better integration and experimentalPushRecycling option

src/Terminal.ts

@@ -106,7 +106,8 @@ const DEFAULT_OPTIONS: ITerminalOptions = {
   theme: null,
   rightClickSelectsWord: Browser.isMac,
   rendererType: 'canvas',
-  experimentalBufferLineImpl: 'JsArray'
+  experimentalBufferLineImpl: 'JsArray',
+  experimentalPushRecycling: false
 };
 
 export class Terminal extends EventEmitter implements ITerminal, IDisposable, IInputHandlingTerminal {
@@ -208,6 +209,9 @@ export class Terminal extends EventEmitter implements ITerminal, IDisposable, II
   private _screenDprMonitor: ScreenDprMonitor;
   private _theme: ITheme;
 
+  // bufferline to clone/copy from for new blank lines
+  private _blankLine: IBufferLine = null;
+
   public cols: number;
   public rows: number;
 
@@ -496,6 +500,7 @@ export class Terminal extends EventEmitter implements ITerminal, IDisposable, II
       case 'experimentalBufferLineImpl':
         this.buffers.normal.setBufferLineFactory(value);
         this.buffers.alt.setBufferLineFactory(value);
+        this._blankLine = null;
         break;
     }
     // Inform renderer of changes
@@ -1174,13 +1179,18 @@ export class Terminal extends EventEmitter implements ITerminal, IDisposable, II
    * @param isWrapped Whether the new line is wrapped from the previous line.
    */
   public scroll(isWrapped?: boolean): void {
-    // TODO: make blank a member
-    let blank: IBufferLine = (this as any)._blank;
-    if (!blank || blank.length !== this.cols) {
-      blank = this.buffer.getBlankLine(DEFAULT_ATTR, isWrapped);
-      (this as any)._blank = blank;
+    let newLine: IBufferLine;
+    const useRecycling = this.options.experimentalPushRecycling;
+    if (useRecycling) {
+      newLine = this._blankLine;
+      if (!newLine || newLine.length !== this.cols) {
+        newLine = this.buffer.getBlankLine(DEFAULT_ATTR, isWrapped);
+        this._blankLine = newLine;
+      }
+      newLine.isWrapped = !!(isWrapped);
+    } else {
+      newLine = this.buffer.getBlankLine(DEFAULT_ATTR, isWrapped);
     }
-    blank.isWrapped = !!(isWrapped);
 
     const topRow = this.buffer.ybase + this.buffer.scrollTop;
     const bottomRow = this.buffer.ybase + this.buffer.scrollBottom;
@@ -1191,9 +1201,13 @@ export class Terminal extends EventEmitter implements ITerminal, IDisposable, II
 
       // Insert the line using the fastest method
       if (bottomRow === this.buffer.lines.length - 1) {
-        (this.buffer.lines as any).pushRecycling((line: IBufferLine | undefined) => (line) ? line.copyFrom(blank) : blank.clone());
+        if (useRecycling) {
+          this.buffer.lines.pushRecycling((item) => (item) ? item.copyFrom(newLine) : newLine.clone());
+        } else {
+          this.buffer.lines.push(newLine);
+        }
       } else {
-        this.buffer.lines.splice(bottomRow + 1, 0, blank.clone());
+        this.buffer.lines.splice(bottomRow + 1, 0, (useRecycling) ? newLine.clone() : newLine);
       }
 
       // Only adjust ybase and ydisp when the buffer is not trimmed
@@ -1215,7 +1229,7 @@ export class Terminal extends EventEmitter implements ITerminal, IDisposable, II
       // scrollback, instead we can just shift them in-place.
       const scrollRegionHeight = bottomRow - topRow + 1/*as it's zero-based*/;
       this.buffer.lines.shiftElements(topRow + 1, scrollRegionHeight - 1, -1);
-      this.buffer.lines.set(bottomRow, blank.clone());
+      this.buffer.lines.set(bottomRow, (useRecycling) ? newLine.clone() : newLine);
     }
 
     // Move the viewport to the bottom of the buffer unless the user is

src/Types.ts

@@ -522,7 +522,7 @@ export interface IBufferLine {
   replaceCells(start: number, end: number, fill: CharData): void;
   resize(cols: number, fill: CharData, shrink?: boolean): void;
   fill(fillCharData: CharData): void;
-  copyFrom(line: IBufferLine): void;
+  copyFrom(line: IBufferLine): IBufferLine;
   clone(): IBufferLine;
 }
 

src/common/CircularList.ts

@@ -105,7 +105,7 @@ export class CircularList<T> extends EventEmitter implements ICircularList<T> {
    * The callback gets the value at the current position to be overwritten.
    * Return the new value from the callback.
    */
-  public pushRecycling(callback: (el: T | undefined) => T): void {
+  public pushRecycling(callback: (item: T | undefined) => T): void {
     this._array[this._getCyclicIndex(this._length)] = callback(this._array[this._getCyclicIndex(this._length)]);
     if (this._length === this._maxLength) {
       this._startIndex++;

src/common/Types.ts

@@ -28,6 +28,7 @@ export interface ICircularList<T> extends IEventEmitter {
   get(index: number): T | undefined;
   set(index: number, value: T): void;
   push(value: T): void;
+  pushRecycling(callback: (item: T | undefined) => T): void;
   pop(): T | undefined;
   splice(start: number, deleteCount: number, ...items: T[]): void;
   trimStart(count: number): void;

typings/xterm.d.ts

@@ -112,6 +112,8 @@ declare module 'xterm' {
      */
     experimentalBufferLineImpl?: 'JsArray' | 'TypedArray';
 
+    experimentalPushRecycling?: boolean;
+
     /**
      * The font size used to render text.
      */