Determine maximum dimensions a Canvas could grow to? - layout

Question

I am using a BorderPane, where the right area is unused. In the center area I have a HBox with a Canvas and another control e.g. a Button. I want the Canvas to have the same width and height with a value of
Canvas width and height = minimum{maximum possible Canvas height, maximum possible Canvas width}
(in other words: Canvas should be a square)
My problem is: How do I determine the maximum width and the maximum height that a Canvas could grow to?
Here is my FXML:
<?xml version="1.0" encoding="UTF-8"?>
<?import java.lang.*?>
<?import java.util.*?>
<?import javafx.scene.control.*?>
<?import javafx.scene.layout.*?>
<?import javafx.scene.paint.*?>
<BorderPane id="BorderPane" maxHeight="-Infinity" maxWidth="-Infinity" minHeight="-Infinity" minWidth="-Infinity" prefHeight="400.0" prefWidth="600.0" xmlns:fx="http://javafx.com/fxml">
<bottom>
<Label text="Bottom area" />
</bottom>
<center>
<HBox>
<children>
<Canvas width="300" height="300" />
<Button mnemonicParsing="false" text="some button next to the Canvas" />
</children>
</HBox>
</center>
<left>
<Button mnemonicParsing="false" text="Left area"/>
</left>
<top>
<MenuBar>
<menus>
<Menu mnemonicParsing="false" text="File">
<items>
<MenuItem mnemonicParsing="false" text="Close" />
</items>
</Menu>
</menus>
</MenuBar>
</top>
</BorderPane>
Thanks for any hint!

Answer 1

The easiest way I can see this being done is: canvas.getwidth() and canvas.getHeight()

Answer 2

You have to add canvas manually, after the GUI is constructed, so you can calculate its size:
public class YourController implements Initializable {
#FXML HBox mHBox;
#FXML Button mButton;
#Override
public void initialize(final URL paramURL, final ResourceBundle paramResourceBundle) {
Platform.runLater(new Runnable() { public void run() {
double w0 = mHBox.getWidth();
double w1 = mButton.getWidth();
double h0 = mHBox.getHeight();
double size = Math.min(w0-w1, h0);
Canvas canvas = new Canvas(size, size);
mHBox.getChildren().add(0, canvas);
}});
}
}
Problem with the Canvas is that is is not resizable :(