Show gtk version in cli and in About window

This change adds the possibility to show the used gtk version either
via `xournalpp --version` or directly in the **About** window.

.github/ISSUE_TEMPLATE/bug_report.md

@@ -12,8 +12,10 @@ assignees: ''
 **Affects versions :**
  - OS: [e.g. Linux (which distro), Mac, Windows]
  - (Linux only) Desktop environment: [e.g. Wayland, Gnome-Wayland, XWayland, X11]
- - Which version of libgtk do you use: [e.g. output of `pkg-config --modversion gtk+-3.0`]
+ - Which version of libgtk do you use
+     - can be obtained by running `xournalpp --version` or in the **About** window
  - Version of Xournal++: [e.g. 1.0.16, specific commit, specific branch]
+     - can be obtained by running `xournalpp --version` or in the **About** window
  - Installation method: [e.g. PPA, Flatpak, official release, etc.]
 
 **Describe the bug**

src/control/XournalMain.cpp

@@ -337,6 +337,7 @@ auto XournalMain::run(int argc, char* argv[]) -> int {
 
     if (showVersion) {
         g_printf("%s %s \n", PROJECT_NAME, PROJECT_VERSION);
+        g_printf("└──%s: %d.%d.%d \n", "libgtk", gtk_get_major_version(), gtk_get_minor_version(), gtk_get_micro_version());
         return 0;
     }
 

src/gui/dialog/AboutDialog.cpp

@@ -1,5 +1,7 @@
 #include "AboutDialog.h"
 
+#include <gtk/gtk.h>
+
 #include <config.h>
 
 #include "StringUtils.h"
@@ -9,6 +11,11 @@ AboutDialog::AboutDialog(GladeSearchpath* gladeSearchPath): GladeGui(gladeSearch
     gtk_label_set_markup(GTK_LABEL(get("lbVersion")), PROJECT_VERSION);
     gtk_label_set_markup(GTK_LABEL(get("lbRevId")), GIT_COMMIT_ID);
 
+    char gtkVersion[10];
+    sprintf(gtkVersion, "%d.%d.%d", gtk_get_major_version(), gtk_get_minor_version(), gtk_get_micro_version());
+
+    gtk_label_set_markup(GTK_LABEL(get("lbGtkVersion")), gtkVersion);
+
     GtkWidget* w = get("vbox1");
     GtkWidget* linkButton = gtk_link_button_new("http://github.com/xournalpp/xournalpp");
     gtk_widget_show(linkButton);

ui/about.glade

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<!-- Generated with glade 3.22.1 -->
+<!-- Generated with glade 3.36.0 -->
 <interface>
   <requires lib="gtk+" version="3.18"/>
   <object class="GtkDialog" id="aboutDialog">
@@ -171,6 +171,31 @@
                     <property name="top_attach">1</property>
                   </packing>
                 </child>
+                <child>
+                  <object class="GtkLabel">
+                    <property name="visible">True</property>
+                    <property name="can_focus">False</property>
+                    <property name="label" translatable="yes">with libgtk</property>
+                    <attributes>
+                      <attribute name="weight" value="bold"/>
+                    </attributes>
+                  </object>
+                  <packing>
+                    <property name="left_attach">0</property>
+                    <property name="top_attach">3</property>
+                  </packing>
+                </child>
+                <child>
+                  <object class="GtkLabel" id="lbGtkVersion">
+                    <property name="visible">True</property>
+                    <property name="can_focus">False</property>
+                    <property name="label" translatable="yes">X.X.X</property>
+                  </object>
+                  <packing>
+                    <property name="left_attach">1</property>
+                    <property name="top_attach">3</property>
+                  </packing>
+                </child>
               </object>
               <packing>
                 <property name="expand">False</property>