try fixing intermittent narrower window

[eagleoflqj]

To reproduce it, apply this patch on current branch, which forces to render based on sizes calculated last time.

diff --git a/page/ux.ts b/page/ux.ts
index f34708b..4b16fa1 100644
--- a/page/ux.ts
+++ b/page/ux.ts
@@ -32,10 +32,12 @@ export function resize (dx: number, dy: number, dragging: boolean) {
   adaptWindowSize()
   if (!dragging) {
     // Sometimes getBoundingClientRect is called when the element is not fully rendered.
-    window.requestAnimationFrame(adaptWindowSize)
+    // window.requestAnimationFrame(adaptWindowSize)
   }
 }
 
+let last = {}
+
 function getBoundingRectWithShadow (element: Element): ShadowBox {
   const rect = element.getBoundingClientRect()
   const elementXHi = rect.x + rect.width
@@ -62,7 +64,8 @@ function getBoundingRectWithShadow (element: Element): ShadowBox {
   // rect.height and rect.width will cover the whole panel and its shadow.
   rect.width = xHi
   rect.height = yHi
-  return {
+  const now = last
+  last = {
     shadowTop: rect.y,
     shadowRight: xHi - elementXHi,
     shadowBottom: yHi - elementYHi,
@@ -70,6 +73,7 @@ function getBoundingRectWithShadow (element: Element): ShadowBox {
     fullWidth: xHi,
     fullHeight: yHi
   }
+  return now
 }
 
 document.addEventListener('mousedown', e => {

In Pinyin, type a s, you should see

every time.
Then uncomment window.requestAnimationFrame(adaptWindowSize), you should see

every time.

[ksqsf]

Can confirm requestAnimationFrame works. LGTM