4bpp tiled surfaces, column major
[Surface functions]

Functions
u32	schr4c_get_pixel (const TSurface *src, int x, int y)
	Get the pixel value of src at (x, y).
void	schr4c_plot (const TSurface *dst, int x, int y, u32 clr)
	Plot a single pixel on a 4bpp tiled surface.
void	schr4c_hline (const TSurface *dst, int x1, int y, int x2, u32 clr)
	Draw a horizontal line on a 4bpp tiled surface.
void	schr4c_vline (const TSurface *dst, int x, int y1, int y2, u32 clr)
	Draw a vertical line on a 4bpp tiled surface.
void	schr4c_line (const TSurface *dst, int x1, int y1, int x2, int y2, u32 clr)
	Draw a line on a 4bpp tiled surface.
void	schr4c_rect (const TSurface *dst, int left, int top, int right, int bottom, u32 clr)
	Render a rectangle on a 4bpp tiled canvas.
void	schr4c_frame (const TSurface *dst, int left, int top, int right, int bottom, u32 clr)
	Draw a rectangle on a 4bpp tiled surface.
void	schr4c_blit (const TSurface *dst, int dstX, int dstY, uint width, uint height, const TSurface *src, int srcX, int srcY)
	Blitter for 4bpp tiled surfaces. Copies a rectangle from one surface to another.
void	schr4c_floodfill (const TSurface *dst, int x, int y, u32 clr)
	Floodfill an area of the same color with new color clr.
void	schr4c_prep_map (const TSurface *srf, u16 *map, u16 se0)
	Prepare a screen-entry map for use with chr4.
u32 *	schr4c_get_ptr (const TSurface *srf, int x, int y)
	Special pointer getter for chr4: start of in-tile line.
INLINE void	_schr4c_plot (const TSurface *dst, int x, int y, u32 clr)
	Plot a single pixel on a 4bpp tiled,col-jamor surface; inline version.
INLINE u32	_schr4c_get_pixel (const TSurface *src, int x, int y)
	Get the pixel value of src at (x, y); inline version.

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Detailed Description

A (4bpp) tiled surface is formed when each tilemap entry references a unique tile (this is done by schr4c_prep_map()). The pixels on the tiles will then uniquely map onto pixels on the screen.

There are two ways of map-layout here: row-major indexing and column-major indexing. The difference if is that tile 1 is to the right of tile 0 in the former, but under it in the latter.

30x20t screen:
  Row-major:
     0  1  2  3 ...
    30 31 32 33 ...
    60 61 62 63 ...

  Column-major:
     0 20 40 60 ...
     1 21 41 61 ...
     2 22 41 62 ...

With 4bpp tiles, the column-major version makes the y coordinate match up nicely with successive words. For this reason, column-major is preferred over row-major.

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Function Documentation

void schr4c_blit	(	const TSurface *	dst,
		int	dstX,
		int	dstY,
		uint	width,
		uint	height,
		const TSurface *	src,
		int	srcX,
		int	srcY
	)

Blitter for 4bpp tiled surfaces. Copies a rectangle from one surface to another.

Parameters:

	dst	Destination surface.
	dstX	Left coord of rectangle on dst.
	dstY	Top coord of rectangle on dst.
	width	Width of rectangle to blit.
	height	Height of rectangle to blit.
	src	Source surface.
	srcX	Left coord of rectangle on src.
	srcY	Top coord of rectangle on src.

Note:

The rectangle will be clipped to both src and dst.

void schr4c_floodfill	(	const TSurface *	dst,
		int	x,
		int	y,
		u32	clr
	)

Floodfill an area of the same color with new color clr.

Parameters:

	dst	Destination surface.
	x	X-coordinate.
	y	Y-coordinate;
	clr	Color.

Note:

This routines is probably very, very slow.

void schr4c_frame	(	const TSurface *	dst,
		int	left,
		int	top,
		int	right,
		int	bottom,
		u32	clr
	)

Draw a rectangle on a 4bpp tiled surface.

Parameters:

	dst	Destination surface.
	left	Left side of rectangle;
	top	Top side of rectangle.
	right	Right side of rectangle.
	bottom	Bottom side of rectangle.
	clr	Color.

Note:

Does normalization, but not bounds checks.

PONDER: RB in- or exclusive?

u32 schr4c_get_pixel	(	const TSurface *	src,
		int	x,
		int	y
	)

Get the pixel value of src at (x, y).

void schr4c_hline	(	const TSurface *	dst,
		int	x1,
		int	y,
		int	x2,
		u32	clr
	)

Draw a horizontal line on a 4bpp tiled surface.

Parameters:

	dst	Destination surface.
	x1	First X-coord.
	y	Y-coord.
	x2	Second X-coord.
	clr	Color.

Note:

Does normalization, but not bounds checks.

void schr4c_line	(	const TSurface *	dst,
		int	x1,
		int	y1,
		int	x2,
		int	y2,
		u32	clr
	)

Draw a line on a 4bpp tiled surface.

Parameters:

	dst	Destination surface.
	x1	First X-coord.
	y1	First Y-coord.
	x2	Second X-coord.
	y2	Second Y-coord.
	clr	Color.

Note:

Does normalization, but not bounds checks.

void schr4c_plot	(	const TSurface *	dst,
		int	x,
		int	y,
		u32	clr
	)

Plot a single pixel on a 4bpp tiled surface.

Parameters:

	dst	Destination surface.
	x	X-coord.
	y	Y-coord.
	clr	Color.

Note:

Fairly slow. Inline plotting functionality if possible.

void schr4c_prep_map	(	const TSurface *	srf,
		u16 *	map,
		u16	se0
	)

Prepare a screen-entry map for use with chr4.

Parameters:

	srf	Surface with size information.
	map	Screen-blocked map to initialize.
	se0	Additive base screen-entry.

void schr4c_rect	(	const TSurface *	dst,
		int	left,
		int	top,
		int	right,
		int	bottom,
		u32	clr
	)

Render a rectangle on a 4bpp tiled canvas.

Parameters:

	dst	Destination surface.
	left	Left side of rectangle;
	top	Top side of rectangle.
	right	Right side of rectangle.
	bottom	Bottom side of rectangle.
	clr	Color-index.

void schr4c_vline	(	const TSurface *	dst,
		int	x,
		int	y1,
		int	y2,
		u32	clr
	)

Draw a vertical line on a 4bpp tiled surface.

Parameters:

	dst	Destination surface.
	x	X-coord.
	y1	First Y-coord.
	y2	Second Y-coord.
	clr	Color.

Note:

Does normalization, but not bounds checks.

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