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apple2_hgr_font_tutorial
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Added ASCII table code and pics

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michaelangel007 2016-01-28 01:05:51 -08:00
parent 29a9e15b72
commit cce6800d06
1 changed files with 94 additions and 20 deletions
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README.md
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@ -2289,6 +2289,83 @@ Here are all the (core) font rendering routines we've entered in so far:
A similiar font is the one used by "Beautiful Boot". Let's examine it.
First, let's write a program to display an ASCII table of the various glyphs.
Listing [Ascii Table:](asm/asciitable.s)
```assembly
KEYBOARD = $C000
KEYSTROBE = $C010
TXTCLR = $C050 ; Mode Graphics
MIXCLR = $C052 ; Full screen
MIXSET = $C053 ; Split screen
PAGE1 = $C054
HIRES = $C057 ; Mode HGR
HgrLo = $F5
HgrHi = $F6
glyph = $FE
row = $FF
DrawChar = $310
HgrLoY = $3A0
HgrHiY = $3B8
START_ROW = 0
ORG $1080
AsciiTable
LDY #(START_ROW-1) & $FF
STY row
LDA #0 ; glyph=0
STA glyph ; save which glyph to draw
BIT PAGE1 ; Page 1
BIT TXTCLR ; not text, but graphics
BIT MIXSET ; Split screen text/graphics
BIT HIRES ; HGR, no GR
_NextRow
INC row
LDY row
LDA HgrLoY,Y
STA HgrLo ; Screen Address Lo
LDA HgrHiY,Y
ORA #$20 ; HGR Page 1
STA HgrHi ; Screen Address Hi
LDY #00 ; Y = col
_NextCol
LDA glyph ; A = glyph
JSR DrawChar
INC glyph ; yes, ++glyph
LDA glyph ;
CMP #$20 ; done 16 chars?
BEQ _NextRow
CMP #$40
BEQ _NextRow
CMP #$60
BEQ _NextRow
CMP #$80
BNE _NextCol
_Done RTS ; Optimization: BEQ _NextRow
```
Enter in:
```
1080:A0 FF 84 FF A9 00 85 FE
1088:2C 54 C0 2C 50 C0 2C 53
1090:C0 2C 57 C0 E6 FF A4 FF
1098:B9 A0 03 85 F5 B9 B8 03
10A0:09 20 85 F6 A0 00 A5 FE
10A8:20 10 03 E6 FE A5 FE C9
10B0:20 F0 E1 C9 40 F0 DD C9
10B8:60 F0 D9 C9 80 D0 E7 60
1080G
```
![Screenshot ASCII Font 7x8](pics/ascii_table_1_font7x8.png?raw=true)
### Beautiful Boot
@ -2399,22 +2476,15 @@ Again copy this to higher memory
8000<6000.63FFM
```
Fire up our ASCII Character Inspector. Recall:
Let's display this just a few lines down at row 6. We need to use `row-1` because of the pre-increment at `$1080`.
```
1000:A9 00 85 FE A9 00 85 F5
1008:A9 20 85 F6 A5 FE A0 00
1010:20 37 10 AD 00 C0 10 FB
1018:8D 10 C0 C9 88 D0 0A C6
1020:FE A5 FE 29 7F 85 FE 10
1028:DB C9 95 D0 05 E6 FE 18
1030:90 EF C9 9B D0 DD 60 48
1038:20 10 03 A9 20 20 10 03
1040:68 4C 01 03
1000G
1081:5
1080G
```
Press `ESC` when done viewing.
![Screenshot ASCII Table Font BB Upside Down](pics/ascii_table_2_fontbb.png?raw=true)
Argh, those glyphs are upside down!
@ -2436,18 +2506,22 @@ Enter in:
35E:CA EA EA 10
```
Hmm, some of those glyphs are badly designed (inconsistent.) :-/ That's the biggest problem amateur artists have; they haven't yet internalized a "consistent style" -- their's is all over the place. This comes with experience of knowing:
Let's try that again:
```
1080G
```
OK, that's much better.
![Screenshot ASCII Table Font BB Upside Down](pics/ascii_table_3_fontbb.png?raw=true)
Hmmm, some of those glyphs are badly designed (inconsistent.) :-/ That's the biggest problem amateur artists have; they haven't yet internalized a "consistent style" -- their's is all over the place. This comes with experience of knowing:
* When to follow the "rules", and
* When to bend/break the "rules".
Let's write a program to view all the ASCII characters.
```Assembly
ORG $1050
; <<Forthcoming!>>
```
Here is a table of all the glyphs that we'll eventually fix:
|Glyph|