LPS-115485 As a developer I can inject custom CSS variables declaring an OSGi component

modules/apps/frontend-css/frontend-css-variables-api/bnd.bnd

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+Bundle-Name: Liferay Frontend CSS Variables API
+Bundle-SymbolicName: com.liferay.frontend.css.variables.api
+Bundle-Version: 1.0.0
+Export-Package: com.liferay.frontend.css.variables

modules/apps/frontend-css/frontend-css-variables-api/build.gradle

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+dependencies {
+	compileOnly group: "com.liferay", name: "biz.aQute.bnd.annotation", version: "4.2.0.LIFERAY-PATCHED-1"
+	compileOnly group: "com.liferay.portal", name: "com.liferay.portal.kernel", version: "default"
+	compileOnly group: "javax.portlet", name: "portlet-api", version: "3.0.1"
+	compileOnly group: "org.apache.felix", name: "org.apache.felix.http.servlet-api", version: "1.1.2"
+	compileOnly group: "org.osgi", name: "org.osgi.service.component.annotations", version: "1.3.0"
+	compileOnly group: "org.osgi", name: "osgi.core", version: "6.0.0"
+}

modules/apps/frontend-css/frontend-css-variables-api/src/main/java/com/liferay/frontend/css/variables/ScopedCSSVariables.java

@@ -0,0 +1,28 @@
+/**
+ * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the Free
+ * Software Foundation; either version 2.1 of the License, or (at your option)
+ * any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
+ * details.
+ */
+
+package com.liferay.frontend.css.variables;
+
+import java.util.Map;
+
+/**
+ * @author Iván Zaera Avellón
+ */
+public interface ScopedCSSVariables {
+
+	public Map<String, String> getCSSVariables();
+
+	public String getScope();
+
+}

modules/apps/frontend-css/frontend-css-variables-api/src/main/java/com/liferay/frontend/css/variables/ScopedCSSVariablesProvider.java

@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the Free
+ * Software Foundation; either version 2.1 of the License, or (at your option)
+ * any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
+ * details.
+ */
+
+package com.liferay.frontend.css.variables;
+
+import java.util.Collection;
+
+import javax.servlet.http.HttpServletRequest;
+
+/**
+ * @author Iván Zaera Avellón
+ */
+public interface ScopedCSSVariablesProvider {
+
+	public Collection<ScopedCSSVariables> getScopedCSSVariablesCollection(
+		HttpServletRequest httpServletRequest);
+
+}

modules/apps/frontend-css/frontend-css-variables-api/src/main/resources/com/liferay/frontend/css/variables/packageinfo

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+version 1.0.0

modules/apps/frontend-css/frontend-css-variables-web/bnd.bnd

@@ -0,0 +1,4 @@
+Bundle-Name: Liferay Frontend CSS Variables Web
+Bundle-SymbolicName: com.liferay.frontend.css.variables.web
+Bundle-Version: 1.0.0
+Web-ContextPath: /frontend-css-variables-web

modules/apps/frontend-css/frontend-css-variables-web/build.gradle

@@ -0,0 +1,15 @@
+dependencies {
+	compileOnly group: "com.liferay", name: "biz.aQute.bnd.annotation", version: "4.2.0.LIFERAY-PATCHED-1"
+	compileOnly group: "com.liferay.portal", name: "com.liferay.portal.kernel", version: "default"
+	compileOnly group: "javax.portlet", name: "portlet-api", version: "3.0.1"
+	compileOnly group: "org.apache.felix", name: "org.apache.felix.http.servlet-api", version: "1.1.2"
+	compileOnly group: "org.osgi", name: "org.osgi.service.component.annotations", version: "1.3.0"
+	compileOnly group: "org.osgi", name: "osgi.core", version: "6.0.0"
+	compileOnly project(":apps:configuration-admin:configuration-admin-api")
+	compileOnly project(":apps:frontend-css:frontend-css-variables-api")
+	compileOnly project(":apps:static:portal-configuration:portal-configuration-metatype-api")
+	compileOnly project(":core:osgi-service-tracker-collections")
+	compileOnly project(":core:petra:petra-string")
+
+	testCompile group: "junit", name: "junit", version: "4.12"
+}

modules/apps/frontend-css/frontend-css-variables-web/src/main/java/com/liferay/frontend/css/variables/web/internal/servlet/taglib/ScopedCSSVariablesTopHeadDynamicInclude.java

@@ -0,0 +1,131 @@
+/**
+ * Copyright (c) 2000-present Liferay, Inc. All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU Lesser General Public License as published by the Free
+ * Software Foundation; either version 2.1 of the License, or (at your option)
+ * any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+ * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
+ * details.
+ */
+
+package com.liferay.frontend.css.variables.web.internal.servlet.taglib;
+
+import com.liferay.frontend.css.variables.ScopedCSSVariables;
+import com.liferay.frontend.css.variables.ScopedCSSVariablesProvider;
+import com.liferay.osgi.service.tracker.collections.list.ServiceTrackerList;
+import com.liferay.osgi.service.tracker.collections.list.ServiceTrackerListFactory;
+import com.liferay.osgi.service.tracker.collections.map.PropertyServiceReferenceComparator;
+import com.liferay.portal.kernel.servlet.taglib.BaseDynamicInclude;
+import com.liferay.portal.kernel.servlet.taglib.DynamicInclude;
+
+import java.io.IOException;
+import java.io.PrintWriter;
+
+import java.util.Collection;
+import java.util.Map;
+
+import javax.servlet.http.HttpServletRequest;
+import javax.servlet.http.HttpServletResponse;
+
+import org.osgi.framework.BundleContext;
+import org.osgi.service.component.annotations.Activate;
+import org.osgi.service.component.annotations.Component;
+import org.osgi.service.component.annotations.Deactivate;
+
+/**
+ * @author Iván Zaera Avellón
+ */
+@Component(service = DynamicInclude.class)
+public class ScopedCSSVariablesTopHeadDynamicInclude
+	extends BaseDynamicInclude {
+
+	@Override
+	public void include(
+			HttpServletRequest httpServletRequest,
+			HttpServletResponse httpServletResponse, String dynamicIncludeKey)
+		throws IOException {
+
+		PrintWriter printWriter = httpServletResponse.getWriter();
+
+		printWriter.print("<style data-senna-track=\"temporary\" ");
+		printWriter.print("type=\"text/css\">\n");
+
+		for (ScopedCSSVariablesProvider scopedCSSVariablesProvider :
+				_scopedCSSVariablesProviders) {
+
+			_writeCSSVariables(
+				printWriter,
+				scopedCSSVariablesProvider.getScopedCSSVariablesCollection(
+					httpServletRequest));
+		}
+
+		printWriter.print("</style>\n");
+	}
+
+	@Override
+	public void register(DynamicIncludeRegistry dynamicIncludeRegistry) {
+		dynamicIncludeRegistry.register(
+			"/html/common/themes/top_head.jsp#post");
+	}
+
+	@Activate
+	protected void activate(BundleContext bundleContext) {
+		_scopedCssVariablesProviderServiceTrackerList =
+			ServiceTrackerListFactory.open(
+				bundleContext, ScopedCSSVariablesProvider.class,
+				new PropertyServiceReferenceComparator<>("service.ranking"));
+
+		setScopedCSSVariablesProviders(
+			_scopedCssVariablesProviderServiceTrackerList);
+	}
+
+	@Deactivate
+	protected void deactivate() {
+		setScopedCSSVariablesProviders(null);
+
+		_scopedCssVariablesProviderServiceTrackerList.close();
+
+		_scopedCssVariablesProviderServiceTrackerList = null;
+	}
+
+	protected void setScopedCSSVariablesProviders(
+		Iterable<ScopedCSSVariablesProvider> scopedCSSVariablesProviders) {
+
+		_scopedCSSVariablesProviders = scopedCSSVariablesProviders;
+	}
+
+	private void _writeCSSVariables(
+		PrintWriter printWriter,
+		Collection<ScopedCSSVariables> scopedCSSVariablesCollection) {
+
+		for (ScopedCSSVariables scopedCSSVariables :
+				scopedCSSVariablesCollection) {
+
+			printWriter.print(scopedCSSVariables.getScope());
+			printWriter.print(" {\n");
+
+			Map<String, String> cssVariables =
+				scopedCSSVariables.getCSSVariables();
+
+			for (Map.Entry<String, String> entry : cssVariables.entrySet()) {
+				printWriter.print("--");
+				printWriter.print(entry.getKey());
+				printWriter.print(": ");
+				printWriter.print(entry.getValue());
+				printWriter.print(";\n");
+			}
+
+			printWriter.print("}\n");
+		}
+	}
+
+	private Iterable<ScopedCSSVariablesProvider> _scopedCSSVariablesProviders;
+	private ServiceTrackerList
+		<ScopedCSSVariablesProvider, ScopedCSSVariablesProvider>
+			_scopedCssVariablesProviderServiceTrackerList;
+
+}