Add feature: get character bounds on screen

[JordanMartinez]

A few questions I have:

• Should selectionShape be used to get the bounds? Will that switch-out approach cause any issues later on? I didn't want to create a new Path object each time the method is called so as to reduce memory usage.
• I used the FORWARD bias in endPosition = offsetToPosition(to, Bias.FORWARD). Is that correct? Or should it be BACKWARD? I still don't understand how that part of the code works.

[JordanMartinez]

Addresses #150.

[JordanMartinez]

Manually tested this code (well, how would you test it via TestFX...?) with:

import javafx.application.Application;
import javafx.geometry.Bounds;
import javafx.scene.Scene;
import javafx.scene.control.Button;
import javafx.scene.control.TextField;
import javafx.scene.layout.BorderPane;
import javafx.scene.layout.HBox;
import javafx.scene.layout.Region;
import javafx.stage.Popup;
import javafx.stage.Stage;
import org.fxmisc.flowless.VirtualizedScrollPane;
import org.fxmisc.richtext.InlineCssTextArea;

import java.util.Optional;

public class CharacterBoundsDemo extends Application {

    @Override
    public void start(Stage primaryStage) throws Exception {
        InlineCssTextArea area = new InlineCssTextArea("0123456789\n123456789\n123456789");
        area.setWrapText(true);
        area.setStyle("-fx-font-size: 32pt;");
        VirtualizedScrollPane<InlineCssTextArea> vsPane = new VirtualizedScrollPane<>(area);

        Region r = new Region();
        r.setStyle("-fx-background-color: red;");
        Popup p = new Popup();
        p.getContent().add(r);

        TextField fromField = new TextField("0");
        TextField toField = new TextField("10");

        Button b = new Button("Show");
        b.setOnAction(ae -> {
            int from = Integer.parseInt(fromField.getText());
            int to = Integer.parseInt(toField.getText());
            Optional<Bounds> optB = area.getCharacterBoundsOnScreen(from, to);
            optB.ifPresent(bounds -> {
                r.setMinSize(bounds.getWidth(), bounds.getHeight());
                p.show(primaryStage, bounds.getMinX(), bounds.getMinY());
            });
        });
        BorderPane root = new BorderPane();
        root.setCenter(vsPane);
        root.setBottom(new HBox(fromField, toField, b));

        primaryStage.setScene(new Scene(root, 200, 400));
        primaryStage.show();
    }
}

[JordanMartinez]

Should selectionShape be used to get the bounds? Will that switch-out approach cause any issues later on? I didn't want to create a new Path object each time the method is called so as to reduce memory usage.

I don't see this as a problem because it'll only run on the JavaFX Application Thread, so there shouldn't be any issue with concurrency-related things. Additionally, selectionShape is already bound to leftInsets and topInsets which does affect the accuracy of the returned Bounds object.

I used the FORWARD bias in endPosition = offsetToPosition(to, Bias.FORWARD). Is that correct? Or should it be BACKWARD? I still don't understand how that part of the code works.

After testing this out, there wasn't any difference between FORWARD and BACKWARD even across multi-line paragraphs or multiple paragraphs. I think that only matters for some other thing Position-related thing, though Tomas could better explain that.