Load ChartImage images on demand.

src/ChartImage.cs

@@ -25,7 +25,7 @@ public class ChartImage
         // initialize the ChartImage
         mFullPath = fullPath ;
         mJsonConfig = new JsonConfig( config ) ;
-        mImage = Image.FromFile( fullPath ) ;
+        mImage = null ; // nb: we load this on demand
 
         // parse the shortcut
         ILog logger = LogManager.GetLogger( "shortcuts" ) ;
@@ -155,8 +155,24 @@ public class ChartImage
         ) ;
     }
 
+    public Image image()
+    {
+        // return the image data
+        // NOTE: It would be nice to reuse the ImageListView cache, but it only seems to cache thumbnails.
+        if ( mImage == null ) {
+            try {
+                mImage = Image.FromFile( mFullPath ) ;
+            } catch( Exception ex ) {
+                // NOTE: This crashes on Linux, but we can live with that - ChartImage's are created by iterating
+                // over files in the data directory, so if we can't load the file, it'll be because the file was deleted
+                // after startup, or a permissions problem i.e. things we don't really need to worry about.
+                Program.showErrorMsg( $"Can't load image file:\n    {mFullPath}\n\n{ex}" ) ;
+            }
+        }
+        return mImage ;
+    }
+
     public JsonConfig jsonConfig { get { return mJsonConfig ; } }
-    public Image image { get { return mImage ; } }
     public ImageListViewItem imageListViewItem { get { return mImageListViewItem ; } }
 
 }

src/MainForm.ui.cs

@@ -439,7 +439,7 @@ public partial class MainForm : Form
         double maxZoom = Program.dataConfig.getDoubleVal( new string[]{"_MaxZoom"}, 2*userZoom ) ;
         if (  mSearchResults.SelectedItems.Count > 0 ) {
             ChartImage chartImage = (ChartImage) mSearchResults.SelectedItems[0].Tag ;
-            mChartImagePictureBox.Image = chartImage.image ;
+            mChartImagePictureBox.Image = chartImage.image() ;
             userZoom = chartImage.jsonConfig.getDoubleVal( new string[]{"defaultZoom"}, userZoom ) ;
             minZoom = chartImage.jsonConfig.getDoubleVal( new string[]{"minZoom"}, minZoom ) ;
             maxZoom = chartImage.jsonConfig.getDoubleVal( new string[]{"maxZoom"}, maxZoom ) ;