Add a loading spinner for TryExamples directive. (#133)

* Remove unused config variable

* Add a spinner

* Add link for example css

* Dynamically adjust spinner position

* Adjust spinner position

* Add spinners for other jupyterlite-sphinx directives

docs/directives/try_examples.md

@@ -137,8 +137,8 @@ Here's an example with some options set
     We've also added the ``blue-bottom`` class, the button should appear as blue,
     below the examples, and on the left side of the screen.
 
-    See ``try_examples.css`` in the Repository to see how we achieved this via
-    custom css.
+    See `try_examples.css <https://github.com/jupyterlite/jupyterlite-sphinx/blob/main/docs/_static/try_examples.css>`_
+    to see how we achieved this via custom css.
 ```
 
 and here is the result
@@ -159,8 +159,8 @@ and here is the result
     We've also added the ``blue-bottom`` class, the button should appear as blue,
     below the examples, and on the left side of the screen.
 
-    See ``try_examples.css`` in the Repository to see how we achieved this via
-    custom css.
+    See `try_examples.css <https://github.com/jupyterlite/jupyterlite-sphinx/blob/main/docs/_static/try_examples.css>`_
+    to see how we achieved this via custom css.
 ```
 
 

jupyterlite_sphinx/jupyterlite_sphinx.css

@@ -38,47 +38,29 @@
     box-shadow: 0 0.2rem 0.5rem #d8d8d8;
 }
 
-.jupyterlite_sphinx_iframe_container:hover .jupyterlite_sphinx_try_it_button_unclicked {
-    -webkit-animation:grow 0.2s ease-in-out;
-    animation:grow 0.2s ease-in-out;
-    transform: translateY(-50%) translateX(-50%) scale(1.2);
-}
-
-.jupyterlite_sphinx_try_it_button_clicked {
-    -webkit-animation:grow 1s infinite alternate;
-    animation:grow 1s infinite alternate;
-    transform: translateY(-50%) translateX(-50%) scale(1.2);
-}
-
-@keyframes grow {
-    from {
-        transform: translateY(-50%) translateX(-50%) scale(1);
-    }
-    to {
-        transform: translateY(-50%) translateX(-50%) scale(1.2);
-    }
-}
-
-@-webkit-keyframes grow {
-    from {
-        transform: translateY(-50%) translateX(-50%) scale(1);
-    }
-    to {
-        transform: translateY(-50%) translateX(-50%) scale(1.2);
-    }
-}
-
-.try_examples_iframe_container {
-    position: relative;
-    cursor: pointer;
-}
-
-
 .try_examples_outer_container {
     position: relative;
 }
 
-
 .hidden {
     display: none;
 }
+
+.jupyterlite_sphinx_spinner {
+    /* From https://css-loaders.com/spinner/ */
+    position: absolute;
+    z-index: 0;
+    top: 50%;
+    left: 50%;
+    width: 50px;
+    aspect-ratio: 1;
+    border-radius: 50%;
+    background:
+        radial-gradient(farthest-side,#ffa516 94%,#0000) top/8px 8px no-repeat,
+        conic-gradient(#0000 30%,#ffa516);
+    -webkit-mask: radial-gradient(farthest-side,#0000 calc(100% - 8px),#000 0);
+    animation: l13 1s infinite linear;
+}
+@keyframes l13{
+    100%{transform: rotate(1turn)}
+}

jupyterlite_sphinx/jupyterlite_sphinx.js

@@ -1,15 +1,27 @@
 window.jupyterliteShowIframe = (tryItButtonId, iframeSrc) => {
   const tryItButton = document.getElementById(tryItButtonId);
   const iframe = document.createElement('iframe');
+  const buttonRect = tryItButton.getBoundingClientRect();
+
+  const spinner = document.createElement('div');
+  // hardcoded spinner height and width needs to match what is in css.
+  const spinnerHeight = 50; // px
+  const spinnerWidth = 50; // px
+  spinner.classList.add('jupyterlite_sphinx_spinner');
+  spinner.style.display = 'none';
+  // Add negative margins to center the spinner
+  spinner.style.marginTop = `-${spinnerHeight/2}px`;
+  spinner.style.marginLeft = `-${spinnerWidth/2}px`;
 
   iframe.src = iframeSrc;
   iframe.width = iframe.height = '100%';
   iframe.classList.add('jupyterlite_sphinx_iframe');
 
+  tryItButton.style.display = 'none';
+  spinner.style.display = 'block';
+
+  tryItButton.parentNode.appendChild(spinner);
   tryItButton.parentNode.appendChild(iframe);
-  tryItButton.innerText = 'Loading ...';
-  tryItButton.classList.remove('jupyterlite_sphinx_try_it_button_unclicked');
-  tryItButton.classList.add('jupyterlite_sphinx_try_it_button_clicked');
 }
 
 window.jupyterliteConcatSearchParams = (iframeSrc, params) => {
@@ -50,9 +62,17 @@ window.tryExamplesShowIframe = (
     const iframeContainer = document.getElementById(iframeContainerId);
     var height;
 
-    let iframe = iframeContainer.querySelector('iframe.jupyterlite_sphinx_raw_iframe');
+    let iframe = iframeContainer.querySelector('iframe.jupyterlite_sphinx_iframe');
 
     if (!iframe) {
+              // Add spinner
+              const spinner = document.createElement('div');
+              // hardcoded spinner width needs to match what is in css.
+              const spinnerHeight = 50; // px
+              const spinnerWidth = 50; // px
+              spinner.classList.add('jupyterlite_sphinx_spinner');
+              iframeContainer.appendChild(spinner);
+
               const examples = examplesContainer.querySelector('.try_examples_content');
               iframe = document.createElement('iframe');
               iframe.src = iframeSrc;
@@ -62,9 +82,23 @@ window.tryExamplesShowIframe = (
               } else {
                   height = Math.max(tryExamplesGlobalMinHeight, examples.offsetHeight);
               }
+
+              /* Get spinner position. It will be centered in the iframe, unless the
+               * iframe extends beyond the viewport, in which case it will be centered
+               * between the top of the iframe and the bottom of the viewport.
+               */
+              const examplesTop = examples.getBoundingClientRect().top;
+              const viewportBottom = window.innerHeight;
+              const spinnerTop = 0.5 * Math.min((viewportBottom - examplesTop), height);
+              spinner.style.top = `${spinnerTop}px`;
+              // Add negative margins to center the spinner
+              spinner.style.marginTop = `-${spinnerHeight/2}px`;
+              spinner.style.marginLeft = `-${spinnerWidth/2}px`;
+
               iframe.style.height = `${height}px`;
-              iframe.classList.add('jupyterlite_sphinx_raw_iframe');
+              iframe.classList.add('jupyterlite_sphinx_iframe');
               examplesContainer.classList.add("hidden");
+
               iframeContainer.appendChild(iframe);
     } else {
               examplesContainer.classList.add("hidden");

jupyterlite_sphinx/jupyterlite_sphinx.py

@@ -436,7 +436,7 @@ def run(self):
         iframe_parent_container_div_end = "</div>"
         iframe_container_div = (
             f'<div id="{iframe_div_id}" '
-            f'class="try_examples_iframe_container">'
+            f'class="jupyterlite_sphinx_iframe_container">'
             f"</div>"
         )
 
@@ -498,7 +498,6 @@ def _process_autodoc_docstrings(app, what, name, obj, options, lines):
     try_examples_options = {
         "theme": app.config.try_examples_global_theme,
         "button_text": app.config.try_examples_global_button_text,
-        "example_class": app.config.try_examples_global_example_class,
     }
     try_examples_options = {
         key: value for key, value in try_examples_options.items() if value is not None