Force a content measure when the editor comes into view

FIX: Fix a bug that could cause the editor to not measure its layout the first time
it came into view.

See https://discuss.codemirror.net/t/bug-gutters-height-miscalculate-when-the-view-is-not-on-viewport/3812

src/domobserver.ts

@@ -99,7 +99,7 @@ export class DOMObserver {
     if (typeof IntersectionObserver == "function") {
       this.intersection = new IntersectionObserver(entries => {
         if (this.parentCheck < 0) this.parentCheck = setTimeout(this.listenForScroll.bind(this), 1000)
-        if (entries.length > 0 && entries[entries.length - 1].intersectionRatio > 0 != this.intersecting) {
+        if (entries.length > 0 && (entries[entries.length - 1].intersectionRatio > 0) != this.intersecting) {
           this.intersecting = !this.intersecting
           if (this.intersecting != this.view.inView)
             this.onScrollChanged(document.createEvent("Event"))

src/viewstate.ts

@@ -239,7 +239,11 @@ export class ViewState {
     let pixelViewport = this.printing ? {top: -1e8, bottom: 1e8, left: -1e8, right: 1e8} : visiblePixelRange(dom, this.paddingTop)
     let dTop = pixelViewport.top - this.pixelViewport.top, dBottom = pixelViewport.bottom - this.pixelViewport.bottom
     this.pixelViewport = pixelViewport
-    this.inView = this.pixelViewport.bottom > this.pixelViewport.top && this.pixelViewport.right > this.pixelViewport.left
+    let inView = this.pixelViewport.bottom > this.pixelViewport.top && this.pixelViewport.right > this.pixelViewport.left
+    if (inView != this.inView) {
+      this.inView = inView
+      if (inView) measureContent = true
+    }
     if (!this.inView) return 0
 
     if (measureContent) {