diff --git a/src/BufferLine.ts b/src/BufferLine.ts
index de36a968..170fc81d 100644
--- a/src/BufferLine.ts
+++ b/src/BufferLine.ts
@@ -17,20 +17,18 @@ export class BufferLineOld implements IBufferLine {
   public isWrapped = false;
   public length: number;
 
-  constructor(cols: number, ch?: CharData, isWrapped?: boolean) {
+  constructor(cols: number, fillCharData?: CharData, isWrapped?: boolean) {
     this._data = [];
-    this.length = this._data.length;
-    if (cols) {
-      if (!ch) {
-        ch = [0, NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE];
-      }
-      for (let i = 0; i < cols; i++) {
-        this._push(ch);  // Note: the ctor ch is not cloned (resembles old behavior)
-      }
+    if (!fillCharData) {
+      fillCharData = [0, NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE];
+    }
+    for (let i = 0; i < cols; i++) {
+      this._push(fillCharData);  // Note: the ctor ch is not cloned (resembles old behavior)
     }
     if (isWrapped) {
       this.isWrapped = true;
     }
+    this.length = this._data.length;
   }
 
   private _pop(): CharData | undefined  {
@@ -67,29 +65,29 @@ export class BufferLineOld implements IBufferLine {
   }
 
   /** delete n cells at pos, right side is filled with fill (stable length) */
-  public deleteCells(pos: number, n: number, fill: CharData): void {
+  public deleteCells(pos: number, n: number, fillCharData: CharData): void {
     while (n--) {
       this._splice(pos, 1);
-      this._push(fill);
+      this._push(fillCharData);
     }
   }
 
   /** replace cells from pos to pos + n - 1 with fill */
-  public replaceCells(start: number, end: number, fill: CharData): void {
+  public replaceCells(start: number, end: number, fillCharData: CharData): void {
     while (start < end  && start < this.length) {
-      this.set(start++, fill);  // Note: fill is not cloned (resembles old behavior)
+      this.set(start++, fillCharData);  // Note: fill is not cloned (resembles old behavior)
     }
   }
 
   /** resize line to cols filling new cells with fill */
-  public resize(cols: number, fill: CharData, shrink: boolean = false): void {
+  public resize(cols: number, fillCharData: CharData, shrink: boolean = false): void {
     if (shrink) {
       while (this._data.length > cols) {
         this._data.pop();
       }
     }
     while (this._data.length < cols) {
-      this._data.push(fill);
+      this._data.push(fillCharData);
     }
     this.length = cols;
   }
@@ -111,17 +109,15 @@ export class BufferLine implements IBufferLine {
   protected _combined: {[index: number]: string} = {};
   public length: number;
 
-  constructor(cols: number, ch?: CharData, public isWrapped: boolean = false) {
-    this.length = cols || 0;
-    if (cols) {
-      if (!ch) {
-        ch = [0, NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE];
-      }
-      this._data = new Uint32Array(cols * Cell.SIZE);
-      for (let i = 0; i < cols; ++i) {
-        this.set(i, ch);
-      }
+  constructor(cols: number, fillCharData?: CharData, public isWrapped: boolean = false) {
+    if (!fillCharData) {
+      fillCharData = [0, NULL_CELL_CHAR, NULL_CELL_WIDTH, NULL_CELL_CODE];
     }
+    this._data = new Uint32Array(cols * Cell.SIZE);
+    for (let i = 0; i < cols; ++i) {
+      this.set(i, fillCharData);
+    }
+    this.length = cols || 0;
   }
 
   public get(index: number): CharData {
@@ -147,45 +143,45 @@ export class BufferLine implements IBufferLine {
     this._data[index * Cell.SIZE + Cell.WIDTH] = value[2];
   }
 
-  public insertCells(pos: number, n: number, fill: CharData): void {
+  public insertCells(pos: number, n: number, fillCharData: CharData): void {
     pos %= this.length;
     if (n < this.length - pos) {
       for (let i = this.length - pos - n - 1; i >= 0; --i) {
         this.set(pos + n + i, this.get(pos + i));
       }
       for (let i = 0; i < n; ++i) {
-        this.set(pos + i, fill);
+        this.set(pos + i, fillCharData);
       }
     } else {
       for (let i = pos; i < this.length; ++i) {
-        this.set(i, fill);
+        this.set(i, fillCharData);
       }
     }
   }
 
-  public deleteCells(pos: number, n: number, fill: CharData): void {
+  public deleteCells(pos: number, n: number, fillCharData: CharData): void {
     pos %= this.length;
     if (n < this.length - pos) {
       for (let i = 0; i < this.length - pos - n; ++i) {
         this.set(pos + i, this.get(pos + n + i));
       }
       for (let i = this.length - n; i < this.length; ++i) {
-        this.set(i, fill);
+        this.set(i, fillCharData);
       }
     } else {
       for (let i = pos; i < this.length; ++i) {
-        this.set(i, fill);
+        this.set(i, fillCharData);
       }
     }
   }
 
-  public replaceCells(start: number, end: number, fill: CharData): void {
+  public replaceCells(start: number, end: number, fillCharData: CharData): void {
     while (start < end  && start < this.length) {
-      this.set(start++, fill);
+      this.set(start++, fillCharData);
     }
   }
 
-  public resize(cols: number, fill: CharData, shrink: boolean = false): void {
+  public resize(cols: number, fillCharData: CharData, shrink: boolean = false): void {
     if (cols === this.length) {
       return;
     }
@@ -196,7 +192,7 @@ export class BufferLine implements IBufferLine {
       }
       this._data = data;
       for (let i = this.length; i < cols; ++i) {
-        this.set(i, fill);
+        this.set(i, fillCharData);
       }
     } else if (shrink) {
       if (cols) {