Add debouncing, zoom with wheel

Author: davidbrochart

environment.yml

@@ -4,3 +4,4 @@ channels:
 dependencies:
   - branca
   - ipycanvas=0.4.1
+  - ipyevents

examples/mapping.ipynb

@@ -8,7 +8,45 @@
    "source": [
     "from math import pow, cos, pi, radians, degrees, atan, tan, sinh, log\n",
     "from ipywidgets import Image, Output, IntSlider\n",
-    "from ipycanvas import Canvas, MultiCanvas"
+    "from ipycanvas import Canvas, MultiCanvas\n",
+    "from ipyevents import Event\n",
+    "import asyncio"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "class Timer:\n",
+    "    def __init__(self, timeout, callback):\n",
+    "        self._timeout = timeout\n",
+    "        self._callback = callback\n",
+    "        self._task = asyncio.ensure_future(self._job())\n",
+    "\n",
+    "    async def _job(self):\n",
+    "        await asyncio.sleep(self._timeout)\n",
+    "        self._callback()\n",
+    "\n",
+    "    def cancel(self):\n",
+    "        self._task.cancel()\n",
+    "\n",
+    "def debounce(wait):\n",
+    "    \"\"\" Decorator that will postpone a function's\n",
+    "        execution until after wait seconds\n",
+    "        have elapsed since the last time it was invoked. \"\"\"\n",
+    "    def decorator(fn):\n",
+    "        def debounced(*args, **kwargs):\n",
+    "            def call_it():\n",
+    "                fn(*args, **kwargs)\n",
+    "            try:\n",
+    "                debounced.t.cancel()\n",
+    "            except(AttributeError):\n",
+    "                pass\n",
+    "            debounced.t = Timer(wait, call_it)\n",
+    "        return debounced\n",
+    "    return decorator"
    ]
   },
   {
@@ -166,7 +204,8 @@
     "        self.dragging = True\n",
     "        self.x_mouse = pixel_x\n",
     "        self.y_mouse = pixel_y\n",
-    "        \n",
+    "    \n",
+    "    @debounce(0.01)\n",
     "    def mouse_move_handler(self, pixel_x, pixel_y):\n",
     "        if self.dragging:\n",
     "            x, y, lat, lon = self.delta(pixel_x, pixel_y)\n",
@@ -205,16 +244,19 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "slider = IntSlider(description='Zoom:', value=m.z, min=3, max=10, step=1)\n",
+    "d = Event(source=m, watched_events=['wheel'])\n",
     "\n",
-    "def on_slider_change(change):\n",
-    "    m.z = slider.value\n",
+    "@out.capture()\n",
+    "def zoom(event):\n",
+    "    m.z -= event['deltaY'] // 3\n",
+    "    m.z = max(m.z, 1)\n",
+    "    m.z = min(m.z, 19)\n",
+    "    print(m.z)\n",
     "    m.tile_nb = numTiles(m.z)\n",
     "    m.x, m.y = latlon2xy(m.lat, m.lon, m.z)\n",
     "    m.show()\n",
     "\n",
-    "slider.observe(on_slider_change, 'value')\n",
-    "slider"
+    "d.on_dom_event(zoom)"
    ]
   },
   {
@@ -243,9 +285,9 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.7.3"
+   "version": "3.8.1"
   }
  },
  "nbformat": 4,
- "nbformat_minor": 2
+ "nbformat_minor": 4
 }