<div id="navi">
   <button mat-icon-button [title]="fullscreen ? 'Vollbild aus' : 'Vollbild ein'" (click)="toggleFullscreen()">
      <mat-icon *ngIf="fullscreen == true">fullscreen_exit</mat-icon>
      <mat-icon *ngIf="fullscreen == false">fullscreen</mat-icon>
   </button>
   <button mat-icon-button *ngIf="current_page && contextView == PAGE_CONTEXT_VIEW" 
     [title]="'Alle Querverweise von ' + current_page.title + ' anzeigen'" (click)="changeContext()">
      <mat-icon>auto_stories</mat-icon>
   </button>
   <button mat-icon-button *ngIf="current_page && contextView != PAGE_CONTEXT_VIEW" 
     [title]="'Querverweise von ' + current_page.title + ' ' + current_page.number + ' anzeigen'" (click)="changeContext()">
      <mat-icon>description</mat-icon>
   </button>
   <button *ngIf="current_page && contextView == PAGE_CONTEXT_VIEW" 
     mat-icon-button [title]="current_page.title + ' ' + current_page.number +' in Seitenansicht anzeigen'" (click)="setCurrentIri(current_page.id)">
      <mat-icon>chrome_reader_mode</mat-icon>
   </button>
   <mat-form-field *ngIf="contextView == PAGE_CONTEXT_VIEW">
      <mat-label>Suche</mat-label>
      <input matInput type="text" [(ngModel)]="findText" (ngModelChange)="updateParams()" (keydown.esc)="clearFindText()">
         <button mat-button *ngIf="findText" matSuffix mat-icon-button aria-label="Clear" (click)="clearFindText()">
            <mat-icon>close</mat-icon>
         </button>
   </mat-form-field>
</div>