[Gtk3] fix for SWTException on Table.remove(...) with focused row #1604

Fix for SWTException on Table.remove(...) with focused row.
This bug happens only in Gtk3.
The cause: `gtk_list_store_remove(...)` for a focused row invokes `Table.cellDataProc(...)` with not-yet-updated `Table.items`.
Fix: remove `TableItem` from `Table.items` before `gtk_list_store_remove(...)`.

Fixes #1604:

The exception only happens in Gtk3.

Java stacktrace:
```java
org.eclipse.swt.SWTException: Widget is disposed
	at org.eclipse.swt.SWT.error(SWT.java:4922)
	at org.eclipse.swt.SWT.error(SWT.java:4837)
	at org.eclipse.swt.SWT.error(SWT.java:4808)
	at org.eclipse.swt.widgets.Widget.error(Widget.java:597)
	at org.eclipse.swt.widgets.Widget.checkWidget(Widget.java:512)
	at org.eclipse.swt.widgets.TableItem.setText(TableItem.java:1363)
	at org.eclipse.swt.tests.gtk.Test_Gtk3_Table_Remove_Focused_Row.lambda$3(Test_Gtk3_Table_Remove_Focused_Row.java:68)
	at org.eclipse.swt.widgets.EventTable.sendEvent(EventTable.java:91)
	at org.eclipse.swt.widgets.Display.sendEvent(Display.java:5857)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1617)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1643)
	at org.eclipse.swt.widgets.Widget.sendEvent(Widget.java:1626)
	at org.eclipse.swt.widgets.Table.checkData(Table.java:289)
	at org.eclipse.swt.widgets.Table.cellDataProc(Table.java:227)
	at org.eclipse.swt.widgets.Display.cellDataProc(Display.java:995)
	at org.eclipse.swt.internal.gtk.GTK.gtk_list_store_remove(Native Method)
	at org.eclipse.swt.widgets.Table.remove(Table.java:2668)
	...
```

The main cause of the error is that:
 1. when a row with focus is deleted with `gtk_list_store_remove(...)`, then cell data function `Table.cellDataProc(...)` is called for a row after the removed one
 2. but inside `Table.cellDataProc(...)` `Table.items` isn't yet updated , therefore `Table.cellDataProc(...)` operates with `TableItem`, which is already disposed but not yet removed from `Table.items`

Inside `gtk_list_store_remove(...)` the row is removed from the `GtkTreeModel`, and only then `GtkTreeView` callbacks are invoked.
It means that when `Table.cellDataProc(...)` is invoked, the row has already been removed in Gtk3.

The fix: remove `TableItem` from `Table.items` before `gtk_list_store_remove(...)` instead of after.

Important: I haven't tried to reproduce this bug in GTK4.

Os:  Ubuntu 24.04.1 LTS
Gtk: 3.24.41
Swt: 4.967.8

=================================================

Why `gtk_list_store_remove(...)` invokes `Table.cellDataProc(...)` only for a row with focus and not for ordinary rows?

The reason is that in gtk3 when a row with focus is deleted, the next row receives focus, which among other things creates `GtkCellAccessible` (a "cell with focus" for assistive technology in gtk3).
Creation of `GtkCellAccessible` invokes cell data function `Table.cellDataProc(...)` - just like it happens when a standard cell in `GtkTreeView` gets rendered.

Here is the stacktrace in gtk3 code:
```c
apply_cell_attributes() at gtkcellarea.c:1257
g_hash_table_foreach() at ghash.c:2117
gtk_cell_area_real_apply_attributes() at gtkcellarea.c:1286
gtk_cell_area_box_apply_attributes() at gtkcellareabox.c:1310
_gtk_marshal_VOID__OBJECT_BOXED_BOOLEAN_BOOLEANv() at gtkmarshalers.c:5447
g_type_class_meta_marshalv() at gclosure.c:1062
_g_closure_invoke_va() at gclosure.c:897
signal_emit_valist_unlocked() at gsignal.c:3424
g_signal_emit_valist() at gsignal.c:3263
g_signal_emit() at gsignal.c:3583
gtk_cell_area_apply_attributes() at gtkcellarea.c:2373
gtk_tree_view_column_cell_set_cell_data() at gtktreeviewcolumn.c:2821
set_cell_data() at gtktreeviewaccessible.c:347
create_cell() at gtktreeviewaccessible.c:439
_gtk_tree_view_accessible_add_state() at gtktreeviewaccessible.c:2053
gtk_tree_view_real_set_cursor() at gtktreeview.c:13377
gtk_tree_view_row_deleted() at gtktreeview.c:9430
g_cclosure_marshal_VOID__BOXED() at gmarshal.c:1628
g_closure_invoke() at gclosure.c:834
signal_emit_unlocked_R() at gsignal.c:3888
signal_emit_valist_unlocked() at gsignal.c:3520
g_signal_emit_valist() at gsignal.c:3263
g_signal_emit() at gsignal.c:3583
gtk_tree_model_row_deleted() at gtktreemodel.c:1914
gtk_list_store_remove() at gtkliststore.c:1219
Java_org_eclipse_swt_internal_gtk_GTK_gtk_1list_1store_1remove()
```

The code that leads to execution of cell data function for a row with focus is in gtktreeview.c:
```
static void
gtk_tree_view_row_deleted (GtkTreeModel *model,
			   GtkTreePath  *path,
			   gpointer      data)
{
  ...
  /* If the cursor row got deleted, move the cursor to the next row */
  if (tree_view->priv->cursor_node &&
      (tree_view->priv->cursor_node == node ||
       (node->children && (tree_view->priv->cursor_tree == node->children ||
                           _gtk_rbtree_contains (node->children, tree_view->priv->cursor_tree)))))
    {
      ...
      cursor_changed = TRUE;
    }
  ...
  if (cursor_changed)
    {
      if (cursor_node)
        {
          ...
          gtk_tree_view_real_set_cursor (tree_view, cursor_path, CLEAR_AND_SELECT | CURSOR_INVALID);
          ...
        }
      ...
    }
  ...
}
```

Author: om-11-2024

bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Table.java

@@ -2663,12 +2663,12 @@ public void remove (int index) {
 		GTK.gtk_tree_model_iter_nth_child (modelHandle, iter, 0, index);
 	}
 	if (!disposed) {
+		System.arraycopy (items, index + 1, items, index, --itemCount - index);
+		items [itemCount] = null;
 		long selection = GTK.gtk_tree_view_get_selection (handle);
 		OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, CHANGED);
 		GTK.gtk_list_store_remove (modelHandle, iter);
 		OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, CHANGED);
-		System.arraycopy (items, index + 1, items, index, --itemCount - index);
-		items [itemCount] = null;
 	}
 	OS.g_free (iter);
 }
@@ -2708,15 +2708,13 @@ public void remove (int start, int end) {
 		if (index == start) GTK.gtk_tree_model_iter_nth_child (modelHandle, iter, 0, index);
 		TableItem item = items [index];
 		if (item != null && !item.isDisposed ()) item.release (false);
+		System.arraycopy (items, index + 1, items, index, --itemCount - index);
+		items [itemCount] = null;
 		OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, CHANGED);
 		GTK.gtk_list_store_remove (modelHandle, iter);
 		OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, CHANGED);
 	}
 	OS.g_free (iter);
-	index = end + 1;
-	System.arraycopy (items, index, items, start, itemCount - index);
-	for (int i=itemCount-(index-start); i<itemCount; i++) items [i] = null;
-	itemCount = itemCount - (index - start);
 }
 
 /**
@@ -2764,11 +2762,11 @@ public void remove (int [] indices) {
 				GTK.gtk_tree_model_iter_nth_child (modelHandle, iter, 0, index);
 			}
 			if (!disposed) {
+				System.arraycopy (items, index + 1, items, index, --itemCount - index);
+				items [itemCount] = null;
 				OS.g_signal_handlers_block_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, CHANGED);
 				GTK.gtk_list_store_remove (modelHandle, iter);
 				OS.g_signal_handlers_unblock_matched (selection, OS.G_SIGNAL_MATCH_DATA, 0, 0, 0, 0, CHANGED);
-				System.arraycopy (items, index + 1, items, index, --itemCount - index);
-				items [itemCount] = null;
 			}
 			last = index;
 		}

tests/org.eclipse.swt.tests.gtk/JUnit Tests/org/eclipse/swt/tests/gtk/Test_Gtk3_Table_Remove_Focused_Row.java

@@ -0,0 +1,93 @@
+package org.eclipse.swt.tests.gtk;
+
+import org.eclipse.swt.SWT;
+import org.eclipse.swt.internal.gtk.GTK;
+import org.eclipse.swt.layout.FillLayout;
+import org.eclipse.swt.widgets.Shell;
+import org.eclipse.swt.widgets.Table;
+import org.eclipse.swt.widgets.TableItem;
+import org.junit.After;
+import org.junit.Assume;
+import org.junit.Before;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+public class Test_Gtk3_Table_Remove_Focused_Row {
+
+	private Shell shell;
+	private Table table;
+
+	@BeforeClass
+	public static void setUpClass() {
+		var isGtk3 = false;
+		if ("gtk".equals(SWT.getPlatform())) {
+			@SuppressWarnings("restriction")
+			var gtkMajorVersion = GTK.GTK_VERSION >>> 16;
+			isGtk3 = (gtkMajorVersion == 3);
+		}
+		Assume.assumeTrue("Test is only for Gtk3.", isGtk3);
+	}
+
+	@Before
+	public void setUp() {
+		shell = new Shell();
+		shell.setMinimumSize(400, 400);
+		shell.setLayout(new FillLayout());
+	}
+
+	@After
+	public void tearDown() {
+		if (table != null) {
+			table.dispose();
+		}
+		if (shell != null) {
+			shell.dispose();
+		}
+	}
+
+	@Test
+	public void test_remove_focused_row_remove_one() {
+		test_remove_focused_row_remove_method_arg(() -> table.remove(0));
+	}
+
+	@Test
+	public void test_remove_focused_row_remove_array() {
+		test_remove_focused_row_remove_method_arg(() -> table.remove(new int[] { 0 }));
+	}
+
+	@Test
+	public void test_remove_focused_row_remove_interval() {
+		test_remove_focused_row_remove_method_arg(() -> table.remove(0, 0));
+	}
+
+	private void test_remove_focused_row_remove_method_arg(Runnable removeRow0) {
+		table = new Table(shell, SWT.VIRTUAL);
+		table.setItemCount(2);
+		table.addListener(SWT.SetData, event -> {
+			var item = (TableItem) event.item;
+			item.setText("Item #" + System.identityHashCode(item) + " " + item.toString());
+		});
+
+		shell.pack();
+		shell.open();
+
+		processUiEvents();
+
+		// set focus on row[0]
+		table.setFocus();
+
+		processUiEvents();
+
+		table.clear(0);
+		removeRow0.run();
+
+		processUiEvents();
+	}
+
+	private void processUiEvents() {
+		while (table.getDisplay().readAndDispatch()) {
+			// continue to next event
+		}
+	}
+
+}