Fifth - virtual machine opcodes 40 – 47

Stack Footprint

addr --

Copies memory from the specified address to the video memory (VGA or VESA mode). Used for displaying images directly on the screen.

Parameters:

• addr (32-bit): Source memory address containing the image data to copy to video memory.

0x10000
vidmap

Stack Footprint:

-- dx dy buttons

Description:

Reads mouse motion and button states from the DOS mouse driver (int 33h). Returns three values on the stack:

• horizontal motion delta,
• vertical motion delta,
• button states.

• Returns:
  • dx (32-bit): Horizontal motion since the last call, in mickeys (signed; negative = moved left).
  • dy (32-bit): Vertical motion since the last call, in mickeys (signed; negative = moved up).
  • buttons (32-bit): Bitmask of button states:
    • Bit 0: Left button (1 = pressed)
    • Bit 1: Right button (1 = pressed)
    • Bit 2: Middle button (1 = pressed)

Note: the values are motion DELTAS (read via mouse function 0Bh), not absolute cursor coordinates. Accumulate them to track a cursor position.

Example:

mouse@

After execution, stack contains buttons (top), dy, dx (bottom).

Stack Footprint:

addr1 addr2 x y --

Copies a portion of image1 to image2 at the specified (x, y) coordinates with clipping. Unlike tvidput, there is no transparency support - every pixel is copied regardless of value.

Parameters:

• addr1 (32-bit): Address of the source image structure (width, height, inline pixel data).
• addr2 (32-bit): Address of the destination image structure (width, height, inline pixel data).
• x (32-bit): X-coordinate in the destination image where the copy starts.
• y (32-bit): Y-coordinate in the destination image where the copy starts.

Image Structure Format:

Identical to tvidput:

• Offset 0: Image width (32-bit)
• Offset 4: Image height (32-bit)
• Offset 8: Pixel data, stored INLINE — one byte per pixel, row-major, starting immediately after the 8-byte header (this is NOT a pointer)

Example:

0x1000  ; Source image structure
0x2000  ; Destination image structure
50      ; x
50      ; y
vidput

• Stack Effect:

addr1 addr2 len --

Copies len bytes from addr1 to addr2. Handles overlapping memory regions correctly.

• Notes: Copy direction is chosen for overlap safety: if addr1 > addr2 (source above destination) it copies FORWARDS; otherwise it copies BACKWARDS.

• Example:

  0x1000  ; Source address
  0x2000  ; Destination address
  100  ; Length
  cmove
  

• Stack Effect: byte addr len --
• Description: Fills len bytes of memory starting at addr with the specified byte value.
• Notes: Simple byte-by-byte filling operation. Used for initializing memory regions.

• Example:

  0xFF  ; Fill byte
  0x1000  ; Start address
  100  ; Length
  cfill
  

Stack Footprint:

addr1 addr2 x y --

Copies a portion of image1 to image2 at the specified (x, y) coordinates with transparency support. Pixels in image1 with value 255 (0xFF) are treated as transparent and are not copied to the destination.

Parameters:

• addr1 (32-bit): Address of the source image structure (contains width, height, and inline pixel data).
• addr2 (32-bit): Address of the destination image structure (contains width, height, and inline pixel data).
• x (32-bit): X-coordinate in the destination image where the copy starts.
• y (32-bit): Y-coordinate in the destination image where the copy starts.

Image Structure Format:

Each image structure is stored in memory as follows:

• Offset 0: Image width (32-bit integer)
• Offset 4: Image height (32-bit integer)
• Offset 8: Pixel data, stored INLINE — one byte per pixel, row-major, starting immediately after the 8-byte header (this is NOT a pointer)

Example:

0x1000  ; Source image structure
0x2000  ; Destination image structure
50      ; x
50      ; y
tvidput

Notes:

• Transparency is fixed at value 255 (0xFF).
• The operation handles clipping automatically to ensure the copy stays within destination bounds.
• Source and destination image structures must be properly formatted.

• Stack Effect: -- depth
• Description: Pushes the current depth (number of items) on the data stack onto the stack.
• Notes: Calculated by comparing the data stack pointer to the base address of the stack.

• Example:

  1 2 3
  depth
  

  After execution, stack contains 3 (depth) followed by 1 2 3.

Stack Footprint: colorfg colorbg addrsrc addrdest x y --

Draws an 8x8 character from a source memory buffer to a destination image buffer at the specified (x, y) coordinates. Each byte in the source buffer represents one row of the character (8 bits per row), where each bit determines whether to use the foreground or background color for that pixel. Bit 7 (the MSB) of each byte is the leftmost pixel of the row; glyphs are fixed at 8x8 pixels.

Parameters:

• colorfg (1 byte): Foreground color value (0-255). Typically a grayscale value where 0 is black and 255 is white.
• colorbg (1 byte): Background color value (0-255).
• addrsrc (32-bit): Memory address pointing to 8 bytes of character data. Each byte represents one row of the character (8 bits per row).
• addrdest (32-bit): Address of the destination image STRUCTURE — i.e. width/height header followed by inline pixel data, as used by vidput. NOT a raw framebuffer address: the width field is read as the row stride.
• x (32-bit): X-coordinate (0-based) where the character's left edge starts.
• y (32-bit): Y-coordinate (0-based) where the character's top edge starts.

Example:

0xFF  ; White foreground
0x00  ; Black background
0x3000  ; Character data address
0x5000  ; Destination image structure
10      ; x
20      ; y
charput

Character data for 'A' (ASCII 65):

0x00, 0x18, 0x24, 0x24, 0x24, 0x3C, 0x24, 0x24

• Each byte represents a row:
  • Row 0: 0x00 → all pixels black
  • Row 1: 0x18 → bits 3-4 set (binary 00011000)
  • Row 2: 0x24 → bits 2 and 5 set (binary 00100100)
  • Row 3: 0x24 → same as row 2
  • Row 4: 0x24 → same as row 2
  • Row 5: 0x3C → bits 2-5 set (binary 00111100)
  • Row 6: 0x24 → same as row 2
  • Row 7: 0x24 → same as row 2