simplify wheel handlers

src/browser/Terminal.ts

@@ -699,8 +699,7 @@ export class Terminal extends CoreTerminal implements ITerminal {
       },
       wheel: (ev: WheelEvent) => {
         sendEvent(ev);
-        ev.preventDefault();
-        return this.cancel(ev);
+        return this.cancel(ev, true);
       },
       mousedrag: (ev: MouseEvent) => {
         // deal only with move while a button is held
@@ -795,33 +794,31 @@ export class Terminal extends CoreTerminal implements ITerminal {
     }));
 
     this.register(addDisposableDomListener(el, 'wheel', (ev: WheelEvent) => {
-      if (!requestedEvents.wheel) {
+      // do nothing, if app side handles wheel itself
+      if (requestedEvents.wheel) return;
+
+      if (!this.buffer.hasScrollback) {
         // Convert wheel events into up/down events when the buffer does not have scrollback, this
         // enables scrolling in apps hosted in the alt buffer such as vim or tmux.
-        if (!this.buffer.hasScrollback) {
-          const amount = this.viewport!.getLinesScrolled(ev);
+        const amount = this.viewport!.getLinesScrolled(ev);
 
-          // Do nothing if there's no vertical scroll
-          if (amount === 0) {
-            return;
-          }
-
-          // Construct and send sequences
-          const sequence = C0.ESC + (this.coreService.decPrivateModes.applicationCursorKeys ? 'O' : '[') + (ev.deltaY < 0 ? 'A' : 'B');
-          let data = '';
-          for (let i = 0; i < Math.abs(amount); i++) {
-            data += sequence;
-          }
-          this.coreService.triggerDataEvent(data, true);
+        // Do nothing if there's no vertical scroll
+        if (amount === 0) {
+          return;
         }
-        return;
-      }
-    }, { passive: true }));
 
-    // allow wheel scrolling in
-    // the shell for example
-    this.register(addDisposableDomListener(el, 'wheel', (ev: WheelEvent) => {
-      if (requestedEvents.wheel) return;
+        // Construct and send sequences
+        const sequence = C0.ESC + (this.coreService.decPrivateModes.applicationCursorKeys ? 'O' : '[') + (ev.deltaY < 0 ? 'A' : 'B');
+        let data = '';
+        for (let i = 0; i < Math.abs(amount); i++) {
+          data += sequence;
+        }
+        this.coreService.triggerDataEvent(data, true);
+        return this.cancel(ev, true);
+      }
+
+      // normal viewport scrolling
+      // conditionally stop event, if the viewport still had rows to scroll within
       if (!this.viewport!.onWheel(ev)) {
         return this.cancel(ev);
       }