added multisampling (anti-aliasing) support to wxGLCanvas (#9145)

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@54022 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

docs/changes.txt

@@ -292,6 +292,7 @@ All (GUI):
 - Added wxWindow::Show/HideWithEffect()
 - Added wxWrapSizer (Arne Steinarson)
 - Added wxSpinCtrlDouble (John Labenski)
+- Added multisample (anti-aliasing) support to wxGLCanvas (Olivier Playez).
 - Added wxNativeContainerWindow to allow embedding wx into native windows
 - Added custom controls support to wxFileDialog (Diaa Sami and Marcin Wojdyr)
 - Added wxDC::StretchBlit() for wxMac and wxMSW (Vince Harron).

include/wx/glcanvas.h

@@ -47,7 +47,9 @@ enum
     WX_GL_MIN_ACCUM_RED,   // use red accum buffer with most bits (> MIN_ACCUM_RED bits)
     WX_GL_MIN_ACCUM_GREEN, // use green buffer with most bits (> MIN_ACCUM_GREEN bits)
     WX_GL_MIN_ACCUM_BLUE,  // use blue buffer with most bits (> MIN_ACCUM_BLUE bits)
-    WX_GL_MIN_ACCUM_ALPHA  // use alpha buffer with most bits (> MIN_ACCUM_ALPHA bits)
+    WX_GL_MIN_ACCUM_ALPHA, // use alpha buffer with most bits (> MIN_ACCUM_ALPHA bits)
+    WX_GL_SAMPLE_BUFFERS,  // 1 for multisampling support (antialiasing)
+    WX_GL_SAMPLES          // 4 for 2x2 antialising supersampling on most graphics cards
 };
 
 #define wxGLCanvasName _T("GLCanvas")
@@ -121,6 +123,13 @@ public:
     bool SetColour(const wxString& colour);
 
 
+    // return true if the extension with given name is supported
+    //
+    // notice that while this function is implemented for all of GLX, WGL and
+    // AGL the extensions names are usually not the same for different
+    // platforms and so the code using it still usually uses conditional
+    // compilation
+    static bool IsExtensionSupported(const char *extension);
 
     // deprecated methods using the implicit wxGLContext
 #if WXWIN_COMPATIBILITY_2_8
@@ -145,6 +154,10 @@ protected:
     // (not supported in most ports)
     virtual wxPalette CreateDefaultPalette() { return wxNullPalette; }
 
+    // check if the given extension name is present in the space-separated list
+    // of extensions supported by the current implementation such as returned
+    // by glXQueryExtensionsString() or glGetString(GL_EXTENSIONS)
+    static bool IsExtensionInList(const char *list, const char *extension);
 
     wxPalette m_palette;
 

include/wx/mac/carbon/glcanvas.h

@@ -67,6 +67,9 @@ public:
     // Mac-specific functions
     // ----------------------
 
+    // return true if multisample extension is supported
+    static bool IsAGLMultiSampleAvailable();
+
     // return the pixel format used by this window
     AGLPixelFormat GetAGLPixelFormat() const { return m_aglFormat; }
 

include/wx/msw/glcanvas.h

@@ -141,10 +141,11 @@ protected:
     // HDC for this window, we keep it all the time
     HDC m_hDC;
 
+    void wxGLCanvas::DestroyWindowPFD(wxWindow *parent);
+
 private:
     DECLARE_EVENT_TABLE()
     DECLARE_CLASS(wxGLCanvas)
 };
 
 #endif // _WX_GLCANVAS_H_
-

include/wx/unix/glx11.h

@@ -66,6 +66,9 @@ public:
     // return GLX version: 13 means 1.3 &c
     static int GetGLXVersion();
 
+    // return true if multisample extension is available
+    static bool IsGLXMultiSampleAvailable();
+
     // get the X11 handle of this window
     virtual Window GetXWindow() const = 0;
 

interface/glcanvas.h

@@ -126,7 +126,13 @@ enum
     WX_GL_MIN_ACCUM_BLUE,
 
     /// Specifies minimal number of alpha accumulator bits.
-    WX_GL_MIN_ACCUM_ALPHA
+    WX_GL_MIN_ACCUM_ALPHA,
+
+    /// 1 for multisampling support (antialiasing)
+    WX_GL_SAMPLE_BUFFERS,
+
+    /// 4 for 2x2 antialising supersampling on most graphics cards
+    WX_GL_SAMPLES
 
 };
 

src/common/glcmn.cpp

@@ -115,5 +115,29 @@ void wxGLCanvasBase::OnSize(wxSizeEvent& WXUNUSED(event))
 
 #endif // WXWIN_COMPATIBILITY_2_8
 
+/* static */
+bool wxGLCanvasBase::IsExtensionInList(const char *list, const char *extension)
+{
+    for ( const char *p = list; *p; p++ )
+    {
+        // advance up to the next possible match
+        p = wxStrstr(p, extension);
+        if ( !p )
+            break;
+
+        // check that the extension appears at the beginning/ending of the list
+        // or is preceded/followed by a space to avoid mistakenly finding
+        // "glExtension" in a list containing some "glFunkyglExtension"
+        if ( (p == list || p[-1] == ' ') )
+        {
+            char c = p[strlen(extension)];
+            if ( c == '\0' || c == ' ' )
+                return true;
+        }
+    }
+
+    return false;
+}
+
 #endif // wxUSE_GLCANVAS
 

src/mac/carbon/glcanvas.cpp

@@ -165,6 +165,34 @@ wxGLCanvas::wxGLCanvas(wxWindow *parent,
 
 #endif // WXWIN_COMPATIBILITY_2_8
 
+/* static */
+bool wxGLCanvasBase::IsExtensionSupported(const char *extension)
+{
+    // we need a valid context to query for extensions.
+    const GLint defaultAttribs[] = { AGL_RGBA, AGL_DOUBLEBUFFER, AGL_NONE };
+    AGLPixelFormat fmt = aglChoosePixelFormat(NULL, 0, defaultAttribs);
+    AGLContext ctx = aglCreateContext(fmt, NULL);
+    if ( !ctx )
+        return false;
+
+    wxString extensions = wxString::FromAscii(glGetString(GL_EXTENSIONS));
+
+    aglDestroyPixelFormat(fmt);
+    aglDestroyContext(ctx);
+
+    return IsExtensionInList(extensions, extension);
+}
+
+/* static */
+bool wxGLCanvas::IsAGLMultiSampleAvailable()
+{
+    static int s_isMultiSampleAvailable = -1;
+    if ( s_isMultiSampleAvailable == -1 )
+        s_isMultiSampleAvailable = IsExtensionSupported("GL_ARB_multisample");
+
+    return s_isMultiSampleAvailable != 0;
+}
+
 static AGLPixelFormat ChoosePixelFormat(const int *attribList)
 {
     GLint data[512];
@@ -271,6 +299,36 @@ static AGLPixelFormat ChoosePixelFormat(const int *attribList)
                     data[p++] = AGL_ACCUM_ALPHA_SIZE;
                     data[p++] = attribList[arg++];
                     break;
+
+                case WX_GL_SAMPLE_BUFFERS:
+                    if ( !wxGLCanvas::IsAGLMultiSampleAvailable() )
+                    {
+                        if ( !attribList[arg++] )
+                            break;
+
+                        return false;
+                    }
+
+                    data[p++] = AGL_SAMPLE_BUFFERS_ARB;
+                    if ( (data[p++] = attribList[arg++]) == true )
+                    {
+                        // don't use software fallback
+                        data[p++] = AGL_NO_RECOVERY;
+                    }
+                    break;
+
+                case WX_GL_SAMPLES:
+                    if ( !wxGLCanvas::IsAGLMultiSampleAvailable() )
+                    {
+                        if ( !attribList[arg++] )
+                            break;
+
+                        return false;
+                    }
+
+                    data[p++] = AGL_SAMPLES_ARB;
+                    data[p++] = attribList[arg++];
+                    break;
             }
         }
 

src/msw/glcanvas.cpp

@@ -46,6 +46,67 @@ LRESULT WXDLLEXPORT APIENTRY _EXPORT wxWndProc(HWND hWnd, UINT message,
     #define WXUNUSED_WITHOUT_GL_EXT_vertex_array(name) WXUNUSED(name)
 #endif
 
+// ----------------------------------------------------------------------------
+// define possibly missing WGL constants
+// ----------------------------------------------------------------------------
+
+#ifndef WGL_ARB_pixel_format
+#define WGL_NUMBER_PIXEL_FORMATS_ARB      0x2000
+#define WGL_DRAW_TO_WINDOW_ARB            0x2001
+#define WGL_DRAW_TO_BITMAP_ARB            0x2002
+#define WGL_ACCELERATION_ARB              0x2003
+#define WGL_NEED_PALETTE_ARB              0x2004
+#define WGL_NEED_SYSTEM_PALETTE_ARB       0x2005
+#define WGL_SWAP_LAYER_BUFFERS_ARB        0x2006
+#define WGL_SWAP_METHOD_ARB               0x2007
+#define WGL_NUMBER_OVERLAYS_ARB           0x2008
+#define WGL_NUMBER_UNDERLAYS_ARB          0x2009
+#define WGL_TRANSPARENT_ARB               0x200A
+#define WGL_TRANSPARENT_RED_VALUE_ARB     0x2037
+#define WGL_TRANSPARENT_GREEN_VALUE_ARB   0x2038
+#define WGL_TRANSPARENT_BLUE_VALUE_ARB    0x2039
+#define WGL_TRANSPARENT_ALPHA_VALUE_ARB   0x203A
+#define WGL_TRANSPARENT_INDEX_VALUE_ARB   0x203B
+#define WGL_SHARE_DEPTH_ARB               0x200C
+#define WGL_SHARE_STENCIL_ARB             0x200D
+#define WGL_SHARE_ACCUM_ARB               0x200E
+#define WGL_SUPPORT_GDI_ARB               0x200F
+#define WGL_SUPPORT_OPENGL_ARB            0x2010
+#define WGL_DOUBLE_BUFFER_ARB             0x2011
+#define WGL_STEREO_ARB                    0x2012
+#define WGL_PIXEL_TYPE_ARB                0x2013
+#define WGL_COLOR_BITS_ARB                0x2014
+#define WGL_RED_BITS_ARB                  0x2015
+#define WGL_RED_SHIFT_ARB                 0x2016
+#define WGL_GREEN_BITS_ARB                0x2017
+#define WGL_GREEN_SHIFT_ARB               0x2018
+#define WGL_BLUE_BITS_ARB                 0x2019
+#define WGL_BLUE_SHIFT_ARB                0x201A
+#define WGL_ALPHA_BITS_ARB                0x201B
+#define WGL_ALPHA_SHIFT_ARB               0x201C
+#define WGL_ACCUM_BITS_ARB                0x201D
+#define WGL_ACCUM_RED_BITS_ARB            0x201E
+#define WGL_ACCUM_GREEN_BITS_ARB          0x201F
+#define WGL_ACCUM_BLUE_BITS_ARB           0x2020
+#define WGL_ACCUM_ALPHA_BITS_ARB          0x2021
+#define WGL_DEPTH_BITS_ARB                0x2022
+#define WGL_STENCIL_BITS_ARB              0x2023
+#define WGL_AUX_BUFFERS_ARB               0x2024
+#define WGL_NO_ACCELERATION_ARB           0x2025
+#define WGL_GENERIC_ACCELERATION_ARB      0x2026
+#define WGL_FULL_ACCELERATION_ARB         0x2027
+#define WGL_SWAP_EXCHANGE_ARB             0x2028
+#define WGL_SWAP_COPY_ARB                 0x2029
+#define WGL_SWAP_UNDEFINED_ARB            0x202A
+#define WGL_TYPE_RGBA_ARB                 0x202B
+#define WGL_TYPE_COLORINDEX_ARB           0x202C
+#endif
+
+#ifndef WGL_ARB_multisample
+#define WGL_SAMPLE_BUFFERS_ARB            0x2041
+#define WGL_SAMPLES_ARB                   0x2042
+#endif
+
 // ----------------------------------------------------------------------------
 // libraries
 // ----------------------------------------------------------------------------
@@ -322,15 +383,213 @@ bool wxGLCanvas::SwapBuffers()
     return true;
 }
 
+
+// ----------------------------------------------------------------------------
+// multi sample support
+// ----------------------------------------------------------------------------
+
+// this macro defines a variable of type "name_t" called "name" and initializes
+// it with the pointer to WGL function "name" (which may be NULL)
+#define wxDEFINE_WGL_FUNC(name) \
+    name##_t name = (name##_t)wglGetProcAddress(#name)
+
+/* static */
+bool wxGLCanvasBase::IsExtensionSupported(const char *extension)
+{
+    static const char *s_extensionsList = (char *)wxUIntPtr(-1);
+    if ( s_extensionsList == (char *)wxUIntPtr(-1) )
+    {
+        typedef const char * (WINAPI *wglGetExtensionsStringARB_t)(HDC hdc);
+
+        wxDEFINE_WGL_FUNC(wglGetExtensionsStringARB);
+        if ( wglGetExtensionsStringARB )
+        {
+            s_extensionsList = wglGetExtensionsStringARB(wglGetCurrentDC());
+        }
+        else
+        {
+            typedef const char * (WINAPI * wglGetExtensionsStringEXT_t)();
+
+            wxDEFINE_WGL_FUNC(wglGetExtensionsStringEXT);
+            if ( wglGetExtensionsStringEXT )
+            {
+                s_extensionsList = wglGetExtensionsStringEXT();
+            }
+            else
+            {
+                s_extensionsList = NULL;
+            }
+        }
+    }
+
+    return s_extensionsList && IsExtensionInList(s_extensionsList, extension);
+}
+
+// this is a wrapper around wglChoosePixelFormatARB(): returns the pixel format
+// index matching the given attributes on success or 0 on failure
+static int ChoosePixelFormatARB(HDC hdc, const int *attribList)
+{
+    if ( !wxGLCanvas::IsExtensionSupported("WGL_ARB_multisample") )
+        return 0;
+
+    typedef BOOL (WINAPI * wglChoosePixelFormatARB_t)
+                 (HDC hdc,
+                  const int *piAttribIList,
+                  const FLOAT *pfAttribFList,
+                  UINT nMaxFormats,
+                  int *piFormats,
+                  UINT *nNumFormats
+                 );
+
+    wxDEFINE_WGL_FUNC(wglChoosePixelFormatARB);
+    if ( !wglChoosePixelFormatARB )
+        return 0; // should not occur if extension is supported
+
+    int iAttributes[128];
+    int dst = 0; // index in iAttributes array
+
+    #define ADD_ATTR(attr, value) \
+        iAttributes[dst++] = attr; iAttributes[dst++] = value
+
+    ADD_ATTR( WGL_DRAW_TO_WINDOW_ARB,    GL_TRUE );
+    ADD_ATTR( WGL_SUPPORT_OPENGL_ARB,    GL_TRUE );
+    ADD_ATTR( WGL_ACCELERATION_ARB,      WGL_FULL_ACCELERATION_ARB );
+
+    if ( !attribList )
+    {
+        ADD_ATTR( WGL_COLOR_BITS_ARB,          24 );
+        ADD_ATTR( WGL_ALPHA_BITS_ARB,           8 );
+        ADD_ATTR( WGL_DEPTH_BITS_ARB,          16 );
+        ADD_ATTR( WGL_STENCIL_BITS_ARB,         0 );
+        ADD_ATTR( WGL_DOUBLE_BUFFER_ARB,  GL_TRUE );
+        ADD_ATTR( WGL_SAMPLE_BUFFERS_ARB, GL_TRUE );
+        ADD_ATTR( WGL_SAMPLES_ARB,              4 );
+    }
+    else // have custom attributes
+    {
+        #define ADD_ATTR_VALUE(attr) ADD_ATTR(attr, attribList[src++])
+
+        int src = 0;
+        while ( attribList[src] )
+        {
+            switch ( attribList[src++] )
+            {
+                case WX_GL_RGBA:
+                    ADD_ATTR( WGL_COLOR_BITS_ARB, 24 );
+                    ADD_ATTR( WGL_ALPHA_BITS_ARB,  8 );
+                    break;
+
+                case WX_GL_BUFFER_SIZE:
+                    ADD_ATTR_VALUE( WGL_COLOR_BITS_ARB);
+                    break;
+
+                case WX_GL_LEVEL:
+                    if ( attribList[src] > 0 )
+                    {
+                        ADD_ATTR( WGL_NUMBER_OVERLAYS_ARB, 1 );
+                    }
+                    else if ( attribList[src] <0 )
+                    {
+                        ADD_ATTR( WGL_NUMBER_UNDERLAYS_ARB, 1 );
+                    }
+                    //else: ignore it
+
+                    src++; // skip the value in any case
+                    break;
+
+                case WX_GL_DOUBLEBUFFER:
+                    ADD_ATTR( WGL_DOUBLE_BUFFER_ARB, GL_TRUE );
+                    break;
+
+                case WX_GL_STEREO:
+                    ADD_ATTR( WGL_STEREO_ARB, GL_TRUE );
+                    break;
+
+                case WX_GL_AUX_BUFFERS:
+                    ADD_ATTR_VALUE( WGL_AUX_BUFFERS_ARB );
+                    break;
+
+                case WX_GL_MIN_RED:
+                    ADD_ATTR_VALUE( WGL_RED_BITS_ARB );
+                    break;
+
+                case WX_GL_MIN_GREEN:
+                    ADD_ATTR_VALUE( WGL_GREEN_BITS_ARB );
+                    break;
+
+                case WX_GL_MIN_BLUE:
+                    ADD_ATTR_VALUE( WGL_BLUE_BITS_ARB );
+                    break;
+
+                case WX_GL_MIN_ALPHA:
+                    ADD_ATTR_VALUE( WGL_ALPHA_BITS_ARB );
+                   break;
+
+                case WX_GL_DEPTH_SIZE:
+                    ADD_ATTR_VALUE( WGL_DEPTH_BITS_ARB );
+                    break;
+
+                case WX_GL_STENCIL_SIZE:
+                    ADD_ATTR_VALUE( WGL_STENCIL_BITS_ARB );
+                    break;
+
+               case WX_GL_MIN_ACCUM_RED:
+                    ADD_ATTR_VALUE( WGL_ACCUM_RED_BITS_ARB );
+                    break;
+
+                case WX_GL_MIN_ACCUM_GREEN:
+                    ADD_ATTR_VALUE( WGL_ACCUM_GREEN_BITS_ARB );
+                    break;
+
+                case WX_GL_MIN_ACCUM_BLUE:
+                    ADD_ATTR_VALUE( WGL_ACCUM_BLUE_BITS_ARB );
+                    break;
+
+                case WX_GL_MIN_ACCUM_ALPHA:
+                    ADD_ATTR_VALUE( WGL_ACCUM_ALPHA_BITS_ARB );
+                    break;
+
+                case WX_GL_SAMPLE_BUFFERS:
+                    ADD_ATTR_VALUE( WGL_SAMPLE_BUFFERS_ARB );
+                    break;
+
+                case WX_GL_SAMPLES:
+                    ADD_ATTR_VALUE( WGL_SAMPLES_ARB );
+                    break;
+            }
+        }
+
+        #undef ADD_ATTR_VALUE
+    }
+
+    #undef ADD_ATTR
+
+    iAttributes[dst++] = 0;
+
+    int pf;
+    UINT numFormats = 0;
+    if ( !wglChoosePixelFormatARB(hdc, iAttributes, NULL, 1, &pf, &numFormats) )
+    {
+        wxLogLastError(_T("wglChoosePixelFormatARB"));
+        return 0;
+    }
+
+    return pf;
+}
+
 // ----------------------------------------------------------------------------
 // pixel format stuff
 // ----------------------------------------------------------------------------
 
-static void
+// returns true if pfd was adjusted accordingly to attributes provided, false
+// if there is an error with attributes or -1 if the attributes indicate
+// features not supported by ChoosePixelFormat() at all (currently only multi
+// sampling)
+static int
 AdjustPFDForAttributes(PIXELFORMATDESCRIPTOR& pfd, const int *attribList)
 {
     if ( !attribList )
-        return;
+        return 1;
 
     // remove default attributes
     pfd.dwFlags &= ~PFD_DOUBLEBUFFER;
@@ -411,8 +670,14 @@ AdjustPFDForAttributes(PIXELFORMATDESCRIPTOR& pfd, const int *attribList)
             case WX_GL_MIN_ACCUM_ALPHA:
                 pfd.cAccumBits += (pfd.cAccumAlphaBits = attribList[arg++]);
                 break;
+
+            case WX_GL_SAMPLE_BUFFERS:
+            case WX_GL_SAMPLES:
+                return -1;
         }
     }
+
+    return 1;
 }
 
 /* static */
@@ -448,9 +713,25 @@ wxGLCanvas::ChooseMatchingPixelFormat(HDC hdc,
     else
         *ppfd = pfd;
 
-    AdjustPFDForAttributes(*ppfd, attribList);
+    // adjust the PFD using the provided attributes and also check if we can
+    // use PIXELFORMATDESCRIPTOR at all: if multisampling is requested, we
+    // can't as it's not supported by ChoosePixelFormat()
+    switch ( AdjustPFDForAttributes(*ppfd, attribList) )
+    {
+        case 1:
+            return ::ChoosePixelFormat(hdc, ppfd);
 
-    return ::ChoosePixelFormat(hdc, ppfd);
+        default:
+            wxFAIL_MSG( "unexpected AdjustPFDForAttributes() return value" );
+            // fall through
+
+        case 0:
+            // error in attributes
+            return 0;
+
+        case -1:
+            return ::ChoosePixelFormatARB(hdc, attribList);
+    }
 }
 
 /* static */
@@ -545,13 +826,12 @@ wxPalette wxGLCanvas::CreateDefaultPalette()
     pPal->palNumEntries = (WORD)paletteSize;
 
     /* build a simple RGB color palette */
-    {
     int redMask = (1 << pfd.cRedBits) - 1;
     int greenMask = (1 << pfd.cGreenBits) - 1;
     int blueMask = (1 << pfd.cBlueBits) - 1;
-    int i;
 
-    for (i=0; i<paletteSize; ++i) {
+    for (int i=0; i<paletteSize; ++i)
+    {
         pPal->palPalEntry[i].peRed =
             (BYTE)((((i >> pfd.cRedShift) & redMask) * 255) / redMask);
         pPal->palPalEntry[i].peGreen =
@@ -560,7 +840,6 @@ wxPalette wxGLCanvas::CreateDefaultPalette()
             (BYTE)((((i >> pfd.cBlueShift) & blueMask) * 255) / blueMask);
         pPal->palPalEntry[i].peFlags = 0;
     }
-    }
 
     HPALETTE hPalette = CreatePalette(pPal);
     free(pPal);

src/unix/glx11.cpp

@@ -122,6 +122,26 @@ wxGLCanvasX11::~wxGLCanvasX11()
 // working with GL attributes
 // ----------------------------------------------------------------------------
 
+/* static */
+bool wxGLCanvasBase::IsExtensionSupported(const char *extension)
+{
+    Display * const dpy = wxGetX11Display();
+
+    return IsExtensionInList(glXQueryExtensionsString(dpy, DefaultScreen(dpy)),
+                             extension);
+}
+
+
+/* static */
+bool wxGLCanvasX11::IsGLXMultiSampleAvailable()
+{
+    static int s_isMultiSampleAvailable = -1;
+    if ( s_isMultiSampleAvailable == -1 )
+        s_isMultiSampleAvailable = IsExtensionSupported("GLX_ARB_multisample");
+
+    return s_isMultiSampleAvailable != 0;
+}
+
 bool
 wxGLCanvasX11::ConvertWXAttrsToGL(const int *wxattrs, int *glattrs, size_t n)
 {
@@ -257,6 +277,32 @@ wxGLCanvasX11::ConvertWXAttrsToGL(const int *wxattrs, int *glattrs, size_t n)
                     glattrs[p++] = GLX_ACCUM_ALPHA_SIZE;
                     break;
 
+                case WX_GL_SAMPLE_BUFFERS:
+                    if ( !IsGLXMultiSampleAvailable() )
+                    {
+                        // if it was specified just to disable it, no problem
+                        if ( !wxattrs[arg++] )
+                            continue;
+
+                        // otherwise indicate that it's not supported
+                        return false;
+                    }
+
+                    glattrs[p++] = GLX_SAMPLE_BUFFERS_ARB;
+                    break;
+
+                case WX_GL_SAMPLES:
+                    if ( !IsGLXMultiSampleAvailable() )
+                    {
+                        if ( !wxattrs[arg++] )
+                            continue;
+
+                        return false;
+                    }
+
+                    glattrs[p++] = GLX_SAMPLES_ARB;
+                    break;
+
                 default:
                     wxLogDebug(_T("Unsupported OpenGL attribute %d"),
                                wxattrs[arg - 1]);