected to be
+ * present, but combining sequences are not supported.
+ * The fonts supplied for use with this data structure have the first 256
+ * glyphs arranged according to IBM code page 437, for simpler support of
+ * the IBM handling mode for the map.
+ */
+
+/* For Unicode lookup, a three level tree provides constant-time access to
+   the glyphs without using an excessive amount of memory.
+   The root has seventeen entries, one for each plane of Unicode. Most fonts
+   will populate only plane 0, and Unicode defines only planes 0, 1, 2, 3, 15
+   and 16.
+   The second level has 256 entries, each pointing to a third level node with
+   256 entries. Each third level entry has type unsigned, and gives the index
+   of the glyph.
+   Given the Unicode code point, we can use bits 20 through 16 to index the
+   root, bits 15 through 8 for the second level and bits 7 through 0 for the
+   third level. */
+
+struct BitmapFont {
+    /* Dimensions of a single glyph */
+    unsigned width;
+    unsigned height;
+
+    /* The glyphs, in the order that they appear in the font */
+    /* IBM handling will index the glyphs this way */
+    /* glyph points to an allocated array, each element of which points to
+       another allocated array */
+    unsigned num_glyphs;
+    unsigned char **glyphs;
+
+    /* The root node of the Unicode tree */
+    unsigned **unicode[17];
+};
+
+extern struct BitmapFont *load_font(const char *filename);
+extern void free_font(struct BitmapFont *font);
+extern const unsigned char *get_font_glyph(
+            struct BitmapFont *font,
+            uint32 ch,
+            boolean unicode);
+
+#endif