A DESCRIPTION OF THE PROBLEM :
The width of the gridpane is wider than it's content. The red border should be the same size as the black gridlines.

Remarks:
The span of the last child of the gridpane seems the cause without span it's seems ok.
If the first text is shorter for example ""TEXT" instead of "TEXT__SPAN___ON___4___Column " the problem also disapear

STEPS TO FOLLOW TO REPRODUCE THE PROBLEM :
launch the attached sample app

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
the red border shouldn't be wider

---------- BEGIN SOURCE ----------
/**
 *
 * @author cfischer
 */
public class GridPaneComputeWidthBug extends Application {

    @Override
    public void start(Stage primaryStage) {
        final GridPane gridPane = new GridPane();
        gridPane.setGridLinesVisible(true);
        gridPane.setStyle("-fx-border-color : red;");

        final Text text1 = new Text();
        text1.setText("TEXT__SPAN___ON___4___Column ");
        gridPane.add(text1, 0, 0, 4, 1);

        final Text text2 = new Text();
        text2.setText(" col4 ");
        gridPane.add(text2, 4, 0, 1, 1);

        gridPane.add(new Text(" col0 "), 0, 1);

        final Text text3 = new Text();
        text3.setText(" col1 ");
        gridPane.add(text3, 1, 1);

        gridPane.add(new Text(" col2 "), 2, 1);

        final Text text4 = new Text();
        text4.setText(" SPAN_ON_COL3_4");
        gridPane.add(text4, 3, 1, 2, 1); //BUG if SPAN 2 work with span 1

        final VBox vBox = new VBox(gridPane);
        vBox.setFillWidth(false);
        StackPane root = new StackPane(vBox);

        Scene scene = new Scene(root, 600, 250);
        primaryStage.setTitle("GridPane bug");
        primaryStage.setScene(scene);
        primaryStage.show();
    }

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        launch(args);
    }

}
---------- END SOURCE ----------

FREQUENCY : always