Fix: split panel properly recalculates when going from hidden to shown

docs/pages/resources/changelog.md

@@ -12,6 +12,10 @@ Components with the <sl-badge variant="warning" pill>Experimental</sl-badge> bad
 
 New versions of Shoelace are released as-needed and generally occur when a critical mass of changes have accumulated. At any time, you can see what's coming in the next release by visiting [next.shoelace.style](https://next.shoelace.style).
 
+## Next
+
+- Fixed a bug in `<sl-split-panel>` that caused it not to recalculate it's position when going from being `display: none;` to its original display value. [#]
+
 ## 2.15.0
 
 - Added the Slovenian translation [#1893]

src/components/split-panel/split-panel.component.ts

@@ -189,6 +189,14 @@ export default class SlSplitPanel extends ShoelaceElement {
     const { width, height } = entries[0].contentRect;
     this.size = this.vertical ? height : width;
 
+    // There's some weird logic that gets `this.cachedPositionInPixels = NaN` or `this.position === Infinity` when
+    // a split-panel goes from `display: none;` to showing.
+    if (isNaN(this.cachedPositionInPixels) || this.position === Infinity) {
+      this.cachedPositionInPixels = Number(this.getAttribute('position-in-pixels'));
+      this.positionInPixels = Number(this.getAttribute('position-in-pixels'));
+      this.position = this.pixelsToPercentage(this.positionInPixels);
+    }
+
     // Resize when a primary panel is set
     if (this.primary) {
       this.position = this.pixelsToPercentage(this.cachedPositionInPixels);