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Enhance howto-drag-and-drop example program.

Browse Source 
Refer to discussion if fltk.general, thread "Drag and drop issue"
in August September 2017.


git-svn-id: file:///fltk/svn/fltk/branches/branch-1.4@12432 ea41ed52-d2ee-0310-a9c1-e6b18d33e121
This commit is contained in:
Albrecht Schlosser
2017-09-08 15:02:04 +00:00
parent 0bf5f9809a
commit ae983b74f2
1 changed files with 76 additions and 12 deletions
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88
examples/howto-drag-and-drop.cxx
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@@ -1,14 +1,17 @@
//
// "$Id$"
//
// A simple demo of drag+drop with FLTK.
// Originally from erco's cheat sheet, permission by author.
// Inspired by Michael Sephton's original example posted on fltk.general.
// A simple demo of 'drag and drop' with FLTK.
// Originally from erco's cheat sheet, permission by author.
// Inspired by Michael Sephton's original example posted on fltk.general.
//
// When you run the program, just drag the red square over
// to the green square to show a 'drag and drop' sequence.
// When you run the program, just drag the red square over
// to the green square to show a 'drag and drop' sequence.
//
// Copyright 1998-2010 by Bill Spitzak and others.
// You can also drag and drop text from another application over
// to the green square to show a 'drag and drop' sequence.
//
// Copyright 1998-2017 by Bill Spitzak and others.
//
// This library is free software. Distribution and use rights are outlined in
// the file "COPYING" which should have been included with this file. If this
@@ -25,6 +28,7 @@
#include <FL/Fl.H>
#include <FL/Fl_Window.H>
#include <FL/Fl_Box.H>
#include <FL/fl_ask.H> // fl_message()
// SIMPLE SENDER CLASS
class Sender : public Fl_Box {
@@ -52,29 +56,89 @@ public:
};
// SIMPLE RECEIVER CLASS
class Receiver : public Fl_Box {
int dnd_inside;
char *dnd_text;
public:
// Ctor
Receiver(int x,int y,int w,int h) : Fl_Box(x,y,w,h) {
box(FL_FLAT_BOX); color(10); label("..to\nhere");
dnd_inside = 0;
dnd_text = 0;
}
// Receiver event handler
int handle(int event) {
int ret = Fl_Box::handle(event);
int len;
switch ( event ) {
case FL_DND_ENTER: // return(1) for these events to 'accept' dnd
case FL_DND_DRAG:
case FL_DND_RELEASE:
case FL_DND_ENTER: // return(1) for this event to 'accept' dnd
label("ENTER"); // visible only if you stop the mouse at the widget's border
fprintf(stderr, "FL_DND_ENTER\n");
dnd_inside = 1; // status: inside the widget, accept drop
ret = 1;
break;
case FL_PASTE: // handle actual drop (paste) operation
label(Fl::event_text());
fprintf(stderr, "Pasted '%s'\n", Fl::event_text());
case FL_DND_DRAG: // return(1) for this event to 'accept' dnd
label("drop\nhere");
fprintf(stderr, "FL_DND_DRAG\n");
ret = 1;
break;
case FL_DND_RELEASE: // return(1) for this event to 'accept' the payload (drop)
fprintf(stderr, "FL_DND_RELEASE\n");
if (dnd_inside) {
ret = 1; // return(1) and expect FL_PASTE event to follow
label("RELEASE");
} else {
ret = 0; // return(0) to reject the DND payload (drop)
label("DND\nREJECTED!");
}
break;
case FL_PASTE: // handle actual drop (paste) operation
fprintf(stderr, "FL_PASTE\n");
copy_label(Fl::event_text());
fprintf(stderr, "Pasted '%s'\n", Fl::event_text());
// Don't pop up dialog windows in FL_DND_* or FL_PASTE event handling
// resulting from DND operations. This may hang or even crash the
// application on *some* platforms. Use a short timer to delay the
// message display after the event processing is completed.
delete[] dnd_text; // don't leak (just in case)
dnd_text = 0;
len = Fl::event_length();
if (len && Fl::event_text()) {
dnd_text = new char[len + 1];
memcpy(dnd_text, Fl::event_text(), len);
dnd_text[len] = '\0';
Fl::add_timeout(0.001, timer_cb, this); // delay message popup
}
ret = 1;
break;
case FL_DND_LEAVE: // not strictly necessary to return(1) for this event
label("..to\nhere"); // reset label
fprintf(stderr, "FL_DND_LEAVE\n");
dnd_inside = 0; // status: mouse is outside, don't accept drop
ret = 1; // return(1) anyway..
break;
}
return(ret);
}
// static timer callback
static void timer_cb(void *data) {
Receiver *r = (Receiver *)data;
r->dnd_cb();
}
// dnd (FL_PASTE) popup method
void dnd_cb() {
if (dnd_text) {
fl_message("%s", dnd_text);
delete[] dnd_text;
dnd_text = 0;
}
}
};
int main(int argc, char **argv) {
// Create sender window and widget
Fl_Window win_a(0,0,200,100,"Sender");