Scrolling inside nested flexboxes

I am working on a React app that has modal content with some tabs that sometimes require scrolling inside. However, the problem is that I cannot get the scrolling of the relevant content.

The modal is split into 3 main sections:

• Heading
  • Should always be visible at the top of the modal
• Content
  • Should fill the gap between the header and footer , but never force it to appear
• Footer
  • Must always be visible under Content
  • This could mean at the bottom of the modal (if the Content is filling the remaining space) or below the Content (if the Content is t filling the space)

While it would be easy to implement (and I've already done it), the problem arises because the Content shouldn't scroll, but rather something inside it. The images below show two examples of intended behavior, one with long content that needs to scroll, and one without.

I am using a custom tab that does something inside a container. This container (white in the images below) is what needs to be scrolled if needed.

The farthest I have come can be found in the following CodePen code and example. Currently, I can scroll to an element containing the intended scrollable content, but I cannot actually scroll that content. If you check Pen, you can see that it (for some reason) passes by the containing element.

Sample code

CodePen example

Html

<div class="modal">
  <div class="background" />
  <div class="modal_content">
    <div class="header">Random header</div>
    <div class="tabbed_content">
      <div class="tabs">
        <div class="tab active">Tab 1</div>
        <div class="tab">Tab 2</div>
      </div>
      <div class="content">
        <div class="scrollable">
          Tabbed Content
          <br /><br /><br /><br /><br /><br />
          Another Couple Lines
          <br /><br /><br /><br /><br /><br />
          More Tabbed Content
          <br /><br /><br /><br /><br /><br />
          Even More Content!
          <br /><br /><br /><br /><br /><br />
          Why not more yet!
          <br /><br /><br /><br /><br /><br />
          Some Ending Content
          <br /><br /><br /><br /><br /><br />
          Final Content!
        </div>
      </div>
    </div>
    <div class='footer'>
      <button class='button'>
        Done
      </button>
    </div>
  </div>
</div>

      

        
        
        
      

    

CSS

body {
  font-family: 'Montserrat', sans-serif;
}

/* Modal wrapper */
.modal {
  position: fixed;
  top: 0;
  right: 0;
  bottom: 0;
  left: 0;
}

/* Modal background styles */
.background {
  position: absolute;
  height: 100%;
  width: 100%;
  background-color: rgba(0, 0, 0, 0.5)
}

/* Modal content */
.modal_content {
  height: 100vh;
  display: flex;
  flex-direction: column;
  width: 85%;
  margin: 0 auto;
  background-color: white;
}

.header {
  margin-bottom: 1rem;
  padding: 1rem;
  font-size: 125%;
  text-align: center;
  font-weight: bold;
  background-color: #EEEEEE;
  border-bottom: 1px solid #CECECE;
}

/* Contains the tabs and content */
.tabbed_content {
  display: flex;
  flex-direction: column;
  align-items: stretch;
}

/* IGNORE */
.tabs {
  display: flex;
  /* NOTE: Added to stop them from hiding */
  flex-shrink: 0;
}

/* IGNORE */
.tab {
  flex-grow: 1;
  margin-top: 8px;
  padding: 0.5rem;
  text-align: center;
  background-color: #CECECE;
}

/* IGNORE */
.tab.active {
  margin-top: 0;
  font-weight: bold;
  background-color: #EEEEEE;
}

/* Contains the current tab content */
/* NOTE: This shouldn't scroll */
.content {
  padding: 1rem;
  background-color: #EEEEEE;

  /* NOTE: Currently the closest I can come */
  /*overflow: auto;*/
}

/* IMPORTANT: This should scroll if necessary! */
.scrollable {
  padding: 0.5rem;
  background-color: white;
  /* NOTE: Can't get this to scroll */
  /*overflow: auto;*/
  border: 1px dashed #CECECE;
}

.footer {
  display: flex;
  flex-align: center;
  flex-shrink: 0;
  justify-content: center;
  margin-top: 1rem;
  padding: 1rem;
  border-top: 1px dashed #CECECE;
}

/* IGNORE */
.button {
  padding: 0.75rem 1rem;
  font-size: 90%;
  color: white;
  background-color: lightseagreen;
  border: none;
  border-radius: 2px;
  cursor: pointer;
}

      

        
        
        
      

    

I'm almost at it with this one (spent 2 hours showing). Thanks in advance for your help!

PS I also need to worry about stopping the background scrolling while the modal is open at some point ...