Spin the event loop to process the paste operation completely.

Manually when copy and paste done on combo it works as expected. But
while calling copy and paste API on combo there is an inconsistency. It
is due to pending UI events before we check text on combo.

see #2485

Author: raghucssit

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

@@ -494,6 +494,12 @@ Point computeNativeSize (long h, int wHint, int hHint, boolean changed) {
  * <p>
  * The current selection is copied to the clipboard.
  * </p>
+ * <strong>Note:</strong> On GTK4, clipboard updates may be asynchronous. This
+ * means that the new clipboard content may not be immediately available right
+ * after calling this method. To ensure the update is visible, spin the event
+ * loop (e.g., using {@link Display#readAndDispatch()} or
+ * {@link Display#asyncExec(Runnable)} before accessing the clipboard.
+ * </p>
  *
  * @exception SWTException <ul>
  *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>
@@ -1955,6 +1961,13 @@ long paintSurface () {
  * The selected text is deleted from the widget
  * and new text inserted from the clipboard.
  * </p>
+ * <p>
+ * <strong>Note:</strong> On GTK4, pasting occurs asynchronously. The widget
+ * text may not reflect the updated value immediately after calling this method.
+ * The new text will appear once pending events are processed in the event loop.
+ * If you need to assert the new value right after calling {@code paste()}, use
+ * {@link Display#readAndDispatch()} or {@link Display#asyncExec(Runnable)}.
+ * </p>
  *
  * @exception SWTException <ul>
  *    <li>ERROR_WIDGET_DISPOSED - if the receiver has been disposed</li>

tests/org.eclipse.swt.tests/JUnit Tests/org/eclipse/swt/tests/junit/Test_org_eclipse_swt_widgets_Combo.java

@@ -34,6 +34,7 @@
 import org.eclipse.swt.graphics.Point;
 import org.eclipse.swt.graphics.Rectangle;
 import org.eclipse.swt.widgets.Combo;
+import org.eclipse.swt.widgets.Display;
 import org.junit.Before;
 import org.junit.Test;
 
@@ -236,6 +237,11 @@ public void test_copy() {
 	combo.copy();
 	combo.setSelection(new Point(0,0));
 	combo.paste();
+	// Spin the event loop to let GTK process the clipboard + entry update
+	Display display = combo.getDisplay();
+	while (display.readAndDispatch()) {
+	    // loop until no more events
+	}
 	assertEquals("23123456", combo.getText());
 }
 
@@ -501,6 +507,11 @@ public void test_paste() {
 	combo.cut();
 	assertEquals("1456", combo.getText());
 	combo.paste();
+	// Spin the event loop to let GTK process the clipboard + entry update
+	Display display = combo.getDisplay();
+	while (display.readAndDispatch()) {
+	    // loop until no more events
+	}
 	assertEquals("123456", combo.getText());
 }