traverseGridSegment16()

template<typename GridVisitor>

void fl::traverseGridSegment16	(	const vec2f &	start,
		const vec2f &	end,
		GridVisitor &	visitor )

Traverse a grid segment using fixed-point 8.8 arithmetic.

Template Parameters

GridVisitor

Parameters

start	start point
end	end point
visitor	called for each cell visited.

UNTESTED!!!!

Definition at line 125 of file traverse_grid.h.

                                                        {
    const i16 FP_SHIFT = 8;
    const i16 FP_ONE = 1 << FP_SHIFT;
    // const i16 FP_MASK = FP_ONE - 1;
 
    // Convert to fixed-point (Q8.8), signed
    i16 startX_fp = static_cast<i16>(start.x * FP_ONE);
    i16 startY_fp = static_cast<i16>(start.y * FP_ONE);
    i16 endX_fp = static_cast<i16>(end.x * FP_ONE);
    i16 endY_fp = static_cast<i16>(end.y * FP_ONE);
 
    i16 x0 = startX_fp >> FP_SHIFT;
    i16 y0 = startY_fp >> FP_SHIFT;
    i16 x1 = endX_fp >> FP_SHIFT;
    i16 y1 = endY_fp >> FP_SHIFT;
 
    i16 stepX = (x1 > x0) ? 1 : (x1 < x0) ? -1 : 0;
    i16 stepY = (y1 > y0) ? 1 : (y1 < y0) ? -1 : 0;
 
    i16 deltaX_fp = endX_fp - startX_fp;
    i16 deltaY_fp = endY_fp - startY_fp;
 
    // Use (max)() to prevent macro expansion by Arduino.h's max macro
    u16 absDeltaX_fp =
        (deltaX_fp != 0) ? static_cast<u16>(
                               fl::abs((i32(FP_ONE) << FP_SHIFT) / deltaX_fp))
                         : (fl::numeric_limits<u16>::max)();
    u16 absDeltaY_fp =
        (deltaY_fp != 0) ? static_cast<u16>(
                               fl::abs((i32(FP_ONE) << FP_SHIFT) / deltaY_fp))
                         : (fl::numeric_limits<u16>::max)();
 
    i16 nextX_fp = (stepX > 0) ? ((x0 + 1) << FP_SHIFT) : (x0 << FP_SHIFT);
    i16 nextY_fp = (stepY > 0) ? ((y0 + 1) << FP_SHIFT) : (y0 << FP_SHIFT);
 
    // Use (max)() to prevent macro expansion by Arduino.h's max macro
    u16 tMaxX_fp =
        (deltaX_fp != 0)
            ? static_cast<u16>(
                  fl::abs(i32(nextX_fp - startX_fp)) * absDeltaX_fp >> FP_SHIFT)
            : (fl::numeric_limits<u16>::max)();
    u16 tMaxY_fp =
        (deltaY_fp != 0)
            ? static_cast<u16>(
                  fl::abs(i32(nextY_fp - startY_fp)) * absDeltaY_fp >> FP_SHIFT)
            : (fl::numeric_limits<u16>::max)();
 
    const u16 maxT_fp = FP_ONE;
 
    i16 currentX = x0;
    i16 currentY = y0;
 
    while (true) {
        visitor.visit(currentX, currentY);
 
        u16 t_fp = (tMaxX_fp < tMaxY_fp) ? tMaxX_fp : tMaxY_fp;
        if (t_fp > maxT_fp)
            break;
 
        if (tMaxX_fp < tMaxY_fp) {
            tMaxX_fp += absDeltaX_fp;
            currentX += stepX;
        } else {
            tMaxY_fp += absDeltaY_fp;
            currentY += stepY;
        }
    }
 
    // Ensure the end cell (x1, y1) is visited at least once
    if (currentX != x1 || currentY != y1) {
        visitor.visit(x1, y1);
    }
}

References abs(), end(), FP_ONE, fl::numeric_limits< T >::max(), fl::vec2< T >::x, and fl::vec2< T >::y.

Referenced by traverseGridSegment().

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