src/msw/dcclient.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        dcclient.cpp
   3 // Purpose:     wxClientDC class
   4 // Author:      Julian Smart
   5 // Modified by:
   6 // Created:     01/02/97
   7 // RCS-ID:      $Id$
   8 // Copyright:   (c) Julian Smart and Markus Holzem
   9 // Licence:     wxWindows licence
  10 /////////////////////////////////////////////////////////////////////////////
  11
  12 // ===========================================================================
  13 // declarations
  14 // ===========================================================================
  15
  16 // ----------------------------------------------------------------------------
  17 // headers
  18 // ----------------------------------------------------------------------------
  19
  20 #ifdef __GNUG__
  21     #pragma implementation "dcclient.h"
  22 #endif
  23
  24 // For compilers that support precompilation, includes "wx.h".
  25 #include "wx/wxprec.h"
  26
  27 #ifdef __BORLANDC__
  28     #pragma hdrstop
  29 #endif
  30
  31 #include "wx/string.h"
  32 #include "wx/log.h"
  33 #include "wx/window.h"
  34
  35 #include "wx/msw/private.h"
  36
  37 #include "wx/dcclient.h"
  38
  39 // ----------------------------------------------------------------------------
  40 // array/list types
  41 // ----------------------------------------------------------------------------
  42
  43 struct WXDLLEXPORT wxPaintDCInfo
  44 {
  45     wxPaintDCInfo(wxWindow *win, wxDC *dc)
  46     {
  47         hwnd = win->GetHWND();
  48         hdc = dc->GetHDC();
  49         count = 1;
  50     }
  51
  52     WXHWND    hwnd;       // window for this DC
  53     WXHDC     hdc;        // the DC handle
  54     size_t    count;      // usage count
  55 };
  56
  57 #include "wx/arrimpl.cpp"
  58
  59 WX_DEFINE_OBJARRAY(wxArrayDCInfo);
  60
  61 // ----------------------------------------------------------------------------
  62 // macros
  63 // ----------------------------------------------------------------------------
  64
  65 #if !USE_SHARED_LIBRARY
  66     IMPLEMENT_DYNAMIC_CLASS(wxWindowDC, wxDC)
  67     IMPLEMENT_DYNAMIC_CLASS(wxClientDC, wxWindowDC)
  68     IMPLEMENT_DYNAMIC_CLASS(wxPaintDC, wxWindowDC)
  69 #endif
  70
  71 // ----------------------------------------------------------------------------
  72 // global variables
  73 // ----------------------------------------------------------------------------
  74
  75 static PAINTSTRUCT g_paintStruct;
  76
  77 #ifdef __WXDEBUG__
  78     // a global variable which we check to verify that wxPaintDC are only
  79     // created in resopnse to WM_PAINT message - doing this from elsewhere is a
  80     // common programming error among wxWindows programmers and might lead to
  81     // very subtle and difficult to debug refresh/repaint bugs.
  82     bool g_isPainting = FALSE;
  83 #endif // __WXDEBUG__
  84
  85 // ===========================================================================
  86 // implementation
  87 // ===========================================================================
  88
  89 // ----------------------------------------------------------------------------
  90 // wxWindowDC
  91 // ----------------------------------------------------------------------------
  92
  93 wxWindowDC::wxWindowDC()
  94 {
  95   m_canvas = NULL;
  96 }
  97
  98 wxWindowDC::wxWindowDC(wxWindow *the_canvas)
  99 {
 100   m_canvas = the_canvas;
 101   m_hDC = (WXHDC) ::GetWindowDC(GetWinHwnd(the_canvas) );
 102   m_hDCCount++;
 103
 104   SetBackground(wxBrush(m_canvas->GetBackgroundColour(), wxSOLID));
 105 }
 106
 107 wxWindowDC::~wxWindowDC()
 108 {
 109   if (m_canvas && m_hDC)
 110   {
 111     SelectOldObjects(m_hDC);
 112
 113     ::ReleaseDC(GetWinHwnd(m_canvas), GetHdc());
 114     m_hDC = 0;
 115   }
 116
 117   m_hDCCount--;
 118 }
 119
 120 // ----------------------------------------------------------------------------
 121 // wxClientDC
 122 // ----------------------------------------------------------------------------
 123
 124 wxClientDC::wxClientDC()
 125 {
 126   m_canvas = NULL;
 127 }
 128
 129 wxClientDC::wxClientDC(wxWindow *the_canvas)
 130 {
 131   m_canvas = the_canvas;
 132   m_hDC = (WXHDC) ::GetDC(GetWinHwnd(the_canvas));
 133
 134   SetBackground(wxBrush(m_canvas->GetBackgroundColour(), wxSOLID));
 135 }
 136
 137 wxClientDC::~wxClientDC()
 138 {
 139   if ( m_canvas && GetHdc() )
 140   {
 141     SelectOldObjects(m_hDC);
 142
 143     ::ReleaseDC(GetWinHwnd(m_canvas), GetHdc());
 144     m_hDC = 0;
 145   }
 146 }
 147
 148 // ----------------------------------------------------------------------------
 149 // wxPaintDC
 150 // ----------------------------------------------------------------------------
 151
 152 // VZ: initial implementation (by JACS) only remembered the last wxPaintDC
 153 //     created and tried to reuse - this was supposed to take care of a
 154 //     situation when a derived class OnPaint() calls base class OnPaint()
 155 //     because in this case ::BeginPaint() shouldn't be called second time.
 156 //
 157 //     I'm not sure how useful this is, however we must remember the HWND
 158 //     associated with the last HDC as well - otherwise we may (and will!) try
 159 //     to reuse the HDC for another HWND which is a nice recipe for disaster.
 160 //
 161 //     So we store a list of windows for which we already have the DC and not
 162 //     just one single hDC. This seems to work, but I'm really not sure about
 163 //     the usefullness of the whole idea - IMHO it's much better to not call
 164 //     base class OnPaint() at all, or, if we really want to allow it, add a
 165 //     "wxPaintDC *" parameter to wxPaintEvent which should be used if it's
 166 //     !NULL instead of creating a new DC.
 167
 168 wxArrayDCInfo wxPaintDC::ms_cache;
 169
 170 wxPaintDC::wxPaintDC()
 171 {
 172     m_canvas = NULL;
 173     m_hDC = 0;
 174 }
 175
 176 wxPaintDC::wxPaintDC(wxWindow *canvas)
 177 {
 178     wxCHECK_RET( canvas, _T("NULL canvas in wxPaintDC ctor") );
 179
 180 #ifdef __WXDEBUG__
 181     if ( !g_isPainting )
 182     {
 183         wxFAIL_MSG( _T("wxPaintDC may be created only in EVT_PAINT handler!") );
 184
 185         return;
 186     }
 187 #endif // __WXDEBUG__
 188
 189     m_canvas = canvas;
 190
 191     // do we have a DC for this window in the cache?
 192     wxPaintDCInfo *info = FindInCache();
 193     if ( info )
 194     {
 195         m_hDC = info->hdc;
 196         info->count++;
 197     }
 198     else // not in cache, create a new one
 199     {
 200         m_hDC = (WXHDC)::BeginPaint(GetWinHwnd(m_canvas), &g_paintStruct);
 201         ms_cache.Add(new wxPaintDCInfo(m_canvas, this));
 202     }
 203
 204     SetBackground(wxBrush(m_canvas->GetBackgroundColour(), wxSOLID));
 205 }
 206
 207 wxPaintDC::~wxPaintDC()
 208 {
 209     if ( m_hDC )
 210     {
 211         size_t index;
 212         wxPaintDCInfo *info = FindInCache(&index);
 213
 214         wxCHECK_RET( info, _T("existing DC should have a cache entry") );
 215
 216         if ( !--info->count )
 217         {
 218             ::EndPaint(GetWinHwnd(m_canvas), &g_paintStruct);
 219
 220             ms_cache.Remove(index);
 221         }
 222         //else: cached DC entry is still in use
 223     }
 224 }
 225
 226 wxPaintDCInfo *wxPaintDC::FindInCache(size_t *index) const
 227 {
 228     wxPaintDCInfo *info = NULL;
 229     size_t nCache = ms_cache.GetCount();
 230     for ( size_t n = 0; n < nCache; n++ )
 231     {
 232         info = &ms_cache[n];
 233         if ( info->hwnd == m_canvas->GetHWND() )
 234         {
 235             if ( index )
 236                 *index = n;
 237             break;
 238         }
 239     }
 240
 241     return info;
 242 }