new approach

src/BufferLine.ts

@@ -94,13 +94,11 @@ export class BufferLine implements IBufferLine {
     }
   }
 
-  public copyFrom(line: IBufferLine): void {
-    this._data = [];
-    for (let i = 0; i < line.length; ++i) {
-      this._push(line.get(i));
-    }
+  public copyFrom(line: BufferLine): IBufferLine {
+    this._data = line._data.slice(0);
     this.length = line.length;
     this.isWrapped = line.isWrapped;
+    return this;
   }
 
   public clone(): IBufferLine {
@@ -249,7 +247,7 @@ export class BufferLineTypedArray implements IBufferLine {
   }
 
   /** alter to a full copy of line  */
-  public copyFrom(line: BufferLineTypedArray): void {
+  public copyFrom(line: BufferLineTypedArray): IBufferLine {
     if (this.length !== line.length) {
       this._data = new Uint32Array(line._data);
     } else {
@@ -262,6 +260,7 @@ export class BufferLineTypedArray implements IBufferLine {
       this._combined[el] = line._combined[el];
     }
     this.isWrapped = line.isWrapped;
+    return this;
   }
 
   /** create a new clone */

src/Terminal.ts

@@ -21,7 +21,7 @@
  *   http://linux.die.net/man/7/urxvt
  */
 
-import { IInputHandlingTerminal, IViewport, ICompositionHelper, ITerminalOptions, ITerminal, IBrowser, ILinkifier, ILinkMatcherOptions, CustomKeyEventHandler, LinkMatcherHandler, CharData, CharacterJoinerHandler } from './Types';
+import { IInputHandlingTerminal, IViewport, ICompositionHelper, ITerminalOptions, ITerminal, IBrowser, ILinkifier, ILinkMatcherOptions, CustomKeyEventHandler, LinkMatcherHandler, CharData, CharacterJoinerHandler, IBufferLine } from './Types';
 import { IMouseZoneManager } from './ui/Types';
 import { IRenderer } from './renderer/Types';
 import { BufferSet } from './BufferSet';
@@ -1174,7 +1174,14 @@ 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 {
-    const newLine = this.buffer.getBlankLine(DEFAULT_ATTR, isWrapped);
+    // 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;
+    }
+    blank.isWrapped = !!(isWrapped);
+
     const topRow = this.buffer.ybase + this.buffer.scrollTop;
     const bottomRow = this.buffer.ybase + this.buffer.scrollBottom;
 
@@ -1184,9 +1191,9 @@ 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.push(newLine);
+        (this.buffer.lines as any).pushRecycling((line: IBufferLine | undefined) => (line) ? line.copyFrom(blank) : blank.clone());
       } else {
-        this.buffer.lines.splice(bottomRow + 1, 0, newLine);
+        this.buffer.lines.splice(bottomRow + 1, 0, blank.clone());
       }
 
       // Only adjust ybase and ydisp when the buffer is not trimmed
@@ -1208,7 +1215,7 @@ 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, newLine);
+      this.buffer.lines.set(bottomRow, blank.clone());
     }
 
     // Move the viewport to the bottom of the buffer unless the user is

src/common/CircularList.ts

@@ -100,6 +100,24 @@ export class CircularList<T> extends EventEmitter implements ICircularList<T> {
     }
   }
 
+  /**
+   * Recycling push variant with a callback.
+   * 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 {
+    this._array[this._getCyclicIndex(this._length)] = callback(this._array[this._getCyclicIndex(this._length)]);
+    if (this._length === this._maxLength) {
+      this._startIndex++;
+      if (this._startIndex === this._maxLength) {
+        this._startIndex = 0;
+      }
+      this.emit('trim', 1);
+    } else {
+      this._length++;
+    }
+  }
+
   /**
    * Removes and returns the last value on the list.
    * @return The popped value.