# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1540923713 -3600
# Node ID e5fd5d81a72a3322407efd3fe712f1d80d2d9ad1
# Parent  d103800bffdadfb6294e20d9983f16adbe8b3d03
Added a bitmap font, a conversion tool, and library code to blit characters.

diff -r d103800bffda -r e5fd5d81a72a data/font.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/data/font.S	Tue Oct 30 19:21:53 2018 +0100
@@ -0,0 +1,1424 @@
+.globl fontchars
+.globl fonttable
+.globl fontbase
+.globl fontlimit
+
+.section .flash, "a"
+
+fontbase:
+.word 33
+
+fontchars:
+/* 33 */
+.byte 2 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10
+.byte 0b10
+.byte 0b10
+.byte 0b10
+.byte 0b10
+.byte 0b00
+.byte 0b10
+.byte 0b00
+.byte 0b00
+
+/* 34 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b1010
+.byte 0b1010
+.byte 0b0000
+.byte 0b0000
+.byte 0b0000
+.byte 0b0000
+.byte 0b0000
+.byte 0b0000
+.byte 0b0000
+
+/* 35 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b010100
+.byte 0b010100
+.byte 0b111110
+.byte 0b010100
+.byte 0b111110
+.byte 0b010100
+.byte 0b010100
+.byte 0b000000
+.byte 0b000000
+
+/* 36 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b001000
+.byte 0b011110
+.byte 0b101000
+.byte 0b011100
+.byte 0b001010
+.byte 0b111100
+.byte 0b001000
+.byte 0b000000
+.byte 0b000000
+
+/* 37 */
+.byte 7 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b0100000
+.byte 0b1010010
+.byte 0b0100100
+.byte 0b0001000
+.byte 0b0010000
+.byte 0b0100100
+.byte 0b1001010
+.byte 0b0000100
+.byte 0b0000000
+
+/* 38 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b010000
+.byte 0b101000
+.byte 0b101000
+.byte 0b010000
+.byte 0b101010
+.byte 0b100100
+.byte 0b011010
+.byte 0b000000
+.byte 0b000000
+
+/* 39 */
+.byte 2 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10
+.byte 0b10
+.byte 0b00
+.byte 0b00
+.byte 0b00
+.byte 0b00
+.byte 0b00
+.byte 0b00
+.byte 0b00
+
+/* 40 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b0110
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b0110
+.byte 0b0000
+
+/* 41 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b1100
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b1100
+.byte 0b0000
+
+/* 42 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b001000
+.byte 0b001000
+.byte 0b101010
+.byte 0b011100
+.byte 0b101010
+.byte 0b001000
+.byte 0b001000
+.byte 0b000000
+.byte 0b000000
+
+/* 43 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b000000
+.byte 0b001000
+.byte 0b001000
+.byte 0b111110
+.byte 0b001000
+.byte 0b001000
+.byte 0b000000
+.byte 0b000000
+.byte 0b000000
+
+/* 44 */
+.byte 3 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b000
+.byte 0b000
+.byte 0b000
+.byte 0b000
+.byte 0b000
+.byte 0b010
+.byte 0b010
+.byte 0b100
+.byte 0b000
+
+/* 45 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b00000
+.byte 0b11110
+.byte 0b00000
+.byte 0b00000
+.byte 0b00000
+.byte 0b00000
+.byte 0b00000
+
+/* 46 */
+.byte 2 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00
+.byte 0b00
+.byte 0b00
+.byte 0b00
+.byte 0b00
+.byte 0b00
+.byte 0b10
+.byte 0b00
+.byte 0b00
+
+/* 47 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00010
+.byte 0b00010
+.byte 0b00100
+.byte 0b00100
+.byte 0b01000
+.byte 0b01000
+.byte 0b10000
+.byte 0b10000
+.byte 0b00000
+
+/* 48 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 49 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b0100
+.byte 0b1100
+.byte 0b0100
+.byte 0b0100
+.byte 0b0100
+.byte 0b0100
+.byte 0b1110
+.byte 0b0000
+.byte 0b0000
+
+/* 50 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b00010
+.byte 0b00100
+.byte 0b01000
+.byte 0b10000
+.byte 0b11110
+.byte 0b00000
+.byte 0b00000
+
+/* 51 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b00010
+.byte 0b01100
+.byte 0b00010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 52 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00010
+.byte 0b00110
+.byte 0b01010
+.byte 0b10010
+.byte 0b11110
+.byte 0b00010
+.byte 0b00010
+.byte 0b00000
+.byte 0b00000
+
+/* 53 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b11110
+.byte 0b10000
+.byte 0b10000
+.byte 0b11100
+.byte 0b00010
+.byte 0b00010
+.byte 0b11100
+.byte 0b00000
+.byte 0b00000
+
+/* 54 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b10000
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 55 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b1110
+.byte 0b0010
+.byte 0b0010
+.byte 0b0100
+.byte 0b0100
+.byte 0b1000
+.byte 0b1000
+.byte 0b0000
+.byte 0b0000
+
+/* 56 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b10010
+.byte 0b01100
+.byte 0b10010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 57 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b10010
+.byte 0b01110
+.byte 0b00010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 58 */
+.byte 2 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00
+.byte 0b00
+.byte 0b00
+.byte 0b10
+.byte 0b00
+.byte 0b10
+.byte 0b00
+.byte 0b00
+.byte 0b00
+
+/* 59 */
+.byte 3 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b000
+.byte 0b000
+.byte 0b000
+.byte 0b010
+.byte 0b000
+.byte 0b010
+.byte 0b010
+.byte 0b100
+.byte 0b000
+
+/* 60 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b0000
+.byte 0b0010
+.byte 0b0100
+.byte 0b1000
+.byte 0b0100
+.byte 0b0010
+.byte 0b0000
+.byte 0b0000
+.byte 0b0000
+
+/* 61 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b0000
+.byte 0b0000
+.byte 0b1110
+.byte 0b0000
+.byte 0b1110
+.byte 0b0000
+.byte 0b0000
+.byte 0b0000
+.byte 0b0000
+
+/* 62 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b0000
+.byte 0b1000
+.byte 0b0100
+.byte 0b0010
+.byte 0b0100
+.byte 0b1000
+.byte 0b0000
+.byte 0b0000
+.byte 0b0000
+
+/* 63 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b00010
+.byte 0b00100
+.byte 0b00100
+.byte 0b00000
+.byte 0b00100
+.byte 0b00000
+.byte 0b00000
+
+/* 64 */
+.byte 7 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b0000000
+.byte 0b0011100
+.byte 0b0100010
+.byte 0b1001110
+.byte 0b1010010
+.byte 0b1001100
+.byte 0b0100000
+.byte 0b0011110
+.byte 0b0000000
+
+/* 65 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b10010
+.byte 0b11110
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b00000
+.byte 0b00000
+
+/* 66 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b11100
+.byte 0b00000
+.byte 0b00000
+
+/* 67 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b10000
+.byte 0b10000
+.byte 0b10000
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 68 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b11100
+.byte 0b00000
+.byte 0b00000
+
+/* 69 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b1110
+.byte 0b1000
+.byte 0b1000
+.byte 0b1110
+.byte 0b1000
+.byte 0b1000
+.byte 0b1110
+.byte 0b0000
+.byte 0b0000
+
+/* 70 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b1110
+.byte 0b1000
+.byte 0b1000
+.byte 0b1110
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b0000
+.byte 0b0000
+
+/* 71 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b10000
+.byte 0b10110
+.byte 0b10010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 72 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b11110
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b00000
+.byte 0b00000
+
+/* 73 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b1110
+.byte 0b0100
+.byte 0b0100
+.byte 0b0100
+.byte 0b0100
+.byte 0b0100
+.byte 0b1110
+.byte 0b0000
+.byte 0b0000
+
+/* 74 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01110
+.byte 0b00100
+.byte 0b00100
+.byte 0b00100
+.byte 0b00100
+.byte 0b00100
+.byte 0b11000
+.byte 0b00000
+.byte 0b00000
+
+/* 75 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10010
+.byte 0b10100
+.byte 0b11000
+.byte 0b11000
+.byte 0b10100
+.byte 0b10010
+.byte 0b10010
+.byte 0b00000
+.byte 0b00000
+
+/* 76 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1110
+.byte 0b0000
+.byte 0b0000
+
+/* 77 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b100010
+.byte 0b110110
+.byte 0b101010
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b000000
+.byte 0b000000
+
+/* 78 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b100010
+.byte 0b110010
+.byte 0b101010
+.byte 0b100110
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b000000
+.byte 0b000000
+
+/* 79 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b011100
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b011100
+.byte 0b000000
+.byte 0b000000
+
+/* 80 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b11100
+.byte 0b10000
+.byte 0b10000
+.byte 0b10000
+.byte 0b00000
+.byte 0b00000
+
+/* 81 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b011100
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b101010
+.byte 0b100100
+.byte 0b011010
+.byte 0b000000
+.byte 0b000000
+
+/* 82 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b00000
+.byte 0b00000
+
+/* 83 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01100
+.byte 0b10010
+.byte 0b10000
+.byte 0b01100
+.byte 0b00010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 84 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b111110
+.byte 0b001000
+.byte 0b001000
+.byte 0b001000
+.byte 0b001000
+.byte 0b001000
+.byte 0b001000
+.byte 0b000000
+.byte 0b000000
+
+/* 85 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 86 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b010100
+.byte 0b001000
+.byte 0b000000
+.byte 0b000000
+
+/* 87 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b101010
+.byte 0b101010
+.byte 0b101010
+.byte 0b010100
+.byte 0b000000
+.byte 0b000000
+
+/* 88 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b100010
+.byte 0b100010
+.byte 0b010100
+.byte 0b001000
+.byte 0b010100
+.byte 0b100010
+.byte 0b100010
+.byte 0b000000
+.byte 0b000000
+
+/* 89 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b010100
+.byte 0b001000
+.byte 0b001000
+.byte 0b001000
+.byte 0b000000
+.byte 0b000000
+
+/* 90 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b11110
+.byte 0b00010
+.byte 0b00100
+.byte 0b01000
+.byte 0b10000
+.byte 0b10000
+.byte 0b11110
+.byte 0b00000
+.byte 0b00000
+
+/* 91 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b1110
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1000
+.byte 0b1110
+.byte 0b0000
+
+/* 92 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10000
+.byte 0b10000
+.byte 0b01000
+.byte 0b01000
+.byte 0b00100
+.byte 0b00100
+.byte 0b00010
+.byte 0b00010
+.byte 0b00000
+
+/* 93 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b1110
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b1110
+.byte 0b0000
+
+/* 94 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b001000
+.byte 0b010100
+.byte 0b100010
+.byte 0b000000
+.byte 0b000000
+.byte 0b000000
+.byte 0b000000
+.byte 0b000000
+.byte 0b000000
+
+/* 95 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b00000
+.byte 0b00000
+.byte 0b00000
+.byte 0b00000
+.byte 0b00000
+.byte 0b11110
+.byte 0b00000
+
+/* 96 */
+.byte 3 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b100
+.byte 0b010
+.byte 0b000
+.byte 0b000
+.byte 0b000
+.byte 0b000
+.byte 0b000
+.byte 0b000
+.byte 0b000
+
+/* 97 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b01100
+.byte 0b00010
+.byte 0b01110
+.byte 0b10010
+.byte 0b01110
+.byte 0b00000
+.byte 0b00000
+
+/* 98 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10000
+.byte 0b10000
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b11100
+.byte 0b00000
+.byte 0b00000
+
+/* 99 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b01110
+.byte 0b10000
+.byte 0b10000
+.byte 0b10000
+.byte 0b01110
+.byte 0b00000
+.byte 0b00000
+
+/* 100 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00010
+.byte 0b00010
+.byte 0b01110
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b01110
+.byte 0b00000
+.byte 0b00000
+
+/* 101 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b01100
+.byte 0b10010
+.byte 0b11110
+.byte 0b10000
+.byte 0b01110
+.byte 0b00000
+.byte 0b00000
+
+/* 102 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00110
+.byte 0b01000
+.byte 0b11110
+.byte 0b01000
+.byte 0b01000
+.byte 0b01000
+.byte 0b01000
+.byte 0b00000
+.byte 0b00000
+
+/* 103 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b01110
+.byte 0b10010
+.byte 0b10010
+.byte 0b01110
+.byte 0b00010
+.byte 0b11100
+.byte 0b00000
+
+/* 104 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10000
+.byte 0b10000
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b00000
+.byte 0b00000
+
+/* 105 */
+.byte 2 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10
+.byte 0b00
+.byte 0b10
+.byte 0b10
+.byte 0b10
+.byte 0b10
+.byte 0b10
+.byte 0b00
+.byte 0b00
+
+/* 106 */
+.byte 4 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b0010
+.byte 0b0000
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b0010
+.byte 0b1100
+.byte 0b0000
+
+/* 107 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b10000
+.byte 0b10000
+.byte 0b10010
+.byte 0b10100
+.byte 0b11000
+.byte 0b10100
+.byte 0b10010
+.byte 0b00000
+.byte 0b00000
+
+/* 108 */
+.byte 3 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b100
+.byte 0b100
+.byte 0b100
+.byte 0b100
+.byte 0b100
+.byte 0b100
+.byte 0b010
+.byte 0b000
+.byte 0b000
+
+/* 109 */
+.byte 8 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000000
+.byte 0b00000000
+.byte 0b01101100
+.byte 0b10010010
+.byte 0b10010010
+.byte 0b10010010
+.byte 0b10010010
+.byte 0b00000000
+.byte 0b00000000
+
+/* 110 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b00000
+.byte 0b00000
+
+/* 111 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b01100
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 112 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b11100
+.byte 0b10010
+.byte 0b10010
+.byte 0b11100
+.byte 0b10000
+.byte 0b10000
+.byte 0b00000
+
+/* 113 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b01110
+.byte 0b10010
+.byte 0b10010
+.byte 0b01110
+.byte 0b00010
+.byte 0b00010
+.byte 0b00000
+
+/* 114 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b10110
+.byte 0b11000
+.byte 0b10000
+.byte 0b10000
+.byte 0b10000
+.byte 0b00000
+.byte 0b00000
+
+/* 115 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b01110
+.byte 0b10000
+.byte 0b01100
+.byte 0b00010
+.byte 0b11100
+.byte 0b00000
+.byte 0b00000
+
+/* 116 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b01000
+.byte 0b01000
+.byte 0b11110
+.byte 0b01000
+.byte 0b01000
+.byte 0b01000
+.byte 0b00110
+.byte 0b00000
+.byte 0b00000
+
+/* 117 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b01100
+.byte 0b00000
+.byte 0b00000
+
+/* 118 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b000000
+.byte 0b000000
+.byte 0b100010
+.byte 0b100010
+.byte 0b100010
+.byte 0b010100
+.byte 0b001000
+.byte 0b000000
+.byte 0b000000
+
+/* 119 */
+.byte 8 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000000
+.byte 0b00000000
+.byte 0b10010010
+.byte 0b10010010
+.byte 0b10010010
+.byte 0b10010010
+.byte 0b01101100
+.byte 0b00000000
+.byte 0b00000000
+
+/* 120 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b000000
+.byte 0b000000
+.byte 0b100010
+.byte 0b010100
+.byte 0b001000
+.byte 0b010100
+.byte 0b100010
+.byte 0b000000
+.byte 0b000000
+
+/* 121 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b10010
+.byte 0b10010
+.byte 0b10010
+.byte 0b01110
+.byte 0b00010
+.byte 0b11100
+.byte 0b00000
+
+/* 122 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00000
+.byte 0b00000
+.byte 0b11110
+.byte 0b00100
+.byte 0b01000
+.byte 0b10000
+.byte 0b11110
+.byte 0b00000
+.byte 0b00000
+
+/* 123 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b00110
+.byte 0b01000
+.byte 0b01000
+.byte 0b11000
+.byte 0b11000
+.byte 0b01000
+.byte 0b01000
+.byte 0b00110
+.byte 0b00000
+
+/* 124 */
+.byte 3 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b010
+.byte 0b010
+.byte 0b010
+.byte 0b010
+.byte 0b010
+.byte 0b010
+.byte 0b010
+.byte 0b010
+.byte 0b000
+
+/* 125 */
+.byte 5 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b11000
+.byte 0b00100
+.byte 0b00100
+.byte 0b00110
+.byte 0b00110
+.byte 0b00100
+.byte 0b00100
+.byte 0b11000
+.byte 0b00000
+
+/* 126 */
+.byte 6 /* width in pixels */
+.byte 9 /* height in pixels */
+
+.byte 0b010000
+.byte 0b101010
+.byte 0b000100
+.byte 0b000000
+.byte 0b000000
+.byte 0b000000
+.byte 0b000000
+.byte 0b000000
+.byte 0b000000
+
+fontlimit:
+.word 127
+fonttable:
+.word 0
+.word 11
+.word 22
+.word 33
+.word 44
+.word 55
+.word 66
+.word 77
+.word 88
+.word 99
+.word 110
+.word 121
+.word 132
+.word 143
+.word 154
+.word 165
+.word 176
+.word 187
+.word 198
+.word 209
+.word 220
+.word 231
+.word 242
+.word 253
+.word 264
+.word 275
+.word 286
+.word 297
+.word 308
+.word 319
+.word 330
+.word 341
+.word 352
+.word 363
+.word 374
+.word 385
+.word 396
+.word 407
+.word 418
+.word 429
+.word 440
+.word 451
+.word 462
+.word 473
+.word 484
+.word 495
+.word 506
+.word 517
+.word 528
+.word 539
+.word 550
+.word 561
+.word 572
+.word 583
+.word 594
+.word 605
+.word 616
+.word 627
+.word 638
+.word 649
+.word 660
+.word 671
+.word 682
+.word 693
+.word 704
+.word 715
+.word 726
+.word 737
+.word 748
+.word 759
+.word 770
+.word 781
+.word 792
+.word 803
+.word 814
+.word 825
+.word 836
+.word 847
+.word 858
+.word 869
+.word 880
+.word 891
+.word 902
+.word 913
+.word 924
+.word 935
+.word 946
+.word 957
+.word 968
+.word 979
+.word 990
+.word 1001
+.word 1012
+.word 1023
diff -r d103800bffda -r e5fd5d81a72a data/font.txt
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/data/font.txt	Tue Oct 30 19:21:53 2018 +0100
@@ -0,0 +1,59 @@
+#- #-#- -#-#-- --#--- -#----- -#---- #- -##- ##-- --#--- ------ --- ----- -- ---#-
+#- #-#- -#-#-- -####- #-#--#- #-#--- #- #--- --#- --#--- --#--- --- ----- -- ---#-
+#- ---- #####- #-#--- -#--#-- #-#--- -- #--- --#- #-#-#- --#--- --- ----- -- --#--
+#- ---- -#-#-- -###-- ---#--- -#---- -- #--- --#- -###-- #####- --- ####- -- --#--
+#- ---- #####- --#-#- --#---- #-#-#- -- #--- --#- #-#-#- --#--- --- ----- -- -#---
+-- ---- -#-#-- ####-- -#--#-- #--#-- -- #--- --#- --#--- --#--- -#- ----- -- -#---
+#- ---- -#-#-- --#--- #--#-#- -##-#- -- #--- --#- --#--- ------ -#- ----- #- #----
+-- ---- ------ ------ ----#-- ------ -- -##- ##-- ------ ------ #-- ----- -- #----
+-- ---- ------ ------ ------- ------ -- ---- ---- ------ ------ --- ----- -- -----
+
+-##-- -#-- -##-- -##-- ---#- ####- -##-- ###- -##-- -##-- -- --- ---- ---- ---- -##-- -------
+#--#- ##-- #--#- #--#- --##- #---- #--#- --#- #--#- #--#- -- --- --#- ---- #--- #--#- --###--
+#--#- -#-- ---#- ---#- -#-#- #---- #---- --#- #--#- #--#- -- --- -#-- ###- -#-- ---#- -#---#-
+#--#- -#-- --#-- -##-- #--#- ###-- ###-- -#-- -##-- -###- #- -#- #--- ---- --#- --#-- #--###-
+#--#- -#-- -#--- ---#- ####- ---#- #--#- -#-- #--#- ---#- -- --- -#-- ###- -#-- --#-- #-#--#-
+#--#- -#-- #---- #--#- ---#- ---#- #--#- #--- #--#- #--#- #- -#- --#- ---- #--- ----- #--##--
+-##-- ###- ####- -##-- ---#- ###-- -##-- #--- -##-- -##-- -- -#- ---- ---- ---- --#-- -#-----
+----- ---- ----- ----- ----- ----- ----- ---- ----- ----- -- #-- ---- ---- ---- ----- --####-
+----- ---- ----- ----- ----- ----- ----- ---- ----- ----- -- --- ---- ---- ---- ----- -------
+
+-##-- ###-- -##-- ###-- ###- ###- -##-- #--#- ###- -###- #--#- #--- #---#- #---#- -###-- ###-- -###-- ###-- -##-- #####- #--#- #---#- #---#- #---#- #---#-
+#--#- #--#- #--#- #--#- #--- #--- #--#- #--#- -#-- --#-- #-#-- #--- ##-##- ##--#- #---#- #--#- #---#- #--#- #--#- --#--- #--#- #---#- #---#- #---#- #---#-
+#--#- #--#- #---- #--#- #--- #--- #---- #--#- -#-- --#-- ##--- #--- #-#-#- #-#-#- #---#- #--#- #---#- #--#- #---- --#--- #--#- #---#- #---#- -#-#-- #---#-
+####- ###-- #---- #--#- ###- ###- #-##- ####- -#-- --#-- ##--- #--- #---#- #--##- #---#- ###-- #---#- ###-- -##-- --#--- #--#- #---#- #-#-#- --#--- -#-#--
+#--#- #--#- #---- #--#- #--- #--- #--#- #--#- -#-- --#-- #-#-- #--- #---#- #---#- #---#- #---- #-#-#- #--#- ---#- --#--- #--#- #---#- #-#-#- -#-#-- --#---
+#--#- #--#- #--#- #--#- #--- #--- #--#- #--#- -#-- --#-- #--#- #--- #---#- #---#- #---#- #---- #--#-- #--#- #--#- --#--- #--#- -#-#-- #-#-#- #---#- --#---
+#--#- ###-- -##-- ###-- ###- #--- -##-- #--#- ###- ##--- #--#- ###- #---#- #---#- -###-- #---- -##-#- #--#- -##-- --#--- -##-- --#--- -#-#-- #---#- --#---
+----- ----- ----- ----- ---- ---- ----- ----- ---- ----- ----- ---- ------ ------ ------ ----- ------ ----- ----- ------ ----- ------ ------ ------ ------
+----- ----- ----- ----- ---- ---- ----- ----- ---- ----- ----- ---- ------ ------ ------ ----- ------ ----- ----- ------ ----- ------ ------ ------ ------
+
+####- ###- #---- ###- --#--- ----- #--
+---#- #--- #---- --#- -#-#-- ----- -#-
+--#-- #--- -#--- --#- #---#- ----- ---
+-#--- #--- -#--- --#- ------ ----- ---
+#---- #--- --#-- --#- ------ ----- ---
+#---- #--- --#-- --#- ------ ----- ---
+####- #--- ---#- --#- ------ ----- ---
+----- ###- ---#- ###- ------ ####- ---
+----- ---- ----- ---- ------ ----- ---
+
+----- #---- ----- ---#- ----- --##- ----- #---- #- --#- #---- #-- -------- ----- ----- ----- ----- ----- ----- -#--- ----- ------ -------- ------ ----- -----
+----- #---- ----- ---#- ----- -#--- ----- #---- -- ---- #---- #-- -------- ----- ----- ----- ----- ----- ----- -#--- ----- ------ -------- ------ ----- -----
+-##-- ###-- -###- -###- -##-- ####- -###- ###-- #- --#- #--#- #-- -##-##-- ###-- -##-- ###-- -###- #-##- -###- ####- #--#- #---#- #--#--#- #---#- #--#- ####-
+---#- #--#- #---- #--#- #--#- -#--- #--#- #--#- #- --#- #-#-- #-- #--#--#- #--#- #--#- #--#- #--#- ##--- #---- -#--- #--#- #---#- #--#--#- -#-#-- #--#- --#--
+-###- #--#- #---- #--#- ####- -#--- #--#- #--#- #- --#- ##--- #-- #--#--#- #--#- #--#- #--#- #--#- #---- -##-- -#--- #--#- #---#- #--#--#- --#--- #--#- -#---
+#--#- #--#- #---- #--#- #---- -#--- -###- #--#- #- --#- #-#-- #-- #--#--#- #--#- #--#- ###-- -###- #---- ---#- -#--- #--#- -#-#-- #--#--#- -#-#-- -###- #----
+-###- ###-- -###- -###- -###- -#--- ---#- #--#- #- --#- #--#- -#- #--#--#- #--#- -##-- #---- ---#- #---- ###-- --##- -##-- --#--- -##-##-- #---#- ---#- ####-
+----- ----- ----- ----- ----- ----- ###-- ----- -- ##-- ----- --- -------- ----- ----- #---- ---#- ----- ----- ----- ----- ------ -------- ------ ###-- -----
+----- ----- ----- ----- ----- ----- ----- ----- -- ---- ----- --- -------- ----- ----- ----- ----- ----- ----- ----- ----- ------ -------- ------ ----- -----
+
+--##- -#- ##--- -#----
+-#--- -#- --#-- #-#-#-
+-#--- -#- --#-- ---#--
+##--- -#- --##- ------
+##--- -#- --##- ------
+-#--- -#- --#-- ------
+-#--- -#- --#-- ------
+--##- -#- ##--- ------
+----- --- ----- ------
diff -r d103800bffda -r e5fd5d81a72a examples/vga-dual/Makefile
--- a/examples/vga-dual/Makefile	Tue Oct 30 18:22:22 2018 +0100
+++ b/examples/vga-dual/Makefile	Tue Oct 30 19:21:53 2018 +0100
@@ -27,8 +27,8 @@
 
 # Ordering of objects is important and cannot be left to replacement rules.
 
-SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S
-OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o
+SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S font.S
+OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o font.o
 
 # Application-specific adjustments.
 # See: examples/vga/Makefile
diff -r d103800bffda -r e5fd5d81a72a examples/vga-dual/font.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/vga-dual/font.S	Tue Oct 30 19:21:53 2018 +0100
@@ -0,0 +1,1 @@
+../../data/font.S
\ No newline at end of file
diff -r d103800bffda -r e5fd5d81a72a examples/vga-pmp/Makefile
--- a/examples/vga-pmp/Makefile	Tue Oct 30 18:22:22 2018 +0100
+++ b/examples/vga-pmp/Makefile	Tue Oct 30 19:21:53 2018 +0100
@@ -27,10 +27,11 @@
 
 # Ordering of objects is important and cannot be left to replacement rules.
 
-SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S
-OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o
+SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S font.S
+OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o font.o
 
 # Application-specific adjustments.
+# See: examples/vga/Makefile
 
 CFLAGS += -DPARALLEL_MODE -I../vga
 
diff -r d103800bffda -r e5fd5d81a72a examples/vga-pmp/font.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/vga-pmp/font.S	Tue Oct 30 19:21:53 2018 +0100
@@ -0,0 +1,1 @@
+../../data/font.S
\ No newline at end of file
diff -r d103800bffda -r e5fd5d81a72a examples/vga-timer/Makefile
--- a/examples/vga-timer/Makefile	Tue Oct 30 18:22:22 2018 +0100
+++ b/examples/vga-timer/Makefile	Tue Oct 30 19:21:53 2018 +0100
@@ -27,8 +27,8 @@
 
 # Ordering of objects is important and cannot be left to replacement rules.
 
-SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S
-OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o
+SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S font.S
+OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o font.o
 
 # Application-specific adjustments.
 # See: examples/vga/Makefile
diff -r d103800bffda -r e5fd5d81a72a examples/vga-timer/font.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/vga-timer/font.S	Tue Oct 30 19:21:53 2018 +0100
@@ -0,0 +1,1 @@
+../../data/font.S
\ No newline at end of file
diff -r d103800bffda -r e5fd5d81a72a examples/vga/Makefile
--- a/examples/vga/Makefile	Tue Oct 30 18:22:22 2018 +0100
+++ b/examples/vga/Makefile	Tue Oct 30 19:21:53 2018 +0100
@@ -27,8 +27,8 @@
 
 # Ordering of objects is important and cannot be left to replacement rules.
 
-SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S
-OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o
+SRC = $(START_SRC) main.c $(COMMON_SRC) $(DISPLAY_SRC) screendata.S sprite.S font.S
+OBJ = $(START_OBJ) main.o $(COMMON_OBJ) $(DISPLAY_OBJ) screendata.o sprite.o font.o
 
 # Application-specific adjustments.
 
diff -r d103800bffda -r e5fd5d81a72a examples/vga/font.S
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/examples/vga/font.S	Tue Oct 30 19:21:53 2018 +0100
@@ -0,0 +1,1 @@
+../../data/font.S
\ No newline at end of file
diff -r d103800bffda -r e5fd5d81a72a examples/vga/main.c
--- a/examples/vga/main.c	Tue Oct 30 18:22:22 2018 +0100
+++ b/examples/vga/main.c	Tue Oct 30 19:21:53 2018 +0100
@@ -24,11 +24,12 @@
 
 /* Specific functionality. */
 
-#include "main.h"
 #include "devconfig.h"
-#include "vga.h"
 #include "display.h"
 #include "display_config.h"
+#include "font.h"
+#include "main.h"
+#include "vga.h"
 #include "vga_display.h"
 
 
@@ -63,13 +64,19 @@
 
 
 
-/* Bundled image data. */
+/* Bundled image and font data. */
 
 extern uint8_t screendata[];
 extern uint32_t screendata_width, screendata_height;
 extern uint8_t sprite[];
 extern uint32_t sprite_width, sprite_height;
 
+extern uint8_t fontchars[];
+extern uint32_t fonttable[];
+extern uint32_t fontbase, fontlimit;
+
+static font_config_t font_config;
+
 
 
 /* Busy wait. */
@@ -125,6 +132,30 @@
             }
 }
 
+/* Fill the screen with characters. */
+
+static void write_chars(void)
+{
+    int x = 0, y = 0;
+    char c;
+
+    font_config.chars = (char_definition_t *) fontchars;
+    font_config.table = fonttable;
+    font_config.base = fontbase;
+    font_config.limit = fontlimit;
+
+    while (y < display_config.line_count)
+        for (c = (char) font_config.base; c < (char) font_config.limit; c++)
+        {
+            x = write_char(&display_config, &font_config, c, x, y, 0xff);
+
+            if (x > display_config.line_length)
+            {
+                x = 0; y += 9;
+            }
+        }
+}
+
 
 
 /* Main program. */
@@ -174,6 +205,10 @@
     copy_display(&display_config, screendata, screendata_width, screendata_height,
          (LINE_LENGTH - screendata_width) / 2, (LINE_COUNT - screendata_height) / 2, -1, 1);
 
+    /* Write a sequence of characters. */
+
+    write_chars();
+
     /* Move a sprite around on the screen with a delay between each movement. */
 
     animate(1 << 24);
diff -r d103800bffda -r e5fd5d81a72a include/font.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/include/font.h	Tue Oct 30 19:21:53 2018 +0100
@@ -0,0 +1,57 @@
+/*
+ * Common font-related functions.
+ *
+ * Copyright (C) 2018 Paul Boddie <paul@boddie.org.uk>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef __FONT_H__
+#define __FONT_H__
+
+#include <stdint.h>
+
+
+
+/* Character definition structure. */
+
+typedef struct
+{
+    uint8_t width;
+    uint8_t height;
+    uint8_t data[];
+
+} char_definition_t;
+
+/* Font configuration type. */
+
+typedef struct
+{
+    char_definition_t *chars;
+    uint32_t *table;
+    uint32_t base;
+    uint32_t limit;
+
+} font_config_t;
+
+
+
+/* Access functions. */
+
+char_definition_t *get_char_definition(font_config_t *cfg, char c);
+
+int write_char(display_config_t *cfg, font_config_t *fcfg, char c,
+               int x, int y, uint8_t colour);
+
+#endif /* __FONT_H__ */
diff -r d103800bffda -r e5fd5d81a72a lib/font.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/font.c	Tue Oct 30 19:21:53 2018 +0100
@@ -0,0 +1,71 @@
+/*
+ * Common font-related functions.
+ *
+ * Copyright (C) 2018 Paul Boddie <paul@boddie.org.uk>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <stdlib.h>
+
+#include "display.h"
+#include "font.h"
+
+
+
+/* Return the character definition for the given character. */
+
+char_definition_t *get_char_definition(font_config_t *fcfg, char c)
+{
+    /* Obtain the offset from the table and combine it with the character
+       definitions base address. */
+
+    if ((c >= fcfg->base) && (c < fcfg->limit))
+        return (char_definition_t *) ((uint8_t *) fcfg->chars + fcfg->table[c - fcfg->base]);
+    else
+        return NULL;
+}
+
+/* Write a character to the screen, returning the next character position. */
+
+int write_char(display_config_t *cfg, font_config_t *fcfg, char c,
+               int x, int y, uint8_t colour)
+{
+    int sy, dx, dy;
+    char_definition_t *chardef = get_char_definition(fcfg, c);
+    uint8_t *imagerow = chardef->data,
+            *displayline = cfg->framebuffer + y * cfg->line_length,
+            bitmap, mask;
+
+    /* Space is a special case. */
+
+    if (c == ' ')
+        return x + 3;
+
+    for (sy = 0, dy = y; (sy < chardef->height) && (dy < cfg->line_count); sy++, dy++)
+    {
+        bitmap = *imagerow;
+
+        for (dx = x, mask = 1 << (chardef->width - 1); (mask) && (dx < cfg->line_length); dx++, mask >>= 1)
+        {
+            if (bitmap & mask)
+                displayline[get_position(cfg, dx)] = colour;
+        }
+
+        imagerow += 1;
+        displayline += cfg->line_length;
+    }
+
+    return x + chardef->width;
+}
diff -r d103800bffda -r e5fd5d81a72a mk/common.mk
--- a/mk/common.mk	Tue Oct 30 18:22:22 2018 +0100
+++ b/mk/common.mk	Tue Oct 30 19:21:53 2018 +0100
@@ -51,8 +51,8 @@
 COMMON_SRC = $(LIBDIR)/payload.c $(LIBDIR)/init.c $(LIBDIR)/debug.c $(LIBDIR)/cpu.S
 COMMON_OBJ = $(LIBDIR)/payload.o $(LIBDIR)/init.o $(LIBDIR)/debug.o $(LIBDIR)/cpu.o
 
-DISPLAY_SRC = $(LIBDIR)/display.c $(LIBDIR)/vga_display.c
-DISPLAY_OBJ = $(LIBDIR)/display.o $(LIBDIR)/vga_display.o
+DISPLAY_SRC = $(LIBDIR)/display.c $(LIBDIR)/vga_display.c $(LIBDIR)/font.c
+DISPLAY_OBJ = $(LIBDIR)/display.o $(LIBDIR)/vga_display.o $(LIBDIR)/font.o
 
 # Common linker script.
 
diff -r d103800bffda -r e5fd5d81a72a tools/makefont.py
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/makefont.py	Tue Oct 30 19:21:53 2018 +0100
@@ -0,0 +1,177 @@
+#!/usr/bin/env python
+
+"""
+Convert simple font bitmaps to GNU assembler data.
+
+Copyright (C) 2018 Paul Boddie <paul@boddie.org.uk>
+
+This program is free software; you can redistribute it and/or modify it under
+the terms of the GNU General Public License as published by the Free Software
+Foundation; either version 3 of the License, or (at your option) any later
+version.
+
+This program 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 General Public License for more details.
+
+You should have received a copy of the GNU General Public License along
+with this program.  If not, see <http://www.gnu.org/licenses/>.
+"""
+
+import sys
+
+class MissingRow(Exception):
+
+    "Indicate a missing row in a character definition."
+
+    def __init__(self, lineno):
+        self.lineno = lineno
+
+    def __repr__(self):
+        return "MissingRow(%r)" % self.lineno
+
+
+
+def get_character_row(f, lineno=0):
+
+    "Return a row of characters from 'f', employing 'lineno' for reference."
+
+    line = f.readline().strip()
+    rows = []
+
+    while line:
+        row = line.split()
+        if rows and len(row) != len(rows[-1]):
+            raise MissingRow, lineno
+
+        rows.append(row)
+        lineno += 1
+        line = f.readline().strip()
+
+    chars = []
+
+    if rows:
+        for i in range(0, len(rows[0])):
+            char = []
+            for row in rows:
+                char.append(row[i])
+            chars.append(char)
+
+    return chars
+
+
+
+def convert(infile, outfile, base=33):
+
+    "Convert textual data in 'infile' to assembler data in 'outfile'."
+
+    f_in = open(infile)
+    f_out = open(outfile, "w")
+    try:
+        print >>f_out, """\
+.globl fontchars
+.globl fonttable
+.globl fontbase
+.globl fontlimit
+
+.section .flash, "a"
+
+fontbase:
+.word %d
+
+fontchars:""" % base
+
+        lineno = 1
+        offset = 0
+        offsets = []
+        point = base
+
+        # Get each row of characters.
+
+        chars = get_character_row(f_in, lineno)
+
+        while chars:
+            lineno += len(chars[0]) + 1
+
+            # Write each character definition.
+
+            for point, char in enumerate(chars, point):
+                offsets.append(offset)
+                offset += write_character(f_out, point, char)
+
+            point += 1
+
+            # Get the next row.
+
+            chars = get_character_row(f_in, lineno)
+
+        # Write the limit of characters.
+
+        print >>f_out, """\
+fontlimit:
+.word %d""" % point
+
+        # Write the offset table.
+
+        print >>f_out, """\
+fonttable:"""
+
+        for offset in offsets:
+            print >>f_out, ".word %d" % offset
+
+    finally:
+        f_in.close()
+        f_out.close()
+
+
+
+def write_character(f, point, char):
+
+    "Write to 'f' for the given 'point' the indicated 'char' definition."
+
+    # Write a comment and pixel width information.
+
+    print >>f, """\
+/* %d */
+.byte %d /* width in pixels */
+.byte %d /* height in pixels */
+""" % (point, len(char[0]), len(char))
+
+    # Write the pixel rows to a sequence of bytes.
+
+    for row in char:
+        print >>f, ".byte 0b%s" % row.replace("-", "0").replace("#", "1")
+
+    print >>f
+
+    # Return the size of the definition as the number of rows plus the width
+    # and height bytes.
+
+    return len(char) + 2
+
+
+
+# Main program.
+
+if __name__ == "__main__":
+
+    # Obtain filenames.
+
+    try:
+        infile, outfile = sys.argv[1:3]
+    except ValueError:
+        print >>sys.stderr, """\
+Usage: %s <input filename> <output filename>
+"""
+        sys.exit(1)
+
+    # Perform the conversion.
+
+    try:
+        convert(infile, outfile)
+    except MissingRow, exc:
+        print >>sys.stderr, """\
+Missing character information at line %d in file %s.
+""" % (exc.lineno, infile)
+
+# vim: tabstop=4 expandtab shiftwidth=4