Do not set IME font if the font is disposed

Prior to PR #2062, the hFont variable in Caret::setIMEFont was
retrieved directly from the font object (using font.handle). Since #2602, hFont is
fetched via SWTFontProvider, which throws an exception if the font is disposed.

Previously, when the font was disposed, hFont (font.handle) would be zero, and the
method would fall back to using defaultFont for setting the IME font.
After #2602, this fallback no longer works because the exception is
thrown before the fallback can occur.

This commit restores the intended behavior by setting hfont as zero if
the font is disposed, preventing the exception.

Fixes #2323

Author: arunjose696

bundles/org.eclipse.swt/Eclipse SWT/win32/org/eclipse/swt/internal/SWTFontProvider.java

@@ -74,6 +74,10 @@ public static long getFontHandle(Font font, int zoom) {
 		if (font == null) {
 			SWT.error(SWT.ERROR_NULL_ARGUMENT);
 		}
+		if(font.isDisposed())
+		{
+			return 0;
+		}
 		return Font.win32_getHandle(getFont(font.getDevice(), font.getFontData()[0], zoom));
 	}
 

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

@@ -108,6 +108,21 @@ public void test_setFontLorg_eclipse_swt_graphics_Font() {
 	font.dispose();
 }
 
+@Test
+public void test_CaretWithDisposedFontDoesNotThrowException_issue2323() {
+    try {
+        Caret caret = new Caret(canvas, SWT.NONE);
+        Font font = new Font(canvas.getDisplay(), "Default", 10, SWT.BOLD);
+        shell.open();
+        caret.setFont(font);
+        font.dispose();
+        canvas.setFocus();
+        canvas.setCaret(caret);
+    } catch (Exception e) {
+        fail("Exception thrown when a canvas sets a caret with a disposed font: " + e.getMessage());
+    }
+}
+
 /* custom*/
 @Test
 public void test_consistency_MenuDetect() {