Have a way to set the length of JFace's ComboViewer? - swt

Question

There is situation that I have a ComboViewer which will have different content in different time.Thus, it will sometimes need to relayout the ComboViewer so that it can show the full content. Is there any way to define the max length of ComboViewer in beginning? I will very appreciate if you can give me some idea.
The following code is the demo I try according to the rudiger.It works well in windows 7, while the length of the comboviewer is still short when it switches to "abcedfgabcedfg" in linux
.
public class ComboViewerTest {
/**
* #param args
*/
public static void main(String[] args) {
Display display = new Display();
Shell shell = new Shell(display);
shell.setText("Comboviewer Test");
shell.setLayout(new GridLayout(1, false));
Composite composite = new Composite(shell,SWT.None);
composite.setLayoutData(new GridData(SWT.FILL, SWT.TOP, true, false, 1, 1));
composite.setLayout(new GridLayout(2, true));
final String[] txtStrings = {"a","abc"};
final String[] txtStrings2 = { "abcedfg", "abcedfgabcedfg"};
Label label = new Label(composite, SWT.NONE);
label.setLayoutData(new GridData(SWT.LEFT, SWT.FILL, false, true, 1, 1));
label.setText("comboviewer");
final ComboViewer comboViewer = new ComboViewer(composite,SWT.NONE | SWT.READ_ONLY);
Combo combo = comboViewer.getCombo();
combo.setLayoutData(new GridData(SWT.LEFT, SWT.CENTER, true, true, 1, 1));
comboViewer.setContentProvider(new ArrayContentProvider());
comboViewer.setInput(txtStrings);
comboViewer.setLabelProvider(new LabelProvider() {
#Override
public String getText(Object element) {
return super.getText(element);
}
});
Composite composite2 = new Composite(shell,SWT.None);
composite2.setLayout(new GridLayout(2, true));
Button btnNewButton = new Button(composite2, SWT.RADIO);
btnNewButton.setBounds(0, 0, 84, 29);
btnNewButton.setText("change the comboviewr");
btnNewButton.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent e) {
comboViewer.setInput(txtStrings2);
comboViewer.getCombo().select(0);
}});
Button btnNewButton2 = new Button(composite2, SWT.RADIO);
btnNewButton2.setBounds(0, 0, 84, 29);
btnNewButton2.setText("reset");
btnNewButton2.addSelectionListener(new SelectionAdapter() {
#Override
public void widgetSelected(SelectionEvent e) {
comboViewer.setInput(txtStrings);
comboViewer.getCombo().select(0);
}});
comboViewer.getCombo().select(0);
setComboViewerLength(comboViewer);
shell.open();
while (!shell.isDisposed()) {
if (!display.readAndDispatch()) {
display.sleep();
}
}
display.dispose();
}
private static void setComboViewerLength(ComboViewer comboViewer) {
String string = "abcedfgabcedfg";
Combo control = comboViewer.getCombo();
GC gc = new GC( control );
Point stringExtent = gc.stringExtent( string );
gc.dispose();
Rectangle bounds = control.computeTrim( 0, 0, stringExtent.x, stringExtent.y );
GridData gridData = new GridData();
gridData.widthHint = bounds.width;
control.setLayoutData( gridData );
}
}

Answer 1

If I understand your question correctly, the problem is twofold.
1. Determining the necessary size to fully display a string of a certain length
The ComboViewer uses SWT's Combo or CCombo widget to display its data. Given the string to display, you can determine the necessary size of the combo in pixels as follows:
String string = "abc";
ComboViewer comboViewer = ...;
Combo control = comboViewer.getCombo();
GC gc = new GC( control );
Point stringExtent = gc.stringExtent( string );
gc.dispose();
Rectangle bounds = control.computeTrim( 0, 0, stringExtent.x, stringExtent.y );
The returned bounds describe a rectangle that if the combo's bounds were set to that rectangle, is large enough to display the string and trimmings (the drop-down button, borders, etc.).
2. Configuring the layout to use the above calculated size for the combo box
How to control the size of a widget depends on which layout manager you are using. The layout manager that is used is set on the parent of your combo.
Some - but not all - layouts allow to give hints or explicitly set the desired width and height of a control.
If you are using a GridLayout, for example, define a GridData for the combo to control its size.
Combo control = comboViewer.getCombo();
GridData gridData = new GridData();
gridData.widthHint = bounds.width;
control.setLayoutData( gridData );
For more on layouts and a description of the SWT standard layouts I recommend reading the Understanding Layouts in SWT article.