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Removed duplicated end section, added another text address table, and Javascript formula for the text y address

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michaelangel007 2020-08-20 06:29:41 -07:00
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@ -1,7 +1,7 @@
#Apple ]\[ //e HGR Font 6502 Assembly Language Tutorial
By: Michael Pohoreski
Revision: 71, Mar 27, 2016.
Revision: 72, Aug 20, 2020.
# Table of Contents
@ -2062,6 +2062,19 @@ For our final trick we are going to copy the characters off the text screen onto
The text screen, like the HGR screen, is also non-linear, and also broken up into a triad:
|First |Middle |Last |Screen Hole|
|:-----------------|:-----------------|:-----------------|:----------|
|$400.. y= 0 ..$427|$428.. y= 8 ..$44F|$450.. y=16 ..$477|$478..$47F |
|$480.. y= 1 ..$4A7|$428.. y= 9 ..$44F|$4D0.. y=17 ..$4F7|$4F8..$4FF |
|$500.. y= 2 ..$527|$528.. y=10 ..$54F|$550.. y=18 ..$577|$578..$57F |
|$580.. y= 3 ..$5A7|$528.. y=11 ..$54F|$5D0.. y=19 ..$5F7|$5F8..$5FF |
|$600.. y= 4 ..$627|$628.. y=12 ..$64F|$650.. y=20 ..$677|$678..$67F |
|$680.. y= 5 ..$6A7|$628.. y=13 ..$64F|$6D0.. y=21 ..$6F7|$678..$6FF |
|$700.. y= 6 ..$727|$728.. y=14 ..$74F|$750.. y=22 ..$777|$778..$77F |
|$780.. y= 7 ..$7A7|$728.. y=15 ..$74F|$7D0.. y=23 ..$7F7|$7F8..$7FF |
Sorting by row:
|Row| Text Address | Screen Hole |
|--:|:------------:|:------------:|
| 0 | $400 .. $427 | n/a |
@ -2091,6 +2104,13 @@ The text screen, like the HGR screen, is also non-linear, and also broken up int
|22 | $750 .. $777 | $778 .. $77F |
|23 | $7D0 .. $7F7 | $7F8 .. $7FF |
Here is a 1-liner Javascript code to print off the y and text address:
```
var base = 0x400; for( var y = 0; y < 24; y++ ) console.log( y + " = $" + (base + (y%8)*128 + Math.floor(y/8)*40).toString(16) );
```
Analyzing both the Text and HGR addresses:
|Row|Text Address|HGR Address|HGR Scanline|
@ -2976,45 +2996,6 @@ Michael "AppleWin Debug Dev"
Figure it out ! You have all the tools and knowledge.
Seriously though, start with the data flow. Let's look at the HGR "text" lines we need to copy from/to:
Src Dst
1 0
2 1
3 2
4 3
5 4
6 5
7 6
8 7
# What's next?
What's left? Quite a few things actually:
* Copy the 80-Column text screen to DHGR (Double High Resolution)
* Hook into the COUT so all text appears onto the HGR or DHGR screen
* Other 7x8 fonts
* Other non-7x8 fonts
# Conclusion
Hope this HGR font tutorial helped you understand the inner workings of a font blitter!
Happy (Apple ]\[ //e //c) Hacking!
Michael "AppleWin Debug Dev"
# Solutions
## Solution 1: ScrollHgrUpLine()
Figure it out ! You have all the tools and knowledge.
Seriously though, start with the data flow. Let's look at the HGR "text" lines we need to copy from/to:
Src Dst