added new interfaces for closure over all flavors and converters when clients ask for a list of known flavors.

widget/public/nsITransferable.h

@@ -37,9 +37,30 @@ class nsITransferable : public nsISupports {
     static const nsIID& GetIID() { static nsIID iid = NS_ITRANSFERABLE_IID; return iid; }
 
   /**
-    * Get the list of data flavors that this transferable supports.  
+    * Computes a list of flavors that the transferable can accept into it, either through
+    * intrinsic knowledge or input data converters.
     *
-    * @param  aDataFlavorList fills list with supported flavors
+    * @param  outFlavorList fills list with supported flavors. This is a copy of
+    *          the internal list, so it may be edited w/out affecting the transferable.
+    */
+  NS_IMETHOD FlavorsTransferableCanImport ( nsISupportsArray** outFlavorList ) = 0;
+
+  /**
+    * Computes a list of flavors that the transferable can export, either through
+    * intrinsic knowledge or output data converters.
+    *
+    * @param  aDataFlavorList fills list with supported flavors. This is a copy of
+    *          the internal list, so it may be edited w/out affecting the transferable.
+    */
+  NS_IMETHOD FlavorsTransferableCanExport ( nsISupportsArray** outFlavorList ) = 0;
+
+  /**
+    * Get the list of data flavors that this transferable supports (w/out conversion). 
+    * (NOTE: We're not sure how useful this is in the presence of the above two methods,
+    * but figured we'd keep it around just in case). 
+    *
+    * @param  aDataFlavorList fills list with supported flavors. This is a copy of
+    *          the internal list, so it may be edited w/out affecting the transferable.
     */
     NS_IMETHOD GetTransferDataFlavors(nsISupportsArray ** aDataFlavorList) = 0;
 
@@ -55,13 +76,14 @@ class nsITransferable : public nsISupports {
     * Given a flavor retrieve the data. 
     *
     * @param  aFlavor the flavor of data to retrieve
-    * @param  aData the data
+    * @param  aData the data. This is NOT a copy, so the caller MUST NOT DELETE it.
     * @param  aDataLen the length of the data
     */
     NS_IMETHOD GetTransferData(nsIDataFlavor * aFlavor, void ** aData, PRUint32 * aDataLen) = 0;
 
   /**
-    * Set Data into the transferable as a specified DataFlavor
+    * Set Data into the transferable as a specified DataFlavor. The transferable now
+    * owns the data, so the caller must not delete it.
     *
     * @param  aFlavor the flavor of data that is being set
     * @param  aData the data 

widget/src/xpwidgets/nsTransferable.cpp

@@ -24,6 +24,7 @@
 #include "nsIFormatConverter.h"
 #include "nsVoidArray.h"
 #include "nsIComponentManager.h"
+#include "nsCOMPtr.h"
 
 
 static NS_DEFINE_IID(kITransferableIID,  NS_ITRANSFERABLE_IID);
@@ -49,7 +50,6 @@ nsTransferable::nsTransferable()
 {
   NS_INIT_REFCNT();
   mDataArray  = new nsVoidArray();
-  mFormatConv = nsnull;
 }
 
 //-------------------------------------------------------------------------
@@ -59,8 +59,6 @@ nsTransferable::nsTransferable()
 //-------------------------------------------------------------------------
 nsTransferable::~nsTransferable()
 {
-  NS_IF_RELEASE(mFormatConv);
-
   PRInt32 i;
   for (i=0;i<mDataArray->Count();i++) {
     DataStruct * data = (DataStruct *)mDataArray->ElementAt(i);
@@ -252,14 +250,7 @@ NS_IMETHODIMP nsTransferable::IsLargeDataSet()
   */
 NS_IMETHODIMP nsTransferable::SetConverter(nsIFormatConverter * aConverter)
 {
-  if (nsnull != mFormatConv) {
-    NS_RELEASE(mFormatConv);
-  }
-
-  mFormatConv = aConverter;
-  if (nsnull != mFormatConv) {
-    NS_ADDREF(mFormatConv);
-  }
+  mFormatConv = dont_QueryInterface(aConverter);
   return NS_OK;
 }
 
@@ -271,8 +262,76 @@ NS_IMETHODIMP nsTransferable::GetConverter(nsIFormatConverter ** aConverter)
 {
   if (nsnull != mFormatConv) {
     *aConverter = mFormatConv;
-    NS_ADDREF(mFormatConv);
+    NS_ADDREF(*aConverter);
   }
   return NS_OK;
 }
 
+
+//
+// FlavorsTransferableCanImport
+//
+// Computes a list of flavors that the transferable can accept into it, either through
+// intrinsic knowledge or input data converters.
+//
+NS_IMETHODIMP
+nsTransferable :: FlavorsTransferableCanImport ( nsISupportsArray** outFlavorList )
+{
+  if ( !outFlavorList )
+    return NS_ERROR_INVALID_ARG;
+  
+  // Get the flavor list, and on to the end of it, append the list of flavors we
+  // can also get to through a converter. This is so that we can just walk the list
+  // in one go, looking for the desired flavor.
+  GetTransferDataFlavors(outFlavorList);  // addrefs
+  nsCOMPtr<nsIFormatConverter> converter;
+  GetConverter(getter_AddRefs(converter));
+  if ( converter ) {
+    nsCOMPtr<nsISupportsArray> convertedList;
+    converter->GetInputDataFlavors(getter_AddRefs(convertedList));
+    if ( convertedList ) {
+      for (int i=0;i<convertedList->Count();i++) {
+  	    nsCOMPtr<nsISupports> temp = getter_AddRefs(convertedList->ElementAt(i));
+        (*outFlavorList)->AppendElement(temp);    // this addref's for us
+      } // foreach flavor that can be converted to
+    }
+  } // if a converter exists
+
+  return NS_OK;
+  
+} // FlavorsTransferableCanImport
+
+
+//
+// FlavorsTransferableCanExport
+//
+// Computes a list of flavors that the transferable can export, either through
+// intrinsic knowledge or output data converters.
+//
+NS_IMETHODIMP
+nsTransferable :: FlavorsTransferableCanExport ( nsISupportsArray** outFlavorList )
+{
+  if ( !outFlavorList )
+    return NS_ERROR_INVALID_ARG;
+  
+  // Get the flavor list, and on to the end of it, append the list of flavors we
+  // can also get to through a converter. This is so that we can just walk the list
+  // in one go, looking for the desired flavor.
+  GetTransferDataFlavors(outFlavorList);  // addrefs
+  nsCOMPtr<nsIFormatConverter> converter;
+  GetConverter(getter_AddRefs(converter));
+  if ( converter ) {
+    nsCOMPtr<nsISupportsArray> convertedList;
+    converter->GetOutputDataFlavors(getter_AddRefs(convertedList));
+    if ( convertedList ) {
+      for (int i=0;i<convertedList->Count();i++) {
+  	    nsCOMPtr<nsISupports> temp = getter_AddRefs(convertedList->ElementAt(i));
+        (*outFlavorList)->AppendElement(temp);    // this addref's for us
+      } // foreach flavor that can be converted to
+    }
+  } // if a converter exists
+
+  return NS_OK;
+  
+} // FlavorsTransferableCanImport
+

widget/src/xpwidgets/nsTransferable.h

@@ -19,13 +19,15 @@
 #ifndef nsTransferable_h__
 #define nsTransferable_h__
 
+#include "nsIFormatConverter.h"
 #include "nsITransferable.h"
+#include "nsCOMPtr.h"
+
 
 class nsISupportsArray;
 class nsIDataFlavor;
 class nsDataObj;
 class nsVoidArray;
-class nsIFormatConverter;
 
 
 /**
@@ -43,11 +45,12 @@ public:
   NS_DECL_ISUPPORTS
   
   //nsITransferable
-    // Returns a copy of the flavor list
+  NS_IMETHOD FlavorsTransferableCanImport ( nsISupportsArray** outFlavorList ) ;
+  NS_IMETHOD FlavorsTransferableCanExport ( nsISupportsArray** outFlavorList ) ;
   NS_IMETHOD GetTransferDataFlavors(nsISupportsArray ** aDataFlavorList);
   NS_IMETHOD IsDataFlavorSupported(nsIDataFlavor * aFlavor);
 
-    // Transferable still owns |aData|. Do not delete it.
+   // Transferable still owns |aData|. Do not delete it.
   NS_IMETHOD GetTransferData(nsIDataFlavor * aFlavor, void ** aData, PRUint32 * aDataLen);
     // Transferable consumes |aData|. Do not delete it.
   NS_IMETHOD SetTransferData(nsIDataFlavor * aFlavor, void * aData, PRUint32 aDataLen);
@@ -58,10 +61,11 @@ public:
   NS_IMETHOD SetConverter(nsIFormatConverter * aConverter);
   NS_IMETHOD GetConverter(nsIFormatConverter ** aConverter);
 
+
 protected:
 
   nsVoidArray        * mDataArray;
-  nsIFormatConverter * mFormatConv;
+  nsCOMPtr<nsIFormatConverter> mFormatConv;
 
 };