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Added the possibility of drawing a vector

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Karma Riuk 2023-04-25 12:02:56 +02:00
parent bf9545a7a0
commit 699490fefc
1 changed files with 30 additions and 0 deletions
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30
vec2d.h
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@ -67,6 +67,36 @@ class vec2d {
return {-y, x}; return {-y, x};
} }
void draw(cairo_t* cr, vec2d p) {
double arrow_lenght_ = 10 * vec2d::norm(*this);
double arrow_degrees_ = .5;
// see
// http://kapo-cpp.blogspot.com/2008/10/drawing-arrows-with-cairo.html
double angle = atan2(y, x) + M_PI;
vec2d end = p + (*this) * 30;
double x1 = end.x + arrow_lenght_ * cos(angle - arrow_degrees_);
double y1 = end.y + arrow_lenght_ * sin(angle - arrow_degrees_);
double x2 = end.x + arrow_lenght_ * cos(angle + arrow_degrees_);
double y2 = end.y + arrow_lenght_ * sin(angle + arrow_degrees_);
cairo_set_source_rgb(cr, 255, 0, 0);
cairo_move_to(cr, p.x, p.y);
cairo_line_to(cr, end.x, end.y);
cairo_stroke(cr);
cairo_move_to(cr, end.x, end.y);
cairo_line_to(cr, x1, y1);
cairo_stroke(cr);
cairo_move_to(cr, end.x, end.y);
cairo_line_to(cr, x2, y2);
cairo_stroke(cr);
}
static double dot(const vec2d& a, const vec2d& b) { static double dot(const vec2d& a, const vec2d& b) {
return a.x * b.x + a.y * b.y; return a.x * b.x + a.y * b.y;
} }