main.c File Reference

Multi-window HDMA — both windows' edges driven per scanline. More...

#include <snes.h>

Macros
#define	VRAM_GFX   0x4000
#define	VRAM_MAP   0x0000
	krom's VRAM layout: map at word $0000, tiles at word $4000

Functions
int	main (void)

Variables
u8	rings_map []
u8	rings_map_end []
u8	rings_pal []
u8	rings_pal_end []
u8	rings_pic []
	256-color ring artwork (original, procedural)
u8	rings_pic_end []
static const u8	window_table []
	krom's exact HDMA window table: 16-line bands alternating "both windows empty" (edges 1..0 = degenerate = fully masked = green) and "two portholes" (W1 16-112, W2 144-240). 5-byte entries: [count][W1L][W1R][W2L][W2R], terminator 0.

Detailed Description

Multi-window HDMA — both windows' edges driven per scanline.

Port of krom (Peter Lemon)'s WindowMultiHDMA demo (PeterLemon/SNES, PPU/Window/WindowMultiHDMA). One HDMA channel in 4-register mode streams WH0-WH3 ($2126-$2129) — BOTH windows' left/right edges — every scanline band, cutting a grid of portholes into BG1. The green backdrop (CGRAM color 0) shows wherever the combined window mask disables the layer; the D-pad scrolls the artwork underneath the static mask.

Window algebra (krom's exact setup): W1 and W2 both enabled on BG1 and both INVERTED, combined with AND — the layer is masked where (outside W1) AND (outside W2), i.e. visible inside either window.

SNES Concepts

• HDMA_MODE_4REG: one channel drives 4 consecutive PPU registers/line
• Two windows animated per scanline (hdmaWindowShape covers only one)
• W12SEL / WBGLOG / TMW via windowEnable/windowSetInvert/ windowSetLogic/windowSetMainMask
• Backdrop color as the "outside the windows" fill

What to Observe

A grid of rectangular portholes over a color-ring artwork; green everywhere else. D-pad scrolls the rings behind the fixed portholes.

Modules Used

console, dma, background, hdma, window, input

See also

https://github.com/PeterLemon/SNES — original demo

window.h, hdma.h (HDMA_MODE_4REG)

Macro Definition Documentation

VRAM_GFX

#define VRAM_GFX   0x4000

VRAM_MAP

#define VRAM_MAP   0x0000

krom's VRAM layout: map at word $0000, tiles at word $4000

Function Documentation

main()

int main

(

void

)

Variable Documentation

rings_map

u8 rings_map[]

extern

rings_map_end

u8 rings_map_end[]

rings_pal

u8 rings_pal[]

extern

rings_pal_end

u8 rings_pal_end[]

rings_pic

u8 rings_pic[]

extern

256-color ring artwork (original, procedural)

rings_pic_end

u8 rings_pic_end[]

window_table

const u8 window_table[]

static

Initial value:

                             = {
    16,   1,   0,   1,   0,
    16,  16, 112, 144, 240,
    16,  16, 112, 144, 240,
    16,  16, 112, 144, 240,
    16,  16, 112, 144, 240,
    16,  16, 112, 144, 240,
    16,   1,   0,   1,   0,
    16,   1,   0,   1,   0,
    16,  16, 112, 144, 240,
    16,  16, 112, 144, 240,
    16,  16, 112, 144, 240,
    16,  16, 112, 144, 240,
    16,  16, 112, 144, 240,
    16,   1,   0,   1,   0,
    0,
}

krom's exact HDMA window table: 16-line bands alternating "both windows empty" (edges 1..0 = degenerate = fully masked = green) and "two portholes" (W1 16-112, W2 144-240). 5-byte entries: [count][W1L][W1R][W2L][W2R], terminator 0.