Atlas - VGA.md
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VGA Subsystem
PhotonX Graphics SDK — VGA driver interface for 8086/8088 systems.
Overview
The VGA subsystem exposes two distinct APIs depending on the active video mode:
a text-mode API for 80x25 character output, and a graphics-mode API for direct
pixel rendering in mode 13h (320x200, 256 colors).


Setting mode outputs
To switch between text and graphics modes, use the vga_set_mode function with 
the appropriate mode constant:
c
vga_set_mode(VGA_MODE_TEXT_80x25); // Switch to text mode
vga_set_mode(VGA_MODE_320x200x256); // Switch to graphics mode
WARNING: It is always important to reset the screen mode back to text mode
before returning the user to the MS-DOS environment, otherwise they will be left
almost like a broken state and could lead to unexpected behavior - It is also
noted that on MS-DOS the cls command does not reset the screen mode. For simple
way to reset the screen mode you should call these functions:
c
vga_set_mode(VGA_MODE_TEXT_80x25); // Reset to text mode
vga_text_setcolor(7, 0); // Set default white on black text color
vga_text_cls(); // Clear the screen
Text Mode
In text mode, you get a character grid of 80 columns and 25 rows and 16 colors.
Color palette
The VGA text mode supports a fixed palette of 16 colors, indexed from 0 to 15:

  
Index
Color name
Color HTML
  
0
Black
#000000
  
1
Blue
#0000AA
  
2
Green
#00AA00
  
3
Cyan
#00AAAA
  
4
Red
#AA0000
  
5
Magenta
#AA00AA
  
6
Brown
#AA5500
  
7
Light Gray
#AAAAAA
  
8
Dark Gray
#555555
  
9
Light Blue
#5555FF
  
10
Light Green
#55FF55
  
11
Light Cyan
#55FFFF
  
12
Light Red
#FF5555
  
13
Light Magenta
#FF55FF
  
14
Yellow
#FFFF55
  
15
White
#FFFFFF

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