src/Viewport.ts

   1 /**
   2  * @license MIT
   3  */
   4
   5 import { ITerminal } from './Interfaces';
   6 import { CharMeasure } from './utils/CharMeasure';
   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 charMeasure: CharMeasure
  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(): void {
  48     if (this.charMeasure.height > 0) {
  49       var rowHeightChanged = this.charMeasure.height !== this.currentRowHeight;
  50       if (rowHeightChanged) {
  51         this.currentRowHeight = this.charMeasure.height;
  52         this.viewportElement.style.lineHeight = this.charMeasure.height + 'px';
  53         this.terminal.rowContainer.style.lineHeight = this.charMeasure.height + 'px';
  54       }
  55       var viewportHeightChanged = this.lastRecordedViewportHeight !== this.terminal.rows;
  56       if (rowHeightChanged || viewportHeightChanged) {
  57         this.lastRecordedViewportHeight = this.terminal.rows;
  58         this.viewportElement.style.height = this.charMeasure.height * this.terminal.rows + 'px';
  59       }
  60       this.scrollArea.style.height = (this.charMeasure.height * this.lastRecordedBufferLength) + 'px';
  61     }
  62   }
  63
  64   /**
  65    * Updates dimensions and synchronizes the scroll area if necessary.
  66    */
  67   public syncScrollArea(): void {
  68     if (this.lastRecordedBufferLength !== this.terminal.lines.length) {
  69       // If buffer height changed
  70       this.lastRecordedBufferLength = this.terminal.lines.length;
  71       this.refresh();
  72     } else if (this.lastRecordedViewportHeight !== this.terminal.rows) {
  73       // If viewport height changed
  74       this.refresh();
  75     } else {
  76       // If size has changed, refresh viewport
  77       if (this.charMeasure.height !== this.currentRowHeight) {
  78         this.refresh();
  79       }
  80     }
  81
  82     // Sync scrollTop
  83     var scrollTop = this.terminal.ydisp * this.currentRowHeight;
  84     if (this.viewportElement.scrollTop !== scrollTop) {
  85       this.viewportElement.scrollTop = scrollTop;
  86     }
  87   }
  88
  89   /**
  90    * Handles scroll events on the viewport, calculating the new viewport and requesting the
  91    * terminal to scroll to it.
  92    * @param ev The scroll event.
  93    */
  94   private onScroll(ev: Event) {
  95     var newRow = Math.round(this.viewportElement.scrollTop / this.currentRowHeight);
  96     var diff = newRow - this.terminal.ydisp;
  97     this.terminal.scrollDisp(diff, true);
  98   }
  99
 100   /**
 101    * Handles mouse wheel events by adjusting the viewport's scrollTop and delegating the actual
 102    * scrolling to `onScroll`, this event needs to be attached manually by the consumer of
 103    * `Viewport`.
 104    * @param ev The mouse wheel event.
 105    */
 106   public onWheel(ev: WheelEvent) {
 107     if (ev.deltaY === 0) {
 108       // Do nothing if it's not a vertical scroll event
 109       return;
 110     }
 111     // Fallback to WheelEvent.DOM_DELTA_PIXEL
 112     var multiplier = 1;
 113     if (ev.deltaMode === WheelEvent.DOM_DELTA_LINE) {
 114       multiplier = this.currentRowHeight;
 115     } else if (ev.deltaMode === WheelEvent.DOM_DELTA_PAGE) {
 116       multiplier = this.currentRowHeight * this.terminal.rows;
 117     }
 118     this.viewportElement.scrollTop += ev.deltaY * multiplier;
 119     // Prevent the page from scrolling when the terminal scrolls
 120     ev.preventDefault();
 121   };
 122 }