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());
}
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