Improve Problems view filter dialog UX and fix vanishing markers

- Replace 5 scope radio buttons with compact Combo dropdown
- Strip mnemonic characters from combo labels
- Disable configuration group when 'Show all items' is checked
- Collapse advanced filter sections (Types) by default
- Combine limit controls into single 'Limit items per group:' row
- Fix vanishing markers when no resources selected (empty resources
  fallback to show all in selectByScope)
- Update ScopeAreaTest for Combo widget, add MarkerFieldFilterGroupTest
  with 8 tests covering selectByScope behavior

Author: vogella

bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/FiltersConfigurationDialog.java

@@ -100,11 +100,10 @@ public class FiltersConfigurationDialog extends TrayDialog {
 	private ScrolledForm form;
 
 	private Collection<FilterConfigurationArea> configAreas;
-	private Label limitsLabel;
 
 	private Object[] previouslyChecked = new Object[0];
 	private Group configComposite;
-	private Composite compositeLimits;
+	private Composite allConfigArea;
 
 	/**
 	 * Create a new instance of the receiver on builder.
@@ -224,7 +223,6 @@ private void updateConfigComposite(boolean enabled) {
 	/** Update the enablement of limitText */
 	private void updateLimitTextEnablement() {
 		boolean useLimits = limitButton.getSelection();
-		limitsLabel.setEnabled(useLimits);
 		limitText.setEnabled(useLimits);
 	}
 
@@ -233,6 +231,10 @@ private void updateShowAll(boolean showAll) {
 		updateConfigComposite(!showAll);
 		updateLimitTextEnablement();
 
+		// Disable the configurations group and limit area when showing all items
+		setEnabled(!showAll, configComposite);
+		setEnabled(!showAll, allConfigArea);
+
 		if (showAll) {
 			previouslyChecked = configsTable.getCheckedElements();
 			configsTable.setAllChecked(false);
@@ -255,39 +257,29 @@ private boolean isShowAll() {
 	 * Create the area of the dialog that apply's to all configurations.
 	 */
 	private void createAllConfigArea(Composite parent) {
-		compositeLimits = new Composite(parent, SWT.NONE);
-		GridLayout glCompositeLimits = new GridLayout(3, false);
-		compositeLimits.setLayout(glCompositeLimits);
+		allConfigArea = new Composite(parent, SWT.NONE);
+		GridLayout layout = new GridLayout(3, false);
+		layout.marginHeight = 0;
+		allConfigArea.setLayout(layout);
+		allConfigArea.setLayoutData(new GridData(GridData.FILL_HORIZONTAL));
 
-		limitButton = new Button(compositeLimits, SWT.CHECK);
-		limitButton.setText(MarkerMessages.MarkerPreferences_MarkerLimits);
+		limitButton = new Button(allConfigArea, SWT.CHECK);
+		limitButton.setText(MarkerMessages.filtersDialog_limitItemsPerGroup);
 		limitButton.addSelectionListener(new SelectionAdapter() {
 
 			@Override
 			public void widgetSelected(SelectionEvent e) {
 				updateLimitTextEnablement();
 			}
 		});
-
 		GridData limitData = new GridData();
 		limitData.verticalIndent = 5;
 		limitButton.setLayoutData(limitData);
 
-		Composite composite = new Composite(parent, SWT.NONE);
-		GridLayout layout = new GridLayout(3, false);
-		layout.marginWidth = 0;
-		layout.marginHeight = 0;
-		composite.setLayout(layout);
-		GridData compositeData = new GridData(GridData.FILL_HORIZONTAL);
-		compositeData.horizontalIndent = 20;
-		composite.setLayoutData(compositeData);
-
-		limitsLabel = new Label(composite, SWT.NONE);
-		limitsLabel.setText(MarkerMessages.MarkerPreferences_VisibleItems);
-
-		limitText = new Text(composite, SWT.BORDER);
+		limitText = new Text(allConfigArea, SWT.BORDER);
 		GridData textData = new GridData();
 		textData.widthHint = convertWidthInCharsToPixels(10);
+		textData.verticalIndent = 5;
 		limitText.setLayoutData(textData);
 		limitText.addVerifyListener(e -> {
 			if (e.character != 0 && e.keyCode != SWT.BS
@@ -312,7 +304,7 @@ public void widgetSelected(SelectionEvent e) {
 			}
 		});
 
-		Composite defaultButtonComposite = new Composite(composite, SWT.NONE);
+		Composite defaultButtonComposite = new Composite(allConfigArea, SWT.NONE);
 		GridLayout defaultButtonLayout = new GridLayout(1, false);
 		defaultButtonComposite.setLayout(defaultButtonLayout);
 		GridData defaultButtonCompositeData = new GridData(SWT.END, SWT.END, true, false);
@@ -414,10 +406,16 @@ private void createConfigDesc(Composite parent) {
 
 		configAreas = generator.createFilterConfigurationFields();
 
+		// Scope and severity/description are always expanded (most used)
 		createFieldArea(toolkit, form, scopeArea, true);
 		Iterator<FilterConfigurationArea> areas = configAreas.iterator();
+		boolean isFirst = true;
 		while (areas.hasNext()) {
-			createFieldArea(toolkit, form, areas.next(), true);
+			FilterConfigurationArea area = areas.next();
+			// First config area (severity/description) is always expanded,
+			// subsequent areas (types) start collapsed to reduce clutter
+			createFieldArea(toolkit, form, area, isFirst);
+			isFirst = false;
 		}
 	}
 

bundles/org.eclipse.ui.ide/src/org/eclipse/ui/internal/views/markers/MarkerFieldFilterGroup.java

@@ -649,6 +649,11 @@ public boolean selectByFilters(MarkerEntry entry) {
 
 	public boolean selectByScope(MarkerEntry entry, IResource[] resources) {
 		int scopeVal = getScope();
+		// When no resources are selected and scope depends on selection,
+		// fall back to showing all markers to avoid confusing empty results
+		if (resources.length == 0 && scopeVal != ON_ANY && scopeVal != ON_WORKING_SET) {
+			return true;
+		}
 		switch (scopeVal) {
 		case MarkerFieldFilterGroup.ON_ANY: {
 			return true;