8389551: Update class docs of MouseEvent

[nlisker]

Adds a section for button events and clarifies the existing sections.

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Issue

• JDK-8389551: Update class docs of MouseEvent (Enhancement - P4)(⚠️ The fixVersion in this issue is [jfx27] but the fixVersion in .jcheck/conf is jfx28, a new backport will be created when this pr is integrated.)

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[bridgekeeper]

👋 Welcome back nlisker! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

❗ This change is not yet ready to be integrated.
See the Progress checklist in the description for automated requirements.

[nlisker]

Notes to reviewers:

• I didn't have a touch screen available for this, so I couldn't verify that the parts that talk about touch screens is correct.
• When testing, I couldn't reproduce the behavior described in the last paragraph for entered/exited events, namely that MOUSE_ENTERED_TARGET and MOUSE_ENTERED can be handled by the same event handler, or that consuming one event stops the other. I didn't try too hard to make it work; I went by what the user will probably try to do. I kept it in this version assuming it's correct somehow.
• I used the following small tester:

import javafx.application.Application;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.input.ClipboardContent;
import javafx.scene.input.Dragboard;
import javafx.scene.input.InputEvent;
import javafx.scene.input.MouseEvent;
import javafx.scene.input.TransferMode;
import javafx.scene.layout.HBox;
import javafx.scene.layout.VBox;
import javafx.scene.paint.Color;
import javafx.scene.shape.Rectangle;
import javafx.stage.Stage;

public class MouseTest extends Application {

    public static void main(String[] args) {
        launch(args);
    }

    @Override
    public void start(@SuppressWarnings("exports") Stage stage) throws Exception {

        var scene = createScene(createSourcePDR(), createSourceMouseFullPDR(), createSourceDnD(), createTarget());
        stage.setScene(scene);
        stage.show();
    }

    private Rectangle createSourcePDR() {
        var source = new Rectangle(50, 50);
        source.setId("PDR");
        source.setFill(Color.YELLOW);
        source.setOnDragDetected(e -> {
            print(source, e);
            e.consume();
        });
        addCommonListeners(source);
        return source;
    }

    private Rectangle createSourceMouseFullPDR() {
        var source = new Rectangle(50, 50);
        source.setId("FullPDR");
        source.setFill(Color.RED);
        source.setOnDragDetected(e -> {
            source.startFullDrag();
            print(source, e);
            e.consume();
        });
        addCommonListeners(source);
        return source;
    }

    private Rectangle createSourceDnD() {
        var source = new Rectangle(50, 50);
        source.setId("DnD");
        source.setFill(Color.GREEN);
        source.setOnDragDetected(e -> {
            Dragboard db = source.startDragAndDrop(TransferMode.ANY);
            var content = new ClipboardContent();
            content.putString("");
            db.setContent(content);
            print(source, e);
            e.consume();
        });
        addCommonListeners(source);
        return source;
    }

    private Rectangle createTarget() {
        var target = new Rectangle(100, 50);
        target.setId("target");
        target.setFill(Color.BLUE);
        target.setOnDragDetected(MouseEvent::consume);
        addCommonListeners(target);
        return target;
    }

    private Scene createScene(Rectangle sourcePDR, Rectangle sourceFullPDR, Rectangle sourceDrag, Rectangle target) {
        var scene = new Scene(new VBox(10, new HBox(sourcePDR, sourceFullPDR, sourceDrag), target), 300, 200);

        scene.setOnMouseEntered(e -> System.out.println(e.getEventType() + " scene"));
        scene.setOnMouseExited(e -> System.out.println(e.getEventType() + " scene"));

        scene.setOnDragDetected(e -> {
            scene.startFullDrag();
            System.out.println(e.getEventType() + " scene");
        });

        scene.setOnDragDone(e -> {
            e.acceptTransferModes(TransferMode.ANY);
            System.out.println(e.getEventType() + " scene");
        });
        scene.setOnMouseDragReleased(e -> System.out.println(e.getEventType() + " scene"));
        scene.setOnMouseDragDone(e -> System.out.println(e.getEventType() + " scene"));
        return scene;
    }

    private static void addCommonListeners(Node node) {
        // MouseEvent
        node.setOnMouseMoved(e -> print(node, e));
        node.setOnMouseDragged(e -> print(node, e));
        node.setOnMouseEntered(e -> print(node, e));
        node.setOnMouseExited(e -> print(node, e));
        node.setOnMouseReleased(e -> print(node, e));
        node.setOnMouseClicked(e -> print(node, e));
        node.addEventHandler(MouseEvent.MOUSE_ENTERED_TARGET, e -> {
            System.out.print("TARGET_ ");
            print(node, e);
        });

        // MouseDragEvent
        node.setOnMouseDragOver(e -> print(node, e));
        node.setOnMouseDragEntered(e -> print(node, e));
        node.setOnMouseDragExited(e -> print(node, e));
        node.setOnMouseDragReleased(e -> print(node, e));
        node.setOnMouseDragDone(e -> System.out.println(e.getEventType() + " " + node.getId()));

        // DragEvent
        node.setOnDragOver(e -> {
            e.acceptTransferModes(TransferMode.ANY);
            print(node, e);
        });
        node.setOnDragEntered(e -> {
            e.acceptTransferModes(TransferMode.ANY);
            print(node, e);
        });
        node.setOnDragExited(e -> {
            print(node, e);
        });
        node.setOnDragDropped(e -> {
            e.acceptTransferModes(TransferMode.ANY);
            e.setDropCompleted(true);
            print(node, e);
        });
        node.setOnDragDone(e -> {
            e.acceptTransferModes(TransferMode.ANY);
            print(node, e);
        });
    }

    private static void print(Node node, InputEvent e) {
        System.out.println(e.getEventType() + " " + node.getId());
    }
}

[nlisker]

/reviewers 2

@andy-goryachev-oracle @kevinrushforth please review. This is a docs-only change that can go into 27.

[openjdk]

@nlisker
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

[mlbridge]

Webrevs

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