Panda3D Drag & Drop Demo

drag_and_drop.py

'''
Drag & Drop Demo
Use the mouse to drag and drop colored squares from moving frames or the background.
Use left mouse click to grab a square, release it to ...well, release it.
'''
from panda3d.core import *
from direct.gui.DirectGui import *
from direct.showbase import ShowBase
from direct.interval.LerpInterval import LerpPosInterval
from direct.interval.MetaInterval import Sequence
import random

#Helper functions
def _pos2d(x,y):
    return Point3(x,0,-y)

def _rec2d(width, height):
    return (width, 0, 0, -height)

class App:
    def __init__(self):
        #add a title/instructions
        wp = WindowProperties.getDefault()
        wp.set_title("Drag & Drop the colored squares")
        WindowProperties.setDefault(wp)
        #init showvase
        base = ShowBase.ShowBase()
        #make a frame
        self.white_frame=DirectFrame(frameColor=(1,1,1,1.0),
                                   frameSize=_rec2d(256, 256),
                                   state=DGG.NORMAL,
                                   parent=pixel2d)
        self.white_frame.set_pos(_pos2d(32, 32))
        #bind the events
        self.white_frame.bind(DGG.WITHIN, self.hover_in, [self.white_frame])
        self.white_frame.bind(DGG.WITHOUT, self.hover_out)
        #make it move
        Sequence(LerpPosInterval(self.white_frame, 5.0,_pos2d(32,256)),
                 LerpPosInterval(self.white_frame, 5.0,_pos2d(32,32)) ).loop()

        #do the same as with the white_frame,
        self.black_frame=DirectFrame(frameColor=(0,0,0,1.0),
                                   frameSize=_rec2d(256, 256),
                                   state=DGG.NORMAL,
                                   parent=pixel2d)
        self.black_frame.set_pos(_pos2d(base.win.get_x_size()-32-256, 32))
        self.black_frame.bind(DGG.WITHIN, self.hover_in, [self.black_frame])
        self.black_frame.bind(DGG.WITHOUT, self.hover_out)
        Sequence(LerpPosInterval(self.black_frame, 3.0,_pos2d(base.win.get_x_size()-32-256,256)),
                 LerpPosInterval(self.black_frame, 3.0,_pos2d(base.win.get_x_size()-32-256, 32)) ).loop()

        #make some squares to be drag/dropped        
        for x in range(8):
            for y in range(8):
                frame=DirectFrame(frameColor=(random.uniform(0, 1),random.uniform(0, 1),random.uniform(0, 1),1.0),
                                   frameSize=_rec2d(30, 30),
                                   state=DGG.NORMAL,
                                   parent=self.black_frame)
                #bind the events
                frame.bind(DGG.B1PRESS, self.drag, [frame])
                frame.bind(DGG.B1RELEASE, self.drop)
                frame.set_pos(_pos2d(x*32,y*32))                

        self.current_dragged=None
        self.last_hover_in=None
        #run a task tracking the mouse cursor
        taskMgr.add(self.update, "update", sort=-50)

    def update(self, task=None):
        '''Track the mouse pos and move self.current_dragged to where the cursor is '''
        if self.current_dragged:
            if base.mouseWatcherNode.has_mouse():
                mpos = base.mouseWatcherNode.get_mouse()
                self.current_dragged.set_pos(pixel2d.get_relative_point(render2d, Point3(mpos.get_x() ,0, mpos.get_y())))
        if task:
            return task.again

    def drag(self, widget, mouse_pos=None):
        '''Set the widget to be the currently dragged object'''
        widget.reparent_to(pixel2d)
        self.current_dragged=widget
        self.update()

    def drop(self, mouse_pos=None):
        '''Drop the currently dragged object on the last object the cursor hovered over'''
        if self.current_dragged:
            if self.last_hover_in:
                self.current_dragged.wrt_reparent_to(self.last_hover_in)
            self.current_dragged=None

    def hover_in(self, widget, mouse_pos=None):
        '''Set the widget to be the target to drop objects onto'''
        self.last_hover_in=widget

    def hover_out(self, mouse_pos=None):
        '''Clear the target to drop objects onto'''
        self.last_hover_in=None

app=App()
base.run()