fix a race condition in handleScrollEvent (#85)

package.json

@@ -1,7 +1,7 @@
 {
   "name": "tinode-webapp",
   "description": "Tinode messenger for the web",
-  "version": "0.17.9",
+  "version": "0.17.10-rc1",
   "repository": {
     "type": "git",
     "url": "https://github.com/tinode/example-react-js.git"
@@ -68,7 +68,7 @@
     "react": "^17.0.2",
     "react-dom": "^17.0.2",
     "react-intl": "^5.20.2",
-    "tinode-sdk": "^0.17.9"
+    "tinode-sdk": "^0.17.10-rc1"
   },
   "devDependencies": {
     "@babel/core": "^7.14.5",

src/version.js

@@ -1,3 +1,3 @@
 // This is a generated file. Don't edit.
 
-export const PACKAGE_VERSION = "0.17.9";
+export const PACKAGE_VERSION = "0.17.10-rc1";

src/views/messages-view.jsx

@@ -365,23 +365,19 @@ class MessagesView extends React.Component {
   // Get older messages
   handleScrollEvent(event) {
     this.setState({scrollPosition: event.target.scrollHeight - event.target.scrollTop});
+    if (this.state.fetchingMessages) {
+      return;
+    }
+
     if (event.target.scrollTop <= 0) {
-      this.setState((prevState, props) => {
-        const newState = {};
-        if (!prevState.fetchingMessages) {
-          const topic = this.props.tinode.getTopic(this.state.topic);
-          if (topic && topic.isSubscribed() && topic.msgHasMoreMessages()) {
-            newState.fetchingMessages = true;
-            topic.getMessagesPage(MESSAGES_PAGE)
-              .then(() => this.setState({fetchingMessages: false}))
-              .catch((err) => {
-                this.setState({fetchingMessages: false});
-                this.props.onError(err.message, 'err');
-              });
-          }
-        }
-        return newState;
-      });
+      const topic = this.props.tinode.getTopic(this.state.topic);
+      if (topic && topic.isSubscribed() && topic.msgHasMoreMessages()) {
+        this.setState({fetchingMessages: true}, () => {
+          topic.getMessagesPage(MESSAGES_PAGE)
+            .catch((err) => this.props.onError(err.message, 'err'))
+            .finally(() => this.setState({fetchingMessages: false}));
+          });
+      }
     }
   }
 

version.js

@@ -1,3 +1,3 @@
 // This is a generated file. Don't edit.
 
-const PACKAGE_VERSION = "0.17.9";
+const PACKAGE_VERSION = "0.17.10-rc1";