src/Viewport.ts

   1 /**
   2  * xterm.js: xterm, in the browser
   3  * Copyright (c) 2014-2016, SourceLair Private Company (www.sourcelair.com (MIT License)
   4  */
   5
   6 import { ITerminal } from './Interfaces';
   7
   8 /**
   9  * Represents the viewport of a terminal, the visible area within the larger buffer of output.
  10  * Logic for the virtual scroll bar is included in this object.
  11  */
  12 export class Viewport {
  13   private currentRowHeight: number;
  14   private lastRecordedBufferLength: number;
  15   private lastRecordedViewportHeight: number;
  16
  17   /**
  18    * Creates a new Viewport.
  19    * @param terminal The terminal this viewport belongs to.
  20    * @param viewportElement The DOM element acting as the viewport.
  21    * @param scrollArea The DOM element acting as the scroll area.
  22    * @param charMeasureElement A DOM element used to measure the character size of. the terminal.
  23    */
  24   constructor(
  25     private terminal: ITerminal,
  26     private viewportElement: HTMLElement,
  27     private scrollArea: HTMLElement,
  28     private charMeasureElement: HTMLElement
  29   ) {
  30     this.currentRowHeight = 0;
  31     this.lastRecordedBufferLength = 0;
  32     this.lastRecordedViewportHeight = 0;
  33
  34     this.terminal.on('scroll', this.syncScrollArea.bind(this));
  35     this.terminal.on('resize', this.syncScrollArea.bind(this));
  36     this.viewportElement.addEventListener('scroll', this.onScroll.bind(this));
  37
  38     this.syncScrollArea();
  39   }
  40
  41   /**
  42    * Refreshes row height, setting line-height, viewport height and scroll area height if
  43    * necessary.
  44    * @param charSize A character size measurement bounding rect object, if it doesn't exist it will
  45    *   be created.
  46    */
  47   private refresh(charSize?: ClientRect): void {
  48     var size = charSize || this.charMeasureElement.getBoundingClientRect();
  49     if (size.height > 0) {
  50       var rowHeightChanged = size.height !== this.currentRowHeight;
  51       if (rowHeightChanged) {
  52         this.currentRowHeight = size.height;
  53         this.viewportElement.style.lineHeight = size.height + 'px';
  54         this.terminal.rowContainer.style.lineHeight = size.height + 'px';
  55       }
  56       var viewportHeightChanged = this.lastRecordedViewportHeight !== this.terminal.rows;
  57       if (rowHeightChanged || viewportHeightChanged) {
  58         this.lastRecordedViewportHeight = this.terminal.rows;
  59         this.viewportElement.style.height = size.height * this.terminal.rows + 'px';
  60       }
  61       this.scrollArea.style.height = (size.height * this.lastRecordedBufferLength) + 'px';
  62     }
  63   }
  64
  65   /**
  66    * Updates dimensions and synchronizes the scroll area if necessary.
  67    */
  68   public syncScrollArea(): void {
  69     if (this.lastRecordedBufferLength !== this.terminal.lines.length) {
  70       // If buffer height changed
  71       this.lastRecordedBufferLength = this.terminal.lines.length;
  72       this.refresh();
  73     } else if (this.lastRecordedViewportHeight !== this.terminal.rows) {
  74       // If viewport height changed
  75       this.refresh();
  76     } else {
  77       // If size has changed, refresh viewport
  78       var size = this.charMeasureElement.getBoundingClientRect();
  79       if (size.height !== this.currentRowHeight) {
  80         this.refresh(size);
  81       }
  82     }
  83
  84     // Sync scrollTop
  85     var scrollTop = this.terminal.ydisp * this.currentRowHeight;
  86     if (this.viewportElement.scrollTop !== scrollTop) {
  87       this.viewportElement.scrollTop = scrollTop;
  88     }
  89   }
  90
  91   /**
  92    * Handles scroll events on the viewport, calculating the new viewport and requesting the
  93    * terminal to scroll to it.
  94    * @param ev The scroll event.
  95    */
  96   private onScroll(ev: Event) {
  97     var newRow = Math.round(this.viewportElement.scrollTop / this.currentRowHeight);
  98     var diff = newRow - this.terminal.ydisp;
  99     this.terminal.scrollDisp(diff, true);
 100   }
 101
 102   /**
 103    * Handles mouse wheel events by adjusting the viewport's scrollTop and delegating the actual
 104    * scrolling to `onScroll`, this event needs to be attached manually by the consumer of
 105    * `Viewport`.
 106    * @param ev The mouse wheel event.
 107    */
 108   public onWheel(ev: WheelEvent) {
 109     if (ev.deltaY === 0) {
 110       // Do nothing if it's not a vertical scroll event
 111       return;
 112     }
 113     // Fallback to WheelEvent.DOM_DELTA_PIXEL
 114     var multiplier = 1;
 115     if (ev.deltaMode === WheelEvent.DOM_DELTA_LINE) {
 116       multiplier = this.currentRowHeight;
 117     } else if (ev.deltaMode === WheelEvent.DOM_DELTA_PAGE) {
 118       multiplier = this.currentRowHeight * this.terminal.rows;
 119     }
 120     this.viewportElement.scrollTop += ev.deltaY * multiplier;
 121     // Prevent the page from scrolling when the terminal scrolls
 122     ev.preventDefault();
 123   };
 124 }