improve signing form header

app/javascript/elements/scroll_buttons.js

@@ -0,0 +1,56 @@
+export default class extends HTMLElement {
+  connectedCallback () {
+    this.header = document.querySelector('#signing_form_header')
+
+    window.addEventListener('scroll', this.onScroll.bind(this))
+    window.addEventListener('resize', this.onResize.bind(this))
+
+    this.onResize()
+  }
+
+  disconnectedCallback () {
+    window.removeEventListener('scroll', this.onScroll.bind(this))
+    window.removeEventListener('resize', this.onResize.bind(this))
+  }
+
+  onResize () {
+    if (this.isNarrow()) {
+      this.hideButtons(true)
+    } else if (this.isHeaderNotVisible()) {
+      this.showButtons()
+    }
+  }
+
+  isNarrow () {
+    return window.innerWidth < 1366
+  }
+
+  onScroll () {
+    if (this.isHeaderNotVisible() && !this.isNarrow()) {
+      this.showButtons()
+    } else {
+      this.hideButtons()
+    }
+  }
+
+  isHeaderNotVisible () {
+    const rect = this.header.getBoundingClientRect()
+    return rect.bottom <= 0 || rect.top >= window.innerHeight
+  }
+
+  showButtons () {
+    this.classList.remove('hidden', '-translate-y-10', 'opacity-0')
+    this.classList.add('translate-y-0', 'opacity-100')
+  }
+
+  hideButtons () {
+    this.classList.remove('translate-y-0', 'opacity-100')
+    this.classList.add('-translate-y-10', 'opacity-0')
+
+    setTimeout(() => {
+      if (this.classList.contains('-translate-y-10')) {
+        this.classList.add('hidden')
+      }
+    }, 300)
+  }
+}

app/javascript/form.js

@@ -4,12 +4,14 @@ import Form from './submission_form/form'
 import DownloadButton from './elements/download_button'
 import ToggleSubmit from './elements/toggle_submit'
 import FetchForm from './elements/fetch_form'
+import ScrollButtons from './elements/scroll_buttons'
 
 const safeRegisterElement = (name, element, options = {}) => !window.customElements.get(name) && window.customElements.define(name, element, options)
 
 safeRegisterElement('download-button', DownloadButton)
 safeRegisterElement('toggle-submit', ToggleSubmit)
 safeRegisterElement('fetch-form', FetchForm)
+safeRegisterElement('scroll-buttons', ScrollButtons)
 safeRegisterElement('submission-form', class extends HTMLElement {
   connectedCallback () {
     this.appElem = document.createElement('div')

app/javascript/submission_form/completed.vue

@@ -193,9 +193,9 @@ export default {
       })
     }
 
-    if (window.decline_button) {
-      window.decline_button.setAttribute('disabled', 'true')
-    }
+    document.querySelectorAll('#decline_button').forEach((button) => {
+      button.setAttribute('disabled', 'true')
+    })
   },
   methods: {
     sendCopyToEmail () {