optional autocomplete support in chevron pop up

Add Autocomplete support in chevron popup with preference toggle in the
eclipse Settings->Preference->General page

Introduced a new autocomplete behavior for the chevron popup filter
text. As the user types, matching editor names are suggested and the
remaining part is auto-filled, improving navigation efficiency within
the chevron pop up.

This is an enhancement done for filtertext and users can enable or
disable the autocomplete option based on their preference. This
behaviour is controlled through a new preference flag
`ENABLE_AUTOCOMPLETE_IN_CHEVRON` stored under
`org.eclipse.ui.workbench`. Users can enable or disable the feature in
the Workbench Preferences. When disabled, the chevron fitering falls
back to
the standard filtering behavior.

Key changes:
- Added `chevronAutocompleteBehavior()` to implement auto completion
  with suggestion.
- Retained existing `normalFilterBehavior()` for plain text filtering
incase  the user wanted to disable the auto complete feature.
- Updated `installFilter()` to switch between behaviors based on user
  preference
- Added `isAutocompleteEnabled()` method to check the preference state

Author: elsazac

bundles/org.eclipse.e4.ui.workbench.renderers.swt/src/org/eclipse/e4/ui/internal/workbench/renderers/swt/AbstractTableInformationControl.java

@@ -13,6 +13,8 @@
  *******************************************************************************/
 package org.eclipse.e4.ui.internal.workbench.renderers.swt;
 
+import org.eclipse.core.runtime.preferences.IEclipsePreferences;
+import org.eclipse.core.runtime.preferences.InstanceScope;
 import org.eclipse.e4.ui.workbench.swt.internal.copy.SearchPattern;
 import org.eclipse.e4.ui.workbench.swt.internal.copy.WorkbenchSWTMessages;
 import org.eclipse.jface.preference.JFacePreferences;
@@ -25,6 +27,8 @@
 import org.eclipse.jface.viewers.Viewer;
 import org.eclipse.jface.viewers.ViewerFilter;
 import org.eclipse.swt.SWT;
+import org.eclipse.swt.events.KeyAdapter;
+import org.eclipse.swt.events.KeyEvent;
 import org.eclipse.swt.events.KeyListener;
 import org.eclipse.swt.events.MouseEvent;
 import org.eclipse.swt.events.MouseListener;
@@ -312,6 +316,19 @@ public TableViewer getTableViewer() {
 		return fTableViewer;
 	}
 
+	private String suggestCompletionFromTable(String Text) {
+		if (Text == null || Text.isEmpty()) {
+			return null;
+		}
+		for (TableItem item : fTableViewer.getTable().getItems()) {
+			String textTable = item.getText();
+			if (textTable.toLowerCase().startsWith(Text.toLowerCase())) {
+				return textTable;
+			}
+		}
+		return null;
+	}
+
 	protected Text createFilterText(Composite parent) {
 		fFilterText = new Text(parent, SWT.NONE);
 
@@ -371,16 +388,54 @@ private void setInfoSystemColor() {
 		setBackgroundColor(background);
 	}
 
-	private void installFilter() {
+	private void chevronAutocompleteBehavior() {
 		fFilterText.setMessage(WorkbenchSWTMessages.FilteredTree_FilterMessage);
 		fFilterText.setText(""); //$NON-NLS-1$
+		setMatcherString(""); //$NON-NLS-1$
+		fTableViewer.refresh();
+
+		fFilterText.addKeyListener(new KeyAdapter() {
+			@Override
+			public void keyReleased(KeyEvent e) {
+				int cursor = fFilterText.getSelection().x;
+				String input = fFilterText.getText().substring(0, cursor);
+				setMatcherString(input);
+				fTableViewer.refresh();
+
+				if (e.keyCode == SWT.BS || e.keyCode == SWT.DEL || !Character.isLetterOrDigit(e.character))
+					return;
+
+				String suggestion = suggestCompletionFromTable(input);
+				if (suggestion != null && suggestion.length() > input.length()) {
+					fFilterText.setText(suggestion);
+					fFilterText.setSelection(input.length(), suggestion.length());
+				}
+			}
+		});
+	}
 
+	private void normalFilterBehavior() {
+		fFilterText.setMessage(WorkbenchSWTMessages.FilteredTree_FilterMessage);
+		fFilterText.setText(""); //$NON-NLS-1$
 		fFilterText.addModifyListener(e -> {
 			String text = ((Text) e.widget).getText();
 			setMatcherString(text);
+			fTableViewer.refresh();
 		});
 	}
 
+	private void installFilter() {
+		if (isAutocompleteEnabled()) {
+			chevronAutocompleteBehavior();
+		} else {
+			normalFilterBehavior();
+		}
+	}
+
+	private boolean isAutocompleteEnabled() {
+		IEclipsePreferences prefs = InstanceScope.INSTANCE.getNode("org.eclipse.ui.workbench"); //$NON-NLS-1$
+		return prefs.getBoolean("ENABLE_AUTOCOMPLETE_IN_CHEVRON", false); //$NON-NLS-1$
+	}
 	/**
 	 * The string matcher has been modified. The default implementation
 	 * refreshes the view and selects the first matched element

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/WorkbenchMessages.java

@@ -455,6 +455,11 @@ public class WorkbenchMessages extends NLS {
 	public static String PreferenceExportWarning_continue;
 	public static String PreferenceExportWarning_applyAndContinue;
 
+	public static String Preference_Enable_Autocomplete_ChevronPopUp;
+	public static String Preference_Autocomplete;
+
+	public static String Preference_Enable_Autocomplete_ChevronPopUp_ToolTip;
+
 	// --- Workbench ---
 	public static String WorkbenchPreference_allowInplaceEditingButton;
 	public static String WorkbenchPreference_useIPersistableEditorButton;

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/dialogs/WorkbenchPreferencePage.java

@@ -18,6 +18,8 @@
 
 import static org.eclipse.swt.events.SelectionListener.widgetSelectedAdapter;
 
+import org.eclipse.core.runtime.preferences.IEclipsePreferences;
+import org.eclipse.core.runtime.preferences.InstanceScope;
 import org.eclipse.jface.dialogs.IDialogConstants;
 import org.eclipse.jface.layout.LayoutConstants;
 import org.eclipse.jface.preference.FieldEditor;
@@ -80,6 +82,8 @@ public class WorkbenchPreferencePage extends PreferencePage implements IWorkbenc
 
 	private Button showInlineRenameButton;
 
+	private Button enableAutocompleteButton;
+
 	protected static int MAX_SAVE_INTERVAL = 9999;
 	protected static int MAX_VIEW_LIMIT = 1_000_000;
 
@@ -112,6 +116,7 @@ protected void createSettings(Composite composite) {
 		createStickyCyclePref(composite);
 		createHeapStatusPref(composite);
 		createLargeViewLimitPref(composite);
+		createAutocompletePref(composite);
 	}
 
 	/**
@@ -388,6 +393,25 @@ protected IPreferenceStore doGetPreferenceStore() {
 		return WorkbenchPlugin.getDefault().getPreferenceStore();
 	}
 
+	protected void createAutocompletePref(Composite parent) {
+		enableAutocompleteButton = new Button(parent, SWT.CHECK);
+		enableAutocompleteButton.setText(WorkbenchMessages.Preference_Enable_Autocomplete_ChevronPopUp);
+		enableAutocompleteButton.setToolTipText(WorkbenchMessages.Preference_Enable_Autocomplete_ChevronPopUp_ToolTip);
+
+		IEclipsePreferences prefs = InstanceScope.INSTANCE.getNode("org.eclipse.ui.workbench"); //$NON-NLS-1$
+		boolean enabled = prefs.getBoolean(WorkbenchMessages.Preference_Autocomplete, false);
+		enableAutocompleteButton.setSelection(enabled);
+
+		enableAutocompleteButton.addListener(SWT.Selection, e -> {
+			prefs.putBoolean(WorkbenchMessages.Preference_Autocomplete, enableAutocompleteButton.getSelection());
+			try {
+				prefs.flush();
+			} catch (Exception ex) {
+				ex.printStackTrace();
+			}
+		});
+	}
+
 	/**
 	 * @see IWorkbenchPreferencePage
 	 */

bundles/org.eclipse.ui.workbench/eclipseui/org/eclipse/ui/internal/messages.properties

@@ -409,6 +409,9 @@ PreferenceExportWarning_title = Possible Unapplied Changes
 PreferenceExportWarning_message = If you changed preferences and want to export them, ensure you click 'Apply and Continue' before the export.
 PreferenceExportWarning_continue = &Continue
 PreferenceExportWarning_applyAndContinue = &Apply and Continue
+Preference_Enable_Autocomplete_ChevronPopUp = Enable autocomplete option in chevron popup
+Preference_Enable_Autocomplete_ChevronPopUp_ToolTip = Enable autocomplete option to complete text as you type in the chevron popup
+Preference_Autocomplete=ENABLE_AUTOCOMPLETE_IN_CHEVRON
 
 # --- Workbench ---
 WorkbenchPreference_allowInplaceEditingButton = Allow in-place &system editors