Generic Types

Unit: GenTypes

Generic pointer, array, and alignment types used across the engine.

Pointer Types

type
  PByte = ^Byte;
  PWord = ^Word;
  PShortString = ^string;

Generic pointer types for type-safe pointer arithmetic and memory access.

Array Types

type
  TByteArray = array[0..65520] of Byte;
  PByteArray = ^TByteArray;

  TWordArray = array[0..32000] of Word;
  PWordArray = ^TWordArray;

Purpose: Large array types for pointer-based memory access.

Sizes:

TByteArray: 65,520 bytes (64KB - 16 bytes)
TWordArray: 32,000 words (64,000 bytes)

Use cases:

Direct memory access
XMS transfers
DMA buffers
Large data structures

Alignment Types

type
  TAlign = Byte;

const
  { Horizontal alignment }
  Align_Left   = 1;
  Align_Center = 2;
  Align_Right  = 4;

  { Vertical alignment }
  Align_Top    = 8;
  Align_Middle = 16;
  Align_Bottom = 32;

Purpose: Text and UI element alignment flags.

Bit flags: Can be combined using or operator for 2D positioning:

Align_Left or Align_Top - Top-left corner
Align_Center or Align_Middle - Centered both ways
Align_Right or Align_Bottom - Bottom-right corner

Usage in engine:

VGAFONT: PrintFontText, PrintFontTextColored (horizontal only)
VGAUI: Widget alignment and text rendering (future 2D support)

Horizontal Alignment

Align_Left (1):

X coordinate specifies left edge of content
Text starts at X position
Most common default alignment

Align_Center (2):

X coordinate specifies center of content
Text centered horizontally around X
Common for titles, centered UI elements

Align_Right (4):

X coordinate specifies right edge of content
Text ends at X position
Common for right-aligned scores, values

Vertical Alignment

Align_Top (8):

Y coordinate specifies top edge of content
Content aligned to top
Most common default alignment

Align_Middle (16):

Y coordinate specifies vertical center of content
Content centered vertically around Y
Common for vertically centered dialogs

Align_Bottom (32):

Y coordinate specifies bottom edge of content
Content aligned to bottom
Common for footer elements

Checking Alignment

{ Check if alignment includes horizontal centering }
if (Align and Align_Center) <> 0 then
  X := X - (Width div 2);

{ Check if alignment includes right alignment }
if (Align and Align_Right) <> 0 then
  X := X - Width;

{ Check if alignment includes vertical middle }
if (Align and Align_Middle) <> 0 then
  Y := Y - (Height div 2);

Pattern: Use bitwise and to test if a specific alignment flag is set.

Usage Examples

Memory Access

var
  Buf: PByteArray;
  W: PWord;
begin
  GetMem(Buf, 1024);

  { Direct byte access }
  Buf^[0] := $FF;
  Buf^[1] := $00;

  { Word access via pointer }
  W := @Buf^[100];
  W^ := $1234;

  FreeMem(Buf, 1024);
end;

Text Alignment

uses VGAFont, GenTypes;

var
  Font: TFont;
  BackBuffer: PFrameBuffer;
begin
  { Left-aligned text }
  PrintFontText(10, 50, 'Score: 1000', Align_Left, Font, BackBuffer);

  { Centered title }
  PrintFontText(160, 10, 'GAME TITLE', Align_Center, Font, BackBuffer);

  { Right-aligned value }
  PrintFontText(310, 50, '9999', Align_Right, Font, BackBuffer);
end;

Combined Alignment (Future)

{ Example of 2D alignment (when supported by widget system) }
const
  TopLeft = Align_Left or Align_Top;
  Centered = Align_Center or Align_Middle;
  BottomRight = Align_Right or Align_Bottom;

{ Position widget at bottom-right corner }
Widget.SetAlignment(BottomRight);

Notes

Array limits: TByteArray max 65,520 bytes, TWordArray max 32,000 words (both fit in 64KB segment)
Alignment flags: Use bitwise operations (and, or) to combine and test flags
Horizontal only: Currently, most engine functions only use horizontal alignment (Left/Center/Right)
Bit flag pattern: Powers of 2 allow combining multiple flags without conflicts
Memory safety: Always ensure array indices stay within bounds (0..65520 for bytes, 0..32000 for words)