You may wish to begin by reading the [text widget conceptual overview][TextWidget] which gives an overview of all the objects and data types related to the text widget and how they work together.
A Gtk.Text_Mark.Gtk_Text_Mark is like a bookmark in a text buffer; it preserves a position in the text. You can convert the mark to an iterator using Gtk.Text_Buffer.Get_Iter_At_Mark. Unlike iterators, marks remain valid across buffer mutations, because their behavior is defined when text is inserted or deleted. When text containing a mark is deleted, the mark remains in the position originally occupied by the deleted text. When text is inserted at a mark, a mark with "left gravity" will be moved to the beginning of the newly-inserted text, and a mark with "right gravity" will be moved to the end.
Note that "left" and "right" here refer to logical direction (left is the toward the start of the buffer); in some languages such as Hebrew the logically-leftmost text is not actually on the left when displayed.
Marks are reference counted, but the reference count only controls the validity of the memory; marks can be deleted from the buffer at any time with Gtk.Text_Buffer.Delete_Mark. Once deleted from the buffer, a mark is essentially useless.
Marks optionally have names; these can be convenient to avoid passing the Gtk.Text_Mark.Gtk_Text_Mark object around.
Marks are typically created using the Gtk.Text_Buffer.Create_Mark function.
function Get_Deleted
(Mark : not null access Gtk_Text_Mark_Record) return Boolean
Returns True if the mark has been removed from its buffer with Gtk.Text_Buffer.Delete_Mark. See Gtk.Text_Buffer.Add_Mark for a way to add it to a buffer again.
whether the mark is deleted
function Get_Left_Gravity
(Mark : not null access Gtk_Text_Mark_Record) return Boolean
Determines whether the mark has left gravity.
True if the mark has left gravity, False otherwise
function Get_Name
(Mark : not null access Gtk_Text_Mark_Record) return UTF8_String
Returns the mark name; returns NULL for anonymous marks.
mark name
function Get_Text_Mark (Val : Glib.Values.GValue) return Gtk_Text_Mark
Set the value of the given GValue to Mark.
function Get_Type return Glib.GType
function Get_Visible
(Mark : not null access Gtk_Text_Mark_Record) return Boolean
Returns True if the mark is visible (i.e. a cursor is displayed for it).
True if visible
procedure Gtk_New
(Mark : out Gtk_Text_Mark;
Name : UTF8_String := "";
Left_Gravity : Boolean)
Creates a text mark. Add it to a buffer using Gtk.Text_Buffer.Add_Mark. If Name is null, the mark is anonymous; otherwise, the mark can be retrieved by name using Gtk.Text_Buffer.Get_Mark. If a mark has left gravity, and text is inserted at the mark's current location, the mark will be moved to the left of the newly-inserted text. If the mark has right gravity (Left_Gravity = False), the mark will end up on the right of newly-inserted text. The standard left-to-right cursor is a mark with right gravity (when you type, the cursor stays on the right side of the text you're typing). Since: gtk+ 2.12 Initialize does nothing if the object was already created with another call to Initialize* or G_New.
mark name or null
whether the mark should have left gravity
type Gtk_Text_Mark is access all Gtk_Text_Mark_Record'Class;
function Gtk_Text_Mark_New
(Name : UTF8_String := "";
Left_Gravity : Boolean) return Gtk_Text_Mark
Creates a text mark. Add it to a buffer using Gtk.Text_Buffer.Add_Mark. If Name is null, the mark is anonymous; otherwise, the mark can be retrieved by name using Gtk.Text_Buffer.Get_Mark. If a mark has left gravity, and text is inserted at the mark's current location, the mark will be moved to the left of the newly-inserted text. If the mark has right gravity (Left_Gravity = False), the mark will end up on the right of newly-inserted text. The standard left-to-right cursor is a mark with right gravity (when you type, the cursor stays on the right side of the text you're typing). Since: gtk+ 2.12
mark name or null
whether the mark should have left gravity
type Gtk_Text_Mark_Record is new GObject_Record with null record;
procedure Initialize
(Mark : not null access Gtk_Text_Mark_Record'Class;
Name : UTF8_String := "";
Left_Gravity : Boolean)
Creates a text mark. Add it to a buffer using Gtk.Text_Buffer.Add_Mark. If Name is null, the mark is anonymous; otherwise, the mark can be retrieved by name using Gtk.Text_Buffer.Get_Mark. If a mark has left gravity, and text is inserted at the mark's current location, the mark will be moved to the left of the newly-inserted text. If the mark has right gravity (Left_Gravity = False), the mark will end up on the right of newly-inserted text. The standard left-to-right cursor is a mark with right gravity (when you type, the cursor stays on the right side of the text you're typing). Since: gtk+ 2.12 Initialize does nothing if the object was already created with another call to Initialize* or G_New.
mark name or null
whether the mark should have left gravity
Left_Gravity_Property : constant Glib.Properties.Property_Boolean;
Whether the mark has left gravity. When text is inserted at the mark's current location, if the mark has left gravity it will be moved to the left of the newly-inserted text, otherwise to the right.
Name_Property : constant Glib.Properties.Property_String;
The name of the mark or null if the mark is anonymous.
procedure Set_Text_Mark
(Val : in out Glib.Values.GValue;
Mark : access Gtk_Text_Mark_Record)
Set the value of the given GValue to Mark.
procedure Set_Visible
(Mark : not null access Gtk_Text_Mark_Record;
Setting : Boolean)
Sets the visibility of Mark; the insertion point is normally visible, i.e. you can see it as a vertical bar. Also, the text widget uses a visible mark to indicate where a drop will occur when dragging-and-dropping text. Most other marks are not visible. Marks are not visible by default.
visibility of mark