Add click to copy button

Adds a click to copy button to code samples that don't use the Prism
highlighter.

assets/js/click-to-copy.js

@@ -0,0 +1,86 @@
+let codeListings = document.querySelectorAll('.highlight > pre');
+
+for (let index = 0; index < codeListings.length; index++)
+{
+  const codeSample = codeListings[index].querySelector('code');
+  const copyButton = document.createElement("button");
+  copyButton.setAttribute('type', 'button');
+  copyButton.onclick = function() { copyCode(codeSample); };
+  copyButton.classList.add('fas', 'fa-copy'); 
+
+  const buttonTooltip = document.createElement('div');
+  buttonTooltip.classList.add('c2c-tooltip');
+  buttonTooltip.setAttribute('role', 'tooltip');
+  buttonTooltip.innerHTML += 'Copy to clipboard';
+
+  const buttonDiv = document.createElement('div');
+  buttonDiv.classList.add('click-to-copy');
+
+  // Use Popper to create and handle the tooltip behavior.
+
+  const popperInstance = Popper.createPopper(copyButton, buttonTooltip,
+  {
+    modifiers:
+    [
+      {  
+        name: 'offset',
+        options:
+        {
+          offset: [0, -48],
+        },
+      },
+    ],
+  });
+
+  copyButton.addEventListener('click', () =>
+  {
+    buttonTooltip.innerHTML = 'Copied!';
+  });
+
+  copyButton.addEventListener('mouseenter', () =>
+  {
+    buttonTooltip.setAttribute('show-tooltip', '');
+
+    // Enable eventListeners when the code block is on the viewport
+
+    popperInstance.setOptions((options) => ({
+       ...options,
+       modifiers:
+       [
+          ...options.modifiers,
+          { name: 'eventListeners', enabled: true },
+       ],
+    }));
+    popperInstance.update();
+  });
+
+  copyButton.addEventListener('mouseleave', () =>
+  {
+    buttonTooltip.removeAttribute('show-tooltip');
+
+    // Reset the message in case the button was clicked
+    buttonTooltip.innerHTML = 'Copy to clipboard';
+
+    // Disble eventListeners when the code block is NOT on the viewport
+
+    popperInstance.setOptions((options) => ({
+       ...options,
+       modifiers:
+       [
+          ...options.modifiers,
+          { name: 'eventListeners', enabled: false },
+       ],
+    }));
+  });
+
+  buttonDiv.append(copyButton);
+  buttonDiv.append(buttonTooltip);
+  codeListings[index].insertBefore(buttonDiv, codeSample);
+
+}
+
+function copyCode(codeSample)
+{
+  navigator.clipboard.writeText(codeSample.textContent.trim());
+}
+

assets/scss/_code.scss

@@ -7,10 +7,56 @@
 
         margin: 2rem 0;
         padding: 0;
-
+        position: relative;
+
+        .click-to-copy {
+            display: block;
+            text-align: right;
+            height: 1ex;
+        }
+
         pre {
             margin: 0;
             padding: 1rem;
+
+            // Default click-to-copy button
+
+            button {
+               position: absolute;
+               color: $gray-400;
+               border-radius: 3px;
+               border-width: 0;
+               background-color: inherit;
+               box-shadow: 1px 1px $gray-400;
+               right: 8px;
+               top: 6px;
+
+               &:hover {
+                  color: $dark;
+                  background-color: $gray-400;
+               }
+               &:active {
+                  color: $dark;
+                  background-color: $gray-400;
+                  transform: translateY(2px);
+               }
+            }
+
+            .c2c-tooltip {
+               background: $dark;
+               color: $white;
+               padding: 2px 4px;
+               border-radius: 3px;
+               display: block;
+               visibility: hidden;
+               opacity: 0;
+               transition: visibility 0s, opacity 0.5s linear;
+            }
+
+            .c2c-tooltip[show-tooltip] {
+               visibility: visible;
+               opacity: 1;
+            }
         }
     }
 

layouts/partials/scripts.html

@@ -48,7 +48,7 @@
     {{ printf "onload='renderMathInElement(%s, %s);'" (( .Site.Params.katex.html_dom_element | default "document.body" ) | safeJS ) ( printf "%s" ( $.Site.Params.katex.options | jsonify )) | safeHTMLAttr }}></script>
 {{ end -}}
 
-{{ $jsPopper := resources.GetRemote "https://cdn.jsdelivr.net/npm/popper.js@1.16.1/dist/umd/popper.min.js" -}}
+{{ $jsPopper := resources.GetRemote "https://cdnjs.cloudflare.com/ajax/libs/popper.js/2.9.2/umd/popper.min.js" -}}
 {{ $jsBs := resources.Get "vendor/bootstrap/dist/js/bootstrap.js" -}}
 {{ $jsBase := resources.Get "js/base.js" -}}
 {{ $jsAnchor := resources.Get "js/anchor.js" -}}
@@ -70,6 +70,9 @@
 
 {{ if .Site.Params.prism_syntax_highlighting -}}
   <script src='{{ "js/prism.js" | relURL }}'></script>
+{{ else -}}
+  {{ $c2cJS := resources.Get "js/click-to-copy.js" | minify |  fingerprint }}
+  <script defer src="{{ $c2cJS.RelPermalink }}" integrity="{{ $c2cJS.Data.Integrity }}" crossorigin="anonymous"></script>
 {{ end -}}
 
 <script src='{{ "js/tabpane-persist.js" | relURL }}'></script>