UXP panel content area does not fill the panel (grey margin right/bottom) – InDesign 21.6 macOS

InDesign
1

Hello,

In InDesign 21.6 on macOS, the content area of UXP panels does not fill the panel.
A grey, unusable margin remains on the right and at the bottom (about 20% of the panel),
whether the panel is floating or docked, and whatever its size.

Steps to reproduce (with the default template, no custom code):

  1. UXP Developer Tool > Create Plugin > InDesign starter template, then Load.

  2. In index.html, replace the body content with:

    Test

  3. Reload and resize the panel.

Result: the red area stops at roughly 80% of the panel width and height;
the rest of the panel stays grey (see screenshot).
Expected: the red area fills the whole panel.

Additional observations from my own plugin:

  • document.documentElement.clientWidth/clientHeight stay fixed (860 x 836)
    whatever the panel size;
  • window.innerWidth / innerHeight are undefined;
  • the window “resize” event never fires.
  • UI scaling is at 100%, devicePixelRatio = 1.

Environment: InDesign 21.6, macOS 26.6.2, UXP Developer Tool 2.3.0.5.

Is this a known issue, and is there a workaround?
Thank you.

Capture d’écran 2026-11-02 à 12.52.33
Capture d’écran 2026-11-02 à 12.52.331574×1356 88.1 KB

2

Hi,

I can’t immediately reproduce what you are talking about, probably because I don’t know what you mean by this:

If you want to share what you have in index.html, I’d be happy to take a look.

Philip

3

Hi Philip,

Thanks for your reply! The forum stripped the HTML from my post. Here is the full index.html of the test plugin (default InDesign template created with UXP Developer Tool, only the body changed):

<!DOCTYPE html>
<html>
<head>
  <script src="main.js"></script>
</head>
<style>
  .wrapper {
    position: absolute;
    top: 0; left: 0; right: 0; bottom: 0;
    width: 100vw; height: 100vh;
    flex-direction: column;
    display: flex;
    padding: 12px;
  }
</style>
<body>
  <div style="background:red; position:absolute; top:0; left:0; right:0; bottom:0;">
    <p> Congratulations! You just created your first plugin.</p>
  </div>
</body>
</html>

The div is anchored to the 4 edges, so it should fill the whole panel. Instead, the red area stops at about 80% of the panel width and height, and the rest stays grey (see the screenshot in my first post). It happens with the panel floating or docked, whatever its size.

In my own plugin, document.documentElement.clientWidth/clientHeight always report 860 x 836, whatever the actual panel size, and window.innerWidth/innerHeight are undefined.

Environment: InDesign 21.6, macOS 26.6.2, UXP Developer Tool 2.3.0.5.

Thanks for looking into it!

4

Note: I’ve edited my reply above to fix the code formatting (it was broken in the email notification). Please check the forum version. Thanks!

5

Very weird!

I still can’t reproduce what you’re seeing.

I’ve started from UXP Developer Tools. Clicked Create Plugin and selected the “quick-starter” template. Then loaded the plugin in UDT (no building or anything like that.). I’ve copied and pasted your code for index.html into my index.html file, reloaded and the panel is filled with red as you expected it to be – no grey margin.

I’m using the same version of Indesign as you and the same version of Developer Tools. I’m also on a Mac but not the same version. I don’t see the problem on my (intel) iMac running Sequoia 15.7.9, nor on my (M1) MacBook running Sonoma 14.2.1.

If you want to package up your rogue plugin and attach it to a message here, I can load it without touching the code just to see what it does. Otherwise, I’m at a bit of a loss. If you’ve really not made any other change to any other file (not changed the manifest in any way, for instance), it’s just weird!

Philip

6

Hi Philip,

Thanks a lot for testing! I’ve done more tests on my side:

  • macOS 26.6.2 (Tahoe), MacBook Apple M1 Max + two Philips 328P6VU 4K monitors.
  • The grey margin appears on all three displays, including the built-in Retina display.
  • Same result with the main display set to “Default” resolution or to a scaled resolution (InDesign restarted each time).
  • InDesign UI scaling is at 100%.

I can’t attach files as a new user, so here is the manifest.json of the test plugin, unchanged from the template (the index.html is in my previous reply):

{
  "id": "Test-s0o1vm",
  "name": "Test PLUG",
  "version": "1.0.0",
  "main": "index.html",
  "host": {
    "app": "ID",
    "minVersion": "21.6.0"
  },
  "manifestVersion": 5,
  "entrypoints": [
    {
      "type": "command",
      "id": "showAlert",
      "label": "Show alert"
    },
    {
      "type": "panel",
      "id": "showPanel",
      "minimumSize": {
        "width": 230,
        "height": 200
      },
      "maximumSize": {
        "width": 2000,
        "height": 2000
      },
      "preferredDockedSize": {
        "width": 300,
        "height": 300
      },
      "preferredFloatingSize": {
        "width": 300,
        "height": 300
      },
      "label": {
        "default": "Show panel"
      },
      "icons": [
        {
          "width": 23,
          "height": 23,
          "path": "icons/dark.png",
          "scale": [
            1,
            2
          ],
          "theme": [
            "darkest",
            "dark",
            "medium"
          ]
        },
        {
          "width": 23,
          "height": 23,
          "path": "icons/light.png",
          "scale": [
            1,
            2
          ],
          "theme": [
            "lightest",
            "light"
          ]
        }
      ]
    }
  ],
  "icons": [
    {
      "width": 48,
      "height": 48,
      "path": "icons/plugin.png",
      "scale": [
        1,
        2
      ],
      "theme": [
        "darkest",
        "dark",
        "medium",
        "lightest",
        "light",
        "all"
      ],
      "species": [
        "pluginList"
      ]
    }
  ]
}

Since you can’t reproduce it on Sequoia or Sonoma, it might be specific to macOS 26 Tahoe. Could someone at Adobe check with macOS 26?

Thanks again,

7

Your manifest looks to be identical to what I have.

Or perhaps there is another developer here who is running Tahoe and could check.

Yes, would be great if someone at Adobe could check. However, I should probably warn you that historically, certainly as far as InDesign is concerned, we haven’t had help from Adobe here. I’d love them to prove me wrong and step in in this instance.

Philip