X-Git-Url: https://git.saurik.com/wxWidgets.git/blobdiff_plain/c32a8bd4dbc7ce0acb5e22e5558f66a566b23cc8..4164a04a98be1066038317c2d16438cce3f59c81:/src/common/dobjcmn.cpp

diff --git a/src/common/dobjcmn.cpp b/src/common/dobjcmn.cpp
index 6a40f0b1d9..7925041420 100644
--- a/src/common/dobjcmn.cpp
+++ b/src/common/dobjcmn.cpp
@@ -1,38 +1,30 @@
 ///////////////////////////////////////////////////////////////////////////////
-// Name:        common/dobjcmn.cpp
+// Name:        src/common/dobjcmn.cpp
 // Purpose:     implementation of data object methods common to all platforms
 // Author:      Vadim Zeitlin, Robert Roebling
 // Modified by:
 // Created:     19.10.99
 // RCS-ID:      $Id$
-// Copyright:   (c) wxWindows Team
-// Licence:     wxWindows license
+// Copyright:   (c) wxWidgets Team
+// Licence:     wxWindows licence
 ///////////////////////////////////////////////////////////////////////////////
 
-// ============================================================================
-// declarations
-// ============================================================================
-
-// ----------------------------------------------------------------------------
-// headers
-// ----------------------------------------------------------------------------
-
-#ifdef __GNUG__
-    #pragma implementation "dataobjbase.h"
-#endif
-
+// For compilers that support precompilation, includes "wx.h".
 #include "wx/wxprec.h"
 
 #ifdef __BORLANDC__
     #pragma hdrstop
 #endif
 
+#if wxUSE_DATAOBJ
+
+#include "wx/dataobj.h"
+
 #ifndef WX_PRECOMP
     #include "wx/app.h"
-    #include "wx/debug.h"
-#endif // WX_PRECOMP
+#endif
 
-#include "wx/dataobj.h"
+#include "wx/textbuf.h"
 
 // ----------------------------------------------------------------------------
 // lists
@@ -40,14 +32,14 @@
 
 #include "wx/listimpl.cpp"
 
-WX_DEFINE_LIST(wxSimpleDataObjectList);
+WX_DEFINE_LIST(wxSimpleDataObjectList)
 
 // ----------------------------------------------------------------------------
 // globals
 // ----------------------------------------------------------------------------
 
 static wxDataFormat dataFormatInvalid;
-const wxDataFormat& wxFormatInvalid = dataFormatInvalid;
+WXDLLEXPORT const wxDataFormat& wxFormatInvalid = dataFormatInvalid;
 
 // ============================================================================
 // implementation
@@ -61,27 +53,62 @@ wxDataObjectBase::~wxDataObjectBase()
 {
 }
 
+bool wxDataObjectBase::IsSupported(const wxDataFormat& format,
+                                   Direction dir) const
+{
+    size_t nFormatCount = GetFormatCount( dir );
+    if ( nFormatCount == 1 )
+    {
+        return format == GetPreferredFormat( dir );
+    }
+    else
+    {
+        wxDataFormat *formats = new wxDataFormat[nFormatCount];
+        GetAllFormats( formats, dir );
+
+        size_t n;
+        for ( n = 0; n < nFormatCount; n++ )
+        {
+            if ( formats[n] == format )
+                break;
+        }
+
+        delete [] formats;
+
+        // found?
+        return n < nFormatCount;
+    }
+}
+
 // ----------------------------------------------------------------------------
 // wxDataObjectComposite
 // ----------------------------------------------------------------------------
 
+wxDataObjectComposite::wxDataObjectComposite()
+{
+    m_preferred = 0;
+    m_receivedFormat = wxFormatInvalid;
+}
+
+wxDataObjectComposite::~wxDataObjectComposite()
+{
+    WX_CLEAR_LIST( wxSimpleDataObjectList, m_dataObjects );
+}
+
 wxDataObjectSimple *
-wxDataObjectComposite::GetObject(const wxDataFormat& format) const
+wxDataObjectComposite::GetObject(const wxDataFormat& format, wxDataObjectBase::Direction dir) const
 {
-    wxSimpleDataObjectList::Node *node = m_dataObjects.GetFirst();
+    wxSimpleDataObjectList::compatibility_iterator node = m_dataObjects.GetFirst();
+
     while ( node )
     {
         wxDataObjectSimple *dataObj = node->GetData();
 
-        if ( dataObj->GetFormat() == format )
-        {
-            return dataObj;
-        }
-
+        if (dataObj->IsSupported(format,dir))
+          return dataObj;
         node = node->GetNext();
     }
-
-    return (wxDataObjectSimple *)NULL;
+    return NULL;
 }
 
 void wxDataObjectComposite::Add(wxDataObjectSimple *dataObject, bool preferred)
@@ -92,10 +119,15 @@ void wxDataObjectComposite::Add(wxDataObjectSimple *dataObject, bool preferred)
     m_dataObjects.Append( dataObject );
 }
 
+wxDataFormat wxDataObjectComposite::GetReceivedFormat() const
+{
+    return m_receivedFormat;
+}
+
 wxDataFormat
 wxDataObjectComposite::GetPreferredFormat(Direction WXUNUSED(dir)) const
 {
-    wxSimpleDataObjectList::Node *node = m_dataObjects.Item( m_preferred );
+    wxSimpleDataObjectList::compatibility_iterator node = m_dataObjects.Item( m_preferred );
 
     wxCHECK_MSG( node, wxFormatInvalid, wxT("no preferred format") );
 
@@ -104,21 +136,72 @@ wxDataObjectComposite::GetPreferredFormat(Direction WXUNUSED(dir)) const
     return dataObj->GetFormat();
 }
 
-size_t wxDataObjectComposite::GetFormatCount(Direction WXUNUSED(dir)) const
+#if defined(__WXMSW__)
+
+size_t wxDataObjectComposite::GetBufferOffset( const wxDataFormat& format )
 {
-    // TODO what about the Get/Set only formats?
-    return m_dataObjects.GetCount();
+    wxDataObjectSimple *dataObj = GetObject(format);
+
+    wxCHECK_MSG( dataObj, 0,
+                 wxT("unsupported format in wxDataObjectComposite"));
+
+    return dataObj->GetBufferOffset( format );
 }
 
-void wxDataObjectComposite::GetAllFormats(wxDataFormat *formats,
-                                          Direction WXUNUSED(dir)) const
+
+const void* wxDataObjectComposite::GetSizeFromBuffer( const void* buffer,
+                                                      size_t* size,
+                                                      const wxDataFormat& format )
+{
+    wxDataObjectSimple *dataObj = GetObject(format);
+
+    wxCHECK_MSG( dataObj, NULL,
+                 wxT("unsupported format in wxDataObjectComposite"));
+
+    return dataObj->GetSizeFromBuffer( buffer, size, format );
+}
+
+
+void* wxDataObjectComposite::SetSizeInBuffer( void* buffer, size_t size,
+                                              const wxDataFormat& format )
+{
+    wxDataObjectSimple *dataObj = GetObject( format );
+
+    wxCHECK_MSG( dataObj, NULL,
+                 wxT("unsupported format in wxDataObjectComposite"));
+
+    return dataObj->SetSizeInBuffer( buffer, size, format );
+}
+
+#endif
+
+size_t wxDataObjectComposite::GetFormatCount(Direction dir) const
 {
     size_t n = 0;
-    wxSimpleDataObjectList::Node *node;
+
+    // NOTE: some wxDataObjectSimple objects may return a number greater than 1
+    //       from GetFormatCount(): this is the case of e.g. wxTextDataObject
+    //       under wxMac and wxGTK
+    wxSimpleDataObjectList::compatibility_iterator node;
+    for ( node = m_dataObjects.GetFirst(); node; node = node->GetNext() )
+        n += node->GetData()->GetFormatCount(dir);
+
+    return n;
+}
+
+void wxDataObjectComposite::GetAllFormats(wxDataFormat *formats,
+                                          Direction dir) const
+{
+    size_t index(0);
+    wxSimpleDataObjectList::compatibility_iterator node;
+
     for ( node = m_dataObjects.GetFirst(); node; node = node->GetNext() )
     {
-        // TODO if ( !outputOnlyToo ) && this one counts ...
-        formats[n++] = node->GetData()->GetFormat();
+        // NOTE: some wxDataObjectSimple objects may return more than 1 format
+        //       from GetAllFormats(): this is the case of e.g. wxTextDataObject
+        //       under wxMac and wxGTK
+        node->GetData()->GetAllFormats(formats+index, dir);
+        index += node->GetData()->GetFormatCount(dir);
     }
 }
 
@@ -135,100 +218,350 @@ size_t wxDataObjectComposite::GetDataSize(const wxDataFormat& format) const
 bool wxDataObjectComposite::GetDataHere(const wxDataFormat& format,
                                         void *buf) const
 {
-    wxDataObjectSimple *dataObj = GetObject(format);
+    wxDataObjectSimple *dataObj = GetObject( format );
 
-    wxCHECK_MSG( dataObj, FALSE,
+    wxCHECK_MSG( dataObj, false,
                  wxT("unsupported format in wxDataObjectComposite"));
 
-    return dataObj->GetDataHere(buf);
+    return dataObj->GetDataHere( buf );
 }
 
 bool wxDataObjectComposite::SetData(const wxDataFormat& format,
                                     size_t len,
                                     const void *buf)
 {
-    wxDataObjectSimple *dataObj = GetObject(format);
+    wxDataObjectSimple *dataObj = GetObject( format );
 
-    wxCHECK_MSG( dataObj, FALSE,
+    wxCHECK_MSG( dataObj, false,
                  wxT("unsupported format in wxDataObjectComposite"));
 
-    return dataObj->SetData(len, buf);
+    m_receivedFormat = format;
+
+    // Notice that we must pass "format" here as wxTextDataObject, that we can
+    // have as one of our "simple" sub-objects actually is not that simple and
+    // can support multiple formats (ASCII/UTF-8/UTF-16/...) and so needs to
+    // know which one it is given.
+    return dataObj->SetData( format, len, buf );
 }
 
 // ----------------------------------------------------------------------------
 // wxTextDataObject
 // ----------------------------------------------------------------------------
 
+#ifdef wxNEEDS_UTF8_FOR_TEXT_DATAOBJ
+
+// FIXME-UTF8: we should be able to merge wchar_t and UTF-8 versions once we
+//             have a way to get UTF-8 string (and its length) in both builds
+//             without loss of efficiency (i.e. extra buffer copy/strlen call)
+
+#if wxUSE_UNICODE_WCHAR
+
+static inline wxMBConv& GetConv(const wxDataFormat& format)
+{
+    // use UTF8 for wxDF_UNICODETEXT and UCS4 for wxDF_TEXT
+    return format == wxDF_UNICODETEXT ? wxConvUTF8 : wxConvLibc;
+}
+
+size_t wxTextDataObject::GetDataSize(const wxDataFormat& format) const
+{
+    wxCharBuffer buffer = GetConv(format).cWX2MB( GetText().c_str() );
+
+    return buffer ? strlen( buffer ) : 0;
+}
+
+bool wxTextDataObject::GetDataHere(const wxDataFormat& format, void *buf) const
+{
+    if ( !buf )
+        return false;
+
+    wxCharBuffer buffer = GetConv(format).cWX2MB( GetText().c_str() );
+    if ( !buffer )
+        return false;
+
+    memcpy( (char*) buf, buffer, GetDataSize(format) );
+    // strcpy( (char*) buf, buffer );
+
+    return true;
+}
+
+bool wxTextDataObject::SetData(const wxDataFormat& format,
+                               size_t WXUNUSED(len), const void *buf)
+{
+    if ( buf == NULL )
+        return false;
+
+    wxWCharBuffer buffer = GetConv(format).cMB2WX( (const char*)buf );
+
+    SetText( buffer );
+
+    return true;
+}
+
+#else // wxUSE_UNICODE_UTF8
+
+size_t wxTextDataObject::GetDataSize(const wxDataFormat& format) const
+{
+    const wxString& text = GetText();
+    if ( format == wxDF_UNICODETEXT || wxLocaleIsUtf8 )
+    {
+        return text.utf8_length();
+    }
+    else // wxDF_TEXT
+    {
+        const wxCharBuffer buf(wxConvLocal.cWC2MB(text.wc_str()));
+        return buf ? strlen(buf) : 0;
+    }
+}
+
+bool wxTextDataObject::GetDataHere(const wxDataFormat& format, void *buf) const
+{
+    if ( !buf )
+        return false;
+
+    const wxString& text = GetText();
+    if ( format == wxDF_UNICODETEXT || wxLocaleIsUtf8 )
+    {
+        memcpy(buf, text.utf8_str(), text.utf8_length());
+    }
+    else // wxDF_TEXT
+    {
+        const wxCharBuffer bufLocal(wxConvLocal.cWC2MB(text.wc_str()));
+        if ( !bufLocal )
+            return false;
+
+        memcpy(buf, bufLocal, strlen(bufLocal));
+    }
+
+    return true;
+}
+
+bool wxTextDataObject::SetData(const wxDataFormat& format,
+                               size_t len, const void *buf_)
+{
+    const char * const buf = static_cast<const char *>(buf_);
+
+    if ( buf == NULL )
+        return false;
+
+    if ( format == wxDF_UNICODETEXT || wxLocaleIsUtf8 )
+    {
+        // normally the data is in UTF-8 so we could use FromUTF8Unchecked()
+        // but it's not absolutely clear what GTK+ does if the clipboard data
+        // is not in UTF-8 so do an extra check for tranquility, it shouldn't
+        // matter much if we lose a bit of performance when pasting from
+        // clipboard
+        SetText(wxString::FromUTF8(buf, len));
+    }
+    else // wxDF_TEXT, convert from current (non-UTF8) locale
+    {
+        SetText(wxConvLocal.cMB2WC(buf, len, NULL));
+    }
+
+    return true;
+}
+
+#endif // wxUSE_UNICODE_WCHAR/wxUSE_UNICODE_UTF8
+
+#elif defined(wxNEEDS_UTF16_FOR_TEXT_DATAOBJ)
+
+namespace
+{
+
+inline wxMBConv& GetConv(const wxDataFormat& format)
+{
+    static wxMBConvUTF16 s_UTF16Converter;
+
+    return format == wxDF_UNICODETEXT ? static_cast<wxMBConv&>(s_UTF16Converter)
+                                      : static_cast<wxMBConv&>(wxConvLocal);
+}
+
+} // anonymous namespace
+
+size_t wxTextDataObject::GetDataSize(const wxDataFormat& format) const
+{
+    return GetConv(format).WC2MB(NULL, GetText().wc_str(), 0);
+}
+
+bool wxTextDataObject::GetDataHere(const wxDataFormat& format, void *buf) const
+{
+    if ( buf == NULL )
+        return false;
+
+    wxCharBuffer buffer(GetConv(format).cWX2MB(GetText().c_str()));
+
+    memcpy(buf, buffer.data(), buffer.length());
+
+    return true;
+}
+
+bool wxTextDataObject::SetData(const wxDataFormat& format,
+                               size_t WXUNUSED(len),
+                               const void *buf)
+{
+    if ( buf == NULL )
+        return false;
+
+    SetText(GetConv(format).cMB2WX(static_cast<const char*>(buf)));
+
+    return true;
+}
+
+#else // !wxNEEDS_UTF{8,16}_FOR_TEXT_DATAOBJ
+
+// NB: This branch, using native wxChar for the clipboard, is only used under
+//     Windows currently. It's just a coincidence, but Windows is also the only
+//     platform where we need to convert the text to the native EOL format, so
+//     wxTextBuffer::Translate() is only used here and not in the code above.
+
 size_t wxTextDataObject::GetDataSize() const
 {
-    return GetTextLength();
+    return (wxTextBuffer::Translate(GetText()).length() + 1)*sizeof(wxChar);
 }
 
 bool wxTextDataObject::GetDataHere(void *buf) const
 {
-    strcpy((char *)buf, GetText().mb_str());
+    const wxString textNative = wxTextBuffer::Translate(GetText());
 
-    return TRUE;
+    // NOTE: use wxTmemcpy() instead of wxStrncpy() to allow
+    //       retrieval of strings with embedded NULLs
+    wxTmemcpy(static_cast<wxChar*>(buf),
+              textNative.t_str(),
+              textNative.length() + 1);
+
+    return true;
 }
 
-bool wxTextDataObject::SetData(size_t WXUNUSED(len), const void *buf)
+bool wxTextDataObject::SetData(size_t len, const void *buf)
 {
-    SetText(wxString((const char *)buf));
+    const wxString
+        text = wxString(static_cast<const wxChar*>(buf), len/sizeof(wxChar));
+    SetText(wxTextBuffer::Translate(text, wxTextFileType_Unix));
 
-    return TRUE;
+    return true;
 }
 
+#endif // different wxTextDataObject implementations
+
 // ----------------------------------------------------------------------------
-// wxFileDataObjectBase
+// wxHTMLDataObject
 // ----------------------------------------------------------------------------
 
-// VZ: I don't need this in MSW finally, so if it is needed in wxGTK, it should
-//     be moved to gtk/dataobj.cpp
-#if 0
-
-wxString wxFileDataObjectBase::GetFilenames() const
+size_t wxHTMLDataObject::GetDataSize() const
 {
-    wxString str;
-    size_t count = m_filenames.GetCount();
-    for ( size_t n = 0; n < count; n++ )
-    {
-        str << m_filenames[n] << wxT('\0');
-    }
+    const wxScopedCharBuffer buffer(GetHTML().utf8_str());
 
-    return str;
+    size_t size = buffer.length();
+
+#ifdef __WXMSW__
+    // On Windows we need to add some stuff to the string to satisfy
+    // its clipboard format requirements.
+    size += 400;
+#endif
+
+    return size;
 }
 
-void wxFileDataObjectBase::SetFilenames(const wxChar* filenames)
+bool wxHTMLDataObject::GetDataHere(void *buf) const
 {
-    m_filenames.Empty();
+    if ( !buf )
+        return false;
+
+    // Windows and Mac always use UTF-8, and docs suggest GTK does as well.
+    const wxScopedCharBuffer html(GetHTML().utf8_str());
+    if ( !html )
+        return false;
+
+    char* const buffer = static_cast<char*>(buf);
+
+#ifdef __WXMSW__
+    // add the extra info that the MSW clipboard format requires.
+
+        // Create a template string for the HTML header...
+    strcpy(buffer,
+        "Version:0.9\r\n"
+        "StartHTML:00000000\r\n"
+        "EndHTML:00000000\r\n"
+        "StartFragment:00000000\r\n"
+        "EndFragment:00000000\r\n"
+        "<html><body>\r\n"
+        "<!--StartFragment -->\r\n");
+
+    // Append the HTML...
+    strcat(buffer, html);
+    strcat(buffer, "\r\n");
+    // Finish up the HTML format...
+    strcat(buffer,
+        "<!--EndFragment-->\r\n"
+        "</body>\r\n"
+        "</html>");
+
+    // Now go back, calculate all the lengths, and write out the
+    // necessary header information. Note, wsprintf() truncates the
+    // string when you overwrite it so you follow up with code to replace
+    // the 0 appended at the end with a '\r'...
+    char *ptr = strstr(buffer, "StartHTML");
+    sprintf(ptr+10, "%08u", (unsigned)(strstr(buffer, "<html>") - buffer));
+    *(ptr+10+8) = '\r';
+
+    ptr = strstr(buffer, "EndHTML");
+    sprintf(ptr+8, "%08u", (unsigned)strlen(buffer));
+    *(ptr+8+8) = '\r';
+
+    ptr = strstr(buffer, "StartFragment");
+    sprintf(ptr+14, "%08u", (unsigned)(strstr(buffer, "<!--StartFrag") - buffer));
+    *(ptr+14+8) = '\r';
+
+    ptr = strstr(buffer, "EndFragment");
+    sprintf(ptr+12, "%08u", (unsigned)(strstr(buffer, "<!--EndFrag") - buffer));
+    *(ptr+12+8) = '\r';
+#else
+    strcpy(buffer, html);
+#endif // __WXMSW__
+
+    return true;
+}
 
-    wxString current;
-    for ( const wxChar *pc = filenames; ; pc++ )
+bool wxHTMLDataObject::SetData(size_t WXUNUSED(len), const void *buf)
+{
+    if ( buf == NULL )
+        return false;
+
+    // Windows and Mac always use UTF-8, and docs suggest GTK does as well.
+    wxString html = wxString::FromUTF8(static_cast<const char*>(buf));
+
+#ifdef __WXMSW__
+    // To be consistent with other platforms, we only add the Fragment part
+    // of the Windows HTML clipboard format to the data object.
+    int fragmentStart = html.rfind("StartFragment");
+    int fragmentEnd = html.rfind("EndFragment");
+
+    if (fragmentStart != wxNOT_FOUND && fragmentEnd != wxNOT_FOUND)
     {
-        if ( *pc )
-        {
-            current += *pc;
-        }
-        else
-        {
-            if ( !current )
-            {
-                // 2 consecutive NULs - this is the end of the string
-                break;
-            }
+        int startCommentEnd = html.find("-->", fragmentStart) + 3;
+        int endCommentStart = html.rfind("<!--", fragmentEnd);
 
-            m_filenames.Add(current);
-            current.Empty();
-        }
+        if (startCommentEnd != wxNOT_FOUND && endCommentStart != wxNOT_FOUND)
+            html = html.Mid(startCommentEnd, endCommentStart - startCommentEnd);
     }
+#endif // __WXMSW__
+
+    SetHTML( html );
+
+    return true;
 }
 
-#endif // 0
 
 // ----------------------------------------------------------------------------
 // wxCustomDataObject
 // ----------------------------------------------------------------------------
 
+wxCustomDataObject::wxCustomDataObject(const wxDataFormat& format)
+    : wxDataObjectSimple(format)
+{
+    m_data = NULL;
+    m_size = 0;
+}
+
 wxCustomDataObject::~wxCustomDataObject()
 {
     Free();
@@ -249,9 +582,9 @@ void *wxCustomDataObject::Alloc(size_t size)
 
 void wxCustomDataObject::Free()
 {
-    delete [] m_data;
+    delete [] (char*)m_data;
     m_size = 0;
-    m_data = (void *)NULL;
+    m_data = NULL;
 }
 
 size_t wxCustomDataObject::GetDataSize() const
@@ -261,13 +594,16 @@ size_t wxCustomDataObject::GetDataSize() const
 
 bool wxCustomDataObject::GetDataHere(void *buf) const
 {
+    if ( buf == NULL )
+        return false;
+
     void *data = GetData();
-    if ( !data )
-        return FALSE;
+    if ( data == NULL )
+        return false;
 
-    memcpy(buf, data, GetSize());
+    memcpy( buf, data, GetSize() );
 
-    return TRUE;
+    return true;
 }
 
 bool wxCustomDataObject::SetData(size_t size, const void *buf)
@@ -275,11 +611,63 @@ bool wxCustomDataObject::SetData(size_t size, const void *buf)
     Free();
 
     m_data = Alloc(size);
-    if ( !m_data )
-        return FALSE;
+    if ( m_data == NULL )
+        return false;
+
+    m_size = size;
+    memcpy( m_data, buf, m_size );
+
+    return true;
+}
+
+// ============================================================================
+// some common dnd related code
+// ============================================================================
 
-    memcpy(m_data, buf, m_size = size);
+#if wxUSE_DRAG_AND_DROP
 
-    return TRUE;
+#include "wx/dnd.h"
+
+// ----------------------------------------------------------------------------
+// wxTextDropTarget
+// ----------------------------------------------------------------------------
+
+// NB: we can't use "new" in ctor initializer lists because this provokes an
+//     internal compiler error with VC++ 5.0 (hey, even gcc compiles this!),
+//     so use SetDataObject() instead
+
+wxTextDropTarget::wxTextDropTarget()
+{
+    SetDataObject(new wxTextDataObject);
 }
 
+wxDragResult wxTextDropTarget::OnData(wxCoord x, wxCoord y, wxDragResult def)
+{
+    if ( !GetData() )
+        return wxDragNone;
+
+    wxTextDataObject *dobj = (wxTextDataObject *)m_dataObject;
+    return OnDropText( x, y, dobj->GetText() ) ? def : wxDragNone;
+}
+
+// ----------------------------------------------------------------------------
+// wxFileDropTarget
+// ----------------------------------------------------------------------------
+
+wxFileDropTarget::wxFileDropTarget()
+{
+    SetDataObject(new wxFileDataObject);
+}
+
+wxDragResult wxFileDropTarget::OnData(wxCoord x, wxCoord y, wxDragResult def)
+{
+    if ( !GetData() )
+        return wxDragNone;
+
+    wxFileDataObject *dobj = (wxFileDataObject *)m_dataObject;
+    return OnDropFiles( x, y, dobj->GetFilenames() ) ? def : wxDragNone;
+}
+
+#endif // wxUSE_DRAG_AND_DROP
+
+#endif // wxUSE_DATAOBJ