wxWidgets/samples/stylus/stylus.cpp

/////////////////////////////////////////////////////////////////////////////
// Name:        stylus.cpp
// Purpose:     Stylus sample
// Author:      Iulian Serbanoiu
// Modified by:
// Created:     2026-02-02
// Copyright:   (c) Iulian Serbanoiu
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////

#include "wx/wx.h"
#include "wx/dcbuffer.h"

#include <array>
#include <deque>

// Define a new application
class wxMyApp: public wxApp
{
public:
    bool OnInit() override;
};

wxDECLARE_APP(wxMyApp);

enum
{
    ID_COLOR_FIRST = wxID_HIGHEST + 1,
    ID_COLOR_BLACK = ID_COLOR_FIRST,
    ID_COLOR_RED,
    ID_COLOR_GREEN,
    ID_COLOR_BLUE,
    ID_COLOR_LAST
};

struct colorInfo {
    int id;
    const char* name;
    const char* accelerator;
    const wxColor *color;
    bool selected;
} clrInfo[] = {
    { ID_COLOR_BLACK,"Black","1",wxBLACK,false},
    { ID_COLOR_RED,"Red","2",wxRED,false},
    { ID_COLOR_GREEN,"Green","3",wxGREEN,false},
    { ID_COLOR_BLUE,"Blue","4",wxBLUE,true},
};

class MyFrame: public wxFrame
{
private:
    wxColor m_drawingColor;
    wxColor m_backgroundColor;
    bool m_penDown;
    wxBitmap m_backingBitmap;
    std::deque<wxPoint> m_positions;
    void DrawLines(int thickness, const wxColor& color);
    void DrawInfo();
public:
    MyFrame(wxFrame *parent, const wxString& title);

    void OnPenDown(wxStylusEvent& event);
    void OnPenUp(wxStylusEvent& event);
    void OnPenUpdate(wxStylusEvent& event);

    void OnPaint(wxPaintEvent& event);
    void OnSize(wxSizeEvent& event);
    void OnQuit(wxCommandEvent& event);
    void OnColorChange(wxCommandEvent& event);
};

wxIMPLEMENT_APP(wxMyApp);

bool wxMyApp::OnInit()
{
    if ( !wxApp::OnInit() )
        return false;

    wxFrame* frame = new MyFrame(nullptr, "Tablet Drawing Test");
    frame->CenterOnScreen();
    frame->Show(true);

    return true;
}

MyFrame::MyFrame(wxFrame *parent, const wxString& title)
    : wxFrame(parent, wxID_ANY, title,
              wxDefaultPosition, wxDefaultSize,
              wxDEFAULT_FRAME_STYLE | wxHSCROLL | wxVSCROLL)
{
    SetBackgroundStyle(wxBG_STYLE_PAINT);
    SetClientSize(FromDIP(wxSize(800, 600)));

    wxMenuBar* menu_bar = new wxMenuBar();
    {
        wxMenu* file_menu = new wxMenu();
        file_menu->Append(wxID_EXIT);
        menu_bar->Append(file_menu, "&File");
    }

    {
        m_drawingColor = *clrInfo[0].color; // make sure it's initialized
        wxMenu* colorMenu = new wxMenu();
        for (int i = 0; i < WXSIZEOF(clrInfo); i++)
        {
            auto& info = clrInfo[i];
            wxString text(info.name);
            text += wxString("\t");
            text += wxString(info.accelerator);
            auto menuItem = colorMenu->AppendRadioItem(info.id, text);
            if (info.selected)
            {
                menuItem->Check();
                m_drawingColor = *info.color;
            }
        }
        menu_bar->Append(colorMenu, "&Color");
    }
    SetMenuBar(menu_bar);

    m_penDown = false;
    m_backgroundColor = *wxWHITE;

    Bind(wxEVT_STYLUS_DOWN, &MyFrame::OnPenDown, this);
    Bind(wxEVT_STYLUS_UP, &MyFrame::OnPenUp, this);
    Bind(wxEVT_STYLUS_UPDATE, &MyFrame::OnPenUpdate, this);

    Bind(wxEVT_MENU, &MyFrame::OnQuit, this, wxID_EXIT);
    Bind(wxEVT_MENU, &MyFrame::OnColorChange, this, ID_COLOR_FIRST, ID_COLOR_LAST-1);

    Bind(wxEVT_PAINT, &MyFrame::OnPaint, this);
    Bind(wxEVT_SIZE, &MyFrame::OnSize, this);
}

void MyFrame::OnQuit(wxCommandEvent& WXUNUSED(event))
{
    Close(true);
}

void MyFrame::OnPaint(wxPaintEvent& WXUNUSED(event))
{
    wxAutoBufferedPaintDC dc(this);
    dc.DrawBitmap(m_backingBitmap, 0, 0);
}

void MyFrame::OnSize(wxSizeEvent& WXUNUSED(event))
{
    wxSize size = GetClientSize();
    m_backingBitmap = wxBitmap(size.x, size.y, 24);

    wxMemoryDC dc(m_backingBitmap);
    dc.SetBackground(*wxWHITE_BRUSH);
    dc.Clear();
    DrawInfo();

    Refresh();
}


void MyFrame::OnPenDown(wxStylusEvent& event)
{
    wxUnusedVar(event);
    SetCursor(*wxCROSS_CURSOR);
    m_positions.clear();
    m_penDown = true;
}

void MyFrame::OnPenUp(wxStylusEvent& event)
{
    wxUnusedVar(event);
    SetCursor(*wxSTANDARD_CURSOR);
    m_positions.clear();
    m_penDown = false;
}

void MyFrame::OnPenUpdate(wxStylusEvent& event)
{
    bool skip = false;
    if (!m_penDown)
    {
        skip = true;
    }
    const double p = event.GetPressure();
    if (p < 0.0)
    {
        skip = true;
    }

    if (skip)
    {
        event.Skip();
        return;
    }

    const bool eraser = event.IsUsingEraser();
    wxColor color = eraser ? m_backgroundColor : m_drawingColor;
    const int maxThicknes = eraser ? 36 : 12;
    const int minThickness = eraser ? 6 : 2;
    const int thickness = minThickness + p * (maxThicknes - minThickness);

    wxPoint newPos = event.GetPosition();
    m_positions.push_back(newPos);

    DrawLines(thickness, color);
}

void MyFrame::OnColorChange(wxCommandEvent& event)
{
    int index = event.GetId() - ID_COLOR_FIRST;
    m_drawingColor = *clrInfo[index].color;
}

void MyFrame::DrawLines(int thickness, const wxColor& color)
{
    if (m_positions.size() < 2) {
        return;
    }
    wxMemoryDC dc(m_backingBitmap);
    dc.SetPen(wxPen(color, thickness));
    dc.SetBrush(wxBrush(color));

    wxPoint p1, p2;
    p1 = m_positions.front();
    for (;;)
    {
        m_positions.pop_front();
        p2 = m_positions.front();

        dc.DrawLine(p1, p2);

        if (m_positions.size() > 1)
        {
            m_positions.pop_front();
            p1 = p2; // last point of line is now the first point of next line
        }
        else
        {
            // only one position left - the last one
            break;
        }
    }
    Refresh();
}

void MyFrame::DrawInfo()
{
    wxMemoryDC dc(m_backingBitmap);
    wxString info("This is a pen drawing demo.");
    info += wxString("\n");
    info += wxString("Only pen events are accepted for drawing.");
    info += wxString("\n");
    info += wxString("This demo uses the pressure and eraser features of the tablet pen.");
    dc.DrawText(info, wxPoint(0, 0));
}