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Fix up TOC DrawChar()
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README.md
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README.md
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#Apple ]\[ HGR Font Tutorial
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#Apple ]\[ HGR Font Tutorial
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Revision: 14, Jan 10, 2016.
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Revision: 15, Jan 10, 2016.
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# Table of Contents
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# Table of Contents
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* Font Data
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* Font Data
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* Raw Font Data
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* Raw Font Data
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* Image to Font Data (Javascript)
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* Image to Font Data (Javascript)
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* Font -> Screen Memory Trace
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* DrawChar()
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* DrawChar version 1
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* Font -> Screen Memory Trace
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* DrawChar() version 1
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* X Cursor Position
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* X Cursor Position
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* CursorCol()
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* CursorCol()
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* DrawChar() version 2
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* DrawChar() version 2
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* Misc. Utilities and Files
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* Misc. Utilities and Files
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* TODO
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* TODO
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## Introduction
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# Introduction
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A lot of people in comp.sys.apple2.programmer and other places on the internet have wondered how to "print" text onto the Apple's High Resolution Graphics (HGR) screen. Here's a tutorial on "6502 Font Blitting."
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A lot of people in comp.sys.apple2.programmer and other places on the internet have wondered how to "print" text onto the Apple's High Resolution Graphics (HGR) screen. Here's a tutorial on "6502 Font Blitting."
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@ -58,7 +59,7 @@ If you use:
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There are other emulators written in Javascript but they are poor due to 2 reasons:
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There are other emulators written in Javascript but they are poor due to 2 reasons:
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* Don't support paste -- you'll be forced to manually enter in the hex code. :-/
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* Don't support paste -- you'll be forced to manually enter in the hex code. :-/ Yeah, right!
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* Don't emulate the half-pixel shift of real hardware at all.
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* Don't emulate the half-pixel shift of real hardware at all.
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@ -240,7 +241,7 @@ Here's the [Javascript source code](list_hgr_table.html) to generate this table:
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Second, each glyph in the Apple font is in a 7x8 cell -- the leading line on the bottom is usually blank but we'll store that too so that we have a true "underline" and bottom descender on 'j', 'y', etc.
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Second, each glyph in the Apple font is in a 7x8 cell -- the leading line on the bottom is usually blank but we'll store that too so that we have a true "underline" and bottom descender on 'j', 'y', etc.
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Unfortunately, the data for the TEXT ROM 25123 hardware chip is *not* accessible from the 6502. :-/ This means you will need to manually enter in the 8 bytes/character. :-( The good news is that I've already done this so you can copy / paste. :-)
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Unfortunately, the data for the TEXT ROM 25123 hardware chip is **not** accessible from the 6502. :-/ This means you will need to manually enter in the 8 bytes/character. :-( The good news is that I've already done this so you can copy / paste. :-)
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You can find a picture of the Apple ][ ROM text font on Page 8-9, diagram 8.4 of "Understanding the Apple ]\["
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You can find a picture of the Apple ][ ROM text font on Page 8-9, diagram 8.4 of "Understanding the Apple ]\["
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https://archive.org/stream/understanding_the_apple_ii#page/n203/mode/2up
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https://archive.org/stream/understanding_the_apple_ii#page/n203/mode/2up
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@ -577,6 +578,8 @@ Note: If you get a retarded `Uncaught SecurityError: Failed to execute 'getImage
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Another solution is to use a web browser that isn't "broken" such as Firefox, etc. when trying to read _local_ files.
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Another solution is to use a web browser that isn't "broken" such as Firefox, etc. when trying to read _local_ files.
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# DrawChar()
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## Font -> Screen Memory Trace
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## Font -> Screen Memory Trace
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OK, so now that we have the font data, how do we draw a character "on screen" ?
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OK, so now that we have the font data, how do we draw a character "on screen" ?
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