vxKernel/src/modules/display/draw/dline.c

#include <vhex/display/draw/line.h>
#include <vhex/display/draw/pixel.h>
#include <vhex/display.h>
#include <vhex/defs/utils.h>

//---
// kernel-level API
//---

/* dline(): Bresenham line drawing algorithm
   Remotely adapted from MonochromeLib code by Pierre "PerriotLL" Le Gall.
   Relies on platform-dependent dhline() and dvline() for optimized situations.
   @x1 @y1 @x2 @y2  Coordinates of endpoints of line (included)
   @color           Any color accepted by dpixel() on the platform */
void dline_render(dsurface_t *s, int x1, int y1, int x2, int y2, int color)
{
	int i;
	int x = x1;
	int y = y1;
	int cumul;
	int dx = x2 - x1;
	int dy = y2 - y1;
	int sx = sgn(dx);
	int sy = sgn(dy);

	dx = (dx >= 0 ? dx : -dx);
	dy = (dy >= 0 ? dy : -dy);

	dpixel_render(s, x1, y1, color);

	if(dx >= dy) {
		/* Start with a non-zero cumul to even the overdue between the
		   two ends of the line (for more regularity) */
		cumul = dx >> 1;
		for(i = 1; i < dx; i++)
		{
			x += sx;
			cumul += dy;
			if(cumul > dx) {
				cumul -= dx;
				y += sy;
			}
			dpixel_render(s, x, y, color);
		}
	} else {
		cumul = dy >> 1;
		for(i = 1; i < dy; i++)
		{
			y += sy;
			cumul += dx;
			if(cumul > dy) {
				cumul -= dy;
				x += sx;
			}
			dpixel_render(s, x, y, color);
		}
	}

	dpixel_render(s, x2, y2, color);
}

/* dhline_render() : optimized horizontal line */
void dhline_render(dsurface_t *surface, int y, int x1, int x2, int color)
{
	/* Order and bounds */
	if(y  < surface->y1 || y  > surface->y2) return;
	if(x1 > surface->x2 || x2 < surface->x1) return;
	if(x1 > x2) swap(x1, x2);
	if(x1 < surface->x1) x1 = surface->x1;
	if(x2 > surface->x2) x2 = surface->x2;
	y  -= surface->y1;
	x1 -= surface->x1;
	x2 -= surface->x1;

	int offset = surface->width * y;

	/* Use longwords to do the copy, but first paint the endpoints to heed
	   for odd x1 and x2. Checking the parity may be a waste of time. */
	uint16_t *vram = surface->vram;
	if (color != C_INVERT) {
		vram[offset + x1] = color;
		vram[offset + x2] = color;
	} else {
		vram[offset + x1] ^= 0xffff;
		vram[offset + x2] ^= 0xffff;
	}

	/* Now round to longword boundaries and copy everything in-between with
	   longwords */
	x1 = x1 + (x1 & 1);
	x2 = (x2 + 1) & ~1;

	uint32_t *start = (void *)(vram + offset + x1);
	uint32_t *end   = (void *)(vram + offset + x2);
	if (color != C_INVERT) {
		uint32_t op = (color << 16) | color;
		while(end > start) {
			*--end = op;
		}
	} else {
		while(end > start) {
			*--end ^= 0xffff;
		}
	}
}

/* dvline_render() : optimized drawing function for vertical line */
void dvline_render(dsurface_t *surface, int x, int y1, int y2, int color)
{
	/* Order and bounds */
	if(x < surface->x1 || x > surface->x2)   return;
	if(y1 > surface->y2 || y2 < surface->y1) return;
	if(y1 > y2) swap(y1, y2);
	if(y1 < surface->y1) y1 = surface->y1;
	if(y2 > surface->y2) y2 = surface->y2;
	x  -= surface->x1;
	y1 -= surface->y1;
	y2 -= surface->y1;

	uint16_t *vram = surface->vram;
	uint16_t *v = &vram[(surface->width * y1) + x];
	int height = y2 - y1;

	if (color != C_INVERT) {
		while(height-- >= 0) {
			*v = color;
			v += surface->width;
		}
	} else {
		while(height-- >= 0) {
			*v ^= 0xffff;
			v += surface->width;
		}
	}
}

//---
// Dstack-level API
//---

/* dline_dstack() : dstack wrapper line primitive */
void dline_dstack(dsurface_t *surface, uint32_t *args)
{
	dline_render(
		surface,
		(int)args[0],
		(int)args[1],
		(int)args[2],
		(int)args[3],
		(int)args[4]
	);
}

/* dhline_dstack() : dstack wrapper horizontal line primitive */
void dhline_dstack(dsurface_t *surface, uint32_t *args)
{
	dhline_render(
		surface,
		(int)args[0],
		(int)args[1],
		(int)args[2],
		(int)args[3]
	);
}

/* dvline_dstack() : dstack wrapper vertical line primitive */
void dvline_dstack(dsurface_t *surface, uint32_t *args)
{
	dvline_render(
		surface,
		(int)args[0],
		(int)args[1],
		(int)args[2],
		(int)args[3]
	);
}

//---
// User-level API
//---

/* dline(): Render a straight line */
void dline(int x1, int y1, int x2, int y2, int color)
{
	if(color == C_NONE) return;

	/* Possible optimizations */
	if(y1 == y2)
	{
		dstack_add_action(
			&DSTACK_CALL(&dhline_dstack, y1, x1, x2, color),
			NULL,
			NULL
		);
		return;
	}
	if(x1 == x2)
	{
		dstack_add_action(
			&DSTACK_CALL(&dvline_dstack, x1, y1, y2, color),
			NULL,
			NULL
		);
		return;
	}
	dstack_add_action(
		&DSTACK_CALL(&dline_dstack, x1, y1, x2, y2, color),
		NULL,
		NULL
	);
}

/* dhline() : render an horizontal line */
void dhline(int y, int x1, int x2, int color)
{
	dstack_add_action(
		&DSTACK_CALL(&dhline_dstack, y, x1, x2, color),
		NULL,
		NULL
	);
}

/* dvline() : render an vertical line */
void dvline(int x, int y1, int y2, int color)
{
	dstack_add_action(
		&DSTACK_CALL(&dvline_dstack, x, y1, y2, color),
		NULL,
		NULL
	);
}