How the hover of Eclipse's jdt is displayed

1. What is the hover of JDT.

See figure below:

2. The different fonts in the hover, and how the colors are displayed.

In fact, in the corresponding hover, the string type is returned, the content is HTML, and then displayed through the Org.eclipse.swt.browser.Browser.

3. Working principle:

3.1 Add Mousetracker to the Sourceviewer, when you open Java file.
Org.eclipse.jdt.internal.ui.javaeditor.compilationuniteditor$adaptedsourceviewer
--> Org.eclipse.jdt.internal.ui.javaeditor.compilationuniteditor$adaptedsourceviewer

    /** * After this method
     has been executed the caller knows-any installed text hover has been installed.
     * *
    private void ensurehovercontrolmanagerinstalled () {
        if (ftexthovers!= null &&!ftexthovers.isempty () && fhovercontrolcreator!= null && Ftexthovermanager = null) {
            ftexthovermanager= new Textviewerh Overmanager (this, fhovercontrolcreator);
            Ftexthovermanager.install (This.gettextwidget ());
            Ftexthovermanager.setsizeconstraints (Text_hover_width_chars, Text_hover_height_chars, False, true);
            Ftexthovermanager.setinformationcontrolreplacer (New Stickyhovermanager (this));
        }
    

--> Org.eclipse.jface.text.TextViewerHoverManager

    public void Install (control Subjectcontrol) {
        if fsubjectcontrol!= null &&!fsubjectcontrol.isdisposed () & amp;& fsubjectcontroldisposelistener!= null)
            Fsubjectcontrol.removedisposelistener ( Fsubjectcontroldisposelistener);

        Fsubjectcontrol= Subjectcontrol;

        if (Fsubjectcontrol!= null)
            Fsubjectcontrol.adddisposelistener (Getsubjectcontroldisposelistener ());

        if (finformationcontrolcloser!= null)
            Finformationcontrolcloser.setsubjectcontrol (Subjectcontrol);

        SetEnabled (true);
        fdisposed= false;
    

--> Org.eclipse.jface.text.TextViewerHoverManager

    public void SetEnabled (Boolean enabled) {

        boolean was= isenabled ();
        super.setenabled (enabled);
        Boolean is= isenabled ();

        If (was!= are && fmousetracker!= null) {
            if (IS)
                Fmousetracker.start (Getsubjectcontrol ());
            else
                fmousetracker.stop ();
        }
    }

--> Org.eclipse.jface.text.abstracthoverinformationcontrolmanager$mousetracker

        public void Start (Control Subjectcontrol) {
            fsubjectcontrol= Subjectcontrol;
            if (Fsubjectcontrol!= null &&!fsubjectcontrol.isdisposed ())
                Fsubjectcontrol.addmousetracklistener ( this);

            Fisinrestartmode= false;
            fiscomputing= false;
            fmouselostwhilecomputing= false;
            fshelldeactivatedwhilecomputing= false;
        

3.2 When your hover mouse on target sourceviewer, it'll show hover
Org.eclipse.jface.text.abstracthoverinformationcontrolmanager$mousetracker

        public void MouseHover (MouseEvent event) {if (fiscomputing | | fisinrestartmode | | (Fsubjectcontrol!= null &&!fsubjectcontrol.isdisposed () && Fsubjectcontrol.getshell ()!= Fsubjectcontrol.getshell (). Getdisplay (). Getactiveshell ()) {if (DEBUG) System.out.pri Ntln ("Abstracthoverinformationcontrolmanager...mousehover: @" + event.x + "/" + Event.y + ": hover Cancelled:fiscomputi Ng= "+ fiscomputing +", fisinrestartmode= "+ Fisinrestartmode";
            $NON-nls-1$//$NON-nls-2$//$NON-nls-3$//$NON-nls-4$ return;
            } fisinrestartmode= true;
            fiscomputing= true;
            Fmouselostwhilecomputing= false;

            Fshelldeactivatedwhilecomputing= false;
            Fhovereventstatemask= Event.statemask;
            Fhoverevent= event;
           Fhoverarea= New Rectangle (Event.x-epsilon, Event.y-epsilon, 2 * EPSILON, 2 * EPSILON); if (fhoverarea.x < 0) fhoverarea.x= 0;
            if (Fhoverarea.y < 0) fhoverarea.y= 0;

            Setsubjectarea (Fhoverarea); if (Fsubjectcontrol!= null &&!fsubjectcontrol.isdisposed ()) {Fsubjectcontrol.addmousemovelisten
                ER (this);
            Fsubjectcontrol.getshell (). Addshelllistener (this);
        } doshowinformation (); }

--> Org.eclipse.jface.text.AbstractInformationControlManager

    protected void Doshowinformation () {
        fsubjectarea= null;
        finformation= null;
        Computeinformation ();
    }

--> Org.eclipse.jface.text.TextViewerHoverManager

    protected void Computeinformation () {
    //create a thread (Text Viewer Hover presenter) to show Hover
    }

...
--> Org.eclipse.jface.text.AbstractInformationControlManager.internalShowInformationControl (Rectangle, Object To "Create control" to show the text.

	private void Internalshowinformationcontrol (Rectangle subjectarea, Object information) {if (this instanceof informatio
			Ncontrolreplacer) {(informationcontrolreplacer) this). Showinformationcontrol (Subjectarea, information);
		Return
		} Iinformationcontrol informationcontrol= Getinformationcontrol (); if (Informationcontrol!= null) {point sizeconstraints= computesizeconstraints (Fsubjectcontrol, Fsubjectarea, Informa
			Tioncontrol); if (Informationcontrol instanceof IInformationControlExtension3) {IInformationControlExtension3 icontrol3= (Iinforma
				TionControlExtension3) Informationcontrol;
				Rectangle trim= Icontrol3.computetrim ();
				Sizeconstraints.x + = Trim.width;
			Sizeconstraints.y + = Trim.height;

			} informationcontrol.setsizeconstraints (Sizeconstraints.x, SIZECONSTRAINTS.Y); if (Informationcontrol instanceof IInformationControlExtension2) ((IInformationControlExtension2)
			Informationcontrol). SetInput (information); else informationcontrOl.setinformation (Information.tostring ()); if (Informationcontrol instanceof iinformationcontrolextension) {iinformationcontrolextension extension= (IInformati
				oncontrolextension) Informationcontrol;
			if (!extension.hascontents ()) return;
			Point size= null;
			Point location= null;

			Rectangle bounds= restoreinformationcontrolbounds ();

				if (bounds!= null) {if (bounds.x > 1 && bounds.y >-1) location= geometry.getlocation (bounds);
			if (Bounds.width > 1 && bounds.height >-1) size= geometry.getsize (bounds);

			} if (size = = null) size= informationcontrol.computesizehint ();
			if (fenforceasminimalsize) size= geometry.max (size, sizeconstraints);

			if (fenforceasmaximalsize) size= geometry.min (size, sizeconstraints);

			if (location = = null) location= computeinformationcontrollocation (subjectarea, size);
			Rectangle controlbounds= geometry.createrectangle (location, size); CroptoclosestmOnitor (Controlbounds);
			location= geometry.getlocation (controlbounds);
			Size= geometry.getsize (controlbounds);
			Informationcontrol.setlocation (location);

			Informationcontrol.setsize (size.x, size.y);
		Showinformationcontrol (Subjectarea); }
	}

--> Org.eclipse.jface.text.AbstractInformationControlManager

    protected void Showinformationcontrol (Rectangle subjectarea) {
        finformationcontrol.setvisible (true);
        
        if (Finformationcontrol = null) return
            ;//could already is disposed if setvisible (..) runs the display loop
        
        if ( ftakesfocuswhenvisible)
            finformationcontrol.setfocus ();

        if (finformationcontrolcloser!= null)
            Finformationcontrolcloser.start (Subjectarea);
    }

Org.eclipse.jdt.internal.ui.text.java.hover.javadochover$hovercontrolcreator

    Public Iinformationcontrol Docreateinformationcontrol (Shell parent) {String tooltipaffordancestring= fAdd Itionalinfoaffordance?
            Javaplugin.getadditionalinfoaffordancestring (): editorsui.gettooltipaffordancestring (); if (browserinformationcontrol.isavailable (parent)) {String Preferenceconstants.appearance_javadoc_f
                ONT;
                    Browserinformationcontrol icontrol= New Browserinformationcontrol (parent, font, tooltipaffordancestring) { * * @see Org.eclipse.jface.text.iinformationcontrolextension5#getinformationpresentercontrolcre Ator () */@Override public iinformationcontrolcreator GetInfo
                    Rmationpresentercontrolcreator () {return finformationpresentercontrolcreator;
                }
                };
                Addlinklistener (icontrol);
            return icontrol;
   } else {             return new Defaultinformationcontrol (parent, tooltipaffordancestring); }
        }

4. Below is the System.out.println HTML content and the effect shown under Firefox.

 
Display effect: