src/msw/dc.cpp

/////////////////////////////////////////////////////////////////////////////
// Name:        dc.cpp
// Purpose:     wxDC class
// Author:      Julian Smart
// Modified by:
// Created:     01/02/97
// RCS-ID:      $Id$
// Copyright:   (c) Julian Smart and Markus Holzem
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////

// ===========================================================================
// declarations
// ===========================================================================

// ---------------------------------------------------------------------------
// headers
// ---------------------------------------------------------------------------

#ifdef __GNUG__
    #pragma implementation "dc.h"
#endif

// For compilers that support precompilation, includes "wx.h".
#include "wx/wxprec.h"

#ifdef __BORLANDC__
    #pragma hdrstop
#endif

#ifndef WX_PRECOMP
    #include "wx/window.h"
    #include "wx/dc.h"
    #include "wx/utils.h"
    #include "wx/dialog.h"
    #include "wx/app.h"
    #include "wx/bitmap.h"
    #include "wx/dcmemory.h"
    #include "wx/log.h"
    #include "wx/icon.h"
#endif

#include "wx/sysopt.h"
#include "wx/dcprint.h"
#include "wx/module.h"

#include <string.h>
#include <math.h>

#include "wx/msw/private.h" // needs to be before #include <commdlg.h>

#if wxUSE_COMMON_DIALOGS && !defined(__WXMICROWIN__)
    #include <commdlg.h>
#endif

#ifndef __WIN32__
    #include <print.h>
#endif

/* Quaternary raster codes */
#ifndef MAKEROP4
#define MAKEROP4(fore,back) (DWORD)((((back) << 8) & 0xFF000000) | (fore))
#endif

IMPLEMENT_ABSTRACT_CLASS(wxDC, wxDCBase)

// ---------------------------------------------------------------------------
// constants
// ---------------------------------------------------------------------------

static const int VIEWPORT_EXTENT = 1000;

static const int MM_POINTS = 9;
static const int MM_METRIC = 10;

// usually this is defined in math.h
#ifndef M_PI
    static const double M_PI = 3.14159265358979323846;
#endif // M_PI

// ROPs which don't have standard names (see "Ternary Raster Operations" in the
// MSDN docs for how this and other numbers in wxDC::Blit() are obtained)
#define DSTCOPY 0x00AA0029      // a.k.a. NOP operation

// ----------------------------------------------------------------------------
// macros for logical <-> device coords conversion
// ----------------------------------------------------------------------------

/*
   We currently let Windows do all the translations itself so these macros are
   not really needed (any more) but keep them to enhance readability of the
   code by allowing to see where are the logical and where are the device
   coordinates used.
 */

// logical to device
#define XLOG2DEV(x) (x)
#define YLOG2DEV(y) (y)

// device to logical
#define XDEV2LOG(x) (x)
#define YDEV2LOG(y) (y)

// ---------------------------------------------------------------------------
// private functions
// ---------------------------------------------------------------------------

// convert degrees to radians
static inline double DegToRad(double deg) { return (deg * M_PI) / 180.0; }

// ----------------------------------------------------------------------------
// private classes
// ----------------------------------------------------------------------------

// instead of duplicating the same code which sets and then restores text
// colours in each wxDC method working with wxSTIPPLE_MASK_OPAQUE brushes,
// encapsulate this in a small helper class

// wxColourChanger: changes the text colours in the ctor if required and
//                  restores them in the dtor
class wxColourChanger
{
public:
    wxColourChanger(wxDC& dc);
   ~wxColourChanger();

private:
    wxDC& m_dc;

    COLORREF m_colFgOld, m_colBgOld;

    bool m_changed;
};

// this class saves the old stretch blit mode during its life time
class StretchBltModeChanger
{
public:
    StretchBltModeChanger(HDC hdc, int mode)
        : m_hdc(hdc)
    {
        m_modeOld = ::SetStretchBltMode(m_hdc, mode);
        if ( !m_modeOld )
            wxLogLastError(_T("SetStretchBltMode"));
    }

    ~StretchBltModeChanger()
    {
        if ( !::SetStretchBltMode(m_hdc, m_modeOld) )
            wxLogLastError(_T("SetStretchBltMode"));
    }

private:
    const HDC m_hdc;

    int m_modeOld;
};

// ===========================================================================
// implementation
// ===========================================================================

// ----------------------------------------------------------------------------
// wxColourChanger
// ----------------------------------------------------------------------------

wxColourChanger::wxColourChanger(wxDC& dc) : m_dc(dc)
{
    const wxBrush& brush = dc.GetBrush();
    if ( brush.Ok() && brush.GetStyle() == wxSTIPPLE_MASK_OPAQUE )
    {
        HDC hdc = GetHdcOf(dc);
        m_colFgOld = ::GetTextColor(hdc);
        m_colBgOld = ::GetBkColor(hdc);

        // note that Windows convention is opposite to wxWindows one, this is
        // why text colour becomes the background one and vice versa
        const wxColour& colFg = dc.GetTextForeground();
        if ( colFg.Ok() )
        {
            ::SetBkColor(hdc, colFg.GetPixel());
        }

        const wxColour& colBg = dc.GetTextBackground();
        if ( colBg.Ok() )
        {
            ::SetTextColor(hdc, colBg.GetPixel());
        }

        SetBkMode(hdc,
                  dc.GetBackgroundMode() == wxTRANSPARENT ? TRANSPARENT
                                                          : OPAQUE);

        // flag which telsl us to undo changes in the dtor
        m_changed = TRUE;
    }
    else
    {
        // nothing done, nothing to undo
        m_changed = FALSE;
    }
}

wxColourChanger::~wxColourChanger()
{
    if ( m_changed )
    {
        // restore the colours we changed
        HDC hdc = GetHdcOf(m_dc);

        ::SetBkMode(hdc, TRANSPARENT);
        ::SetTextColor(hdc, m_colFgOld);
        ::SetBkColor(hdc, m_colBgOld);
    }
}

// ---------------------------------------------------------------------------
// wxDC
// ---------------------------------------------------------------------------

// Default constructor
wxDC::wxDC()
{
    m_canvas = NULL;

    m_oldBitmap = 0;
    m_oldPen = 0;
    m_oldBrush = 0;
    m_oldFont = 0;
#if wxUSE_PALETTE
    m_oldPalette = 0;
#endif // wxUSE_PALETTE

    m_bOwnsDC = FALSE;
    m_hDC = 0;
}

wxDC::~wxDC()
{
    if ( m_hDC != 0 )
    {
        SelectOldObjects(m_hDC);

        // if we own the HDC, we delete it, otherwise we just release it

        if ( m_bOwnsDC )
        {
            ::DeleteDC(GetHdc());
        }
        else // we don't own our HDC
        {
            if (m_canvas)
            {
                ::ReleaseDC(GetHwndOf(m_canvas), GetHdc());
            }
            else
            {
                // Must have been a wxScreenDC
                ::ReleaseDC((HWND) NULL, GetHdc());
            }
        }
    }
}

// This will select current objects out of the DC,
// which is what you have to do before deleting the
// DC.
void wxDC::SelectOldObjects(WXHDC dc)
{
    if (dc)
    {
        if (m_oldBitmap)
        {
            ::SelectObject((HDC) dc, (HBITMAP) m_oldBitmap);
            if (m_selectedBitmap.Ok())
            {
                m_selectedBitmap.SetSelectedInto(NULL);
            }
        }
        m_oldBitmap = 0;
        if (m_oldPen)
        {
            ::SelectObject((HDC) dc, (HPEN) m_oldPen);
        }
        m_oldPen = 0;
        if (m_oldBrush)
        {
            ::SelectObject((HDC) dc, (HBRUSH) m_oldBrush);
        }
        m_oldBrush = 0;
        if (m_oldFont)
        {
            ::SelectObject((HDC) dc, (HFONT) m_oldFont);
        }
        m_oldFont = 0;

#if wxUSE_PALETTE
        if (m_oldPalette)
        {
            ::SelectPalette((HDC) dc, (HPALETTE) m_oldPalette, FALSE);
        }
        m_oldPalette = 0;
#endif // wxUSE_PALETTE
    }

    m_brush = wxNullBrush;
    m_pen = wxNullPen;
#if wxUSE_PALETTE
    m_palette = wxNullPalette;
#endif // wxUSE_PALETTE
    m_font = wxNullFont;
    m_backgroundBrush = wxNullBrush;
    m_selectedBitmap = wxNullBitmap;
}

// ---------------------------------------------------------------------------
// clipping
// ---------------------------------------------------------------------------

void wxDC::UpdateClipBox()
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    RECT rect;
    ::GetClipBox(GetHdc(), &rect);

    m_clipX1 = (wxCoord) XDEV2LOG(rect.left);
    m_clipY1 = (wxCoord) YDEV2LOG(rect.top);
    m_clipX2 = (wxCoord) XDEV2LOG(rect.right);
    m_clipY2 = (wxCoord) YDEV2LOG(rect.bottom);
}

// common part of DoSetClippingRegion() and DoSetClippingRegionAsRegion()
void wxDC::SetClippingHrgn(WXHRGN hrgn)
{
    wxCHECK_RET( hrgn, wxT("invalid clipping region") );

#ifdef __WXMICROWIN__
    if (!GetHdc()) return;
#endif // __WXMICROWIN__

    // note that we combine the new clipping region with the existing one: this
    // is compatible with what the other ports do and is the documented
    // behaviour now (starting with 2.3.3)
#ifdef __WIN16__
    RECT rectClip;
    if ( !::GetClipBox(GetHdc(), &rectClip) )
        return;

    HRGN hrgnDest = ::CreateRectRgn(0, 0, 0, 0);
    HRGN hrgnClipOld = ::CreateRectRgn(rectClip.left, rectClip.top,
                                       rectClip.right, rectClip.bottom);

    if ( ::CombineRgn(hrgnDest, hrgnClipOld, (HRGN)hrgn, RGN_AND) != ERROR )
    {
        ::SelectClipRgn(GetHdc(), hrgnDest);
    }

    ::DeleteObject(hrgnClipOld);
    ::DeleteObject(hrgnDest);
#else // Win32
    if ( ::ExtSelectClipRgn(GetHdc(), (HRGN)hrgn, RGN_AND) == ERROR )
    {
        wxLogLastError(_T("ExtSelectClipRgn"));

        return;
    }
#endif // Win16/32

    m_clipping = TRUE;

    UpdateClipBox();
}

void wxDC::DoSetClippingRegion(wxCoord x, wxCoord y, wxCoord w, wxCoord h)
{
    // the region coords are always the device ones, so do the translation
    // manually
    //
    // FIXME: possible +/-1 error here, to check!
    HRGN hrgn = ::CreateRectRgn(LogicalToDeviceX(x),
                                LogicalToDeviceY(y),
                                LogicalToDeviceX(x + w),
                                LogicalToDeviceY(y + h));
    if ( !hrgn )
    {
        wxLogLastError(_T("CreateRectRgn"));
    }
    else
    {
        SetClippingHrgn((WXHRGN)hrgn);

        ::DeleteObject(hrgn);
    }
}

void wxDC::DoSetClippingRegionAsRegion(const wxRegion& region)
{
    SetClippingHrgn(region.GetHRGN());
}

void wxDC::DestroyClippingRegion()
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    if (m_clipping && m_hDC)
    {
        // TODO: this should restore the previous clipping region,
        //       so that OnPaint processing works correctly, and the update
        //       clipping region doesn't get destroyed after the first
        //       DestroyClippingRegion.
        HRGN rgn = CreateRectRgn(0, 0, 32000, 32000);
        ::SelectClipRgn(GetHdc(), rgn);
        ::DeleteObject(rgn);
    }

    m_clipping = FALSE;
}

// ---------------------------------------------------------------------------
// query capabilities
// ---------------------------------------------------------------------------

bool wxDC::CanDrawBitmap() const
{
    return TRUE;
}

bool wxDC::CanGetTextExtent() const
{
#ifdef __WXMICROWIN__
    // TODO Extend MicroWindows' GetDeviceCaps function
    return TRUE;
#else
    // What sort of display is it?
    int technology = ::GetDeviceCaps(GetHdc(), TECHNOLOGY);

    return (technology == DT_RASDISPLAY) || (technology == DT_RASPRINTER);
#endif
}

int wxDC::GetDepth() const
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return 16;
#endif

    return (int)::GetDeviceCaps(GetHdc(), BITSPIXEL);
}

// ---------------------------------------------------------------------------
// drawing
// ---------------------------------------------------------------------------

void wxDC::Clear()
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    RECT rect;
    if ( m_canvas )
    {
        GetClientRect((HWND) m_canvas->GetHWND(), &rect);
    }
    else
    {
        // No, I think we should simply ignore this if printing on e.g.
        // a printer DC.
        // wxCHECK_RET( m_selectedBitmap.Ok(), wxT("this DC can't be cleared") );
        if (!m_selectedBitmap.Ok())
            return;

        rect.left = 0; rect.top = 0;
        rect.right = m_selectedBitmap.GetWidth();
        rect.bottom = m_selectedBitmap.GetHeight();
    }

    (void) ::SetMapMode(GetHdc(), MM_TEXT);

    DWORD colour = ::GetBkColor(GetHdc());
    HBRUSH brush = ::CreateSolidBrush(colour);
    ::FillRect(GetHdc(), &rect, brush);
    ::DeleteObject(brush);

    int width = DeviceToLogicalXRel(VIEWPORT_EXTENT)*m_signX,
        height = DeviceToLogicalYRel(VIEWPORT_EXTENT)*m_signY;

    ::SetMapMode(GetHdc(), MM_ANISOTROPIC);
    ::SetViewportExtEx(GetHdc(), VIEWPORT_EXTENT, VIEWPORT_EXTENT, NULL);
    ::SetWindowExtEx(GetHdc(), width, height, NULL);
    ::SetViewportOrgEx(GetHdc(), (int)m_deviceOriginX, (int)m_deviceOriginY, NULL);
    ::SetWindowOrgEx(GetHdc(), (int)m_logicalOriginX, (int)m_logicalOriginY, NULL);
}

bool wxDC::DoFloodFill(wxCoord x, wxCoord y, const wxColour& col, int style)
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return FALSE;
#endif

    bool success = (0 != ::ExtFloodFill(GetHdc(), XLOG2DEV(x), YLOG2DEV(y),
                         col.GetPixel(),
                         style == wxFLOOD_SURFACE ? FLOODFILLSURFACE
                                                  : FLOODFILLBORDER) ) ;
    if (!success)
    {
        // quoting from the MSDN docs:
        //
        //      Following are some of the reasons this function might fail:
        //
        //      * The filling could not be completed.
        //      * The specified point has the boundary color specified by the
        //        crColor parameter (if FLOODFILLBORDER was requested).
        //      * The specified point does not have the color specified by
        //        crColor (if FLOODFILLSURFACE was requested)
        //      * The point is outside the clipping region that is, it is not
        //        visible on the device.
        //
        wxLogLastError(wxT("ExtFloodFill"));
    }

    CalcBoundingBox(x, y);

    return success;
}

bool wxDC::DoGetPixel(wxCoord x, wxCoord y, wxColour *col) const
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return FALSE;
#endif

    wxCHECK_MSG( col, FALSE, _T("NULL colour parameter in wxDC::GetPixel") );

    // get the color of the pixel
    COLORREF pixelcolor = ::GetPixel(GetHdc(), XLOG2DEV(x), YLOG2DEV(y));

    wxRGBToColour(*col, pixelcolor);

    return TRUE;
}

void wxDC::DoCrossHair(wxCoord x, wxCoord y)
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    wxCoord x1 = x-VIEWPORT_EXTENT;
    wxCoord y1 = y-VIEWPORT_EXTENT;
    wxCoord x2 = x+VIEWPORT_EXTENT;
    wxCoord y2 = y+VIEWPORT_EXTENT;

    (void)MoveToEx(GetHdc(), XLOG2DEV(x1), YLOG2DEV(y), NULL);
    (void)LineTo(GetHdc(), XLOG2DEV(x2), YLOG2DEV(y));

    (void)MoveToEx(GetHdc(), XLOG2DEV(x), YLOG2DEV(y1), NULL);
    (void)LineTo(GetHdc(), XLOG2DEV(x), YLOG2DEV(y2));

    CalcBoundingBox(x1, y1);
    CalcBoundingBox(x2, y2);
}

void wxDC::DoDrawLine(wxCoord x1, wxCoord y1, wxCoord x2, wxCoord y2)
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    (void)MoveToEx(GetHdc(), XLOG2DEV(x1), YLOG2DEV(y1), NULL);
    (void)LineTo(GetHdc(), XLOG2DEV(x2), YLOG2DEV(y2));

    CalcBoundingBox(x1, y1);
    CalcBoundingBox(x2, y2);
}

// Draws an arc of a circle, centred on (xc, yc), with starting point (x1, y1)
// and ending at (x2, y2)
void wxDC::DoDrawArc(wxCoord x1, wxCoord y1,
                     wxCoord x2, wxCoord y2,
                     wxCoord xc, wxCoord yc)
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    wxColourChanger cc(*this); // needed for wxSTIPPLE_MASK_OPAQUE handling

    double dx = xc - x1;
    double dy = yc - y1;
    double radius = (double)sqrt(dx*dx+dy*dy);
    wxCoord r = (wxCoord)radius;

    // treat the special case of full circle separately
    if ( x1 == x2 && y1 == y2 )
    {
        DrawEllipse(xc - r, yc - r, 2*r, 2*r);
        return;
    }

    wxCoord xx1 = XLOG2DEV(x1);
    wxCoord yy1 = YLOG2DEV(y1);
    wxCoord xx2 = XLOG2DEV(x2);
    wxCoord yy2 = YLOG2DEV(y2);
    wxCoord xxc = XLOG2DEV(xc);
    wxCoord yyc = YLOG2DEV(yc);
    wxCoord ray = (wxCoord) sqrt(double((xxc-xx1)*(xxc-xx1)+(yyc-yy1)*(yyc-yy1)));

    wxCoord xxx1 = (wxCoord) (xxc-ray);
    wxCoord yyy1 = (wxCoord) (yyc-ray);
    wxCoord xxx2 = (wxCoord) (xxc+ray);
    wxCoord yyy2 = (wxCoord) (yyc+ray);

    if ( m_brush.Ok() && m_brush.GetStyle() != wxTRANSPARENT )
    {
        // Have to add 1 to bottom-right corner of rectangle
        // to make semi-circles look right (crooked line otherwise).
        // Unfortunately this is not a reliable method, depends
        // on the size of shape.
        // TODO: figure out why this happens!
        Pie(GetHdc(),xxx1,yyy1,xxx2+1,yyy2+1, xx1,yy1,xx2,yy2);
    }
    else
    {
        Arc(GetHdc(),xxx1,yyy1,xxx2,yyy2, xx1,yy1,xx2,yy2);
    }

    CalcBoundingBox(xc - r, yc - r);
    CalcBoundingBox(xc + r, yc + r);
}

void wxDC::DoDrawCheckMark(wxCoord x1, wxCoord y1,
                           wxCoord width, wxCoord height)
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    wxCoord x2 = x1 + width,
            y2 = y1 + height;

#if defined(__WIN32__) && !defined(__SC__) && !defined(__WXMICROWIN__)
    RECT rect;
    rect.left   = x1;
    rect.top    = y1;
    rect.right  = x2;
    rect.bottom = y2;

    DrawFrameControl(GetHdc(), &rect, DFC_MENU, DFCS_MENUCHECK);
#else // Win16
    // In WIN16, draw a cross
    HPEN blackPen = ::CreatePen(PS_SOLID, 1, RGB(0, 0, 0));
    HPEN whiteBrush = (HPEN)::GetStockObject(WHITE_BRUSH);
    HPEN hPenOld = (HPEN)::SelectObject(GetHdc(), blackPen);
    HPEN hBrushOld = (HPEN)::SelectObject(GetHdc(), whiteBrush);
    ::SetROP2(GetHdc(), R2_COPYPEN);
    Rectangle(GetHdc(), x1, y1, x2, y2);
    MoveToEx(GetHdc(), x1, y1, NULL);
    LineTo(GetHdc(), x2, y2);
    MoveToEx(GetHdc(), x2, y1, NULL);
    LineTo(GetHdc(), x1, y2);
    ::SelectObject(GetHdc(), hPenOld);
    ::SelectObject(GetHdc(), hBrushOld);
    ::DeleteObject(blackPen);
#endif // Win32/16

    CalcBoundingBox(x1, y1);
    CalcBoundingBox(x2, y2);
}

void wxDC::DoDrawPoint(wxCoord x, wxCoord y)
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    COLORREF color = 0x00ffffff;
    if (m_pen.Ok())
    {
        color = m_pen.GetColour().GetPixel();
    }

    SetPixel(GetHdc(), XLOG2DEV(x), YLOG2DEV(y), color);

    CalcBoundingBox(x, y);
}

void wxDC::DoDrawPolygon(int n, wxPoint points[], wxCoord xoffset, wxCoord yoffset,int fillStyle)
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    wxColourChanger cc(*this); // needed for wxSTIPPLE_MASK_OPAQUE handling

    // Do things less efficiently if we have offsets
    if (xoffset != 0 || yoffset != 0)
    {
        POINT *cpoints = new POINT[n];
        int i;
        for (i = 0; i < n; i++)
        {
            cpoints[i].x = (int)(points[i].x + xoffset);
            cpoints[i].y = (int)(points[i].y + yoffset);

            CalcBoundingBox(cpoints[i].x, cpoints[i].y);
        }
        int prev = SetPolyFillMode(GetHdc(),fillStyle==wxODDEVEN_RULE?ALTERNATE:WINDING);
        (void)Polygon(GetHdc(), cpoints, n);
        SetPolyFillMode(GetHdc(),prev);
        delete[] cpoints;
    }
    else
    {
        int i;
        for (i = 0; i < n; i++)
            CalcBoundingBox(points[i].x, points[i].y);

        int prev = SetPolyFillMode(GetHdc(),fillStyle==wxODDEVEN_RULE?ALTERNATE:WINDING);
        (void)Polygon(GetHdc(), (POINT*) points, n);
        SetPolyFillMode(GetHdc(),prev);
    }
}

void wxDC::DoDrawLines(int n, wxPoint points[], wxCoord xoffset, wxCoord yoffset)
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    // Do things less efficiently if we have offsets
    if (xoffset != 0 || yoffset != 0)
    {
        POINT *cpoints = new POINT[n];
        int i;
        for (i = 0; i < n; i++)
        {
            cpoints[i].x = (int)(points[i].x + xoffset);
            cpoints[i].y = (int)(points[i].y + yoffset);

            CalcBoundingBox(cpoints[i].x, cpoints[i].y);
        }
        (void)Polyline(GetHdc(), cpoints, n);
        delete[] cpoints;
    }
    else
    {
        int i;
        for (i = 0; i < n; i++)
            CalcBoundingBox(points[i].x, points[i].y);

        (void)Polyline(GetHdc(), (POINT*) points, n);
    }
}

void wxDC::DoDrawRectangle(wxCoord x, wxCoord y, wxCoord width, wxCoord height)
{
#ifdef __WXMICROWIN__
    if (!GetHDC()) return;
#endif

    wxColourChanger cc(*this); // needed for wxSTIPPLE_MASK_OPAQUE handling

    wxCoord x2 = x + width;
    wxCoord y2 = y + height;

    if ((m_logicalFunction == wxCOPY) && (m_pen.GetStyle() == wxTRANSPARENT))
    {
        RECT rect;
        rect.left = XLOG2DEV(x);
        rect.top = YLOG2DEV(y);
        rect.right = XLOG2DEV(x2);
        rect.bottom = YLOG2DEV(y2);
        (void)FillRect(GetHdc(), &rect, (HBRUSH)m_brush.GetResourceHandle() );
    }
    else
    {
        // Windows draws the filled rectangles without outline (i.e. drawn with a
        // transparent pen) one pixel smaller in both directions and we want them
        // to have the same size regardless of which pen is used - adjust