Fix infinite Text redraw for SWT.SEARCH with custom background on macOS

On cocoa, Text.drawInteriorWithFrame_inView_searchfield queried the
search field text via NSControl.stringValue to decide whether to draw
the cancel icon. That call schedules a setNeedsDisplay: on the view
from inside the paint pass. Widget.setNeedsDisplay then enqueues the
view in display.needsDisplay, which is flushed after paint, marking
the view dirty again and causing readAndDispatch() to spin forever.

Read the text through NSCell.stringValue instead, which bypasses the
control-level side effect. Also add the JUnit regression test from
PR eclipse-platform#3260 reproducing the loop.

Fixes eclipse-platform/eclipse.platform.ui#3920

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: vogella

bundles/org.eclipse.swt/Eclipse SWT PI/cocoa/org/eclipse/swt/internal/cocoa/NSCell.java

@@ -174,6 +174,11 @@ public void setWraps(boolean wraps) {
 	OS.objc_msgSend(this.id, OS.sel_setWraps_, wraps);
 }
 
+public NSString stringValue() {
+	long result = OS.objc_msgSend(this.id, OS.sel_stringValue);
+	return result != 0 ? new NSString(result) : null;
+}
+
 public NSString title() {
 	long result = OS.objc_msgSend(this.id, OS.sel_title);
 	return result != 0 ? new NSString(result) : null;

bundles/org.eclipse.swt/Eclipse SWT/cocoa/org/eclipse/swt/widgets/Text.java

@@ -748,7 +748,14 @@ void drawInteriorWithFrame_inView_searchfield (long id, long sel, NSRect cellFra
 		cell.searchButtonCell().drawInteriorWithFrame(cell.searchButtonRectForBounds(cellFrame), view);
 	}
 
-	if (cell.cancelButtonCell() != null && ((NSSearchField) view).stringValue().length() > 0) {
+	/*
+	 * Read the text through NSCell.stringValue rather than NSControl.stringValue.
+	 * The NSControl variant triggers setNeedsDisplay: on the view from inside
+	 * the draw pass, which Widget.setNeedsDisplay then enqueues for another redraw
+	 * after paint, looping indefinitely (eclipse.platform.ui#3920).
+	 */
+	NSString cellValue = _cell.stringValue();
+	if (cell.cancelButtonCell() != null && cellValue != null && cellValue.length() > 0) {
 		cell.cancelButtonCell().drawInteriorWithFrame(cell.cancelButtonRectForBounds(cellFrame), view);
 	}
 }

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

@@ -13,12 +13,14 @@
  *******************************************************************************/
 package org.eclipse.swt.tests.junit;
 
+import static java.lang.System.currentTimeMillis;
 import static org.eclipse.swt.tests.junit.SwtTestUtil.JENKINS_DETECT_ENV_VAR;
 import static org.eclipse.swt.tests.junit.SwtTestUtil.JENKINS_DETECT_REGEX;
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
+import static org.junit.jupiter.api.Assertions.fail;
 
 import org.eclipse.swt.SWT;
 import org.eclipse.swt.events.ModifyListener;
@@ -1376,6 +1378,31 @@ public void test_showSelection() {
 	text.showSelection();
 }
 
+// Originally reported as https://github.com/eclipse-platform/eclipse.platform.ui/issues/3920
+@Test
+public void test_finiteRedraw() {
+	if ( text != null ) text.dispose();
+	// Style constants are causing
+	// org.eclipse.swt.widgets.Text.drawInteriorWithFrame_inView_searchfield(long, long, NSRect, long)
+	// to call
+	// org.eclipse.swt.internal.cocoa.NSControl.stringValue()
+	// which schedules redraw
+	text = new Text(shell, SWT.SEARCH | SWT.ICON_CANCEL);
+	// Background prevents early exit from drawInteriorWithFrame_inView_searchfield(long, long, NSRect, long)
+	text.setBackground(shell.getDisplay().getSystemColor(SWT.COLOR_RED));
+	setWidget(text);
+	Display display = shell.getDisplay();
+	text.forceFocus();
+	long stop = currentTimeMillis() + 1000;
+	// If redraws are constantly scheduled, readAndDispatch() will never return false.
+	// Side effects - high CPU usage, asyncExec() stops working in modal contexts
+	while (display.readAndDispatch()) {
+		if (currentTimeMillis() > stop) {
+			fail("UI should eventually stop refreshing");
+		}
+	}
+}
+
 /* custom */
 Text text;
 String delimiterString;