Function ImBezierCubicClosestPointCasteljauStep

KBotExt/imgui/imgui.cpp:1629–1660

Closely mimics PathBezierToCasteljau() in imgui_draw.cpp

// Closely mimics PathBezierToCasteljau() in imgui_draw.cpp
static void ImBezierCubicClosestPointCasteljauStep(const ImVec2& p, ImVec2& p_closest, ImVec2& p_last, float& p_closest_dist2, float x1, float y1, float x2, float y2, float x3, float y3, float x4, float y4, float tess_tol, int level)
{
	float dx = x4 - x1;
	float dy = y4 - y1;
	float d2 = ((x2 - x4) * dy - (y2 - y4) * dx);
	float d3 = ((x3 - x4) * dy - (y3 - y4) * dx);
	d2 = (d2 >= 0) ? d2 : -d2;
	d3 = (d3 >= 0) ? d3 : -d3;
	if ((d2 + d3) * (d2 + d3) < tess_tol * (dx * dx + dy * dy))
	{
		ImVec2 p_current(x4, y4);
		ImVec2 p_line = ImLineClosestPoint(p_last, p_current, p);
		float dist2 = ImLengthSqr(p - p_line);
		if (dist2 < p_closest_dist2)
		{
			p_closest = p_line;
			p_closest_dist2 = dist2;
		}
		p_last = p_current;
	}
	else if (level < 10)
	{
		float x12 = (x1 + x2) * 0.5f, y12 = (y1 + y2) * 0.5f;
		float x23 = (x2 + x3) * 0.5f, y23 = (y2 + y3) * 0.5f;
		float x34 = (x3 + x4) * 0.5f, y34 = (y3 + y4) * 0.5f;
		float x123 = (x12 + x23) * 0.5f, y123 = (y12 + y23) * 0.5f;
		float x234 = (x23 + x34) * 0.5f, y234 = (y23 + y34) * 0.5f;
		float x1234 = (x123 + x234) * 0.5f, y1234 = (y123 + y234) * 0.5f;
		ImBezierCubicClosestPointCasteljauStep(p, p_closest, p_last, p_closest_dist2, x1, y1, x12, y12, x123, y123, x1234, y1234, tess_tol, level + 1);
		ImBezierCubicClosestPointCasteljauStep(p, p_closest, p_last, p_closest_dist2, x1234, y1234, x234, y234, x34, y34, x4, y4, tess_tol, level + 1);
	}
}

// tess_tol is generally the same value you would find in ImGui::GetStyle().CurveTessellationTol
// Because those ImXXX functions are lower-level than ImGui:: we cannot access this value automatically.