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Signed-off-by: Peter Siegmund <mars3142@noreply.mars3142.dev>

libs/wxWidgets-3.3.1/docs/doxygen/overviews/validator.h

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+/////////////////////////////////////////////////////////////////////////////
+// Name:        validator.h
+// Purpose:     topic overview
+// Author:      wxWidgets team
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+/**
+
+@page overview_validator wxValidator Overview
+
+@tableofcontents
+
+The aim of the validator concept is to make dialogs very much easier to write.
+A validator is an object that can be plugged into a control (such as a
+wxTextCtrl), and mediates between C++ data and the control, transferring the
+data in either direction and validating it. It also is able to intercept events
+generated by the control, providing filtering behaviour without the need to
+derive a new control class.
+
+You can use a stock validator, such as wxTextValidator (which does text control
+data transfer, validation and filtering) and wxGenericValidator (which does
+data transfer for a range of controls); or you can write your own.
+
+Here is an example of wxTextValidator usage.
+
+@code
+wxTextCtrl *txt1 = new wxTextCtrl(
+    this, -1, "", wxDefaultPosition, wxDefaultSize, 0,
+    wxTextValidator(wxFILTER_ALPHA, &g_data.m_string));
+@endcode
+
+In this example, the text validator object provides the following
+functionality:
+
+@li It transfers the value of g_data.m_string (a wxString variable) to the
+    wxTextCtrl when the dialog is initialised.
+@li It transfers the wxTextCtrl data back to this variable when the dialog is
+    dismissed.
+@li It filters input characters so that only alphabetic characters are allowed.
+
+The validation and filtering of input is accomplished in two ways. When a
+character is input, wxTextValidator checks the character against the allowed
+filter flag (@c wxFILTER_ALPHA in this case). If the character is inappropriate,
+it is vetoed (does not appear) and a warning beep sounds (unless
+wxValidator::SetBellOnError(false) has been called).
+The second type of validation is performed when the dialog is about to be dismissed,
+so if the default string contained invalid characters already, a dialog box is shown
+giving the error, and the dialog is not dismissed.
+
+Note that any wxWindow may have a validator and it will be used when
+transferring data to or from the parent window.
+
+@see wxValidator, wxTextValidator, wxGenericValidator, wxIntegerValidator,
+     wxFloatingPointValidator
+
+
+
+@section overview_validator_anatomy Anatomy of a Validator
+
+A programmer creating a new validator class should provide the following
+functionality.
+
+A validator constructor is responsible for allowing the programmer to specify
+the kind of validation required, and perhaps a pointer to a C++ variable that
+is used for storing the data for the control. If such a variable address is not
+supplied by the user, then the validator should store the data internally.
+
+The wxValidator::Validate member function should return @true if the data in
+the control (not the C++ variable) is valid. It should also show an appropriate
+message if data was not valid.
+
+The wxValidator::TransferToWindow member function should transfer the data from
+the validator or associated C++ variable to the control.
+
+The wxValidator::TransferFromWindow member function should transfer the data
+from the control to the validator or associated C++ variable.
+
+There should be a copy constructor, and a wxValidator::Clone function which
+returns a copy of the validator object. This is important because validators
+are passed by reference to window constructors, and must therefore be cloned
+internally.
+
+You can optionally define event handlers for the validator, to implement
+filtering. These handlers will capture events before the control itself does
+(see @ref overview_events_processing).
+For an example implementation, see the @c valtext.h and @c valtext.cpp files in the
+wxWidgets library.
+
+
+@section overview_validator_dialogs How Validators Interact with Dialogs
+
+For validators to work correctly, validator functions must be called at the
+right times during dialog initialisation and dismissal.
+
+When a wxDialog::Show is called (for a modeless dialog) or wxDialog::ShowModal
+is called (for a modal dialog), the function wxWindow::InitDialog is
+automatically called. This in turn sends an initialisation event to the dialog.
+The default handler for the @c wxEVT_INIT_DIALOG event is defined in the wxWindow
+class to simply call the function wxWindow::TransferDataToWindow.
+This function finds all the validators in the window's children and calls the
+wxValidator::TransferToWindow function for each. Thus, data is transferred from C++
+variables to the dialog just as the dialog is being shown.
+
+@note If you are using a window or panel instead of a dialog, you will need to
+call wxWindow::InitDialog explicitly before showing the window.
+
+When the user clicks on a button, for example the OK button, the application
+should first call wxWindow::Validate, which returns @false if any of the child
+window validators failed to validate the window data. The button handler should
+return immediately if validation failed. Secondly, the application should call
+wxWindow::TransferDataFromWindow and return if this failed. It is then safe to
+end the dialog by calling wxDialog::EndModal (if modal) or wxDialog::Show (if modeless).
+
+In fact, wxDialog contains a default command event handler for the @c wxID_OK
+button. It goes like this:
+
+@code
+void wxDialog::OnOK(wxCommandEvent& event)
+{
+    if ( Validate() && TransferDataFromWindow() )
+    {
+        if ( IsModal() )
+            EndModal(wxID_OK);
+        else
+        {
+            SetReturnCode(wxID_OK);
+            this->Show(false);
+        }
+    }
+}
+@endcode
+
+So if using validators and a normal OK button, you may not even need to write
+any code for handling dialog dismissal.
+
+If you load your dialog from a resource file, you will need to iterate through
+the controls setting validators, since validators can't be specified in a
+dialog resource.
+
+*/