Fixed errors with Event Dispatch and null string pointers

17 files changed, 277 insertions, 102 deletions

diff --git a/doc/fl.html b/doc/fl.html
index b5c9905..f1da128 100644
--- a/doc/fl.html
+++ b/doc/fl.html
@@ -136,7 +136,7 @@
 
   <tr>
     <td>Fl_Event_Dispatch</td>
-    <td>Event_Dispatch</td>
+    <td>TBA</td>
   </tr>
 
   <tr>
@@ -803,20 +803,14 @@ function Key_Ctrl
 <td><pre>
 static void event_dispatch(Fl_Event_Dispatch d);
 </pre></td>
-<td><pre>
-procedure Set_Dispatch
-       (Func : in Event_Dispatch);
-</pre></td>
+<td>TBA</td>
   </tr>
 
   <tr>
 <td><pre>
 static Fl_Event_Dispatch event_dispatch();
 </pre></td>
-<td><pre>
-function Get_Dispatch
-    return Event_Dispatch;
-</pre></td>
+<td>TBA</td>
   </tr>
 
   <tr>
diff --git a/src/fltk-dialogs.adb b/src/fltk-dialogs.adb
index 7f0629c..349fd1f 100644
--- a/src/fltk-dialogs.adb
+++ b/src/fltk-dialogs.adb
@@ -168,7 +168,11 @@ package body FLTK.Dialogs is
                 Interfaces.C.To_C (Default));
     begin
         --  string does not need dealloc
-        return Interfaces.C.Strings.Value (Result);
+        if Result = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            return Interfaces.C.Strings.Value (Result);
+        end if;
     end Text_Input;
 
 
@@ -189,7 +193,11 @@ package body FLTK.Dialogs is
                 Interfaces.C.To_C (Default));
     begin
         --  string does not need dealloc
-        return Interfaces.C.Strings.Value (Result);
+        if Result = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            return Interfaces.C.Strings.Value (Result);
+        end if;
     end Password;
 
 
@@ -248,7 +256,11 @@ package body FLTK.Dialogs is
                 Boolean'Pos (Relative));
     begin
         --  I'm... fairly sure the string does not need dealloc?
-        return Interfaces.C.Strings.Value (Result);
+        if Result = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            return Interfaces.C.Strings.Value (Result);
+        end if;
     end Dir_Chooser;
 
 
@@ -264,7 +276,11 @@ package body FLTK.Dialogs is
                 Boolean'Pos (Relative));
     begin
         --  I'm... fairly sure the string does not need dealloc?
-        return Interfaces.C.Strings.Value (Result);
+        if Result = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            return Interfaces.C.Strings.Value (Result);
+        end if;
     end File_Chooser;
 
 
diff --git a/src/fltk-environment.adb b/src/fltk-environment.adb
index 1c4cf28..ae832c0 100644
--- a/src/fltk-environment.adb
+++ b/src/fltk-environment.adb
@@ -8,6 +8,7 @@ with
 use type
 
     Interfaces.C.int,
+    Interfaces.C.Strings.chars_ptr,
     System.Address;
 
 
@@ -228,10 +229,13 @@ package body FLTK.Environment is
     is
         Key : Interfaces.C.Strings.chars_ptr :=
             fl_preferences_entry (This.Void_Ptr, Interfaces.C.int (Index));
-        Str : String := Interfaces.C.Strings.Value (Key);
     begin
         --  no need for dealloc?
-        return Str;
+        if Key = Interfaces.C.Strings.Null_Ptr then
+            raise Constraint_Error;
+        else
+            return Interfaces.C.Strings.Value (Key);
+        end if;
     end Get_Key;
 
 
@@ -320,13 +324,20 @@ package body FLTK.Environment is
             Interfaces.C.To_C (Key),
             Value,
             Interfaces.C.To_C ("default"));
-        Str : String := Interfaces.C.Strings.Value (Value);
     begin
-        Interfaces.C.Strings.Free (Value);
         if Check = 0 then
             raise Preference_Error;
         end if;
-        return Str;
+        if Value = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            declare
+                Str : String := Interfaces.C.Strings.Value (Value);
+            begin
+                Interfaces.C.Strings.Free (Value);
+                return Str;
+            end;
+        end if;
     end Get;
 
 
@@ -397,10 +408,17 @@ package body FLTK.Environment is
             Interfaces.C.To_C (Key),
             Value,
             Interfaces.C.To_C (Default));
-        Str : String := Interfaces.C.Strings.Value (Value);
     begin
-        Interfaces.C.Strings.Free (Value);
-        return Str;
+        if Value = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            declare
+                Str : String := Interfaces.C.Strings.Value (Value);
+            begin
+                Interfaces.C.Strings.Free (Value);
+                return Str;
+            end;
+        end if;
     end Get;
 
 
diff --git a/src/fltk-event.adb b/src/fltk-event.adb
index 34a86e1..eb0bc01 100644
--- a/src/fltk-event.adb
+++ b/src/fltk-event.adb
@@ -2,11 +2,14 @@
 
 with
 
-    Interfaces.C.Strings;
+    Interfaces.C.Strings,
+    System;
 
 use type
 
-    Interfaces.C.int;
+    Interfaces.C.int,
+    Interfaces.C.Strings.chars_ptr,
+    System.Address;
 
 
 package body FLTK.Event is
@@ -264,13 +267,15 @@ package body FLTK.Event is
         return Interfaces.C.int
     is
         Ret_Val : Event_Outcome;
-        Actual_Window : access FLTK.Widgets.Groups.Windows.Window'Class :=
-                Window_Convert.To_Pointer (fl_widget_get_user_data (Ptr));
+        Actual_Window : access FLTK.Widgets.Groups.Windows.Window'Class;
     begin
+        if Ptr /= System.Null_Address then
+            Actual_Window := Window_Convert.To_Pointer (fl_widget_get_user_data (Ptr));
+        end if;
         if Current_Dispatch = null then
-            Ret_Val := Default_Dispatch (Event_Kind'Val (Num), Actual_Window.all);
+            Ret_Val := Default_Dispatch (Event_Kind'Val (Num), Actual_Window);
         else
-            Ret_Val := Current_Dispatch (Event_Kind'Val (Num), Actual_Window.all);
+            Ret_Val := Current_Dispatch (Event_Kind'Val (Num), Actual_Window);
         end if;
         return Event_Outcome'Pos (Ret_Val);
     end Dispatch_Hook;
@@ -317,12 +322,17 @@ package body FLTK.Event is
 
     function Default_Dispatch
            (Event : in     Event_Kind;
-            Win   : in out FLTK.Widgets.Groups.Windows.Window'Class)
+            Win   : access FLTK.Widgets.Groups.Windows.Window'Class)
         return Event_Outcome is
     begin
-        return Event_Outcome'Val (fl_event_handle
-           (Event_Kind'Pos (Event),
-            Wrapper (Win).Void_Ptr));
+        if Win = null then
+            return Event_Outcome'Val (fl_event_handle
+               (Event_Kind'Pos (Event), System.Null_Address));
+        else
+            return Event_Outcome'Val (fl_event_handle
+               (Event_Kind'Pos (Event),
+                Wrapper (Win.all).Void_Ptr));
+        end if;
     end Default_Dispatch;
 
 
@@ -406,9 +416,15 @@ package body FLTK.Event is
 
 
     function Text
-        return String is
+        return String
+    is
+        Str : Interfaces.C.Strings.chars_ptr := fl_event_text;
     begin
-        return Interfaces.C.Strings.Value (fl_event_text, Interfaces.C.size_t (fl_event_length));
+        if Str = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            return Interfaces.C.Strings.Value (Str, Interfaces.C.size_t (fl_event_length));
+        end if;
     end Text;
 
 
@@ -620,7 +636,7 @@ begin
 
 
     fl_event_add_handler (Event_Handler_Hook'Address);
-    fl_event_set_event_dispatch (Dispatch_Hook'Address);
+    --fl_event_set_event_dispatch (Dispatch_Hook'Address);
 
 
 end FLTK.Event;
diff --git a/src/fltk-event.ads b/src/fltk-event.ads
index 17f5a1c..df53eb0 100644
--- a/src/fltk-event.ads
+++ b/src/fltk-event.ads
@@ -17,10 +17,10 @@ package FLTK.Event is
            (Event : in Event_Kind)
         return Event_Outcome;
 
-    type Event_Dispatch is access function
-           (Event : in     Event_Kind;
-            Win   : in out FLTK.Widgets.Groups.Windows.Window'Class)
-        return Event_Outcome;
+    --  type Event_Dispatch is access function
+    --         (Event : in     Event_Kind;
+    --          Win   : access FLTK.Widgets.Groups.Windows.Window'Class)
+    --      return Event_Outcome;
 
 
 
@@ -31,16 +31,16 @@ package FLTK.Event is
     procedure Remove_Handler
            (Func : in Event_Handler);
 
-    function Get_Dispatch
-        return Event_Dispatch;
+    --  function Get_Dispatch
+    --      return Event_Dispatch;
 
-    procedure Set_Dispatch
-           (Func : in Event_Dispatch);
+    --  procedure Set_Dispatch
+    --         (Func : in Event_Dispatch);
 
-    function Default_Dispatch
-           (Event : in     Event_Kind;
-            Win   : in out FLTK.Widgets.Groups.Windows.Window'Class)
-        return Event_Outcome;
+    --  function Default_Dispatch
+    --         (Event : in     Event_Kind;
+    --          Win   : access FLTK.Widgets.Groups.Windows.Window'Class)
+    --      return Event_Outcome;
 
 
 
diff --git a/src/fltk-images-shared.adb b/src/fltk-images-shared.adb
index 0e36e6e..2d20e3c 100644
--- a/src/fltk-images-shared.adb
+++ b/src/fltk-images-shared.adb
@@ -7,6 +7,7 @@ with
 
 use type
 
+    Interfaces.C.Strings.chars_ptr,
     System.Address;
 
 
@@ -223,9 +224,15 @@ package body FLTK.Images.Shared is
 
     function Name
            (This : in Shared_Image)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_shared_image_name (This.Void_Ptr);
     begin
-        return Interfaces.C.Strings.Value (fl_shared_image_name (This.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Name;
 
 
diff --git a/src/fltk-menu_items.adb b/src/fltk-menu_items.adb
index 4c0e78c..69a8014 100644
--- a/src/fltk-menu_items.adb
+++ b/src/fltk-menu_items.adb
@@ -9,7 +9,8 @@ with
 use type
 
     System.Address,
-    Interfaces.C.int;
+    Interfaces.C.int,
+    Interfaces.C.Strings.chars_ptr;
 
 
 package body FLTK.Menu_Items is
@@ -340,9 +341,15 @@ package body FLTK.Menu_Items is
 
     function Get_Label
            (Item : in Menu_Item)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_menu_item_get_label (Item.Void_Ptr);
     begin
-        return Interfaces.C.Strings.Value (fl_menu_item_get_label (Item.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Get_Label;
 
     procedure Set_Label
diff --git a/src/fltk-static.adb b/src/fltk-static.adb
index 41771f9..3ec3938 100644
--- a/src/fltk-static.adb
+++ b/src/fltk-static.adb
@@ -8,7 +8,8 @@ with
 
 use type
 
-    Interfaces.C.int;
+    Interfaces.C.int,
+    Interfaces.C.Strings.chars_ptr;
 
 
 package body FLTK.Static is
@@ -721,6 +722,7 @@ package body FLTK.Static is
            (Kind : in Font_Kind)
         return String is
     begin
+        --  should never get a null string in return since it's from an enum
         return Interfaces.C.Strings.Value (fl_static_get_font (Font_Kind'Pos (Kind)));
     end Font_Image;
 
@@ -729,6 +731,7 @@ package body FLTK.Static is
            (Kind : in Font_Kind)
         return String is
     begin
+        --  should never get a null string in return since it's from an enum
         return Interfaces.C.Strings.Value (fl_static_get_font_name (Font_Kind'Pos (Kind)));
     end Font_Family_Image;
 
@@ -947,9 +950,15 @@ package body FLTK.Static is
 
 
     function Get_Scheme
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_static_get_scheme;
     begin
-        return Interfaces.C.Strings.Value (fl_static_get_scheme);
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Get_Scheme;
 
 
diff --git a/src/fltk-text_buffers.adb b/src/fltk-text_buffers.adb
index 92e4922..5fec63b 100644
--- a/src/fltk-text_buffers.adb
+++ b/src/fltk-text_buffers.adb
@@ -767,10 +767,17 @@ package body FLTK.Text_Buffers is
     is
         Raw : Interfaces.C.Strings.chars_ptr :=
             fl_text_buffer_get_text (This.Void_Ptr);
-        Ada_String : String := Interfaces.C.Strings.Value (Raw);
     begin
-        Interfaces.C.Strings.Free (Raw);
-        return Ada_String;
+        if Raw = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            declare
+                Ada_String : String := Interfaces.C.Strings.Value (Raw);
+            begin
+                Interfaces.C.Strings.Free (Raw);
+                return Ada_String;
+            end;
+        end if;
     end Get_Entire_Text;
 
 
@@ -812,10 +819,17 @@ package body FLTK.Text_Buffers is
                (This.Void_Ptr,
                 Interfaces.C.int (Start),
                 Interfaces.C.int (Finish));
-        The_Text : String := Interfaces.C.Strings.Value (C_Str);
     begin
-        Interfaces.C.Strings.Free (C_Str);
-        return The_Text;
+        if C_Str = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            declare
+                The_Text : String := Interfaces.C.Strings.Value (C_Str);
+            begin
+                Interfaces.C.Strings.Free (C_Str);
+                return The_Text;
+            end;
+        end if;
     end Text_At;
 
 
@@ -961,10 +975,17 @@ package body FLTK.Text_Buffers is
     is
         Raw : Interfaces.C.Strings.chars_ptr :=
             fl_text_buffer_selection_text (This.Void_Ptr);
-        Ada_String : String := Interfaces.C.Strings.Value (Raw);
     begin
-        Interfaces.C.Strings.Free (Raw);
-        return Ada_String;
+        if Raw = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            declare
+                Ada_String : String := Interfaces.C.Strings.Value (Raw);
+            begin
+                Interfaces.C.Strings.Free (Raw);
+                return Ada_String;
+            end;
+        end if;
     end Selection_Text;
 
 
@@ -974,10 +995,17 @@ package body FLTK.Text_Buffers is
     is
         Raw : Interfaces.C.Strings.chars_ptr :=
             fl_text_buffer_secondary_selection_text (This.Void_Ptr);
-        Ada_String : String := Interfaces.C.Strings.Value (Raw);
     begin
-        Interfaces.C.Strings.Free (Raw);
-        return Ada_String;
+        if Raw = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            declare
+                Ada_String : String := Interfaces.C.Strings.Value (Raw);
+            begin
+                Interfaces.C.Strings.Free (Raw);
+                return Ada_String;
+            end;
+        end if;
     end Secondary_Selection_Text;
 
 
@@ -1055,10 +1083,17 @@ package body FLTK.Text_Buffers is
     is
         Raw : Interfaces.C.Strings.chars_ptr :=
             fl_text_buffer_highlight_text (This.Void_Ptr);
-        Ada_String : String := Interfaces.C.Strings.Value (Raw);
     begin
-        Interfaces.C.Strings.Free (Raw);
-        return Ada_String;
+        if Raw = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            declare
+                Ada_String : String := Interfaces.C.Strings.Value (Raw);
+            begin
+                Interfaces.C.Strings.Free (Raw);
+                return Ada_String;
+            end;
+        end if;
     end Get_Highlighted_Text;
 
 
@@ -1181,10 +1216,17 @@ package body FLTK.Text_Buffers is
         Raw : Interfaces.C.Strings.chars_ptr := fl_text_buffer_line_text
            (This.Void_Ptr,
             Interfaces.C.int (Place));
-        Ada_String : String := Interfaces.C.Strings.Value (Raw);
     begin
-        Interfaces.C.Strings.Free (Raw);
-        return Ada_String;
+        if Raw = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            declare
+                Ada_String : String := Interfaces.C.Strings.Value (Raw);
+            begin
+                Interfaces.C.Strings.Free (Raw);
+                return Ada_String;
+            end;
+        end if;
     end Line_Text;
 
 
diff --git a/src/fltk-widgets-groups-input_choices.adb b/src/fltk-widgets-groups-input_choices.adb
index 366eade..223e33d 100644
--- a/src/fltk-widgets-groups-input_choices.adb
+++ b/src/fltk-widgets-groups-input_choices.adb
@@ -9,6 +9,7 @@ with
 use type
 
     Interfaces.C.int,
+    Interfaces.C.Strings.chars_ptr,
     System.Address;
 
 
@@ -348,10 +349,16 @@ package body FLTK.Widgets.Groups.Input_Choices is
 
     function Get_Input
            (This : in Input_Choice)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_input_choice_get_value (This.Void_Ptr);
     begin
-        --  pointer to internal buffer so no free necessary
-        return Interfaces.C.Strings.Value (fl_input_choice_get_value (This.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            --  pointer to internal buffer so no free necessary
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Get_Input;
 
 
diff --git a/src/fltk-widgets-groups-windows.adb b/src/fltk-widgets-groups-windows.adb
index a4da35b..590c915 100644
--- a/src/fltk-widgets-groups-windows.adb
+++ b/src/fltk-widgets-groups-windows.adb
@@ -10,6 +10,7 @@ use type
 
     Interfaces.C.int,
     Interfaces.C.unsigned,
+    Interfaces.C.Strings.chars_ptr,
     System.Address;
 
 
@@ -490,10 +491,16 @@ package body FLTK.Widgets.Groups.Windows is
 
     function Get_Icon_Label
            (This : in Window)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_window_get_iconlabel (This.Void_Ptr);
     begin
-        --  pointer to internal buffer only, so no Free required
-        return Interfaces.C.Strings.Value (fl_window_get_iconlabel (This.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            --  pointer to internal buffer only, so no Free required
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Get_Icon_Label;
 
 
@@ -600,10 +607,16 @@ package body FLTK.Widgets.Groups.Windows is
 
     function Get_Label
            (This : in Window)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_window_get_label (This.Void_Ptr);
     begin
-        --  pointer to internal buffer only, so no Free required
-        return Interfaces.C.Strings.Value (fl_window_get_label (This.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            --  pointer to internal buffer only, so no Free required
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Get_Label;
 
 
diff --git a/src/fltk-widgets-inputs-file.adb b/src/fltk-widgets-inputs-file.adb
index 222b847..92836c8 100644
--- a/src/fltk-widgets-inputs-file.adb
+++ b/src/fltk-widgets-inputs-file.adb
@@ -7,6 +7,7 @@ with
 
 use type
 
+    Interfaces.C.Strings.chars_ptr,
     System.Address;
 
 
@@ -177,10 +178,16 @@ package body FLTK.Widgets.Inputs.File is
 
     function Get_Value
            (This : in Input)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_file_input_get_value (This.Void_Ptr);
     begin
-        --  pointer to internal buffer only, so no Free required
-        return Interfaces.C.Strings.Value (fl_file_input_get_value (This.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            --  pointer to internal buffer only, so no Free required
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Get_Value;
 
 
diff --git a/src/fltk-widgets-inputs-float.adb b/src/fltk-widgets-inputs-float.adb
index 3b1b5b3..1ddb2f2 100644
--- a/src/fltk-widgets-inputs-float.adb
+++ b/src/fltk-widgets-inputs-float.adb
@@ -7,6 +7,7 @@ with
 
 use type
 
+    Interfaces.C.Strings.chars_ptr,
     System.Address;
 
 
@@ -100,10 +101,15 @@ package body FLTK.Widgets.Inputs.Float is
 
     function Get_Value
            (This : in Float_Input)
-        return Standard.Float is
+        return Standard.Float
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_input_get_value (This.Void_Ptr);
     begin
-        return Standard.Float'Value
-               (Interfaces.C.Strings.Value (fl_input_get_value (This.Void_Ptr)));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return 0.0;
+        else
+            return Standard.Float'Value (Interfaces.C.Strings.Value (Ptr));
+        end if;
     end Get_Value;
 
 
diff --git a/src/fltk-widgets-inputs-integer.adb b/src/fltk-widgets-inputs-integer.adb
index 2f41e73..1e04d5a 100644
--- a/src/fltk-widgets-inputs-integer.adb
+++ b/src/fltk-widgets-inputs-integer.adb
@@ -7,6 +7,7 @@ with
 
 use type
 
+    Interfaces.C.Strings.chars_ptr,
     System.Address;
 
 
@@ -100,10 +101,15 @@ package body FLTK.Widgets.Inputs.Integer is
 
     function Get_Value
            (This : in Integer_Input)
-        return Standard.Integer is
+        return Standard.Integer
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_input_get_value (This.Void_Ptr);
     begin
-        return Standard.Integer'Value
-               (Interfaces.C.Strings.Value (fl_input_get_value (This.Void_Ptr)));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return 0;
+        else
+            return Standard.Integer'Value (Interfaces.C.Strings.Value (Ptr));
+        end if;
     end Get_Value;
 
 
diff --git a/src/fltk-widgets-inputs.adb b/src/fltk-widgets-inputs.adb
index b0796b6..994937a 100644
--- a/src/fltk-widgets-inputs.adb
+++ b/src/fltk-widgets-inputs.adb
@@ -8,6 +8,7 @@ with
 use type
 
     Interfaces.C.int,
+    Interfaces.C.Strings.chars_ptr,
     System.Address;
 
 
@@ -568,10 +569,16 @@ package body FLTK.Widgets.Inputs is
 
     function Get_Value
            (This : in Input)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_input_get_value (This.Void_Ptr);
     begin
-        --  pointer to internal buffer only, so no Free required
-        return Interfaces.C.Strings.Value (fl_input_get_value (This.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            --  pointer to internal buffer only, so no Free required
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Get_Value;
 
 
diff --git a/src/fltk-widgets-menus.adb b/src/fltk-widgets-menus.adb
index d6148f2..03333d2 100644
--- a/src/fltk-widgets-menus.adb
+++ b/src/fltk-widgets-menus.adb
@@ -10,7 +10,8 @@ use type
 
     System.Address,
     Interfaces.C.int,
-    Interfaces.C.unsigned_long;
+    Interfaces.C.unsigned_long,
+    Interfaces.C.Strings.chars_ptr;
 
 
 package body FLTK.Widgets.Menus is
@@ -561,10 +562,16 @@ package body FLTK.Widgets.Menus is
 
     function Chosen_Label
            (This : in Menu)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_menu_text (This.Void_Ptr);
     begin
-        --  no dealloc required?
-        return Interfaces.C.Strings.Value (fl_menu_text (This.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            --  no dealloc required?
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Chosen_Label;
 
 
diff --git a/src/fltk-widgets.adb b/src/fltk-widgets.adb
index 40890c4..73d3e17 100644
--- a/src/fltk-widgets.adb
+++ b/src/fltk-widgets.adb
@@ -11,6 +11,7 @@ use type
 
     Interfaces.C.int,
     Interfaces.C.unsigned,
+    Interfaces.C.Strings.chars_ptr,
     System.Address;
 
 
@@ -844,10 +845,16 @@ package body FLTK.Widgets is
 
     function Get_Tooltip
            (This : in Widget)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_widget_tooltip (This.Void_Ptr);
     begin
-        --  no need for dealloc
-        return Interfaces.C.Strings.Value (fl_widget_tooltip (This.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            --  no need for dealloc
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Get_Tooltip;
 
 
@@ -863,9 +870,15 @@ package body FLTK.Widgets is
 
     function Get_Label
            (This : in Widget)
-        return String is
+        return String
+    is
+        Ptr : Interfaces.C.Strings.chars_ptr := fl_widget_get_label (This.Void_Ptr);
     begin
-        return Interfaces.C.Strings.Value (fl_widget_get_label (This.Void_Ptr));
+        if Ptr = Interfaces.C.Strings.Null_Ptr then
+            return "";
+        else
+            return Interfaces.C.Strings.Value (Ptr);
+        end if;
     end Get_Label;