Enable text display on Sharp display

1. Add basic code for Sharp Display
2. Add embedded font (generated by fontem)
3. Add the worst code possible to print strings to the display
4. Rejoice in the beautiful (small) text.

lib/fonts/fontem.h

@@ -0,0 +1,84 @@
+/** Font structure definitions.
+ *
+ * This file is distributed under the terms of the MIT License.
+ * See the LICENSE file at the top of this tree, or if it is missing a copy can
+ * be found at http://opensource.org/licenses/MIT
+ */
+
+#ifndef _FONTEM_H
+#define _FONTEM_H
+
+#include <stdint.h>
+#include <stdio.h>
+
+/** Alpha compositing "A over B" mechanism */
+#define alpha_blend(in, in_alpha, out, out_alpha) \
+	((0x100 * in * in_alpha * (255 - out_alpha) + out * out_alpha * (255 - in_alpha)) >> 16)
+#define blend(a, b, alpha) \
+	(((a) * (255 - (alpha)) + (b) * (alpha)) >> 8)
+
+/** Extract the Alpha channel from a 32-bit RGBA value */
+#define rgba32_get_a(rgba) ((rgba >> 24) & 0xff)
+/** Extract the Red channel from a 32-bit RGBA value */
+#define rgba32_get_r(rgba) ((rgba >> 16) & 0xff)
+/** Extract the Green channel from a 32-bit RGBA value */
+#define rgba32_get_g(rgba) ((rgba >> 8) & 0xff)
+/** Extract the Blue channel from a 32-bit RGBA value */
+#define rgba32_get_b(rgba) (rgba & 0xff)
+
+/** Extract the Red channel from a 16-bit RGB value */
+#define rgb16_get_r(rgb) ((rgb >> 8) & 0xf8)
+/** Extract the Green channel from a 16-bit RGB value */
+#define rgb16_get_g(rgb) ((rgb >> 3) & 0xfc)
+/** Extract the Blue channel from a 16-bit RGB value */
+#define rgb16_get_b(rgb) ((rgb << 3) & 0xf8)
+/** Combine Red, Green and Blue channels into a 16-bit RGB value */
+#define rgb16_combine(r, g, b) \
+	((((r) & 0xf8) << 8) | \
+	 (((g) & 0xfc) << 3) | \
+	 (((b) & 0xf8) >> 3))
+
+
+/** Glyph character value rype */
+typedef uint16_t glyph_t;
+
+/** Description of a glyph; a single character in a font. */
+struct glyph {
+	glyph_t			glyph;          /** The glyph this entry refers to */
+
+	int16_t			left;           /** Offset of the left edge of the glyph */
+	int16_t			top;            /** Offset of the top edge of the glyph */
+	int16_t			advance;        /** Horizonal offset when advancing to the next glyph */
+
+	uint16_t		cols;           /** Width of the bitmap */
+	uint16_t		rows;           /** Height of the bitmap */
+	const uint8_t		*bitmap;        /** Bitmap data */
+
+	const struct kerning	*kerning;       /** Font kerning data */
+};
+
+/** Kerning table; for a pair of glyphs, provides the horizontal adjustment. */
+struct kerning {
+	glyph_t left;   /** The left-glyph */
+	int16_t offset; /** The kerning offset for this glyph pair */
+};
+
+/** Description of a font. */
+struct font {
+	char			*name;          /** Name of the font */
+	char			*style;         /** Style of the font */
+
+	uint16_t		size;           /** Point size of the font */
+	uint16_t		dpi;            /** Resolution of the font */
+
+	int16_t			ascender;       /** Ascender height */
+	int16_t			descender;      /** Descender height */
+	int16_t			height;         /** Baseline-to-baseline height */
+
+	uint16_t		count;          /** Number of glyphs */
+	uint16_t		max;            /** Maximum glyph index */
+	const struct glyph	**glyphs;       /** Font glyphs */
+	char			compressed;     /** TRUE if glyph bitmaps are RLE compressed */
+};
+
+#endif /* _FONTEM_H */