Set preserveDrawingBuffer in webgl and add example to freeze notebooks

examples/Freezing vispy visualizations.ipynb

@@ -0,0 +1,105 @@
+{
+ "cells": [
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "## Overview\n",
+    "\n",
+    "This notebook shows how to embed a static views of interactive vispy scenes into notebooks after using them."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {
+    "scrolled": false
+   },
+   "outputs": [],
+   "source": [
+    "import sys\n",
+    "sys.path.append('../test')\n",
+    "import test_scenes\n",
+    "\n",
+    "import plato, plato.draw.vispy as draw\n",
+    "\n",
+    "test_scenes.colored_spheres().convert(draw).show()"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "%%javascript\n",
+    "// This snippet automatically exports all vispy canvases in a notebook into a\n",
+    "// static form that can be exported to HTML, for example\n",
+    "var cells = Jupyter.notebook.get_cells()\n",
+    "\n",
+    "for(var cellix = 0; cellix < cells.length; ++cellix)\n",
+    "{\n",
+    "    var cell = cells[cellix]\n",
+    "\n",
+    "    var new_nodes = []\n",
+    "    var output_area = cell.output_area\n",
+    "\n",
+    "    if(typeof output_area !== 'undefined')\n",
+    "    {\n",
+    "        var canvases = output_area.element[0].querySelectorAll('canvas')\n",
+    "        for(var i = 0; i < canvases.length; ++i)\n",
+    "        {\n",
+    "            var new_node = document.createElement('img')\n",
+    "            new_node.src = canvases[i].toDataURL('image/jpeg')\n",
+    "            canvases[i].parentElement.replaceChild(new_node, canvases[i])\n",
+    "            new_nodes.push(new_node)\n",
+    "        }\n",
+    "\n",
+    "        for(var outix = 0; outix < output_area.outputs.length; ++outix)\n",
+    "        {\n",
+    "            var output = output_area.outputs[outix]\n",
+    "\n",
+    "            if(output.output_type == 'display_data' &&\n",
+    "               typeof output.data !== 'undefined' &&\n",
+    "               output.data['text/plain'].startsWith('VispyWidget'))\n",
+    "            {\n",
+    "                var contents = new_nodes.pop(0).outerHTML\n",
+    "                output.data = {\n",
+    "                    'text/plain': '<embedded image>',\n",
+    "                    'text/html': contents}\n",
+    "            }\n",
+    "        }\n",
+    "    }\n",
+    "}"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  }
+ ],
+ "metadata": {
+  "kernelspec": {
+   "display_name": "Python 3",
+   "language": "python",
+   "name": "python3"
+  },
+  "language_info": {
+   "codemirror_mode": {
+    "name": "ipython",
+    "version": 3
+   },
+   "file_extension": ".py",
+   "mimetype": "text/x-python",
+   "name": "python",
+   "nbconvert_exporter": "python",
+   "pygments_lexer": "ipython3",
+   "version": "3.8.1"
+  }
+ },
+ "nbformat": 4,
+ "nbformat_minor": 2
+}

plato/draw/vispy/Canvas.py

@@ -454,6 +454,11 @@ def __init__(self, scene, **kwargs):
         self._selection_callback = None
         self._clip_planes = np.array([1, 100], dtype=np.float32)
 
+        if self._webgl:
+            backend_kwargs = kwargs.setdefault('backend_kwargs', {})
+            webgl_kwargs = backend_kwargs.setdefault('webgl', {})
+            webgl_kwargs['preserveDrawingBuffer'] = True
+
         super(Canvas, self).__init__(size=scene.size_pixels.astype(np.uint32), **kwargs)
 
         gloo.set_viewport(0, 0, *scene.size_pixels.astype(np.uint32))

setup.py

@@ -26,8 +26,8 @@
       ],
       description='Geometry and visualization tools for collections of particles',
       extras_require={
-          'pyside': ['pyside', 'vispy >= 0.5.3'],
-          'pyside2': ['pyside2', 'vispy >= 0.6'],
+          'pyside': ['pyside', 'vispy >= 0.7'],
+          'pyside2': ['pyside2', 'vispy >= 0.7'],
           'pythreejs': ['pythreejs'],
       },
       install_requires=['numpy', 'scipy', 'rowan'],