Bug 549733: [GTK] [API] Query the current system setting for dark mode

Adjust the original patch such that it works with both GTK_THEME
and the system GTK theme.

Change-Id: I9e0db81274123ea054539c343a58a1d9fe221740
Signed-off-by: Eric Williams <ericwill@redhat.com>

6 files changed, 111 insertions, 20 deletions

diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.c b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.c
index e0326b8506..81feb4b3ab 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.c
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os.c
@@ -15483,6 +15483,23 @@ fail:
 }
 #endif
 
+#ifndef NO__1g_1object_1get__J_3B_3ZJ
+JNIEXPORT void JNICALL OS_NATIVE(_1g_1object_1get__J_3B_3ZJ)
+	(JNIEnv *env, jclass that, jlong arg0, jbyteArray arg1, jbooleanArray arg2, jlong arg3)
+{
+	jbyte *lparg1=NULL;
+	jboolean *lparg2=NULL;
+	OS_NATIVE_ENTER(env, that, _1g_1object_1get__J_3B_3ZJ_FUNC);
+	if (arg1) if ((lparg1 = (*env)->GetByteArrayElements(env, arg1, NULL)) == NULL) goto fail;
+	if (arg2) if ((lparg2 = (*env)->GetBooleanArrayElements(env, arg2, NULL)) == NULL) goto fail;
+	g_object_get((GObject *)arg0, (const gchar *)lparg1, lparg2, (const gchar *)NULL);
+fail:
+	if (arg2 && lparg2) (*env)->ReleaseBooleanArrayElements(env, arg2, lparg2, 0);
+	if (arg1 && lparg1) (*env)->ReleaseByteArrayElements(env, arg1, lparg1, JNI_ABORT);
+	OS_NATIVE_EXIT(env, that, _1g_1object_1get__J_3B_3ZJ_FUNC);
+}
+#endif
+
 #ifndef NO__1g_1object_1get_1qdata
 JNIEXPORT jlong JNICALL OS_NATIVE(_1g_1object_1get_1qdata)
 	(JNIEnv *env, jclass that, jlong arg0, jint arg1)
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.c b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.c
index 3512668735..c99927c3f5 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.c
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.c
@@ -1276,6 +1276,7 @@ char * OS_nativeFunctionNames[] = {
 	"_1g_1object_1class_1find_1property",
 	"_1g_1object_1get__J_3B_3IJ",
 	"_1g_1object_1get__J_3B_3JJ",
+	"_1g_1object_1get__J_3B_3ZJ",
 	"_1g_1object_1get_1qdata",
 	"_1g_1object_1new",
 	"_1g_1object_1notify",
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.h b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.h
index 642bc88848..b368da0b32 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.h
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/library/os_stats.h
@@ -1250,6 +1250,7 @@ typedef enum {
 	_1g_1object_1class_1find_1property_FUNC,
 	_1g_1object_1get__J_3B_3IJ_FUNC,
 	_1g_1object_1get__J_3B_3JJ_FUNC,
+	_1g_1object_1get__J_3B_3ZJ_FUNC,
 	_1g_1object_1get_1qdata_FUNC,
 	_1g_1object_1new_FUNC,
 	_1g_1object_1notify_FUNC,
diff --git a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/OS.java b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/OS.java
index b6a3080f7f..813c4b0e64 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/OS.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT PI/gtk/org/eclipse/swt/internal/gtk/OS.java
@@ -715,13 +715,7 @@ public class OS extends C {
 	 * A string containing the theme name supplied via the GTK_THEME
 	 * environment variable. Otherwise this will contain an empty string.
 	 */
-	public static final String GTK_THEME_NAME;
-	/**
-	 * True if GTK_THEME_SET is true, and if the dark variant was
-	 * specified via the GTK_THEME environment variable.
-	 */
-	public static final boolean GTK_THEME_DARK;
-
+	public static final String GTK_THEME_SET_NAME;
 	/**
 	 * True if SWT is running on the GNOME desktop environment.
 	 */
@@ -768,16 +762,12 @@ public class OS extends C {
 		String gtkThemeCheck = getEnvironmentalVariable(gtkThemeProperty);
 		boolean gtkThemeSet = false;
 		String gtkThemeName = "";
-		boolean gtkThemeDark = false;
 		if (gtkThemeCheck != null && !gtkThemeCheck.isEmpty()) {
 			gtkThemeSet = true;
-			gtkThemeDark = gtkThemeCheck.contains(":dark") ? true : false;
-			String [] themeNameSplit = gtkThemeCheck.split(":");
-			gtkThemeName = themeNameSplit[0];
+			gtkThemeName = gtkThemeCheck;
 		}
 		GTK_THEME_SET = gtkThemeSet;
-		GTK_THEME_NAME = gtkThemeName;
-		GTK_THEME_DARK = gtkThemeDark;
+		GTK_THEME_SET_NAME = gtkThemeName;
 
 		Map<String, String> env = System.getenv();
 		String desktopEnvironment = env.get("XDG_CURRENT_DESKTOP");
@@ -2041,6 +2031,20 @@ public static final void g_object_get(long object, byte[] first_property_name, l
 }
 /**
  * @param object cast=(GObject *)
+ * @param first_property_name cast=(const gchar *),flags=no_out
+ * @param terminator cast=(const gchar *),flags=sentinel
+ */
+public static final native void _g_object_get(long object, byte[] first_property_name, boolean[] value, long terminator);
+public static final void g_object_get(long object, byte[] first_property_name, boolean[] value, long terminator) {
+	lock.lock();
+	try {
+		_g_object_get(object, first_property_name, value, terminator);
+	} finally {
+		lock.unlock();
+	}
+}
+/**
+ * @param object cast=(GObject *)
  * @param quark cast=(GQuark)
  */
 public static final native long _g_object_get_qdata(long object, int quark);
diff --git a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Display.java b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Display.java
index 624d3ec2f8..152a7d6a7b 100644
--- a/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Display.java
+++ b/bundles/org.eclipse.swt/Eclipse SWT/gtk/org/eclipse/swt/widgets/Display.java
@@ -330,6 +330,12 @@ public class Display extends Device {
 	final int SWT_COLOR_LIST_SELECTION_TEXT_INACTIVE = 38;
 	final int SWT_COLOR_LIST_SELECTION_INACTIVE = 39;
 
+	/* Theme related */
+	/** The name of the current theme, including the theme named by GTK_THEME. */
+	static String themeName;
+	/** True if the current theme is dark. This includes the theme set in GTK_THEME. */
+	static boolean themeDark;
+
 	/* Popup Menus */
 	Menu [] popups;
 
@@ -1070,17 +1076,43 @@ void checkIMModule () {
 	}
 }
 
+/**
+ * Sets the org.eclipse.swt.internal.gtk.theme value with the current
+ * GTK theme name. Checks if the current theme SWT is running with
+ * is dark or not. This includes checking the GTK_THEME environment
+ * variable, the theme name, and GSettings.
+ *
+ * @param themeName the full name of the current theme SWT is running with
+ * @return true if the current theme is dark
+ */
+boolean checkAndSetThemeDetails (String themeName) {
+	if (themeName.endsWith("-dark") || themeName.endsWith(":dark")) {
+		System.setProperty("org.eclipse.swt.internal.gtk.theme", themeName);
+		return true;
+	}
+	long settings = GTK.gtk_settings_get_default ();
+	boolean [] darkThemePreferred = new boolean [1];
+	OS.g_object_get(settings, GTK.gtk_application_prefer_dark_theme, darkThemePreferred, 0);
+	if (darkThemePreferred[0]) {
+		/*
+		 * When 'gtk-application-prefer-dark-theme' is set to true, GTK uses the 'dark'
+		 * variant of the theme specified in the system settings -- see 'get_theme_name'
+		 * in the GtkSettings source code for more context.
+		 */
+		System.setProperty("org.eclipse.swt.internal.gtk.theme", themeName.concat(":dark"));
+	} else {
+		System.setProperty("org.eclipse.swt.internal.gtk.theme", themeName);
+	}
+	return darkThemePreferred[0];
+}
+
 void createDisplay (DeviceData data) {
 	boolean init = GTK.GTK4 ? GTK.gtk_init_check () : GTK.gtk_init_check (new long [] {0}, null);
 	if (!init) SWT.error (SWT.ERROR_NO_HANDLES, null, " [gtk_init_check() failed]"); //$NON-NLS-1$
 	checkIMModule();
 	//set GTK+ Theme name as property for introspection purposes
-	if (OS.GTK_THEME_SET) {
-		String themeName = OS.GTK_THEME_NAME + (OS.GTK_THEME_DARK ? ":dark" : "");
-		System.setProperty("org.eclipse.swt.internal.gtk.theme", themeName);
-	} else {
-		System.setProperty("org.eclipse.swt.internal.gtk.theme", OS.getThemeName());
-	}
+	themeName = OS.GTK_THEME_SET ? OS.GTK_THEME_SET_NAME : OS.getThemeName();
+	themeDark = checkAndSetThemeDetails(themeName);
 	if (OS.isX11()) {
 		xDisplay = GTK.GTK4 ? 0 : GDK.gdk_x11_get_default_xdisplay();
 	}
@@ -2442,7 +2474,7 @@ public Point [] getIconSizes () {
  * @since 3.112
  */
 public static boolean isSystemDarkTheme () {
-	return OS.GTK_THEME_DARK;
+	return themeDark;
 }
 
 int getLastEventTime () {
diff --git a/tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Bug549733_GTKDarkAPI.java b/tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Bug549733_GTKDarkAPI.java
new file mode 100644
index 0000000000..d95df18d66
--- /dev/null
+++ b/tests/org.eclipse.swt.tests.gtk/ManualTests/org/eclipse/swt/tests/gtk/snippets/Bug549733_GTKDarkAPI.java
@@ -0,0 +1,36 @@
+/*******************************************************************************
+ * Copyright (c) 2019 Red Hat and others. All rights reserved.
+ * The contents of this file are made available under the terms
+ * of the GNU Lesser General Public License (LGPL) Version 2.1 that
+ * accompanies this distribution (lgpl-v21.txt).  The LGPL is also
+ * available at http://www.gnu.org/licenses/lgpl.html.  If the version
+ * of the LGPL at http://www.gnu.org is different to the version of
+ * the LGPL accompanying this distribution and there is any conflict
+ * between the two license versions, the terms of the LGPL accompanying
+ * this distribution shall govern.
+ *
+ * Contributors:
+ *     Red Hat - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.swt.tests.gtk.snippets;
+
+import org.eclipse.swt.layout.FillLayout;
+import org.eclipse.swt.widgets.Display;
+import org.eclipse.swt.widgets.Shell;
+
+public class Bug549733_GTKDarkAPI {
+
+	public static void main(String[] args) {
+		Display display = new Display();
+		Shell shell = new Shell(display);
+		shell.setLayout(new FillLayout());
+		shell.setSize(500, 200);
+		System.out.println("Display.isThemeDark(): " + Display.isSystemDarkTheme());
+		System.out.println("Theme name set in SWT: " + System.getProperty("org.eclipse.swt.internal.gtk.theme"));
+		shell.open();
+		while (!shell.isDisposed()) {
+			if (!display.readAndDispatch())
+				display.sleep();
+		}
+	}
+}