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ti/lcd: allow for fonts smaller than 5 pixels

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That's a lot of code for such a small change, but there's a big difference
between 5 pixels and 4 pixels: 4 pixels requires compositing.
This commit is contained in:
Virgil Dupras 2019-11-09 22:55:15 -05:00
parent 6d9f96aee6
commit c4658591bd
3 changed files with 141 additions and 41 deletions
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BIN
kernel/fnt/5x7.bin
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Binary file not shown.

171
kernel/ti/lcd.asm
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@ -26,6 +26,25 @@
; when active row is 0, Z is FNT_HEIGHT+1, when row is 1, Z is (FNT_HEIGHT+1)*2,
; When row is 8, Z is 0.
;
; *** 6/8 bit columns and smaller fonts ***
;
; If your glyphs, including padding, are 6 or 8 pixels wide, you're in luck
; because pushing them to the LCD can be done in a very efficient manner.
; Unfortunately, this makes the LCD unsuitable for a Collapse OS shell: 6
; pixels per glyph gives us only 16 characters per line, which is hardly
; usable.
;
; This is why we have this buffering system. How it works is that we're always
; in 8-bit mode and we hold the whole area (8 pixels wide by FNT_HEIGHT high)
; in memory. When we want to put a glyph to screen, we first read the contents
; of that area, then add our new glyph, offsetted and masked, to that buffer,
; then push the buffer back to the LCD. If the glyph is split, move to the next
; area and finish the job.
;
; That being said, it's important to define clearly what CURX and CURY variable
; mean. Those variable keep track of the current position *in pixels*, in both
; axes.
;
; *** Requirements ***
; fnt/mgm
;
@ -37,7 +56,9 @@
.equ LCD_CMD_8BIT 0x01
.equ LCD_CMD_DISABLE 0x02
.equ LCD_CMD_ENABLE 0x03
.equ LCD_CMD_XDEC 0x04
.equ LCD_CMD_XINC 0x05
.equ LCD_CMD_YDEC 0x06
.equ LCD_CMD_YINC 0x07
.equ LCD_CMD_COL 0x20
.equ LCD_CMD_ZOFFSET 0x40
@ -45,19 +66,22 @@
.equ LCD_CMD_CONTRAST 0xc0
; *** Variables ***
; Current row being written on. In terms of pixels, not of glyphs. During a
; linefeed, this increases by FNT_HEIGHT+1.
.equ LCD_CURROW LCD_RAMSTART
; Current column
.equ LCD_CURCOL @+1
.equ LCD_RAMEND @+1
; Current Y position on the LCD, that is, where re're going to spit our next
; glyph.
.equ LCD_CURY LCD_RAMSTART
; Current X position
.equ LCD_CURX @+1
; two pixel buffers that are 8 pixels wide (1b) by FNT_HEIGHT pixels high.
; This is where we compose our resulting pixels blocks when spitting a glyph.
.equ LCD_BUF @+1
.equ LCD_RAMEND @+FNT_HEIGHT*2
; *** Code ***
lcdInit:
; Initialize variables
xor a
ld (LCD_CURROW), a
ld (LCD_CURCOL), a
ld (LCD_CURY), a
ld (LCD_CURX), a
; Clear screen
call lcdClrScr
@ -82,12 +106,8 @@ lcdInit:
ld a, LCD_CMD_CONTRAST+0x34
call lcdCmd
; Enable 6-bit mode.
ld a, LCD_CMD_6BIT
call lcdCmd
; Enable X-increment mode
ld a, LCD_CMD_XINC
; Enable 8-bit mode.
ld a, LCD_CMD_8BIT
call lcdCmd
ret
@ -109,10 +129,15 @@ lcdCmd:
jr lcdWait
; Send data A to LCD
lcdData:
lcdDataSet:
out (LCD_PORT_DATA), a
jr lcdWait
; Get data from LCD into A
lcdDataGet:
in a, (LCD_PORT_DATA)
jr lcdWait
; Turn LCD off
lcdOff:
push af
@ -140,52 +165,126 @@ lcdSetRow:
pop af
ret
; Send the 5x7 glyph that HL points to to the LCD, at its current position.
; Send the glyph that HL points to to the LCD, at its current position.
; After having called this, the LCD's position will have advanced by one
; position
lcdSendGlyph:
push af
push bc
push hl
push ix
ld a, (LCD_CURROW)
ld a, (LCD_CURY)
call lcdSetRow
ld a, (LCD_CURCOL)
ld a, (LCD_CURX)
srl a \ srl a \ srl a ; div by 8
call lcdSetCol
; First operation: read the LCD memory for the "left" side of the
; buffer. We assume the right side to always be empty, so we don't
; read it. After having read each line, compose it with glyph line at
; HL
; Before we start, what is our bit offset?
ld a, (LCD_CURX)
and 0b111
; that's our offset, store it in C
ld c, a
ld a, LCD_CMD_XINC
call lcdCmd
ld ix, LCD_BUF
ld b, FNT_HEIGHT
.loop:
; A dummy read is needed after a movement.
call lcdDataGet
.loop1:
; let's go get that glyph data
ld a, (hl)
ld (ix), a
call .shiftIX
; now let's go get existing pixel on LCD
call lcdDataGet
; and now let's do some compositing!
or (ix)
ld (ix), a
inc hl
call lcdData
djnz .loop
inc ix
djnz .loop1
; Buffer set! now let's send it.
ld a, (LCD_CURY)
call lcdSetRow
ld hl, LCD_BUF
ld b, FNT_HEIGHT
.loop2:
ld a, (hl)
call lcdDataSet
inc hl
djnz .loop2
; And finally, let's send the "right side" of the buffer
ld a, (LCD_CURY)
call lcdSetRow
ld a, (LCD_CURX)
srl a \ srl a \ srl a ; div by 8
inc a
call lcdSetCol
ld hl, LCD_BUF+FNT_HEIGHT
ld b, FNT_HEIGHT
.loop3:
ld a, (hl)
call lcdDataSet
inc hl
djnz .loop3
; Increase column and wrap if necessary
ld a, (LCD_CURCOL)
inc a
ld (LCD_CURCOL), a
cp 16
jr nz, .skip
ld a, (LCD_CURX)
add a, FNT_WIDTH+1
ld (LCD_CURX), a
cp 96-FNT_WIDTH
jr c, .skip ; A < 96-FNT_WIDTH
call lcdLinefeed
.skip:
pop ix
pop hl
pop bc
pop af
ret
; Shift glyph in (IX) to the right C times, sending carry into (IX+FNT_HEIGHT)
.shiftIX:
dec c \ inc c
ret z ; zero? nothing to do
push bc ; --> lvl 1
xor a
ld b, a
ld a, (ix)
; TODO: support SRL (IX) and RR (IX) in zasm
.shiftLoop:
srl a
rr b
dec c
jr nz, .shiftLoop
ld (ix), a
ld a, b
ld (ix+FNT_HEIGHT), a
pop bc ; <-- lvl 1
ret
; Changes the current line and go back to leftmost column
lcdLinefeed:
push af
ld a, (LCD_CURROW)
ld a, (LCD_CURY)
call .addFntH
ld (LCD_CURROW), a
ld (LCD_CURY), a
call lcdClrLn
; Now, lets set Z offset which is CURROW+FNT_HEIGHT+1
call .addFntH
add a, LCD_CMD_ZOFFSET
call lcdCmd
xor a
ld (LCD_CURCOL), a
ld (LCD_CURX), a
pop af
ret
.addFntH:
@ -201,8 +300,6 @@ lcdLinefeed:
lcdClrX:
push af
call lcdSetRow
ld a, LCD_CMD_8BIT
call lcdCmd
.outer:
push bc ; --> lvl 1
ld b, 11
@ -211,16 +308,14 @@ lcdClrX:
xor a
call lcdSetCol
.inner:
call lcdData
call lcdDataSet
djnz .inner
ld a, LCD_CMD_XINC
call lcdCmd
xor a
call lcdData
call lcdDataSet
pop bc ; <-- lvl 1
djnz .outer
ld a, LCD_CMD_6BIT
call lcdCmd
pop af
ret
@ -251,10 +346,10 @@ lcdPutC:
pop hl
ret
.bs:
ld a, (LCD_CURCOL)
ld a, (LCD_CURX)
or a
ret z ; going back one line is too complicated.
; not implemented yet
dec a
ld (LCD_CURCOL), a
sub FNT_WIDTH+1
ld (LCD_CURX), a
ret

11
tools/font_compile.pl
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@ -3,11 +3,16 @@ use strict;
# This script converts "space-dot" fonts to binary "glyph rows". One byte for
# each row. In a 5x7 font, each glyph thus use 7 bytes.
# Resulting bytes are aligned to the **left** of the byte. Therefore, for
# a 5-bit wide char, ". . ." translates to 0b10101000
# Left-aligned bytes are easier to work with when compositing glyphs.
my $fn = @ARGV[0];
unless ($fn =~ /.*(\d)x(\d)\.txt/) { die "$fn isn't a font filename" };
my ($width, $height) = ($1, $2);
if ($width > 8) { die "Can't have a width > 8"; }
print STDERR "Reading a $width x $height font.\n";
my $handle;
@ -21,9 +26,9 @@ while (<$handle>) {
unless (/( |\.){${width}}\n/) { die "Invalid line format '$_'"; }
my @line = split //, $_;
my $num = 0;
for (my $i=$width-1; $i>=0; $i--) {
if (@line[$width-$i-1] eq '.') {
$num += (1 << $i);
for (my $i=0; $i<8; $i++) {
if (@line[$i] eq '.') {
$num += (1 << (7-$i));
}
}
print pack('C', $num);