Improve keyboard navigation

The Return key was mapped to View Files, but it's better if it acts
the same as double-click, which descends into directories and opens
embedded archives and disk images.

We now put the focus back on the file list after moving to a new
directory or moving up a level.  This allows keyboard navigation
through the directory tree while in single-dir view mode.

(issue #25)

cp2_wpf/MainController.cs

@@ -363,6 +363,7 @@ public void NavToParent(bool dirOnly) {
                 return;
             }
             if (dirSel.Parent != null) {
+                mSwitchFocusToFileList = true;     // keep focus on file list, for keyboard nav
                 dirSel.Parent.IsSelected = true;
                 DirectoryTreeItem.BringItemIntoView(mMainWin.directoryTree, dirSel.Parent);
             } else if (!dirOnly) {
@@ -973,7 +974,8 @@ public bool GetFileSelection(bool omitDir, bool omitOpenArc, bool closeOpenArc,
             // Get the list of selected items.  The behavior is a little strange: if you select
             // an item in the middle, and then use select-all, the item you selected will be at
             // the top (unless your selection was at the very bottom).  Everything else will be
-            // in the expected order.
+            // in the expected order.  Control-clicking multiple items appears to add them to
+            // the selection set in the order in which they are clicked.
             DataGrid dg = mMainWin.fileListDataGrid;
             IList listSel = dg.SelectedItems;
             if (listSel.Count == 0) {

cp2_wpf/MainController_Panels.cs

@@ -538,6 +538,8 @@ internal void DirectoryTree_SelectionChanged(DirectoryTreeItem? newSel) {
         ///   should be set for all file operations, but not during archive or directory
         ///   tree traversal.</param>
         internal void RefreshDirAndFileList(bool focusOnFileList = true) {
+            //Debug.WriteLine("RefreshDirAndFileList: focus=" + focusOnFileList +
+            //    " mSwitch=" + mSwitchFocusToFileList);
             mSwitchFocusToFileList |= focusOnFileList;
             if (CurrentWorkObject == null) {
                 return;
@@ -690,9 +692,11 @@ private bool VerifyFileList() {
         ///   have strange effects.)</param>
         internal void PopulateFileList(IFileEntry selEntry, bool focusOnFileList) {
             if (selEntry != IFileEntry.NO_ENTRY) {
-                Debug.WriteLine("Populate: current item is " + selEntry.FileName);
+                Debug.WriteLine("Populate: current item is " + selEntry.FileName +
+                    " (focus=" + focusOnFileList + " mSwitch=" + mSwitchFocusToFileList + ")");
             } else {
-                Debug.WriteLine("Populate: no selected item in file list");
+                Debug.WriteLine("Populate: no selected item in file list " +
+                    " (focus=" + focusOnFileList + " mSwitch=" + mSwitchFocusToFileList + ")");
             }
             ObservableCollection<FileListItem> fileList = mMainWin.FileList;
 
@@ -919,9 +923,14 @@ private void ClearEntryCounts() {
         /// <summary>
         /// Handles a double-click on an item in the file list grid.
         /// </summary>
-        public void HandleFileListDoubleClick(FileListItem item, int row, int col,
-                ArchiveTreeItem arcTreeSel, DirectoryTreeItem dirTreeSel) {
-            //Debug.WriteLine("DCLICK: r=" + row + " c=" + col + " item=" + item);
+        public void HandleFileListDoubleClick() {
+            //Debug.WriteLine("HandleFileListDoubleClick");
+            ArchiveTreeItem? arcTreeSel = mMainWin.SelectedArchiveTreeItem;
+            DirectoryTreeItem? dirTreeSel = mMainWin.SelectedDirectoryTreeItem;
+            if (arcTreeSel == null || dirTreeSel == null) {
+                Debug.Assert(false, "tree is missing selection");
+                return;
+            }
 
             //
             // Something has been double-clicked.  If it's a single entry:
@@ -958,15 +967,16 @@ public void HandleFileListDoubleClick(FileListItem item, int row, int col,
             // or disk image and requires special handling.  Otherwise we'll just hand everything
             // over to the file viewer.
             if (dg.SelectedItems.Count == 1) {
-                IFileEntry entry = item.FileEntry;
+                FileListItem fli = (FileListItem)dg.SelectedItems[0]!;
+                IFileEntry entry = fli.FileEntry;
                 if (entry.IsDirectory) {
                     if (fs != null) {
                         // Select the entry in the dir tree.  This may rewrite the file list.
+                        // We want to keep the focus on the file list to support keyboard nav.
+                        mSwitchFocusToFileList = true;
                         if (!DirectoryTreeItem.SelectItemByEntry(mMainWin, entry)) {
                             Debug.WriteLine("Unable to find dir tree entry for " + entry);
-                        } else {
-                            // TODO: the focus will move to the directory tree.  We may want
-                            // to put it on the first item in the file list instead.
+                            mSwitchFocusToFileList = false;
                         }
                     } else {
                         // Directory file in a file archive.  Nothing for us to do.

cp2_wpf/MainWindow.xaml.cs

@@ -674,7 +674,8 @@ private void ToggleInfoCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
             SetShowCenterInfo(CenterPanelChange.Toggle);
         }
         private void ViewFilesCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
-            mMainCtrl.ViewFiles();
+            //mMainCtrl.ViewFiles();
+            mMainCtrl.HandleFileListDoubleClick();
         }
 
         private void Debug_BulkCompressTestCmd_Executed(object sender, ExecutedRoutedEventArgs e) {
@@ -1212,14 +1213,8 @@ private void FileList_MouseDoubleClick(object sender, MouseButtonEventArgs e) {
                 return;
             }
             FileListItem fli = (FileListItem)item;
-
-            ArchiveTreeItem? arcTreeSel = archiveTree.SelectedItem as ArchiveTreeItem;
-            DirectoryTreeItem? dirTreeSel = directoryTree.SelectedItem as DirectoryTreeItem;
-            if (arcTreeSel == null || dirTreeSel == null) {
-                Debug.Assert(false, "tree is missing selection");
-                return;
-            }
-            mMainCtrl.HandleFileListDoubleClick(fli, row, col, arcTreeSel, dirTreeSel);
+            //Debug.WriteLine("Double-click on " + fli.FileEntry);
+            mMainCtrl.HandleFileListDoubleClick();
         }
 
         /// <summary>

cp2_wpf/WPFCommon/WPFExtensions.cs

@@ -178,8 +178,8 @@ public static int GetClickEventColumn(this ListView lv, MouseButtonEventArgs e)
     /// Helper functions for working with DataGrids.
     /// </summary>
     /// <remarks>
-    /// <para>It's tempting to handle double-click actions by using the selected row.  This gets a
-    /// little weird, though, because double-clicking on a header or blank area doesn't
+    /// <para>It's tempting to simply handle double-click actions by using the selected row.  This
+    /// gets a little weird, though, because double-clicking on a header or blank area doesn't
     /// clear the selection.</para>
     /// <para>Great explanation of row/cell selection in a DataGrid:
     /// <see href="https://blog.magnusmontin.net/2013/11/08/how-to-programmatically-select-and-focus-a-row-or-cell-in-a-datagrid-in-wpf/"/>;
@@ -194,13 +194,21 @@ public static class DataGridExtensions {
         /// Based on
         /// <see href="https://blog.scottlogic.com/2008/12/02/wpf-datagrid-detecting-clicked-cell-and-row.html"/>.
         /// </remarks>
+        /// <param name="e">Arguments received from event.</param>
+        /// <param name="rowIndex">Result: index of clicked row.</param>
+        /// <param name="colIndex">Result: index of clicked column.</param>
+        /// <param name="item">Result: if a data item was clicked, the data item; otherwise
+        ///   null.</param>
         /// <returns>True if the click was on a data item.</returns>
         public static bool GetClickRowColItem(this DataGrid dg, MouseButtonEventArgs e,
                 out int rowIndex, out int colIndex, [NotNullWhen(true)] out object? item) {
             return GetRowColItem(dg, (DependencyObject)e.OriginalSource, out rowIndex,
                 out colIndex, out item);
         }
 
+        /// <summary>
+        /// Determines which row and column was the target of a drop action.
+        /// </summary>
         public static bool GetDropRowColItem(this DataGrid dg, DragEventArgs e,
                 out int rowIndex, out int colIndex, [NotNullWhen(true)] out object? item) {
             return GetRowColItem(dg, (DependencyObject)e.OriginalSource, out rowIndex,
@@ -370,6 +378,9 @@ public static void ResetSort(this DataGrid grid) {
             }
         }
 
+        /// <summary>
+        /// Scrolls the DataGrid to the top.
+        /// </summary>
         public static void ScrollToTop(this DataGrid dg) {
             VirtualizingStackPanel? virtPanel =
                 VisualHelper.GetVisualChild<VirtualizingStackPanel>(dg);
@@ -468,6 +479,9 @@ public static void BringIndexIntoView_Public(this VirtualizingPanel virtPanel, i
     /// TreeView extensions.
     /// </summary>
     public static class TreeViewExtensions {
+        /// <summary>
+        /// Scrolls the TreeView to the top.
+        /// </summary>
         public static void ScrollToTop(this TreeView tv) {
             VirtualizingStackPanel? virtPanel =
                 VisualHelper.GetVisualChild<VirtualizingStackPanel>(tv);