void add_curve_segment(float cx, float cy, float ax, float ay)
// Add a curve segment to the shape. The curve segment is a
// quadratic bezier, running from the previous anchor point to
// the given new anchor point (ax, ay), with (cx, cy) acting
// as the control point in between.
{
if (cx == ax && cy == ay) {
// Early-out for degenerate straight segments.
add_line_segment(ax, ay);
} else {
// Subdivide, and add line segments...
curve(s_last_point.m_x, s_last_point.m_y, cx, cy, ax, ay);
}
}
static void curve(float p0x, float p0y, float p1x, float p1y, float p2x, float p2y)
// Recursive routine to generate bezier curve within tolerance.
{
#ifndef NDEBUG
static int recursion_count = 0;
recursion_count++;
if (recursion_count > 500)
{
assert(0); // probably a bug!
}
#endif // not NDEBUG
// @@ use struct point in here?
// Midpoint on line between two endpoints.
float midx = (p0x + p2x) * 0.5f;
float midy = (p0y + p2y) * 0.5f;
// Midpoint on the curve.
float qx = (midx + p1x) * 0.5f;
float qy = (midy + p1y) * 0.5f;
float dist = fabsf(midx - qx) + fabsf(midy - qy);
if (dist < s_tolerance)
{
// Emit edge.
add_line_segment(p2x, p2y);
}
else
{
// Error is too large; subdivide.
curve(p0x, p0y, (p0x + p1x) * 0.5f, (p0y + p1y) * 0.5f, qx, qy);
curve(qx, qy, (p1x + p2x) * 0.5f, (p1y + p2y) * 0.5f, p2x, p2y);
}
#ifndef NDEBUG
recursion_count--;
#endif // not NDEBUG
}
int process_eraseline(Drawing d) {
double x1, x2, y1, y2, t;
if (stack_size(d->stack) < 5) {
return throw_error("Impossivel realizar operação. Motivo: há menos elementos na pilha do que o necessário (stack underflow).\n", PROCESSOR_ERROR_ERASELINE);
}
// printf("[DEBUG] Showing stack before creating line.\n");
// process_show(d->stack);
t = stack_pop(d->stack);
y2 = stack_pop(d->stack);
x2 = stack_pop(d->stack);
y1 = stack_pop(d->stack);
x1 = stack_pop(d->stack);
if (t < 0) {
return throw_error("Impossivel realizar operação. Motivo: ao criar uma borracha com segmento de reta, a grossura não pode ser negativa.\n", PROCESSOR_ERROR_ERASELINE);
}
return add_line_segment(d, x1, y1, x2, y2, -t) ? PROCESSOR_SUCCESS : PROCESSOR_ERROR_ERASELINE;
}