lazy cleanup on buffer

src/common/Types.d.ts

@@ -206,6 +206,7 @@ export interface IBufferLine {
   deleteCells(pos: number, n: number, fill: ICellData, eraseAttr?: IAttributeData): void;
   replaceCells(start: number, end: number, fill: ICellData, eraseAttr?: IAttributeData, respectProtect?: boolean): void;
   resize(cols: number, fill: ICellData): boolean;
+  cleanupMemory(): number;
   fill(fillCellData: ICellData, respectProtect?: boolean): void;
   copyFrom(line: IBufferLine): void;
   clone(): IBufferLine;

src/common/buffer/Buffer.ts

@@ -14,6 +14,7 @@ import { Marker } from 'common/buffer/Marker';
 import { IOptionsService, IBufferService } from 'common/services/Services';
 import { DEFAULT_CHARSET } from 'common/data/Charsets';
 import { ExtendedAttrs } from 'common/buffer/AttributeData';
+import { DebouncedIdleTask } from 'common/TaskQueue';
 
 export const MAX_BUFFER_SIZE = 4294967295; // 2^32 - 1
 
@@ -151,6 +152,9 @@ export class Buffer implements IBuffer {
     // store reference to null cell with default attrs
     const nullCell = this.getNullCell(DEFAULT_ATTR_DATA);
 
+    // defer memory cleanup of bufferlines
+    let needsCleanup = 0;
+
     // Increase max length if needed before adjustments to allow space to fill
     // as required.
     const newMaxLength = this._getCorrectBufferLength(newRows);
@@ -164,7 +168,7 @@ export class Buffer implements IBuffer {
       // Deal with columns increasing (reducing needs to happen after reflow)
       if (this._cols < newCols) {
         for (let i = 0; i < this.lines.length; i++) {
-          this.lines.get(i)!.resize(newCols, nullCell);
+          needsCleanup |= +this.lines.get(i)!.resize(newCols, nullCell);
         }
       }
 
@@ -243,13 +247,34 @@ export class Buffer implements IBuffer {
       // Trim the end of the line off if cols shrunk
       if (this._cols > newCols) {
         for (let i = 0; i < this.lines.length; i++) {
-          this.lines.get(i)!.resize(newCols, nullCell);
+          needsCleanup |= +this.lines.get(i)!.resize(newCols, nullCell);
         }
       }
     }
 
     this._cols = newCols;
     this._rows = newRows;
+
+    if (needsCleanup) {
+      this._memoryCleanupTask.set(() => this._cleanupMemory());
+    } else {
+      // FIXME: DebouncedIdleTask has no clear method?
+      this._memoryCleanupTask.set(() => {});
+    }
+  }
+
+  private _memoryCleanupTask: DebouncedIdleTask = new DebouncedIdleTask();
+
+  private _cleanupMemory(): void {
+    let counted = 0;
+    for (let i = 0; i < this.lines.length; i++) {
+      counted += this.lines.get(i)!.cleanupMemory();
+      // throttle to 5k lines
+      if (counted > 5000) {
+        this._memoryCleanupTask.set(() => this._cleanupMemory());
+        break;
+      }
+    }
   }
 
   private get _isReflowEnabled(): boolean {

src/common/buffer/BufferLine.ts

@@ -347,7 +347,7 @@ export class BufferLine implements IBufferLine {
    */
   public resize(cols: number, fillCellData: ICellData): boolean {
     if (cols === this.length) {
-      return this._data.length * 4 < this._data.buffer.byteLength * CLEANUP_THRESHOLD;
+      return this._data.length * 4 * CLEANUP_THRESHOLD < this._data.buffer.byteLength;
     }
     const uint32Cells = cols * CELL_SIZE;
     if (cols > this.length) {
@@ -384,7 +384,7 @@ export class BufferLine implements IBufferLine {
       }
     }
     this.length = cols;
-    return uint32Cells * 4 < this._data.buffer.byteLength * CLEANUP_THRESHOLD;
+    return uint32Cells * 4 * CLEANUP_THRESHOLD < this._data.buffer.byteLength;
   }
 
   /**
@@ -393,8 +393,8 @@ export class BufferLine implements IBufferLine {
    * memory by a factor of CLEANUP_THRESHOLD.
    * Returns 0 or 1 indicating whether a cleanup happened.
    */
-  public cleanupBuffer(): number {
-    if (this._data.length * 4 < this._data.buffer.byteLength * CLEANUP_THRESHOLD) {
+  public cleanupMemory(): number {
+    if (this._data.length * 4 * CLEANUP_THRESHOLD < this._data.buffer.byteLength) {
       const data = new Uint32Array(this._data.length);
       data.set(this._data);
       this._data = data;