Bug 570489 - [GTK] Combo's selection background is broken after Combo.setBackground()

In Bug 543908, author succumbed to the sin of copy&paste and incorrectly
replaced 'buttonProvider' with 'provider', causing two bugs at once:
* Selection background and foreground colors no longer apply
* Combo's button is no longer styled

Let's fix that. I also added a small code readability refactoring in
'Combo.setBackgroundGdkRGBA()'.

Change-Id: Ic0137cf4f01b151e3565553159cffafa23985000
Signed-off-by: Alexandr Miloslavskiy <alexandr.miloslavskiy@syntevo.com>

2 files changed, 67 insertions, 5 deletions

diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Combo.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Combo.java
index 7c2d3d10b3..1eb9f99d7e 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Combo.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Combo.java
@@ -2216,9 +2216,9 @@ void setButtonBackgroundGdkRGBA (GdkRGBA rgba) {
 		OS.g_object_unref(buttonProvider);
 	}
 	if (GTK.GTK4) {
-		GTK.gtk_css_provider_load_from_data (provider, Converter.wcsToMbcs (finalCss, true), -1);
+		GTK.gtk_css_provider_load_from_data (buttonProvider, Converter.wcsToMbcs (finalCss, true), -1);
 	} else {
-		GTK.gtk_css_provider_load_from_data (provider, Converter.wcsToMbcs (finalCss, true), -1, null);
+		GTK.gtk_css_provider_load_from_data (buttonProvider, Converter.wcsToMbcs (finalCss, true), -1, null);
 	}
 }
 
@@ -2253,8 +2253,7 @@ void setBackgroundGdkRGBA (long context, long handle, GdkRGBA rgba) {
 	} else {
 		background = rgba;
 	}
-	// CSS to be parsed for various widgets within Combo
-	String css = "* {";
+
 	String color, menuColor;
 	if (rgba != null) {
 		color = display.gtk_rgba_to_css_string (rgba);
@@ -2268,8 +2267,9 @@ void setBackgroundGdkRGBA (long context, long handle, GdkRGBA rgba) {
 
 		menuColor = display.gtk_rgba_to_css_string (display.COLOR_LIST_BACKGROUND_RGBA);
 	}
-	css += "background: " + color + ";}\n";
 
+	// CSS to be parsed for various widgets within Combo
+	String css = "* {background: " + color + ";}\n";
 	// Set the selected background color
 	GdkRGBA selectedBackground = display.getSystemColor(SWT.COLOR_LIST_SELECTION).handle;
 	GdkRGBA selectedForeground = display.getSystemColor(SWT.COLOR_LIST_SELECTION_TEXT).handle;
diff --git a/tests/org.eclipse.swt.tests/ManualTests/org/eclipse/swt/tests/manual/Bug570489_Gtk_ComboSetBackground.java b/tests/org.eclipse.swt.tests/ManualTests/org/eclipse/swt/tests/manual/Bug570489_Gtk_ComboSetBackground.java
new file mode 100644
index 0000000000..f50036e914
--- /dev/null
+++ b/tests/org.eclipse.swt.tests/ManualTests/org/eclipse/swt/tests/manual/Bug570489_Gtk_ComboSetBackground.java
@@ -0,0 +1,62 @@
+/*******************************************************************************
+ * Copyright (c) 2021 Syntevo and others.
+ *
+ * This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License 2.0
+ * which accompanies this distribution, and is available at
+ * https://www.eclipse.org/legal/epl-2.0/
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ * Contributors:
+ *     Syntevo - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.swt.tests.manual;
+
+import org.eclipse.swt.*;
+import org.eclipse.swt.graphics.*;
+import org.eclipse.swt.layout.*;
+import org.eclipse.swt.widgets.*;
+
+public class Bug570489_Gtk_ComboSetBackground {
+	public static void main(String[] args) {
+		Display display = new Display();
+		Shell shell = new Shell(display);
+		shell.setLayout(new GridLayout(1, true));
+
+		final Text hint = new Text(shell, SWT.READ_ONLY | SWT.MULTI);
+		hint.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
+		hint.setText(
+			"1) Run this snippet on GTK\n" +
+			"2) Check checkbox below\n" +
+			"3) Notice that combo's selection background is no longer visible\n" +
+			"4) Notice that combo's button wasn't styled"
+		);
+
+		final Combo combo = new Combo(shell, 0);
+		combo.setLayoutData(new GridData(SWT.FILL, SWT.FILL, true, true));
+		combo.setText("Test combo text");
+		combo.setSelection(new Point(5, 10));
+
+		Button button = new Button(shell, SWT.CHECK);
+		button.setText("Set custom background color");
+		button.addListener(SWT.Selection, e -> {
+			final boolean isSelected = ((Button)e.widget).getSelection();
+			if (isSelected) {
+				combo.setForeground(new Color(0xCF, 0xCF, 0xCF));
+				combo.setBackground(new Color(0x41, 0x41, 0x41));
+			} else {
+				combo.setForeground(null);
+				combo.setBackground(null);
+			}
+		});
+
+		shell.pack();
+		shell.open();
+		while (!shell.isDisposed()) {
+			if (!display.readAndDispatch())
+				display.sleep();
+		}
+		display.dispose();
+	}
+}