How to make a point appear using fltk? - c++

Question

After creating a window and drawing some shapes in it, I realized I cant make a point and just appear it on the window. I've searched the manual but I cant make anything out of it. Im using the fltk 1.3.0. How can I do it ?

Answer 1

Fltk comes with a bunch of example projects that are helpful. If you look at the line_style example you can easily reduce it to something drawing points like this:
#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/fl_draw.H>
class TestWindow : public Fl_Window {
void draw()
{
fl_color(255, 0, 0);
fl_begin_points();
fl_point(50, 50);
fl_point(51, 51);
fl_end_points();
}
public:
TestWindow(int w, int h, const char *l = 0)
: Fl_Window(w, h, l) {}
};
int main(int argc, char ** argv) {
Fl_Window *window = new TestWindow(200, 200);
window->end();
window->show(argc, argv);
return Fl::run();
}
But just as a word of advice, drawing single points directly onto the window is rarely the smart thing to do. Drawing into images/buffers and then displaying them is the better alternative most of the time.
edit:
here's is an example of putting the drawing code in the main function.
#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/fl_draw.H>
class TestWindow : public Fl_Window {
void draw() {}
public:
TestWindow(int w, int h, const char *l = 0) : Fl_Window(w, h, l) {}
};
int main(int argc, char ** argv) {
Fl_Window *window = new TestWindow(200, 200);
window->end();
window->show(argc, argv);
window->make_current();
fl_color(255, 0, 0);
fl_begin_points();
fl_point(50, 50);
fl_point(51, 51);
fl_end_points();
return Fl::run();
}
You should take notice of the disclaimer for make_current in the manual
Danger: incremental update is very hard to debug and maintain!
None of this is good practise beyond using it for simple exercises.

Answer 2

Based on the previous answer to this question, I found this in the documentation:
fl_begin_points()
Starts drawing a list of points.
Points are added to the list with fl_vertex()
So this is some code that shows some points (I added more to really see the points):
#include <FL/fl_draw.H>
#include <FL/Fl.H>
#include <FL/Fl_Window.H>
class Drawing : public Fl_Window {
void draw(){
fl_begin_points();
//adding cushion to points to be able to see them.
//center at 10,10
fl_vertex(9,9);
fl_vertex(9,10);
fl_vertex(9,11);
fl_vertex(10,9);
fl_vertex(10,10);
fl_vertex(10,11);
fl_vertex(11,9);
fl_vertex(11,10);
fl_vertex(11,11);
fl_end_points();
fl_color(FL_BLACK);
}
public:
Drawing(int w, int h, const char *l = 0) : Fl_Window(w, h, l){}
};
int main(int argc, char **argv){
Fl_Window *window = new Drawing(340,180);
window->end();
window->show(argc, argv);
return Fl::run();
}