1 files changed, 121 insertions, 0 deletions
diff --git a/web_src/js/utils/dom.js b/web_src/js/utils/dom.js
index c160d37f6c..6a9ee56eeb 100644
--- a/web_src/js/utils/dom.js
+++ b/web_src/js/utils/dom.js
@@ -49,3 +49,124 @@ export function onDomReady(cb) {
     cb();
   }
 }
+
+// autosize a textarea to fit content. Based on
+// https://github.com/github/textarea-autosize
+// ---------------------------------------------------------------------
+// Copyright (c) 2018 GitHub, Inc.
+//
+// Permission is hereby granted, free of charge, to any person obtaining
+// a copy of this software and associated documentation files (the
+// "Software"), to deal in the Software without restriction, including
+// without limitation the rights to use, copy, modify, merge, publish,
+// distribute, sublicense, and/or sell copies of the Software, and to
+// permit persons to whom the Software is furnished to do so, subject to
+// the following conditions:
+//
+// The above copyright notice and this permission notice shall be
+// included in all copies or substantial portions of the Software.
+// ---------------------------------------------------------------------
+export function autosize(textarea, {viewportMarginBottom = 0} = {}) {
+  let isUserResized = false;
+  // lastStyleHeight and initialStyleHeight are CSS values like '100px'
+  let lastMouseX, lastMouseY, lastStyleHeight, initialStyleHeight;
+
+  function onUserResize(event) {
+    if (isUserResized) return;
+    if (lastMouseX !== event.clientX || lastMouseY !== event.clientY) {
+      const newStyleHeight = textarea.style.height;
+      if (lastStyleHeight && lastStyleHeight !== newStyleHeight) {
+        isUserResized = true;
+      }
+      lastStyleHeight = newStyleHeight;
+    }
+
+    lastMouseX = event.clientX;
+    lastMouseY = event.clientY;
+  }
+
+  function overflowOffset() {
+    let offsetTop = 0;
+    let el = textarea;
+
+    while (el !== document.body && el !== null) {
+      offsetTop += el.offsetTop || 0;
+      el = el.offsetParent;
+    }
+
+    const top = offsetTop - document.defaultView.scrollY;
+    const bottom = document.documentElement.clientHeight - (top + textarea.offsetHeight);
+    return {top, bottom};
+  }
+
+  function resizeToFit() {
+    if (isUserResized) return;
+    if (textarea.offsetWidth <= 0 && textarea.offsetHeight <= 0) return;
+
+    try {
+      const {top, bottom} = overflowOffset();
+      const isOutOfViewport = top < 0 || bottom < 0;
+
+      const computedStyle = getComputedStyle(textarea);
+      const topBorderWidth = parseFloat(computedStyle.borderTopWidth);
+      const bottomBorderWidth = parseFloat(computedStyle.borderBottomWidth);
+      const isBorderBox = computedStyle.boxSizing === 'border-box';
+      const borderAddOn = isBorderBox ? topBorderWidth + bottomBorderWidth : 0;
+
+      const adjustedViewportMarginBottom = bottom < viewportMarginBottom ? bottom : viewportMarginBottom;
+      const curHeight = parseFloat(computedStyle.height);
+      const maxHeight = curHeight + bottom - adjustedViewportMarginBottom;
+
+      textarea.style.height = 'auto';
+      let newHeight = textarea.scrollHeight + borderAddOn;
+
+      if (isOutOfViewport) {
+        // it is already out of the viewport:
+        // * if the textarea is expanding: do not resize it
+        if (newHeight > curHeight) {
+          newHeight = curHeight;
+        }
+        // * if the textarea is shrinking, shrink line by line (just use the
+        //   scrollHeight). do not apply max-height limit, otherwise the page
+        //   flickers and the textarea jumps
+      } else {
+        // * if it is in the viewport, apply the max-height limit
+        newHeight = Math.min(maxHeight, newHeight);
+      }
+
+      textarea.style.height = `${newHeight}px`;
+      lastStyleHeight = textarea.style.height;
+    } finally {
+      // ensure that the textarea is fully scrolled to the end, when the cursor
+      // is at the end during an input event
+      if (textarea.selectionStart === textarea.selectionEnd &&
+          textarea.selectionStart === textarea.value.length) {
+        textarea.scrollTop = textarea.scrollHeight;
+      }
+    }
+  }
+
+  function onFormReset() {
+    isUserResized = false;
+    if (initialStyleHeight !== undefined) {
+      textarea.style.height = initialStyleHeight;
+    } else {
+      textarea.style.removeProperty('height');
+    }
+  }
+
+  textarea.addEventListener('mousemove', onUserResize);
+  textarea.addEventListener('input', resizeToFit);
+  textarea.form?.addEventListener('reset', onFormReset);
+  initialStyleHeight = textarea.style.height ?? undefined;
+  if (textarea.value) resizeToFit();
+
+  return {
+    resizeToFit,
+    destroy() {
+      textarea.removeEventListener('mousemove', onUserResize);
+      textarea.removeEventListener('input', resizeToFit);
+      textarea.form?.removeEventListener('reset', onFormReset);
+    }
+  };
+}