1 files changed, 82 insertions, 74 deletions

diff --git a/draw_linear_bezier_reference.c b/draw_linear_bezier_reference.c
index dbfb87f..b7dab11 100644
--- a/draw_linear_bezier_reference.c
+++ b/draw_linear_bezier_reference.c
@@ -14,86 +14,94 @@
  */
 
 
+static void
+draw_cell(RASTER *restrict raster, double x1, double y1, double x2, double y2, double dx, double dy,
+          double cxmin, double cxmax, double rxmin, double rxmax, double rymin, double rymax, ssize_t x, size_t cellY)
+{
+	double cy1, cy2, ydir = (double)SIGNUM(dy);
+	double rightedge, opposite, midadjacent;
+	size_t cell;
+
+	rightedge = cxmax;
+	cxmin = fmax(cxmin, rxmin);
+	cxmax = fmin(cxmax, rxmax);
+	cy1 = dx ? y1 + (cxmin - x1) * dy / dx : y1;
+	cy2 = dx ? y2 + (cxmax - x2) * dy / dx : y2;
+	cy1 = fmin(fmax(cy1, rymin), rymax);
+	cy2 = fmin(fmax(cy2, rymin), rymax);
+
+	opposite = ydir * fabs(cy2 - cy1);
+	midadjacent = (cxmin + cxmax) / 2.0;
+
+	if (x < 0) {
+		raster->cells[cellY].opposite_coverage += opposite;
+		raster->cells[cellY].cell_coverage += opposite;
+	} else if ((size_t)x >= raster->width) {
+		cell = cellY + (raster->width - 1);
+		raster->cells[cell].opposite_coverage += opposite;
+	} else {
+		cell = cellY + (size_t)x;
+		raster->cells[cell].opposite_coverage += opposite;
+		raster->cells[cell].cell_coverage += opposite * fabs(rightedge - midadjacent);
+	}
+}
+
 void
 draw_linear_bezier_reference(RASTER *restrict raster, double x1, double y1, double x2, double y2)
 {
+	ssize_t iwidth = (ssize_t)raster->width;
+	double width = (double)raster->width;
+	double height = (double)raster->height;
 	double dx = x2 - x1;
 	double dy = y2 - y1;
-	int xdir = SIGNUM(dx);
-	int ydir = SIGNUM(dy);
-	double kx = dx / dy;
-	double ky = dy / dx;
-	double prevX, prevY, x, y, cx, cy, h2x, h2y;
-	double xfloor, yfloor;
-	ssize_t cellX, cellY;
-	size_t cell;
-
-	prevX = x1;
-	prevY = y1;
-
-	for (; prevX != x2 || prevY != y2; prevX = x, prevY = y) {
-		/* Find next vertical and next hozitonal grid line */
-		x = xdir < 0 ? floor(prevX) : xdir > 0 ? ceil(prevX) : prevX;
-		y = ydir < 0 ? floor(prevY) : ydir > 0 ? ceil(prevY) : prevY;
-		x = iszeroish(x - prevX) ? x + xdir : x;
-		y = iszeroish(y - prevY) ? y + ydir : y;
-
-		/* Limit to the extend of the drawn line segment */
-		if ((xdir < 0 && x < x2) || (xdir > 0 && x > x2))
-			x = x2;
-		if ((ydir < 0 && y < y2) || (ydir > 0 && y > y2))
-			y = y2;
-
-		/* Find next cell edge */
-		if (xdir && ydir) {
-			cy = y1 + (x - x1) * ky;
-			cx = x1 + (y - y1) * kx;
-			h2x = (cy - prevY) * (cy - prevY) + (x - prevX) * (x - prevX);
-			h2y = (cx - prevX) * (cx - prevX) + (y - prevY) * (y - prevY);
-			if (h2x < h2y)
-				y = cy;
-			else
-				x = cx;
-
-			/* Make sure loop will exit when we reach the end */
-			if ((xdir < 0 && x <= x2) || (xdir > 0 && x >= x2) ||
-			    (ydir < 0 && y <= y2) || (ydir > 0 && y >= y2)) {
-				x = x2;
-				y = y2;
-			}
+	double fymin = fmin(fmax(fmin(y1, y2), 0.0), height);
+	double fymax = fmin(fmax(fmax(y1, y2), 0.0), height);
+	double floor_fymin = floor(fymin);
+	double ceil_fymax = ceil(fymax);
+	size_t ymin = (size_t)floor_fymin;
+	size_t ymax = (size_t)ceil_fymax;
+	size_t y, cellY;
+	double rowx1, rowx2;
+	double rxmin, rxmax, floor_rxmin;
+	double rymax, rymin, ceil_rxmax;
+	ssize_t x, xmin, xmax, xmin_cropped, xmax_cropped;
+	double cxmin, cxmax;
+
+	ymax += (size_t)(ymax == ymin);
+	for (y = ymin; y < ymax; y++) {
+		rymin = (double)y;
+		rymax = (double)y + 1.0;
+		rymin = fmax(rymin, fymin);
+		rymax = fmin(rymax, fymax);
+		rowx1 = dy ? x1 + (rymin - y1) * dx / dy : x1;
+		rowx2 = dy ? x2 + (rymax - y2) * dx / dy : x2;
+		rxmin = fmin(rowx1, rowx2);
+		rxmax = fmax(rowx1, rowx2);
+		cellY = y * raster->width;
+
+		floor_rxmin = floor(rxmin);
+		ceil_rxmax = ceil(rxmax);
+		xmin = (ssize_t)floor_rxmin;
+		xmax = (ssize_t)ceil_rxmax;
+		xmax += (ssize_t)(xmax == xmin);
+		xmin_cropped = xmin;
+		xmax_cropped = xmax;
+		if (xmin < 0.0) {
+			cxmin = (double)xmin;
+			cxmax = xmax < 0 ? (double)(xmax + 1) : 0.0;
+			draw_cell(raster, x1, y1, x2, y2, dx, dy, cxmin, cxmax, rxmin, rxmax, rymin, rymax, xmin, cellY);
+			xmin_cropped = 0;
 		}
-
-		/* Select cell to draw in */
-		xfloor = xdir >= 0 ? floor(prevX) : floor(x);
-		yfloor = ydir >= 0 ? floor(prevY) : floor(y);
-		cellX = (ssize_t)xfloor;
-		cellY = (ssize_t)yfloor;
-
-		/* Do not draw if above or below the raster */
-		if (cellY < 0 || (size_t)cellY >= raster->height)
-			continue;
-
-		if (cellX < 0) {
-			/* Draw on first column in raster of outside of raster on the left side,
-			 * with full horizontal coverage, `.opposite_coverage` one the actual
-			 * cell (outside of the raster) will contribute to the first column's
-			 * `.cell_coverage` */
-			cell = (size_t)cellY * raster->width;
-			raster->cells[cell].opposite_coverage += y - prevY;
-			raster->cells[cell].cell_coverage += y - prevY;
-
-		} else if ((size_t)cellX >= raster->width) {
-			/* If outside of the raster, on the right side, add to the last
-			 * columns contributions to the next column, so that the ink level
-			 * balances out to zero */
-			cell = (size_t)cellY * raster->width + (raster->width - 1);
-			raster->cells[cell].opposite_coverage += y - prevY;
-
-		} else {
-			/* If inside the raster, just draw the line */
-			cell = (size_t)cellY * raster->width + (size_t)cellX;
-			raster->cells[cell].opposite_coverage += y - prevY;
-			raster->cells[cell].cell_coverage += (y - prevY) * fabs(xfloor + 1.0 - (x + prevX) / 2.0);
+		if (xmax > iwidth) {
+			cxmin = fmax(floor_rxmin, width);
+			cxmax = (double)xmax;
+			draw_cell(raster, x1, y1, x2, y2, dx, dy, cxmin, cxmax, rxmin, rxmax, rymin, rymax, (ssize_t)cxmin, cellY);
+			xmax_cropped = iwidth;
+		}
+		for (x = xmin_cropped; x < xmax_cropped; x++) {
+			cxmin = (double)x;
+			cxmax = (double)x + 1.0;
+			draw_cell(raster, x1, y1, x2, y2, dx, dy, cxmin, cxmax, rxmin, rxmax, rymin, rymax, x, cellY);
 		}
 	}
 }