From 16641a5bb1e012d8c7d6f17ab249c4eec7c30644 Mon Sep 17 00:00:00 2001
From: Megan Rogge <merogge@microsoft.com>
Date: Fri, 5 Nov 2021 11:08:23 -0700
Subject: [PATCH] Revert "Revert "Avoid property use and float->number
 conversion""

This reverts commit b627f003e3c8c62e14500bf2adc6f4d210491070.
---
 src/browser/Viewport.ts | 17 ++++++++++++++---
 1 file changed, 14 insertions(+), 3 deletions(-)

diff --git a/src/browser/Viewport.ts b/src/browser/Viewport.ts
index d8df4efa..3c9bea4c 100644
--- a/src/browser/Viewport.ts
+++ b/src/browser/Viewport.ts
@@ -8,6 +8,8 @@ import { addDisposableDomListener } from 'browser/Lifecycle';
 import { IColorSet, IViewport } from 'browser/Types';
 import { ICharSizeService, IRenderService } from 'browser/services/Services';
 import { IBufferService, IOptionsService } from 'common/services/Services';
+import { IBuffer } from 'common/buffer/Types';
+import { IRenderDimensions } from 'browser/renderer/Types';
 
 const FALLBACK_SCROLL_BAR_WIDTH = 15;
 
@@ -18,12 +20,15 @@ const FALLBACK_SCROLL_BAR_WIDTH = 15;
 export class Viewport extends Disposable implements IViewport {
   public scrollBarWidth: number = 0;
   private _currentRowHeight: number = 0;
+  private _currentScaledCellHeight: number = 0;
   private _lastRecordedBufferLength: number = 0;
   private _lastRecordedViewportHeight: number = 0;
   private _lastRecordedBufferHeight: number = 0;
   private _lastTouchY: number = 0;
   private _lastScrollTop: number = 0;
   private _lastHadScrollBar: boolean = false;
+  private _activeBuffer: IBuffer;
+  private _renderDimensions: IRenderDimensions;
 
   // Stores a partial line amount when scrolling, this is used to keep track of how much of a line
   // is scrolled so we can "scroll" over partial lines and feel natural on touchpads. This is a
@@ -51,6 +56,12 @@ export class Viewport extends Disposable implements IViewport {
     this._lastHadScrollBar = true;
     this.register(addDisposableDomListener(this._viewportElement, 'scroll', this._onScroll.bind(this)));
 
+    // Track properties used in performance critical code manually to avoid using slow getters
+    this._activeBuffer = this._bufferService.buffer;
+    this.register(this._bufferService.buffers.onBufferActivate(e => this._activeBuffer = e.activeBuffer));
+    this._renderDimensions = this._renderService.dimensions;
+    this.register(this._renderService.onDimensionsChange(e => this._renderDimensions = e));
+
     // Perform this async to ensure the ICharSizeService is ready.
     setTimeout(() => this.syncScrollArea(), 0);
   }
@@ -79,6 +90,7 @@ export class Viewport extends Disposable implements IViewport {
   private _innerRefresh(): void {
     if (this._charSizeService.height > 0) {
       this._currentRowHeight = this._renderService.dimensions.scaledCellHeight / window.devicePixelRatio;
+      this._currentScaledCellHeight = this._renderService.dimensions.scaledCellHeight;
       this._lastRecordedViewportHeight = this._viewportElement.offsetHeight;
       const newBufferHeight = Math.round(this._currentRowHeight * this._lastRecordedBufferLength) + (this._lastRecordedViewportHeight - this._renderService.dimensions.canvasHeight);
       if (this._lastRecordedBufferHeight !== newBufferHeight) {
@@ -126,14 +138,13 @@ export class Viewport extends Disposable implements IViewport {
     }
 
     // If the buffer position doesn't match last scroll top
-    const newScrollTop = this._bufferService.buffer.ydisp * this._currentRowHeight;
-    if (this._lastScrollTop !== newScrollTop) {
+    if (this._lastScrollTop !== this._activeBuffer.ydisp * this._currentRowHeight) {
       this._refresh(immediate);
       return;
     }
 
     // If row height changed
-    if (this._renderService.dimensions.scaledCellHeight / window.devicePixelRatio !== this._currentRowHeight) {
+    if (this._renderDimensions.scaledCellHeight !== this._currentScaledCellHeight) {
       this._refresh(immediate);
       return;
     }