[Win32] Do not set IME font if the font is disposed eclipse-platform#2323

Prior to recent changes that ensure that a font handle is always
retrieved via the SWTFontProvider, the hFont variable in
Caret::setIMEFont was retrieved directly from the font object (using
font.handle). Since those recent changes, 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. Now, 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 eclipse-platform#2323

Author: arunjose696

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

@@ -74,6 +74,9 @@ 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 +108,17 @@ public void test_setFontLorg_eclipse_swt_graphics_Font() {
 	font.dispose();
 }
 
+@Test
+public void test_CaretWithDisposedFontDoesNotThrowException_issue2323() {
+	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);
+}
+
 /* custom*/
 @Test
 public void test_consistency_MenuDetect() {