code: function showPreview(editor, popover) {
          var token, cm;
  
          // Figure out which editor we are over
          if (!editor) {
              editor = getHoveredEditor(lastMousePos);
          }
  
          if (!editor || !editor._codeMirror) {
              hidePreview();
              return;
          }
  
          cm = editor._codeMirror;
  
          // Find char mouse is over
          var pos = cm.coordsChar({left: lastMousePos.clientX, top: lastMousePos.clientY});
  
          // No preview if mouse is past last char on line
          if (pos.ch >= editor.document.getLine(pos.line).length) {
              return;
          }
  
          if (popover) {
              popoverState = popover;
          } else {
              // Query providers and append to popoverState
              token = TokenUtils.getTokenAt(cm, pos);
              popoverState = $.extend({}, popoverState, queryPreviewProviders(editor, pos, token));
          }
  
          if (popoverState && popoverState.start && popoverState.end) {
              popoverState.marker = cm.markText(
                  popoverState.start,
                  popoverState.end,
                  {className: "quick-view-highlight"}
              );
  
              $previewContent.append(popoverState.content);
              $previewContainer.show();
  
              popoverState.visible = true;
  
              if (popoverState.onShow) {
                  popoverState.onShow();
              } else {
                  positionPreview(editor, popoverState.xpos, popoverState.ytop, popoverState.ybot);
              }
          }
      }
docs: Changes the current hidden popoverState to visible, showing it in the UI and highlighting
  its matching text in the editor.