Bug 58777 [Viewers] add API to not deactivate CellEditor on FocusLost
TableViewerImpl installs a FocusListener on CellEditors, which calls applyEditorValue() on focusLost events. This FocusListener must be removed since applying the editor value is not always the wanted behavior on focusLost. Subclasses of CellEditor already handle focus loss in an extensible way: they install their own FocusListener and call a hook method focusLost() (which can be extended or reimplemented by subclasses with special needs). To support content assist in table cells (such as in the Change Method Signature dialog), we need to stay in editing mode even while the proposal list has focus. This is currently not implementable, since TableViewerImpl deactivates the CellEditor even if the CellEditor's focusLost() is reimplemented. The fix is to simply remove the redundant FocusListener in TableViewerImpl.
bundles/org.eclipse.jface/src/org/eclipse/jface/viewers/TextCellEditor.java
new Object[] { value }));
        }
        valueChanged(oldValidState, newValidState);
    }
    /**
     * Since a text editor field is scrollable we don't
     * set a minimumSize.
     */
    public LayoutData getLayoutData() {
        return new LayoutData();
    }
    /**
     * Return the modify listener.
     */
    private ModifyListener getModifyListener() {
        if (modifyListener == null) {
            modifyListener = new ModifyListener() {
                public void modifyText(ModifyEvent e) {
                    editOccured(e);
                }
            };
        }
        return modifyListener;
    }
    /**
     * Handles a default selection event from the text control by applying the editor
     * value and deactivating this cell editor.
     * 
     * @param event the selection event
     *