do not force CSD in dialogs

resources/history_dialog.ui

@@ -15,13 +15,23 @@
       <object class="GtkBox" id="dialog-vbox1">
         <property name="can_focus">False</property>
         <property name="orientation">vertical</property>
-        <property name="spacing">12</property>
+        <property name="spacing">6</property>
         <child internal-child="action_area">
           <object class="GtkButtonBox" id="dialog-action_area1">
             <property name="can_focus">False</property>
-            <property name="layout_style">end</property>
             <child>
-              <placeholder/>
+              <object class="GtkButton" id="close_button">
+                <property name="label" translatable="yes">_Close</property>
+                <property name="visible">True</property>
+                <property name="can_focus">True</property>
+                <property name="receives_default">False</property>
+                <property name="use_underline">True</property>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="fill">True</property>
+                <property name="position">0</property>
+              </packing>
             </child>
           </object>
           <packing>
@@ -57,5 +67,11 @@
         </child>
       </object>
     </child>
+    <action-widgets>
+      <action-widget response="-7">close_button</action-widget>
+    </action-widgets>
+    <child>
+      <placeholder/>
+    </child>
   </template>
 </interface>

src/choose_ignorepkgs_dialog.vala

@@ -28,7 +28,9 @@ namespace Pamac {
 		public Gtk.ListStore pkgs_list;
 
 		public ChooseIgnorepkgsDialog (Gtk.Window window) {
-			Object (transient_for: window, use_header_bar: 1);
+			int use_header_bar;
+			Gtk.Settings.get_default ().get ("gtk-dialogs-use-header", out use_header_bar);
+			Object (transient_for: window, use_header_bar: use_header_bar);
 
 			pkgs_list = new Gtk.ListStore (2, typeof (bool), typeof (string));
 			treeview.set_model (pkgs_list);

src/choose_provider_dialog.vala

@@ -23,7 +23,9 @@ namespace Pamac {
 	class ChooseProviderDialog : Gtk.Dialog {
 
 		public ChooseProviderDialog (Gtk.ApplicationWindow? window) {
-			Object (transient_for: window, use_header_bar: 1);
+			int use_header_bar;
+			Gtk.Settings.get_default ().get ("gtk-dialogs-use-header", out use_header_bar);
+			Object (transient_for: window, use_header_bar: use_header_bar);
 		}
 	}
 }

src/history_dialog.vala

@@ -26,7 +26,9 @@ namespace Pamac {
 		public Gtk.TextView textview;
 
 		public HistoryDialog (Gtk.ApplicationWindow window) {
-			Object (transient_for: window, use_header_bar: 1);
+			int use_header_bar;
+			Gtk.Settings.get_default ().get ("gtk-dialogs-use-header", out use_header_bar);
+			Object (transient_for: window, use_header_bar: use_header_bar);
 		}
 	}
 }

src/transaction.vala

@@ -279,12 +279,15 @@ namespace Pamac {
 		}
 
 		public void run_about_dialog () {
+			string[] authors = {"Guillaume Benoit"};
 			Gtk.show_about_dialog (
 				application_window,
 				"program_name", "Pamac",
+				"icon_name", "system-software-install",
 				"logo_icon_name", "system-software-install",
 				"comments", dgettext (null, "A Gtk3 frontend for libalpm"),
 				"copyright", "Copyright © 2017 Guillaume Benoit",
+				"authors", authors,
 				"version", VERSION,
 				"license_type", Gtk.License.GPL_3_0,
 				"website", "http://github.com/manjaro/pamac");
@@ -1481,9 +1484,17 @@ namespace Pamac {
 
 		void show_warnings () {
 			if (warning_textbuffer.len > 0) {
+				var flags = Gtk.DialogFlags.MODAL;
+				int use_header_bar;
+				Gtk.Settings.get_default ().get ("gtk-dialogs-use-header", out use_header_bar);
+				if (use_header_bar == 1) {
+					flags |= Gtk.DialogFlags.USE_HEADER_BAR;
+				}
 				var dialog = new Gtk.Dialog.with_buttons (dgettext (null, "Warning"),
 														application_window,
-														Gtk.DialogFlags.MODAL | Gtk.DialogFlags.USE_HEADER_BAR);
+														flags);
+				dialog.border_width = 6;
+				dialog.icon_name = "system-software-install";
 				dialog.deletable = false;
 				unowned Gtk.Widget widget = dialog.add_button (dgettext (null, "_Close"), Gtk.ResponseType.CLOSE);
 				widget.can_focus = true;
@@ -1508,9 +1519,17 @@ namespace Pamac {
 		}
 
 		void display_error (string message, string[] details) {
+			var flags = Gtk.DialogFlags.MODAL;
+			int use_header_bar;
+			Gtk.Settings.get_default ().get ("gtk-dialogs-use-header", out use_header_bar);
+			if (use_header_bar == 1) {
+				flags |= Gtk.DialogFlags.USE_HEADER_BAR;
+			}
 			var dialog = new Gtk.Dialog.with_buttons (message,
 													application_window,
-													Gtk.DialogFlags.MODAL | Gtk.DialogFlags.USE_HEADER_BAR);
+													flags);
+			dialog.border_width = 6;
+			dialog.icon_name = "system-software-install";
 			var textbuffer = new StringBuilder ();
 			if (details.length != 0) {
 				show_in_term (message + ":");

src/transaction_sum_dialog.vala

@@ -30,7 +30,9 @@ namespace Pamac {
 		public Gtk.ListStore sum_list;
 
 		public TransactionSumDialog (Gtk.ApplicationWindow? window) {
-			Object (transient_for: window, use_header_bar: 1);
+			int use_header_bar;
+			Gtk.Settings.get_default ().get ("gtk-dialogs-use-header", out use_header_bar);
+			Object (transient_for: window, use_header_bar: use_header_bar);
 
 			sum_list = new Gtk.ListStore (4, typeof (string), typeof (string), typeof (string), typeof (string));
 			treeview.set_model (sum_list);