Dynamically resize columns in css grid layout with mouse

The solution is to not use explicit fixed column size (grid-template-columns: 200px 1fr;) but use instead relative column sizes such as grid-template-columns: 0.2fr 1fr; — then the grid CSS engine will handle the resizing of adjacent boxes. Next thing is to add nested divs inside the grid boxes, set their min-height/width to 100% and make them resizable via jqueryui resizable.

The fixed jsfiddle.

/* Javscript */

$('.left_inner').resizable();
$('.right_top_inner').resizable();
$('.right_bottom_inner').resizable();
/* CSS */

	.grid {
		display: grid;
		grid-template-columns: 0.2fr 1fr;
		grid-template-rows: 1fr 4fr;
        grid-gap: 3px;
		position: relative;
	}

	.left {
		grid-row: 1 / span 2;
	}

	.right_top {
		grid-column: 2;
		grid-row: 1;
	}

	.right_bottom {
		grid-column: 2;
		grid-row: 2;
	}

	.left_inner {
		background-color: #fedcd2;
		padding: 0;
		width: 100%;
		min-width: 100%;
		height: 100%;
		min-height: 100%;
		text-align: center;
	}

	.right_top_inner {
		background-color: #f9cf00;
		padding: 0;
		width: 100%;
		min-width: 100%;
		height: 100%;
		min-height: 100%;
		text-align: center;
	}

	.right_bottom_inner {
		background-color: #f8eee7;
		padding: 0;
		width: 100%;
		min-width: 100%;
		height: 100%;
		min-height: 100%;
		text-align: center;
	}
<!-- HTML -->

<script src="//code.jquery.com/jquery-2.1.3.min.js"></script>
<link rel="stylesheet" href="//cdnjs.cloudflare.com/ajax/libs/jqueryui/1.10.0/css/smoothness/jquery-ui-1.10.0.custom.min.css" />
<script src="//cdnjs.cloudflare.com/ajax/libs/jqueryui/1.10.0/jquery-ui.js"></script>

	<main class="grid">
	 <aside class='left'>
	  <div class="left_inner">
		drag the bottom right handle to resize
	  </div>
	 </aside>
	 <section class="right_top">
	  <div class="right_top_inner">right_top_inner</div>
	 </section>
	 <section class="right_bottom">
	  <div class="right_bottom_inner">right_bottom_inner</div>
	 </section>
	</main>

❗️ While this works in the simplest possible scenario, it gets problematic in a real life use case. I tried jquery-ui layout which worked somewhat better (here is a demo), but the lib is outdated and is glitchy with frames, so I went with angular-split-pane (based on angular 1) which works fine and is smaller in size. (update: it appears that the project is currently abandoned so probably not the best choice)


What you are looking to achieve is possible using only css. I've modified your example. The main takeaways are this:

  1. Most importantly, try not to insert raw content in your semantic layout tags. Use header, paragraph, and list tags rather than text and br tags. This makes your code both easier to read and easier to reason about. Many of your problems happened because of how reflow is handled in grid areas.
  2. Use grid-template to simplify your layout as it will make breakpoint reflow easier later on.
  3. Use overflow: auto; along with specifying resize: vertical/horizontal. Without setting overflow, resize will fail.
  4. Use min/max width/height values to create boundaries for resizing.

body {
    margin: 10px;
    height: 100%;
}

main {
    display: grid;
    border: 3px dotted red;
    padding: 3px;
    grid-gap: 3px;
    
    grid-template: 
    "nav head" min-content
    "nav main" 1fr
        / min-content 1fr;
}

nav {
    grid-area: nav;
    border: 3px dotted blue;
    overflow: auto;
    resize: horizontal;
    
    min-width: 120px;
    max-width: 50vw;
}

header {
    grid-area: head;
    border: 3px dotted orange;
    overflow: auto;
    resize: vertical;
    
    min-height: min-content;
    max-height: 200px;
}

section {
    grid-area: main;
    border: 3px dotted gray;
}
<main>
  <nav>
    <ul>
      <li>Nav Item</li>
      <li>Nav Item</li>
      <li>Nav Item</li>
      <li>Nav Item</li>
      <li>Nav Item</li>
      <li>Nav Item</li>
    </ul>
  </nav>

  <header>
    <h1>Header Title</h1>
    <small>Header Subtitle</small>
  </header>

  <section>
    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</p>
  </section>
</main>

Tags:

Javascript

Css

Jquery

Resize

Css Grid

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