Add css style

Flos_Gtk4/CMakeLists.txt

@@ -25,7 +25,9 @@ link_directories (${GTK4_LIBRARY_DIRS})
 
 set(RESOURCE_LIST
     flos.png
-    menubar.xml)
+    menubar.xml
+    style.css
+    reset.css)
 
 compile_gresources(RESOURCE_FILE
                    XML_OUT

Flos_Gtk4/res/reset.css

@@ -0,0 +1,12 @@
+/* @import this colorsheet to get the default values for every property.
+ * This is useful when writing special CSS tests that should not be
+ * inluenced by themes - not even the default ones.
+ * Keep in mind that the output will be very ugly and not look like
+ * anything GTK.
+ * Also, when adding new style properties, please add them here.
+ */
+
+ * {
+    all: unset;
+  }
+  

Flos_Gtk4/res/style.css

@@ -0,0 +1,12 @@
+/*
+您可以在这里输入任何 GTK 可识别的 CSS 规则。
+您可以点击上面的“暂停”按钮来暂时停用这个自定义 CSS。
+
+变更会立即应用到全局，影响整个应用程序。
+*/
+@import url("resource://org/gtk/daleclack/reset.css");
+
+/*Style for menubar*/
+menubar{
+	background-color:#FFFA;
+}

Flos_Gtk4/src/core/MainWin.cpp

@@ -25,22 +25,20 @@ static void main_win_init(MainWin * win){
     g_object_unref(pixbuf);
     g_object_unref(sized);
 
-    //Add button for menubar
-    GtkWidget * back_button = gtk_button_new_with_label("   ");
-    gtk_widget_set_valign(back_button,GTK_ALIGN_START);
-    gtk_widget_set_halign(back_button,GTK_ALIGN_FILL);
-    gtk_widget_set_sensitive(back_button,FALSE);
-    gtk_widget_set_opacity(back_button,0.7);
-    gtk_overlay_add_overlay(GTK_OVERLAY(win->overlay),back_button);
-
     //Add MenuBar
     GtkBuilder * builder = gtk_builder_new_from_resource("/org/gtk/daleclack/menubar.xml");
     GMenuModel * model = G_MENU_MODEL(gtk_builder_get_object(builder,"model"));
     GtkWidget * menubar = gtk_popover_menu_bar_new_from_model(model);
+    //gtk_button_set_child(GTK_BUTTON(back_button),menubar);
     gtk_widget_set_valign(menubar,GTK_ALIGN_START);
     gtk_widget_set_halign(menubar,GTK_ALIGN_FILL);
     gtk_overlay_add_overlay(GTK_OVERLAY(win->overlay),menubar);
 
+    //Apply Style for menubar
+    GtkStyleProvider * provider = GTK_STYLE_PROVIDER(gtk_css_provider_new());
+    gtk_css_provider_load_from_resource(GTK_CSS_PROVIDER(provider),"/org/gtk/daleclack/style.css");
+    gtk_style_context_add_provider(gtk_widget_get_style_context(menubar),provider,G_MAXINT);
+    
     //Add widgets
     gtk_overlay_set_child(GTK_OVERLAY(win->overlay),win->background);
     gtk_window_set_child(GTK_WINDOW(win),win->overlay);