Added problem decorators in the Project Explorer.

Files with compilation errors and warnings are now decorated with a little icon.
The icons were borrowed from the JDT.

net.sf.eclipsefp.haskell.ui/plugin.properties

@@ -5,6 +5,8 @@ bundleName = Haskell Plug-in UI
 # extensions
 haskellDecorator_name = Haskell Project Folders
 haskellDecorator_desc = Decorates source and binary folders in Haskell projects.
+problemDecorator_name = Haskell Problems
+problemDecorator_desc = Decorates problems in Haskell source files and folders.
 
 haskellPerspective_name = Haskell
 

net.sf.eclipsefp.haskell.ui/plugin.xml

@@ -115,6 +115,19 @@
             %haskellDecorator_desc
          </description>
       </decorator>
+      <decorator
+            label="%haskellDecorator_name"
+            lightweight="true"
+            class="net.sf.eclipsefp.haskell.ui.decorators.ProblemsLabelDecorator"
+            state="true"
+            id="net.sf.eclipsefp.haskell.ui.decorators.ProblemsLabelDecorator">
+            <enablement>
+              <objectClass name="org.eclipse.core.resources.IResource"/> 
+            </enablement>
+         <description>
+            %haskellDecorator_desc
+         </description>
+      </decorator>
    </extension>
    <extension
          point="org.eclipse.ui.perspectives">

net.sf.eclipsefp.haskell.ui/src/net/sf/eclipsefp/haskell/ui/decorators/ProblemsLabelDecorator.java

@@ -0,0 +1,87 @@
+package net.sf.eclipsefp.haskell.ui.decorators;
+
+import net.sf.eclipsefp.haskell.core.util.ResourceUtil;
+import net.sf.eclipsefp.haskell.ui.HaskellUIPlugin;
+import net.sf.eclipsefp.haskell.ui.util.HaskellUIImages;
+import net.sf.eclipsefp.haskell.ui.util.IImageNames;
+import org.eclipse.core.resources.IFile;
+import org.eclipse.core.resources.IFolder;
+import org.eclipse.core.resources.IMarker;
+import org.eclipse.core.resources.IResource;
+import org.eclipse.core.runtime.CoreException;
+import org.eclipse.core.runtime.ListenerList;
+import org.eclipse.jface.resource.ImageDescriptor;
+import org.eclipse.jface.viewers.IDecoration;
+import org.eclipse.jface.viewers.ILabelProviderListener;
+import org.eclipse.jface.viewers.ILightweightLabelDecorator;
+
+/**
+ * LabelDecorator that decorates an element's image with error and warning
+ * overlays that represent the severity of markers attached to the element's
+ * underlying resource. To see a problem decoration for a marker, the marker
+ * needs to be a subtype of <code>IMarker.PROBLEM</code>.
+ *
+ * @author Thomas ten Cate
+ */
+public class ProblemsLabelDecorator implements ILightweightLabelDecorator {
+
+  private final ListenerList listeners = new ListenerList();
+
+  public void decorate( final Object element, final IDecoration decoration ) {
+    int adornmentFlags = computeAdornmentFlags( element );
+    ImageDescriptor desc;
+    switch (adornmentFlags) {
+      case IMarker.SEVERITY_ERROR:
+        desc = getImageDescriptor( IImageNames.ERROR_OVERLAY );
+        break;
+      case IMarker.SEVERITY_WARNING:
+        desc = getImageDescriptor( IImageNames.WARNING_OVERLAY );
+        break;
+      default:
+        desc = null; // unchanged
+        break;
+    }
+    if (desc != null) {
+      decoration.addOverlay( desc, IDecoration.BOTTOM_LEFT );
+    }
+  }
+
+  protected int computeAdornmentFlags( final Object obj ) {
+    try {
+      if( obj instanceof IFile
+          && ResourceUtil.hasHaskellExtension( ( IResource )obj ) ) {
+        return ( ( IResource )obj ).findMaxProblemSeverity( IMarker.PROBLEM,
+            true, IResource.DEPTH_ZERO );
+      } else if( obj instanceof IFolder
+          && ResourceUtil.isSourceFolder( ( IFolder )obj ) ) {
+        return ( ( IResource )obj ).findMaxProblemSeverity( IMarker.PROBLEM,
+            true, IResource.DEPTH_INFINITE );
+      }
+    } catch( CoreException e ) {
+      HaskellUIPlugin.log( e );
+    }
+    return 0;
+  }
+
+  private ImageDescriptor getImageDescriptor(final String name) {
+    return HaskellUIImages.getImageDescriptor( name );
+  }
+
+  public boolean isLabelProperty( final Object element, final String property ) {
+    // We currently only support labelling (some kinds of) resources
+    return element instanceof IResource;
+  }
+
+  public void dispose() {
+    // nothing to dispose
+  }
+
+  public void removeListener( final ILabelProviderListener listener ) {
+    listeners.remove(listener);
+  }
+
+  public void addListener( final ILabelProviderListener listener ) {
+    listeners.add(listener);
+  }
+
+}

net.sf.eclipsefp.haskell.ui/src/net/sf/eclipsefp/haskell/ui/util/HaskellUIImages.java

@@ -5,9 +5,7 @@
 import java.net.URL;
 import java.util.HashMap;
 import java.util.Map;
-
 import net.sf.eclipsefp.haskell.ui.HaskellUIPlugin;
-
 import org.eclipse.jface.resource.CompositeImageDescriptor;
 import org.eclipse.jface.resource.ImageDescriptor;
 import org.eclipse.jface.resource.ImageRegistry;
@@ -61,6 +59,9 @@ private static void declareImages() {
 
     // decorators
     declare( SRC_FOLDER_DECORATOR, OVR + "sourceFolder.gif" );
+    declare( ERROR_OVERLAY,        OVR + "error_co.gif");
+    declare( WARNING_OVERLAY,      OVR + "warning_co.gif");
+
     // views
     declare( DEP_VIEW_IMPORTS,     ACTION + "mdep_imports.gif" );
     declare( DEP_VIEW_IMPORTEDBY,  ACTION + "mdep_importedby.gif" );

net.sf.eclipsefp.haskell.ui/src/net/sf/eclipsefp/haskell/ui/util/IImageNames.java

@@ -68,4 +68,8 @@ public interface IImageNames {
   String NEW_MODULE           = ID + ".NEW_MODULE";
   String IMPORT_CABAL_PACKAGE = ID + "IMPORT_CABAL_PACKAGE";
 
+  // overlays
+  String ERROR_OVERLAY        = ID + ".ERROR_OVERLAY";
+  String WARNING_OVERLAY      = ID + ".WARNING_OVERLAY";
+
 }