Add sample code showing how to create a new wxEvent class

In the event sample, show how create and use a new
wxEvent-derived class.

Closes https://github.com/wxWidgets/wxWidgets/pull/1633

samples/event/chessboard.cpp

@@ -0,0 +1,214 @@
+/////////////////////////////////////////////////////////////////////////////
+// Name:        samples/event/chessboard.cpp
+// Purpose:     Part of wxWidgets event sample, shows how to create a new wxEvent class
+// Author:      PB <pbfordev@gmail.com>
+// Created:     2019-10-29
+// Copyright:   (c) 2019 wxWidgets development team
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+#include "chessboard.h"
+
+
+//
+// ChessBoardEvent
+//
+
+// Define new event types associated with ChessBoardEvent
+wxDEFINE_EVENT(myEVT_CHESSBOARD_CLICKED, ChessBoardEvent);
+wxDEFINE_EVENT(myEVT_CHESSBOARD_DRAGGED, ChessBoardEvent);
+
+
+//
+// ChessBoard
+//
+class ChessBoard : public wxPanel
+{
+public:
+    ChessBoard(wxWindow* parent);
+
+private:
+    static const wxUint8 SquaresPerSide = 8;
+    static const int SquareSizeInDIPs   = 40;
+
+    // square on which mouse left button was pressed
+    char m_fileLeftMDown;
+    wxUint8 m_rankLeftMDown;
+
+    bool ConvertMousePosToFileAndRank(const wxPoint& pos,
+                                      char& file, wxUint8& rank) const;
+
+    void OnPaint(wxPaintEvent& event);
+    void OnMouseLeftDown(wxMouseEvent& event);
+    void OnMouseLeftUp(wxMouseEvent& event);
+
+    virtual wxSize DoGetBestClientSize() const wxOVERRIDE;
+};
+
+ChessBoard::ChessBoard(wxWindow* parent)
+    : wxPanel(parent, wxID_ANY, wxDefaultPosition, wxDefaultSize, wxBORDER_RAISED),
+      m_fileLeftMDown('a'), m_rankLeftMDown(1)
+{
+    SetCursor(wxCursor(wxCURSOR_HAND));
+    SetBackgroundColour(*wxWHITE);
+
+    Bind(wxEVT_PAINT, &ChessBoard::OnPaint, this);
+    Bind(wxEVT_LEFT_DOWN, &ChessBoard::OnMouseLeftDown, this);
+    Bind(wxEVT_LEFT_UP, &ChessBoard::OnMouseLeftUp, this);
+}
+
+ bool ChessBoard::ConvertMousePosToFileAndRank(const wxPoint& pos,
+                                               char& file, wxUint8& rank) const
+{
+    static const char FileLetters[SquaresPerSide] = {'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h'};
+
+    const int squareSizeInPx = FromDIP(SquareSizeInDIPs);
+    const int colIdx = pos.x / squareSizeInPx;
+    const int rowIdx = pos.y / squareSizeInPx;
+
+    if ( colIdx < 0 || colIdx >= SquaresPerSide
+         || rowIdx < 0 || rowIdx >= SquaresPerSide )
+    {
+        return false; // not on a square
+    }
+
+    file = FileLetters[colIdx],
+    // convert rowIdx (top to down 0 to 7) to rank (top to down 8 to 1)
+    rank = static_cast<wxUint8>(SquaresPerSide - rowIdx);
+
+    return true;
+}
+
+// Background is already painted white,
+// so we need to draw only the black squares over it.
+void ChessBoard::OnPaint(wxPaintEvent& WXUNUSED(event))
+{
+    const int squareSizeInPx = FromDIP(SquareSizeInDIPs);
+
+    wxPaintDC dc(this);
+    wxDCPenChanger penChanger(dc, *wxTRANSPARENT_PEN);
+    wxDCBrushChanger brushChanger(dc, *wxBLACK_BRUSH);
+    wxRect squareRect(wxSize(squareSizeInPx, squareSizeInPx));
+
+    // draw from top to down, left to right
+    for ( size_t rank = SquaresPerSide; rank >= 1; --rank )
+    {
+        if ( rank % 2 )
+            squareRect.SetLeft(0); // odd ranks start with a black square
+        else
+            squareRect.SetLeft(squareSizeInPx); // even ranks start with a white square
+
+        for ( size_t file = 0; file < SquaresPerSide / 2; ++file )
+        {
+            dc.DrawRectangle(squareRect);
+            squareRect.Offset(2 * squareSizeInPx, 0);
+        }
+
+        squareRect.Offset(0, squareSizeInPx);
+    }
+}
+
+void ChessBoard::OnMouseLeftDown(wxMouseEvent& event)
+{
+    char file;
+    wxUint8 rank;
+
+    event.Skip();
+
+    if ( !ConvertMousePosToFileAndRank(event.GetPosition(), file, rank) )
+        return; // mouse cursor not on a square
+
+    m_fileLeftMDown = file;
+    m_rankLeftMDown = rank;
+    CaptureMouse();
+}
+
+void ChessBoard::OnMouseLeftUp(wxMouseEvent& event)
+{
+    event.Skip();
+
+    if ( !HasCapture() )
+        return; // capture lost or mouse left down was not on a square
+
+    const wxRect clientRect = GetClientRect();
+    char file;
+    wxUint8 rank;
+
+    ReleaseMouse();
+
+    if (  !clientRect.Contains(event.GetPosition()) ||
+          !ConvertMousePosToFileAndRank(event.GetPosition(), file, rank) )
+    {
+        return; // mouse cursor not on a square
+    }
+
+    ChessBoardEvent chessBoardEvent;
+
+    chessBoardEvent.SetId(GetId());
+    chessBoardEvent.SetEventObject(this);
+    chessBoardEvent.SetFile(m_fileLeftMDown);
+    chessBoardEvent.SetRank(m_rankLeftMDown);
+
+    if ( file == m_fileLeftMDown && rank == m_rankLeftMDown )
+    {   // mouse left and down on the same square, consider it a click
+        chessBoardEvent.SetEventType(myEVT_CHESSBOARD_CLICKED);
+    }
+    else
+    {   // mouse dragged from one square to another
+        chessBoardEvent.SetEventType(myEVT_CHESSBOARD_DRAGGED);
+        chessBoardEvent.SetFileTo(file);
+        chessBoardEvent.SetRankTo(rank);
+    }
+
+    ProcessWindowEvent(chessBoardEvent);
+}
+
+wxSize ChessBoard::DoGetBestClientSize() const
+{
+    const int boardSideSizeInPx = SquaresPerSide * FromDIP(SquareSizeInDIPs);
+
+    return wxSize(boardSideSizeInPx, boardSideSizeInPx);
+}
+
+//
+// MyChessBoardDialog implementation
+//
+
+// For demonstration, event table is used for myEVT_CHESSBOARD_CLICKED
+// while Bind() is used for myEVT_CHESSBOARD_DRAGGED.
+wxBEGIN_EVENT_TABLE(MyChessBoardDialog, wxDialog)
+    EVT_CHESSBOARD_CLICKED(wxID_ANY, MyChessBoardDialog::OnChessBoardClicked)
+wxEND_EVENT_TABLE()
+
+MyChessBoardDialog::MyChessBoardDialog(wxWindow* parent)
+    : wxDialog(parent, wxID_ANY, "New event class demonstration")
+{
+    wxSizer* mainSizer = new wxBoxSizer(wxVERTICAL);
+
+    mainSizer->Add(
+        new wxStaticText(this, wxID_ANY, "Click or drag the mouse over the chessboard"),
+        wxSizerFlags().Border().CenterHorizontal());
+
+    mainSizer->Add(new ChessBoard(this),
+        wxSizerFlags().TripleBorder().CenterHorizontal());
+
+    mainSizer->Add(CreateStdDialogButtonSizer(wxCLOSE),
+        wxSizerFlags().Expand().Border());
+
+    SetSizerAndFit(mainSizer);
+
+    Bind(myEVT_CHESSBOARD_DRAGGED, &MyChessBoardDialog::OnChessBoardDragged, this);
+}
+
+void MyChessBoardDialog::OnChessBoardClicked(ChessBoardEvent& event)
+{
+    wxLogMessage("myEVT_CHESSBOARD_CLICKED: %c%hhu",
+        event.GetFile(), event.GetRank());
+}
+
+void MyChessBoardDialog::OnChessBoardDragged(ChessBoardEvent& event)
+{
+    wxLogMessage("myEVT_CHESSBOARD_DRAGGED: from %c%hhu to %c%hhu",
+        event.GetFile(), event.GetRank(),
+        event.GetFileTo(), event.GetRankTo());
+}