examples/drag_and_drop_example.ipynb

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   "source": [
    "from ipycanvas import Canvas, hold_canvas\n",
    "\n",
    "canvas = Canvas(width=600, height=600)\n",
    "canvas.fill_style = \"#584f4e\"\n",
    "canvas.fill_rect(0, 0, 600, 600)\n",
    "\n",
    "\n",
    "objects_to_draw = []\n",
    "\n",
    "\n",
    "class Square_obj:\n",
    "    def __init__(self, x, y, width=100, height=40):\n",
    "        self.x = x\n",
    "        self.y = y\n",
    "        self.width = width\n",
    "        self.height = height\n",
    "        self.selected = False\n",
    "        objects_to_draw.append(self)\n",
    "\n",
    "    def set_x_y(self, x_in, y_in):\n",
    "        self.x = x_in\n",
    "        self.y = y_in\n",
    "\n",
    "    def draw(self):\n",
    "        canvas.fill_style = \"#38a8a4\"\n",
    "        canvas.fill_rect(\n",
    "            self.x - (self.width * 0.5), self.y - (self.height), self.width, self.height\n",
    "        )\n",
    "        if self.selected:\n",
    "            canvas.fill_style = \"#9dcea6\"\n",
    "        else:\n",
    "            canvas.fill_style = \"#dee7bc\"\n",
    "        canvas.fill_rect(\n",
    "            self.x - (self.width * 0.5),\n",
    "            self.y - (self.height * 0.5),\n",
    "            self.width,\n",
    "            self.height,\n",
    "        )\n",
    "\n",
    "    def is_selected(self, x_in, y_in):\n",
    "        x_coord = self.x - (self.width * 0.5)\n",
    "        y_coord = self.y - (self.height * 0.5)\n",
    "\n",
    "        if (\n",
    "            x_in > x_coord\n",
    "            and x_in < (x_coord + self.width)\n",
    "            and y_in > y_coord\n",
    "            and y_in < (y_coord + self.height)\n",
    "        ):\n",
    "            self.set_selected(True)\n",
    "            return True\n",
    "        else:\n",
    "            self.set_selected(False)\n",
    "            return False\n",
    "\n",
    "    def set_selected(self, state):\n",
    "        self.selected = state\n",
    "\n",
    "\n",
    "def canvas_restart():\n",
    "    canvas.clear()\n",
    "    canvas.fill_style = \"#584f4e\"\n",
    "    canvas.fill_rect(0, 0, 600, 600)\n",
    "\n",
    "\n",
    "def handle_mouse_down(x, y):\n",
    "    if [o for o in objects_to_draw if o.selected]:\n",
    "        [o.set_selected(False) for o in objects_to_draw if o.selected]\n",
    "        return False\n",
    "\n",
    "    check_bool_pos = list(\n",
    "        set([check_region.is_selected(x, y) for check_region in objects_to_draw])\n",
    "    )\n",
    "    if len(check_bool_pos) == 1:\n",
    "        if check_bool_pos[0] == False:\n",
    "            s = Square_obj(x, y)\n",
    "            s.set_selected(False)\n",
    "            s.draw()\n",
    "\n",
    "        else:\n",
    "            canvas_restart()\n",
    "            [o.draw() for o in objects_to_draw]\n",
    "\n",
    "    if len(check_bool_pos) == 0:\n",
    "        s = Square_obj(x, y)\n",
    "        s.set_selected(False)\n",
    "        s.draw()\n",
    "\n",
    "\n",
    "def handle_mouse_move(x, y):\n",
    "    if [o for o in objects_to_draw if o.selected]:\n",
    "        with hold_canvas():\n",
    "            [o for o in objects_to_draw if o.selected][-1].set_x_y(x, y)\n",
    "            canvas_restart()\n",
    "            [o.draw() for o in objects_to_draw]\n",
    "\n",
    "\n",
    "canvas.on_mouse_down(handle_mouse_down)\n",
    "canvas.on_mouse_move(handle_mouse_move)\n",
    "\n",
    "\n",
    "canvas"
   ]
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  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
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