webview js [nfc]: Make at-bottom logic more explicit in resize handler.

This version is algebraically equivalent... but seems more like what we really mean here.
zulip · May 5, 2020 · d047118 · d047118
1 parent b88af49
commit d047118
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diff --git a/src/webview/js/generatedEs3.js b/src/webview/js/generatedEs3.js
@@ -139,8 +139,9 @@ var compiledWebviewJs = (function (exports) {
   window.addEventListener('resize', function (event) {
     var heightChange = documentBody.clientHeight - viewportHeight;
     viewportHeight = documentBody.clientHeight;
+    var maxScrollTop = documentBody.scrollHeight - documentBody.clientHeight;
 
-    if (documentBody.scrollHeight === documentBody.scrollTop + documentBody.clientHeight) {
+    if (documentBody.scrollTop === maxScrollTop) {
       return;
     }
 

diff --git a/src/webview/js/js.js b/src/webview/js/js.js
@@ -183,7 +183,8 @@ window.addEventListener('resize', event => {
   // higher than we started.
   //
   // If that happened, we'll be at the very bottom now.
-  if (documentBody.scrollHeight === documentBody.scrollTop + documentBody.clientHeight) {
+  const maxScrollTop = documentBody.scrollHeight - documentBody.clientHeight;
+  if (documentBody.scrollTop === maxScrollTop) {
     // We're at the very bottom of the content.  Don't scroll.
     //
     // This does mean if you're near the bottom, and then the viewport grows