A clarification

[wxWidgets.git] / samples / scroll / scroll.cpp

diff --git a/samples/scroll/scroll.cpp b/samples/scroll/scroll.cpp
index ece802323fbcccc0f0ab39ad8eb3d0cfc77e23aa..0d439109626fc9449c37184174009c7fabc5ab76 100644 (file)
--- a/samples/scroll/scroll.cpp
+++ b/samples/scroll/scroll.cpp
@@ -4,6 +4,7 @@
  * Author: Robert Roebling
  *
  * Copyright: (C) 1998, Robert Roebling
  * Author: Robert Roebling
  *
  * Copyright: (C) 1998, Robert Roebling

+ *                2002, Ron Lee

  *
  */
 
  *
  */
 


@@ -19,6 +20,10 @@
 #endif
 
 #include "wx/image.h"
 #endif
 
 #include "wx/image.h"

+#include "wx/listctrl.h"
+#include "wx/sizer.h"
+#include "wx/log.h"
+

 
 // derived classes
 
 
 // derived classes
 


@@ -30,16 +35,109 @@ class MyApp;
 class MyCanvas: public wxScrolledWindow
 {
 public:
 class MyCanvas: public wxScrolledWindow
 {
 public:

-    MyCanvas() {};
+    MyCanvas() {}

     MyCanvas( wxWindow *parent, wxWindowID, const wxPoint &pos, const wxSize &size );
     ~MyCanvas();
     void OnPaint( wxPaintEvent &event );
     MyCanvas( wxWindow *parent, wxWindowID, const wxPoint &pos, const wxSize &size );
     ~MyCanvas();
     void OnPaint( wxPaintEvent &event );

+    void OnQueryPosition( wxCommandEvent &event );
+    void OnAddButton( wxCommandEvent &event );
+    void OnDeleteButton( wxCommandEvent &event );
+    void OnMoveButton( wxCommandEvent &event );
+    void OnScrollWin( wxCommandEvent &event );
+    void OnMouseDown( wxMouseEvent &event );
+
+    wxButton *m_button;

 
     DECLARE_DYNAMIC_CLASS(MyCanvas)
     DECLARE_EVENT_TABLE()
 };
 
 
     DECLARE_DYNAMIC_CLASS(MyCanvas)
     DECLARE_EVENT_TABLE()
 };
 

+
+// ----------------------------------------------------------------------------
+// Autoscrolling example.
+// ----------------------------------------------------------------------------
+
+// this class uses the 'virtual' size attribute along with an internal
+// sizer to automatically set up scrollbars as needed
+
+class MyAutoScrollWindow : public wxScrolledWindow
+{
+private:
+
+    wxButton    *m_button;
+
+public:
+
+    MyAutoScrollWindow( wxWindow *parent );
+
+    void OnResizeClick( wxCommandEvent &WXUNUSED( event ) );
+
+    DECLARE_EVENT_TABLE()
+};
+
+
+// ----------------------------------------------------------------------------
+// MyScrolledWindow classes: examples of wxScrolledWindow usage
+// ----------------------------------------------------------------------------
+
+// base class for both of them
+class MyScrolledWindowBase : public wxScrolledWindow
+{
+public:
+    MyScrolledWindowBase(wxWindow *parent)
+        : wxScrolledWindow(parent)
+        , m_nLines( 100 )
+    {
+        wxClientDC dc(this);
+        dc.GetTextExtent(_T("Line 17"), NULL, &m_hLine);
+    }
+
+protected:
+    // the height of one line on screen
+    wxCoord m_hLine;
+
+    // the number of lines we draw
+    size_t m_nLines;
+};
+
+// this class does "stupid" redrawing - it redraws everything each time
+// and sets the scrollbar extent directly.
+
+class MyScrolledWindowDumb : public MyScrolledWindowBase
+{
+public:
+    MyScrolledWindowDumb(wxWindow *parent) : MyScrolledWindowBase(parent)
+    {
+        // no horz scrolling
+        SetScrollbars(0, m_hLine, 0, m_nLines + 1, 0, 0, TRUE /* no refresh */);
+    }
+
+    virtual void OnDraw(wxDC& dc);
+};
+
+// this class does "smart" redrawing - only redraws the lines which must be
+// redrawn and sets the scroll rate and virtual size to affect the
+// scrollbars.
+//
+// Note that this class should produce identical results to the one above.
+
+class MyScrolledWindowSmart : public MyScrolledWindowBase
+{
+public:
+    MyScrolledWindowSmart(wxWindow *parent) : MyScrolledWindowBase(parent)
+    {
+        // no horz scrolling
+        SetScrollRate( 0, m_hLine );
+        SetVirtualSize( -1, ( m_nLines + 1 ) * m_hLine );
+    }
+
+    virtual void OnDraw(wxDC& dc);
+};
+
+
+// ----------------------------------------------------------------------------

 // MyFrame
 // MyFrame

+// ----------------------------------------------------------------------------

 
 class MyFrame: public wxFrame
 {
 
 class MyFrame: public wxFrame
 {


@@ -48,8 +146,11 @@ public:
 
     void OnAbout( wxCommandEvent &event );
     void OnQuit( wxCommandEvent &event );
 
     void OnAbout( wxCommandEvent &event );
     void OnQuit( wxCommandEvent &event );

+    void OnDeleteAll( wxCommandEvent &event );
+    void OnInsertNew( wxCommandEvent &event );

 
     MyCanvas         *m_canvas;
 
     MyCanvas         *m_canvas;

+    wxTextCtrl       *m_log;

 
     DECLARE_DYNAMIC_CLASS(MyFrame)
     DECLARE_EVENT_TABLE()
 
     DECLARE_DYNAMIC_CLASS(MyFrame)
     DECLARE_EVENT_TABLE()


@@ -67,18 +168,44 @@ public:
 
 IMPLEMENT_APP(MyApp)
 
 
 IMPLEMENT_APP(MyApp)
 

+// ids
+
+const long   ID_ADDBUTTON   = wxNewId();
+const long   ID_DELBUTTON   = wxNewId();
+const long   ID_MOVEBUTTON  = wxNewId();
+const long   ID_SCROLLWIN   = wxNewId();
+const long   ID_QUERYPOS    = wxNewId();
+
+const long   ID_NEWBUTTON   = wxNewId();
+

 // MyCanvas
 
 IMPLEMENT_DYNAMIC_CLASS(MyCanvas, wxScrolledWindow)
 
 BEGIN_EVENT_TABLE(MyCanvas, wxScrolledWindow)
 // MyCanvas
 
 IMPLEMENT_DYNAMIC_CLASS(MyCanvas, wxScrolledWindow)
 
 BEGIN_EVENT_TABLE(MyCanvas, wxScrolledWindow)

-  EVT_PAINT(MyCanvas::OnPaint)
+  EVT_PAINT(                  MyCanvas::OnPaint)
+  EVT_MOUSE_EVENTS(           MyCanvas::OnMouseDown)
+  EVT_BUTTON( ID_QUERYPOS,    MyCanvas::OnQueryPosition)
+  EVT_BUTTON( ID_ADDBUTTON,   MyCanvas::OnAddButton)
+  EVT_BUTTON( ID_DELBUTTON,   MyCanvas::OnDeleteButton)
+  EVT_BUTTON( ID_MOVEBUTTON,  MyCanvas::OnMoveButton)
+  EVT_BUTTON( ID_SCROLLWIN,   MyCanvas::OnScrollWin)

 END_EVENT_TABLE()
 
 MyCanvas::MyCanvas( wxWindow *parent, wxWindowID id,
                     const wxPoint &pos, const wxSize &size )
 END_EVENT_TABLE()
 
 MyCanvas::MyCanvas( wxWindow *parent, wxWindowID id,
                     const wxPoint &pos, const wxSize &size )

-        : wxScrolledWindow( parent, id, pos, size, wxSUNKEN_BORDER | wxTAB_TRAVERSAL )
+    : wxScrolledWindow( parent, id, pos, size, wxSUNKEN_BORDER | wxTAB_TRAVERSAL, _T("test canvas") )

 {
 {

+    SetScrollRate( 10, 10 );
+    SetVirtualSize( 500, 1000 );
+
+    (void) new wxButton( this, ID_ADDBUTTON,  _T("add button"), wxPoint(10,10) );
+    (void) new wxButton( this, ID_DELBUTTON,  _T("del button"), wxPoint(10,40) );
+    (void) new wxButton( this, ID_MOVEBUTTON, _T("move button"), wxPoint(150,10) );
+    (void) new wxButton( this, ID_SCROLLWIN,  _T("scroll win"), wxPoint(250,10) );
+
+#if 0
+

     wxString choices[] =
     {
         "This",
     wxString choices[] =
     {
         "This",


@@ -87,69 +214,278 @@ MyCanvas::MyCanvas( wxWindow *parent, wxWindowID id,
         "wonderful",
         "examples."
     };
         "wonderful",
         "examples."
     };

-  
-//  (void) new wxButton( this, -1, "wxButton", wxPoint(10,10) );
-  
-//  (void) new wxTextCtrl( this, -1, "wxTextCtrl", wxPoint(10,50) );
-  
-  (void) new wxRadioButton( this, -1, "Disable", wxPoint(10,90) );
-  
-//  (void) new wxComboBox( this, -1, "This", wxPoint(10,130), wxDefaultSize, 5, choices );
-  
-  (void) new wxRadioBox( this, -1, "This", wxPoint(10,200), wxDefaultSize, 5, choices );
-  
-  SetBackgroundColour( *wxWHITE );
+
+    m_button = new wxButton( this, ID_QUERYPOS, "Query position", wxPoint(10,110) );
+
+    (void) new wxTextCtrl( this, -1, "wxTextCtrl", wxPoint(10,150), wxSize(80,-1) );
+
+    (void) new wxRadioButton( this, -1, "Disable", wxPoint(10,190) );
+
+    (void) new wxComboBox( this, -1, "This", wxPoint(10,230), wxDefaultSize, 5, choices );
+
+    (void) new wxRadioBox( this, -1, "This", wxPoint(10,310), wxDefaultSize, 5, choices, 2, wxRA_SPECIFY_COLS );
+
+    (void) new wxRadioBox( this, -1, "This", wxPoint(10,440), wxDefaultSize, 5, choices, 2, wxRA_SPECIFY_ROWS );
+
+    wxListCtrl *m_listCtrl = new wxListCtrl(
+            this, -1, wxPoint(200, 110), wxSize(180, 120),
+            wxLC_REPORT | wxSIMPLE_BORDER | wxLC_SINGLE_SEL );
+
+    m_listCtrl->InsertColumn(0, "First", wxLIST_FORMAT_LEFT, 90);
+    m_listCtrl->InsertColumn(1, "Last", wxLIST_FORMAT_LEFT, 90);
+
+    for ( int i=0; i < 30; i++)
+    {
+        char buf[20];
+        sprintf(buf, "Item %d", i);
+        m_listCtrl->InsertItem(i, buf);
+    }
+    m_listCtrl->SetItemState( 3, wxLIST_STATE_SELECTED, wxLIST_STATE_SELECTED );
+
+    (void) new wxListBox( this, -1, wxPoint(260,280), wxSize(120,120), 5, choices, wxLB_ALWAYS_SB );
+
+#endif
+
+    wxPanel *test = new wxPanel( this, -1, wxPoint(10, 110), wxSize(130,50), wxSIMPLE_BORDER | wxTAB_TRAVERSAL );
+    test->SetBackgroundColour( wxT("WHEAT") );
+
+#if 0
+
+    wxButton *test2 = new wxButton( test, -1, "Hallo", wxPoint(10,10) );
+
+    test = new wxPanel( this, -1, wxPoint(160, 530), wxSize(130,120), wxSUNKEN_BORDER | wxTAB_TRAVERSAL );
+    test->SetBackgroundColour( wxT("WHEAT") );
+    test->SetCursor( wxCursor( wxCURSOR_NO_ENTRY ) );
+    test2 = new wxButton( test, -1, "Hallo", wxPoint(10,10) );
+    test2->SetCursor( wxCursor( wxCURSOR_PENCIL ) );
+
+    test = new wxPanel( this, -1, wxPoint(310, 530), wxSize(130,120), wxRAISED_BORDER | wxTAB_TRAVERSAL );
+    test->SetBackgroundColour( wxT("WHEAT") );
+    test->SetCursor( wxCursor( wxCURSOR_PENCIL ) );
+    test2 = new wxButton( test, -1, "Hallo", wxPoint(10,10) );
+    test2->SetCursor( wxCursor( wxCURSOR_NO_ENTRY ) );
+
+#endif
+
+    SetBackgroundColour( wxT("BLUE") );
+
+    SetCursor( wxCursor( wxCURSOR_IBEAM ) );

 }
 
 MyCanvas::~MyCanvas()
 {
 }
 
 }
 
 MyCanvas::~MyCanvas()
 {
 }
 

+void MyCanvas::OnMouseDown( wxMouseEvent &event )
+{
+    if (event.LeftDown())
+    {
+        wxPoint pt( event.GetPosition() );
+        int x,y;
+        CalcUnscrolledPosition( pt.x, pt.y, &x, &y );
+        wxLogMessage( wxT("Mouse down event at: %d %d, scrolled: %d %d"), pt.x, pt.y, x, y );
+
+        if ( !event.LeftIsDown() )
+            wxLogMessage( wxT("Error: LeftIsDown() should be TRUE if for LeftDown()") );
+    }
+}
+

 void MyCanvas::OnPaint( wxPaintEvent &WXUNUSED(event) )
 {
 void MyCanvas::OnPaint( wxPaintEvent &WXUNUSED(event) )
 {

-  return;
+    wxPaintDC dc( this );
+    PrepareDC( dc );
+
+    dc.DrawText( _T("Press mouse button to test calculations!"), 160, 50 );
+
+    dc.DrawText( _T("Some text"), 140, 140 );
+
+    dc.DrawRectangle( 100, 160, 200, 200 );
+}
+
+void MyCanvas::OnQueryPosition( wxCommandEvent &WXUNUSED(event) )
+{
+    wxPoint pt( m_button->GetPosition() );
+    wxLogMessage( wxT("Position of \"Query position\" is %d %d"), pt.x, pt.y );
+    pt = ClientToScreen( pt );
+    wxLogMessage( wxT("Position of \"Query position\" on screen is %d %d"), pt.x, pt.y );
+}
+
+void MyCanvas::OnAddButton( wxCommandEvent &WXUNUSED(event) )
+{
+    wxLogMessage( wxT("Inserting button at position 10,70...") );
+    wxButton *button = new wxButton( this, ID_NEWBUTTON, wxT("new button"), wxPoint(10,70), wxSize(80,25) );
+    wxPoint pt( button->GetPosition() );
+    wxLogMessage( wxT("-> Position after inserting %d %d"), pt.x, pt.y );
+}
+
+void MyCanvas::OnDeleteButton( wxCommandEvent &WXUNUSED(event) )
+{
+    wxLogMessage( wxT("Deleting button inserted with \"Add button\"...") );
+    wxWindow *win = FindWindow( ID_NEWBUTTON );
+    if (win)
+       win->Destroy();
+    else
+       wxLogMessage( wxT("-> No window with id = ID_NEWBUTTON found.") );
+}
+
+void MyCanvas::OnMoveButton( wxCommandEvent &event )
+{
+    wxLogMessage( wxT("Moving button 10 pixels downward..") );
+    wxWindow *win = FindWindow( event.GetId() );
+    wxPoint pt( win->GetPosition() );
+    wxLogMessage( wxT("-> Position before move is %d %d"), pt.x, pt.y );
+    win->Move( -1, pt.y + 10 );
+    pt = win->GetPosition();
+    wxLogMessage( wxT("-> Position after move is %d %d"), pt.x, pt.y );
+}
+
+void MyCanvas::OnScrollWin( wxCommandEvent &WXUNUSED(event) )
+{
+    wxLogMessage( wxT("Scrolling 2 units up.\nThe white square and the controls should move equally!") );
+    int x,y;
+    GetViewStart( &x, &y );
+    Scroll( -1, y+2 );
+}
+
+// MyAutoScrollWindow
+
+const long   ID_RESIZEBUTTON = wxNewId();
+const wxSize SMALL_BUTTON( 100, 50 );
+const wxSize LARGE_BUTTON( 300, 100 );
+
+BEGIN_EVENT_TABLE( MyAutoScrollWindow, wxScrolledWindow)
+  EVT_BUTTON( ID_RESIZEBUTTON,    MyAutoScrollWindow::OnResizeClick)
+END_EVENT_TABLE()
+
+MyAutoScrollWindow::MyAutoScrollWindow( wxWindow *parent )
+    : wxScrolledWindow( parent )
+{
+    SetBackgroundColour( wxT("GREEN") );
+
+    // Set the rate we'd like for scrolling.
+
+    SetScrollRate( 5, 5 );
+
+    // Populate a sizer with a 'resizing' button and some
+    // other static decoration
+
+    wxFlexGridSizer  *innersizer = new wxFlexGridSizer( 2, 2 );
+
+    m_button = new wxButton( this,
+                             ID_RESIZEBUTTON,
+                             _T("Press me"),
+                             wxDefaultPosition,
+                             SMALL_BUTTON );
+
+    // We need to do this here, because wxADJUST_MINSIZE below
+    // will cause the initial size to be ignored for Best/Min size.
+    // It would be nice to fix the sizers to handle this a little
+    // more cleanly.
+
+    m_button->SetSizeHints( SMALL_BUTTON.GetWidth(), SMALL_BUTTON.GetHeight() );
+
+    innersizer->Add( m_button,
+                     0,
+                     wxALIGN_CENTER | wxALL | wxADJUST_MINSIZE,
+                     20 );
+
+    innersizer->Add( new wxStaticText( this, -1, _T("This is just") ),
+                    0,
+                    wxALIGN_CENTER );
+
+    innersizer->Add( new wxStaticText( this, -1, _T("some decoration") ),
+                    0,
+                    wxALIGN_CENTER );
+
+    innersizer->Add( new wxStaticText( this, -1, _T("for you to scroll...") ),
+                    0,
+                    wxALIGN_CENTER );
+
+    // Then use the sizer to set the scrolled region size.
+
+    SetSizer( innersizer );
+}
+
+void MyAutoScrollWindow::OnResizeClick( wxCommandEvent &WXUNUSED( event ) )
+{
+    // Arbitrarily resize the button to change the minimum size of
+    // the (scrolled) sizer.

 
 

-  wxPaintDC dc( this );
-  PrepareDC( dc );
+    if( m_button->GetSize() == SMALL_BUTTON )
+        m_button->SetSizeHints( LARGE_BUTTON.GetWidth(), LARGE_BUTTON.GetHeight() );
+    else
+        m_button->SetSizeHints( SMALL_BUTTON.GetWidth(), SMALL_BUTTON.GetHeight() );

 
 

-  dc.DrawText( "Some text", 10, 10 );
-  
-  dc.DrawRectangle( 50, 30, 200, 200 );
+    // Force update layout and scrollbars, since nothing we do here
+    // necessarily generates a size event which would do it for us.
+
+    FitInside();

 }
 
 // MyFrame
 
 }
 
 // MyFrame
 

-const int ID_QUIT  = 108;
-const int ID_ABOUT = 109;
+const long ID_QUIT       = wxNewId();
+const long ID_ABOUT      = wxNewId();
+const long ID_DELETE_ALL = wxNewId();
+const long ID_INSERT_NEW = wxNewId();

 
 IMPLEMENT_DYNAMIC_CLASS( MyFrame, wxFrame )
 
 BEGIN_EVENT_TABLE(MyFrame,wxFrame)
 
 IMPLEMENT_DYNAMIC_CLASS( MyFrame, wxFrame )
 
 BEGIN_EVENT_TABLE(MyFrame,wxFrame)

+  EVT_MENU    (ID_DELETE_ALL, MyFrame::OnDeleteAll)
+  EVT_MENU    (ID_INSERT_NEW,  MyFrame::OnInsertNew)

   EVT_MENU    (ID_ABOUT, MyFrame::OnAbout)
   EVT_MENU    (ID_QUIT,  MyFrame::OnQuit)
 END_EVENT_TABLE()
 
 MyFrame::MyFrame()
   EVT_MENU    (ID_ABOUT, MyFrame::OnAbout)
   EVT_MENU    (ID_QUIT,  MyFrame::OnQuit)
 END_EVENT_TABLE()
 
 MyFrame::MyFrame()

-       : wxFrame( (wxFrame *)NULL, -1, "wxScrolledWindow sample",
-                  wxPoint(20,20), wxSize(470,360) )
+       : wxFrame( (wxFrame *)NULL, -1, _T("wxScrolledWindow sample"),
+                  wxPoint(20,20), wxSize(470,500) )

 {
 {

-/*
-  wxMenu *file_menu = new wxMenu();
-  file_menu->Append( ID_ABOUT, "&About..");
-  file_menu->Append( ID_QUIT, "E&xit\tAlt-X");
+    wxMenu *file_menu = new wxMenu();
+    file_menu->Append( ID_DELETE_ALL, _T("Delete all"));
+    file_menu->Append( ID_INSERT_NEW, _T("Insert new"));
+    file_menu->Append( ID_ABOUT,      _T("&About.."));
+    file_menu->Append( ID_QUIT,       _T("E&xit\tAlt-X"));

 
 

-  wxMenuBar *menu_bar = new wxMenuBar();
-  menu_bar->Append(file_menu, "&File");
+    wxMenuBar *menu_bar = new wxMenuBar();
+    menu_bar->Append(file_menu, _T("&File"));

 
 

-  SetMenuBar( menu_bar );
+    SetMenuBar( menu_bar );

 
 

-  CreateStatusBar(2);
-  int widths[] = { -1, 100 };
-  SetStatusWidths( 2, widths );
+    CreateStatusBar(2);
+    int widths[] = { -1, 100 };
+    SetStatusWidths( 2, widths );

 
 

-*/
-  m_canvas = new MyCanvas( this, -1, wxPoint(0,0), wxSize(10,10) );
-  m_canvas->SetScrollbars( 10, 10, 50, 100 );
+    wxBoxSizer *topsizer = new wxBoxSizer( wxVERTICAL );
+
+    // Setting an explicit size here is superfluous, it will be overridden
+    // by the sizer in any case.
+    m_canvas = new MyCanvas( this, -1, wxPoint(0,0), wxSize(100,100) );
+
+    // This is done with ScrollRate/VirtualSize in MyCanvas ctor now,
+    // both should produce identical results.
+    //m_canvas->SetScrollbars( 10, 10, 50, 100 );
+
+    topsizer->Add( m_canvas, 1, wxEXPAND );
+    topsizer->Add( new MyAutoScrollWindow( this ), 1, wxEXPAND );
+
+    wxSizer *sizerBtm = new wxBoxSizer(wxHORIZONTAL);
+    sizerBtm->Add( new MyScrolledWindowDumb(this), 1, wxEXPAND );
+    sizerBtm->Add( new MyScrolledWindowSmart(this), 1, wxEXPAND );
+    topsizer->Add( sizerBtm, 1, wxEXPAND );
+
+    SetSizer( topsizer );
+}
+
+void MyFrame::OnDeleteAll( wxCommandEvent &WXUNUSED(event) )
+{
+    m_canvas->DestroyChildren();
+}
+
+void MyFrame::OnInsertNew( wxCommandEvent &WXUNUSED(event) )
+{
+    (void)new wxButton( m_canvas, -1, _T("Hello"), wxPoint(100,100) );

 }
 
 void MyFrame::OnQuit( wxCommandEvent &WXUNUSED(event) )
 }
 
 void MyFrame::OnQuit( wxCommandEvent &WXUNUSED(event) )


@@ -159,9 +495,12 @@ void MyFrame::OnQuit( wxCommandEvent &WXUNUSED(event) )
 
 void MyFrame::OnAbout( wxCommandEvent &WXUNUSED(event) )
 {
 
 void MyFrame::OnAbout( wxCommandEvent &WXUNUSED(event) )
 {

-  (void)wxMessageBox( "wxScroll demo\n"
-                      "Robert Roebling (c) 1998",
-                      "About wxScroll Demo", wxICON_INFORMATION | wxOK );
+  (void)wxMessageBox( _T("wxScroll demo\n"
+                         "Robert Roebling (c) 1998\n"
+                         "Autoscrolling examples\n"
+                         "Ron Lee (c) 2002"),
+                      _T("About wxScroll Demo"),
+                      wxICON_INFORMATION | wxOK );

 }
 
 //-----------------------------------------------------------------------------
 }
 
 //-----------------------------------------------------------------------------


@@ -176,3 +515,53 @@ bool MyApp::OnInit()
   return TRUE;
 }
 
   return TRUE;
 }
 

+// ----------------------------------------------------------------------------
+// MyScrolledWindowXXX
+// ----------------------------------------------------------------------------
+
+void MyScrolledWindowDumb::OnDraw(wxDC& dc)
+{
+    // this is useful to see which lines are redrawn
+    static size_t s_redrawCount = 0;
+    dc.SetTextForeground(s_redrawCount++ % 2 ? *wxRED : *wxBLUE);
+
+    wxCoord y = 0;
+    for ( size_t line = 0; line < m_nLines; line++ )
+    {
+        wxCoord yPhys;
+        CalcScrolledPosition(0, y, NULL, &yPhys);
+
+        dc.DrawText(wxString::Format(_T("Line %u (logical %d, physical %d)"),
+                                     line, y, yPhys), 0, y);
+        y += m_hLine;
+    }
+}
+
+void MyScrolledWindowSmart::OnDraw(wxDC& dc)
+{
+    // this is useful to see which lines are redrawn
+    static size_t s_redrawCount = 0;
+    dc.SetTextForeground(s_redrawCount++ % 2 ? *wxRED : *wxBLUE);
+
+    // update region is always in device coords, translate to logical ones
+    wxRect rectUpdate = GetUpdateRegion().GetBox();
+    CalcUnscrolledPosition(rectUpdate.x, rectUpdate.y,
+                           &rectUpdate.x, &rectUpdate.y);
+
+    size_t lineFrom = rectUpdate.y / m_hLine,
+           lineTo = rectUpdate.GetBottom() / m_hLine;
+
+    if ( lineTo > m_nLines - 1)
+        lineTo = m_nLines - 1;
+
+    wxCoord y = lineFrom*m_hLine;
+    for ( size_t line = lineFrom; line <= lineTo; line++ )
+    {
+        wxCoord yPhys;
+        CalcScrolledPosition(0, y, NULL, &yPhys);
+
+        dc.DrawText(wxString::Format(_T("Line %u (logical %d, physical %d)"),
+                                     line, y, yPhys), 0, y);
+        y += m_hLine;
+    }
+}