Drawing

The clip rectangle, pixels, lines, rectangles, circles and sprite blits, drawn into the 4 bpp framebuffer. More...

Functions
void	gfx_setClip (int x, int y, int w, int h)
	Sets the clip rectangle every drawing call stays inside.
void	gfx_resetClip (void)
	Puts the clip rectangle back to the whole screen.
void	gfx_getClip (int *x, int *y, int *w, int *h)
	Reads the clip rectangle, as intersected with the screen.
void	gfx_clear (uint8_t c)
	Fills the clip rectangle (normally the whole screen) with one colour.
void	gfx_pixel (int x, int y, uint8_t c)
	Sets one pixel.
uint8_t	gfx_getPixel (int x, int y)
	Reads one pixel of the framebuffer (the clip is ignored).
void	gfx_hline (int x, int y, int w, uint8_t c)
	Draws a horizontal line from (x, y), w pixels to the right.
void	gfx_vline (int x, int y, int h, uint8_t c)
	Draws a vertical line from (x, y), h pixels down.
void	gfx_fillRect (int x, int y, int w, int h, uint8_t c)
	Fills a rectangle.
void	gfx_rect (int x, int y, int w, int h, uint8_t c)
	Draws a rectangle's 1-pixel outline.
void	gfx_line (int x0, int y0, int x1, int y1, uint8_t c)
	Draws a line between two points, both ends included.
void	gfx_circle (int cx, int cy, int r, uint8_t c)
	Draws a circle's 1-pixel outline, 2*r+1 pixels across.
void	gfx_fillCircle (int cx, int cy, int r, uint8_t c)
	Draws a filled circle, 2*r+1 pixels across.
void	gfx_blit (const uint8_t *spr, int x, int y, int w, int h, int transparent)
	Copies a 4 bpp bitmap into the framebuffer, optionally with one colour transparent.

Variables
uint8_t	gfx_fb [GFX_FB_BYTES]
	The framebuffer: GFX_FB_BYTES of 4 bpp pixels, two per byte.

Detailed Description

The clip rectangle, pixels, lines, rectangles, circles and sprite blits, drawn into the 4 bpp framebuffer.

Every colour is a palette index, 0..15 (only the low 4 bits are used). Every call is clipped to the clip rectangle, and nothing reaches the panel until a flush. Draw only after gfx_wait() (or gfx_waitRow() for the rows you touch).

The clip rectangle. Every call that paints pixels - fills, lines, shapes, text, sprites, gfx_clear() - stays inside it. It is intersected with the screen; an empty one (w or h <= 0) stops all drawing. Defaults to the whole screen. gfx_getPixel(), gfx_scroll() and the flush ignore it. Changing it costs nothing, so set it around a panel or a HUD and put it back:

gfx_setClip(0, 10, 128, 118);   drawBoard();   gfx_resetClip();

Function Documentation

gfx_setClip()

void gfx_setClip	(	int	x,
		int	y,
		int	w,
		int	h
	)

Sets the clip rectangle every drawing call stays inside.

Parameters

x	Left edge, in pixels.
y	Top edge, in pixels.
w	Width; 0 or less stops all drawing.
h	Height; 0 or less stops all drawing.

gfx_resetClip()

void gfx_resetClip

(

void

)

Puts the clip rectangle back to the whole screen.

gfx_getClip()

void gfx_getClip	(	int *	x,
		int *	y,
		int *	w,
		int *	h
	)

Reads the clip rectangle, as intersected with the screen.

Parameters

[out]	x	Left edge (may be nullptr).
[out]	y	Top edge (may be nullptr).
[out]	w	Width (may be nullptr).
[out]	h	Height (may be nullptr).

gfx_clear()

void gfx_clear

(

uint8_t

c

)

Fills the clip rectangle (normally the whole screen) with one colour.

The whole screen is one word store per 8 pixels, from SRAM.

Parameters

c	Palette index.

gfx_pixel()

void gfx_pixel	(	int	x,
		int	y,
		uint8_t	c
	)

Sets one pixel.

Parameters

x	Column.
y	Row.
c	Palette index.

gfx_getPixel()

uint8_t gfx_getPixel	(	int	x,
		int	y
	)

Reads one pixel of the framebuffer (the clip is ignored).

Parameters

x	Column.
y	Row.

Returns

The palette index there, or 0 off the screen.

gfx_hline()

void gfx_hline	(	int	x,
		int	y,
		int	w,
		uint8_t	c
	)

Draws a horizontal line from (x, y), w pixels to the right.

Parameters

x	Left end.
y	Row.
w	Length in pixels; 0 or less draws nothing.
c	Palette index.

gfx_vline()

void gfx_vline	(	int	x,
		int	y,
		int	h,
		uint8_t	c
	)

Draws a vertical line from (x, y), h pixels down.

Parameters

x	Column.
y	Top end.
h	Length in pixels; 0 or less draws nothing.
c	Palette index.

gfx_fillRect()

void gfx_fillRect	(	int	x,
		int	y,
		int	w,
		int	h,
		uint8_t	c
	)

Fills a rectangle.

Parameters

x	Left edge.
y	Top edge.
w	Width; 0 or less draws nothing.
h	Height; 0 or less draws nothing.
c	Palette index.

gfx_rect()

void gfx_rect	(	int	x,
		int	y,
		int	w,
		int	h,
		uint8_t	c
	)

Draws a rectangle's 1-pixel outline.

Parameters

x	Left edge.
y	Top edge.
w	Width; 0 or less draws nothing.
h	Height; 0 or less draws nothing.
c	Palette index.

gfx_line()

void gfx_line	(	int	x0,
		int	y0,
		int	x1,
		int	y1,
		uint8_t	c
	)

Draws a line between two points, both ends included.

Parameters

x0	Start column.
y0	Start row.
x1	End column.
y1	End row.
c	Palette index.

gfx_circle()

void gfx_circle	(	int	cx,
		int	cy,
		int	r,
		uint8_t	c
	)

Draws a circle's 1-pixel outline, 2*r+1 pixels across.

Parameters

cx	Centre column.
cy	Centre row.
r	Radius in pixels.
c	Palette index.

gfx_fillCircle()

void gfx_fillCircle	(	int	cx,
		int	cy,
		int	r,
		uint8_t	c
	)

Draws a filled circle, 2*r+1 pixels across.

Parameters

cx	Centre column.
cy	Centre row.
r	Radius in pixels.
c	Palette index.

gfx_blit()

void gfx_blit	(	const uint8_t *	spr,
		int	x,
		int	y,
		int	w,
		int	h,
		int	transparent
	)

Copies a 4 bpp bitmap into the framebuffer, optionally with one colour transparent.

Source rows are packed the same way as the framebuffer (2 px/byte, even x low nibble), each row padded to a whole byte. The opaque even-x case runs at memcpy speed. For art with many runs of one colour, the compact span sprites are smaller.

Parameters

spr	The bitmap, (w + 1) / 2 bytes a row.
x	Left edge on screen.
y	Top edge on screen.
w	Width in pixels.
h	Height in pixels.
transparent	Colour index skipped, or -1 for an opaque copy.

Variable Documentation

gfx_fb

uint8_t gfx_fb[GFX_FB_BYTES]

extern

The framebuffer: GFX_FB_BYTES of 4 bpp pixels, two per byte.

Row y starts at gfx_fb + y * GFX_FB_STRIDE. Even x is in the LOW nibble, odd x in the HIGH nibble - that ordering makes the expansion LUT a single uint32 store with no shuffling on a little-endian core. Each nibble is a palette index. Write it directly only for primitives of your own, and only when no flush is reading it (after gfx_wait()).