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   private lastTouchY: number;
  17
  18   /**
  19    * Creates a new Viewport.
  20    * @param terminal The terminal this viewport belongs to.
  21    * @param viewportElement The DOM element acting as the viewport.
  22    * @param scrollArea The DOM element acting as the scroll area.
  23    * @param charMeasure A DOM element used to measure the character size of. the terminal.
  24    */
  25   constructor(
  26     private terminal: ITerminal,
  27     private viewportElement: HTMLElement,
  28     private scrollArea: HTMLElement,
  29     private charMeasure: CharMeasure
  30   ) {
  31     this.currentRowHeight = 0;
  32     this.lastRecordedBufferLength = 0;
  33     this.lastRecordedViewportHeight = 0;
  34
  35     this.terminal.on('scroll', this.syncScrollArea.bind(this));
  36     this.terminal.on('resize', this.syncScrollArea.bind(this));
  37     this.viewportElement.addEventListener('scroll', this.onScroll.bind(this));
  38
  39     // Perform this async to ensure the CharMeasure is ready.
  40     setTimeout(() => this.syncScrollArea(), 0);
  41   }
  42
  43   /**
  44    * Refreshes row height, setting line-height, viewport height and scroll area height if
  45    * necessary.
  46    */
  47   private refresh(): void {
  48     if (this.charMeasure.height > 0) {
  49       const 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       const 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         this.terminal.selectionContainer.style.height = this.viewportElement.style.height;
  60       }
  61       this.scrollArea.style.height = (this.charMeasure.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.buffer.lines.length) {
  70       // If buffer height changed
  71       this.lastRecordedBufferLength = this.terminal.buffer.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       if (this.charMeasure.height !== this.currentRowHeight) {
  79         this.refresh();
  80       }
  81     }
  82
  83     // Sync scrollTop
  84     const scrollTop = this.terminal.buffer.ydisp * this.currentRowHeight;
  85     if (this.viewportElement.scrollTop !== scrollTop) {
  86       this.viewportElement.scrollTop = scrollTop;
  87     }
  88   }
  89
  90   /**
  91    * Handles scroll events on the viewport, calculating the new viewport and requesting the
  92    * terminal to scroll to it.
  93    * @param ev The scroll event.
  94    */
  95   private onScroll(ev: Event) {
  96     const newRow = Math.round(this.viewportElement.scrollTop / this.currentRowHeight);
  97     const diff = newRow - this.terminal.buffer.ydisp;
  98     this.terminal.scrollDisp(diff, true);
  99   }
 100
 101   /**
 102    * Handles mouse wheel events by adjusting the viewport's scrollTop and delegating the actual
 103    * scrolling to `onScroll`, this event needs to be attached manually by the consumer of
 104    * `Viewport`.
 105    * @param ev The mouse wheel event.
 106    */
 107   public onWheel(ev: WheelEvent) {
 108     if (ev.deltaY === 0) {
 109       // Do nothing if it's not a vertical scroll event
 110       return;
 111     }
 112     // Fallback to WheelEvent.DOM_DELTA_PIXEL
 113     let multiplier = 1;
 114     if (ev.deltaMode === WheelEvent.DOM_DELTA_LINE) {
 115       multiplier = this.currentRowHeight;
 116     } else if (ev.deltaMode === WheelEvent.DOM_DELTA_PAGE) {
 117       multiplier = this.currentRowHeight * this.terminal.rows;
 118     }
 119     this.viewportElement.scrollTop += ev.deltaY * multiplier;
 120     // Prevent the page from scrolling when the terminal scrolls
 121     ev.preventDefault();
 122   };
 123
 124   /**
 125    * Handles the touchstart event, recording the touch occurred.
 126    * @param ev The touch event.
 127    */
 128   public onTouchStart(ev: TouchEvent) {
 129     this.lastTouchY = ev.touches[0].pageY;
 130   };
 131
 132   /**
 133    * Handles the touchmove event, scrolling the viewport if the position shifted.
 134    * @param ev The touch event.
 135    */
 136   public onTouchMove(ev: TouchEvent) {
 137     let deltaY = this.lastTouchY - ev.touches[0].pageY;
 138     this.lastTouchY = ev.touches[0].pageY;
 139     if (deltaY === 0) {
 140       return;
 141     }
 142     this.viewportElement.scrollTop += deltaY;
 143     ev.preventDefault();
 144   };
 145 }