Implement fucntion to force sort of the layer selector

glade/main.glade

@@ -2,6 +2,16 @@
 <!-- Generated with glade 3.22.1 -->
 <interface>
   <requires lib="gtk+" version="3.20"/>
+  <object class="GtkImage" id="image1">
+    <property name="visible">True</property>
+    <property name="can_focus">False</property>
+    <property name="stock">gtk-go-up</property>
+  </object>
+  <object class="GtkImage" id="image2">
+    <property name="visible">True</property>
+    <property name="can_focus">False</property>
+    <property name="stock">gtk-go-down</property>
+  </object>
   <object class="GtkWindow" id="main-window">
     <property name="height_request">250</property>
     <property name="can_focus">False</property>
@@ -131,6 +141,50 @@
             <property name="position">0</property>
           </packing>
         </child>
+        <child>
+          <object class="GtkBox">
+            <property name="visible">True</property>
+            <property name="can_focus">False</property>
+            <property name="orientation">vertical</property>
+            <child>
+              <object class="GtkBox">
+                <property name="visible">True</property>
+                <property name="can_focus">False</property>
+                <child>
+                  <object class="GtkButton" id="button-up-sort">
+                    <property name="visible">True</property>
+                    <property name="can_focus">True</property>
+                    <property name="receives_default">True</property>
+                    <property name="image">image1</property>
+                    <property name="always_show_image">True</property>
+                  </object>
+                  <packing>
+                    <property name="expand">False</property>
+                    <property name="fill">True</property>
+                    <property name="position">0</property>
+                  </packing>
+                </child>
+                <child>
+                  <object class="GtkButton" id="button-down-sort">
+                    <property name="visible">True</property>
+                    <property name="can_focus">True</property>
+                    <property name="receives_default">True</property>
+                    <property name="image">image2</property>
+                    <property name="always_show_image">True</property>
+                  </object>
+                  <packing>
+                    <property name="expand">False</property>
+                    <property name="fill">True</property>
+                    <property name="position">1</property>
+                  </packing>
+                </child>
+              </object>
+              <packing>
+                <property name="expand">False</property>
+                <property name="fill">False</property>
+                <property name="position">0</property>
+              </packing>
+            </child>
             <child>
               <object class="GtkScrolledWindow">
                 <property name="visible">True</property>
@@ -158,6 +212,13 @@
               </packing>
             </child>
           </object>
+          <packing>
+            <property name="expand">True</property>
+            <property name="fill">True</property>
+            <property name="position">1</property>
+          </packing>
+        </child>
+      </object>
     </child>
   </object>
 </interface>

layer-selector.c

@@ -155,19 +155,30 @@ static void analyze_cell_layers(GtkListBox *listbox, struct gds_cell *cell)
  * @param row1
  * @param row2
  * @param unused
- * @note Do not use this function
- * @return
+ * @note Do not use this function. This is an internal callback
+ * @return See sort function documentation of GTK+
  */
 static gint sort_func(GtkListBoxRow *row1, GtkListBoxRow *row2, gpointer unused)
 {
 	LayerElement *le1, *le2;
 	gint ret;
+	static const enum layer_selector_sort_algo default_sort = LAYER_SELECTOR_SORT_DOWN;
+	const enum layer_selector_sort_algo *algo = (const enum layer_selector_sort_algo *)unused;
+
+	/* Assume downward sorting */
+	/* TODO: This is nasty. Find a better way */
+	if (!algo)
+		algo = &default_sort;
 
 	le1 = LAYER_ELEMENT(row1);
 	le2 = LAYER_ELEMENT(row2);
 
+	/* Determine sort fow downward sort */
 	ret = layer_element_get_layer(le1) - layer_element_get_layer(le2);
 
+	/* Change order if upward sort is requested */
+	ret *= (*algo == LAYER_SELECTOR_SORT_DOWN ? 1 : -1);
+
 	return ret;
 }
 
@@ -179,7 +190,6 @@ void generate_layer_widgets(GtkListBox *listbox, GList *libs)
 	global_list_box = listbox;
 
 	clear_list_box_widgets(listbox);
-	gtk_list_box_set_sort_func(listbox, sort_func, NULL, NULL);
 
 	for (; libs != NULL; libs = libs->next) {
 		lib = (struct gds_library *)libs->data;
@@ -188,11 +198,8 @@ void generate_layer_widgets(GtkListBox *listbox, GList *libs)
 		} /* For Cell List */
 	} /* For libs */
 
-	/* Force sort */
-	gtk_list_box_invalidate_sort(listbox);
-
-	/* Disable sort, so user can sort layers */
-	gtk_list_box_set_sort_func(listbox, NULL, NULL, NULL);
+	/* Sort the layers */
+	layer_selector_force_sort(LAYER_SELECTOR_SORT_DOWN);
 
 	/* Activate Buttons */
 	gtk_widget_set_sensitive(global_load_button, TRUE);
@@ -435,4 +442,15 @@ void setup_save_mapping_callback(GtkWidget *button,  GtkWindow *main_window)
 	g_signal_connect(button, "clicked", G_CALLBACK(save_mapping_clicked), main_window);
 }
 
+void layer_selector_force_sort(enum layer_selector_sort_algo sort_function)
+{
+	if (!global_list_box)
+		return;
+
+	/* Set dorting function, sort, and disable sorting function */
+	gtk_list_box_set_sort_func(global_list_box, sort_func, (gpointer)&sort_function, NULL);
+	gtk_list_box_invalidate_sort(global_list_box);
+	gtk_list_box_set_sort_func(global_list_box, NULL, NULL, NULL);
+}
+
 /** @} */

layer-selector.h

@@ -30,6 +30,11 @@
 #include <glib.h>
 #include "mapping-parser.h"
 
+/**
+ * @brief Defines how to sort the layer selector list box.
+ */
+enum layer_selector_sort_algo {LAYER_SELECTOR_SORT_DOWN = 0, LAYER_SELECTOR_SORT_UP};
+
 /**
  * @brief Generate layer widgets in \p listbox
  * @note This clears all previously inserted elements
@@ -64,4 +69,14 @@ GList *export_rendered_layer_info();
  * @note The layer_info::name Element has to be freed manually
  */
 void delete_layer_info_struct(struct layer_info *info);
+
+/**
+ * @brief Force sorting of the layer selector in a specified way
+ *
+ * If the layer selector is not yet set up, this function has no effect.
+ *
+ * @param sort_function Sorting direction
+ */
+void layer_selector_force_sort(enum layer_selector_sort_algo sort_function);
+
 #endif /* __LAYER_SELECTOR_H__ */