> On 07/01/12 20:51, Greg Ercolano wrote:
> >> int handle (int e) {
> >> // DRAW vertical lines
> >> int ret = Fl_Widget::handle (e);
> >> switch (e) {
> >> case FL_PUSH:
> >> lines++;
> >> int x1 = x();
> >> int y1 = y(), y2 = y()+h()-1;
> >> fl_line(x1 + 10 * lines, y1, x1 + 10 * lines, y2);
> >
> > You can't do any drawing functions (like fl_line) inside
> > an event handler.
> >
> > The only time you can draw anything is inside draw().
> >
> > So to do what you want, you have to modify some variables
> > and call redraw() which will flag FLTK to call draw(),
>
> Looking at your program, what I think you want is:
>
> #include <FL/Fl.H>
> #include <FL/fl_draw.H>
> #include <FL/Fl_Double_Window.H>
> class DrawX : public Fl_Widget {
> private:
> int lines;
> public:
> DrawX(int X, int Y, int W, int H, const char*L=0) : Fl_Widget(X,Y,W,H,L),
> lines(0) {
> }
> void draw() {
> fl_color(FL_BLACK);
> int x1 = x();
> int y1 = y(), y2 = y()+h()-1;
> for (int i = 1; i <= lines; i++) {
> fl_line(x1 + 10 * i, y1, x1 + 10 * i, y2);
> }
> }
> int handle(int e) {
> int ret = Fl_Widget::handle(e);
> switch(e) {
> case FL_PUSH:
> lines++;
> redraw(); // tells FLTK to schedule redrawing the widget
> return(1);
> }
> return(ret);
> }
> };
> int main() {
> Fl_Double_Window win(200,200,"Draw vertical lines");
> DrawX draw_x(0, 0, win.w(), win.h());
> win.resizable(draw_x);
> win.show();
> return(Fl::run());
> }
>
>
Now everything works correctly.
I really don't know how to thank you for the help.
Thanks Greg.
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