Make constructors of abstract classes protected

src/classes/action/action_mapping.vala

@@ -48,7 +48,7 @@ namespace pdfpc {
          * methods, and we need blank objects to call them.  Thus, this blank
          * constructor.
          */
-        public ActionMapping() {
+        protected ActionMapping() {
             base();
         }
 

src/classes/drawings/storage.vala

@@ -35,7 +35,7 @@ namespace pdfpc.Drawings.Storage {
          */
         protected Metadata.Pdf metadata;
 
-        public Base(Metadata.Pdf metadata) {
+        protected Base(Metadata.Pdf metadata) {
             this.metadata = metadata;
         }
 

src/classes/renderer/cache/base.vala

@@ -37,7 +37,7 @@ namespace pdfpc.Renderer.Cache {
         /**
          * Initialize the cache store
          */
-        public Base(Metadata.Pdf metadata) {
+        protected Base(Metadata.Pdf metadata) {
             this.metadata = metadata;
         }
 

src/classes/timer_label.vala

@@ -95,7 +95,7 @@ namespace pdfpc {
          * Default constructor taking the initial time as argument, as well as
          * the time to countdown until the talk actually starts.
          */
-        public TimerLabel(PresentationController controller, time_t start_time = 0) {
+        protected TimerLabel(PresentationController controller, time_t start_time = 0) {
             this.controller = controller;
             this.start_time = start_time;
         }

src/classes/view/behaviour/base.vala

@@ -41,7 +41,7 @@ namespace pdfpc.View {
         /**
          * Base constructor not taking any arguments
          */
-        public Base() {
+        protected Base() {
             // Nothing to do here
         }