Follow-up: Stabilize Canvas preview for in-place `vh` updates and tall content
>>> [!note] Migrated issue
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Reported by: [lauriii](https://www.drupal.org/user/1078742)
Related to !1043
>>>
<h3 id="overview">Overview</h3>
<p>Follow-up to <span class="drupalorg-gitlab-issue-link drupalorg-gitlab-link-wrapper"><a href="https://git.drupalcode.org/project/canvas/-/work_items/3587909" class="drupalorg-gitlab-link">https://git.drupalcode.org/project/canvas/-/work_items/3587909</a></span>. Pinning <code>vh</code>-style blocks on iframe load can still fail when editing prop values for code components: <code>canvas-island</code> re-renders replace DOM and drop inline constraints until a full iframe swap, so the iframe height can spiral again.</p>
<h3 id="proposed-resolution">Proposed resolution</h3>
<p>Re-apply <code>vh</code> detection after <code><canvas-island></code> subtree update and harden ratio logic for content taller than one viewport.</p>
<h3 id="ui-changes">User interface changes</h3>
<p>None</p>
issue