Modified the following files to get Unix ENDER to save Multi-part MIME:

cmd/xfe/forms.c
    include/edt.h
    lib/layout/editor.cpp
    lib/mailto/mhtmlstm.cpp

cmd/xfe/forms.c

@@ -2501,7 +2501,7 @@ htmlarea_get_value(FEFormData *fed, LO_FormElementStruct *form, XP_Bool delete_p
 
   EDT_SaveToBuffer(ha_fed->editor_context, &text);
 
-  if (! text) return;
+  /* if (! text) return; */
 
   current_text = XP_FormGetCurrentText(form_data);
   default_text = XP_FormGetDefaultText(form_data);
@@ -2512,6 +2512,26 @@ htmlarea_get_value(FEFormData *fed, LO_FormElementStruct *form, XP_Bool delete_p
   /* XXX: Get rid of this PA_Block cast! */
   XP_FormSetCurrentText(form_data, (PA_Block)text);
 
+#ifdef MOZ_ENDER_MIME
+
+  if (submit)
+  {
+    if (form_data->ele_mimearea.mime_bits)
+    {
+      XP_FREE(form_data->ele_mimearea.mime_bits);
+      form_data->ele_mimearea.mime_bits = 0;
+    }
+
+    EDT_SaveMimeToBuffer(ha_fed->editor_context,
+                         (XP_HUGE_CHAR_PTR *)&form_data->ele_mimearea.mime_bits,
+                         FALSE);
+
+    if (text)
+      EDT_SetDefaultMimeHTML(ha_fed->editor_context, text);
+  }
+
+#endif /* MOZ_ENDER_MIME */
+
   if (delete_p)
   {
     extern Widget XFE_DestroyEmbeddedEditor(Widget, MWContext *);

include/edt.h

@@ -160,6 +160,7 @@ void EDT_SaveToBuffer ( MWContext * pContext, XP_HUGE_CHAR_PTR* pBuffer );
 void EDT_ReadFromBuffer ( MWContext * pContext, XP_HUGE_CHAR_PTR pBuffer );
 
 #ifdef MOZ_ENDER_MIME
+ED_FileError EDT_SaveMimeToBuffer(MWContext *pContext, XP_HUGE_CHAR_PTR *pBuffer, XP_Bool async);
 void EDT_ReadMimeFromBuffer ( MWContext * pContext, XP_HUGE_CHAR_PTR pBuffer );
 #endif /*MOZ_ENDER_MIME*/
 

lib/layout/editor.cpp

@@ -40,7 +40,6 @@ extern "C" {
 #include "msgcom.h"
 #include "intl_csi.h"
 
-
 //extern "C" int XP_EDT_HEAD_FAILED;
 
 CBitArray *edt_setNoEndTag = 0;
@@ -972,6 +971,34 @@ void EDT_ReadFromBuffer(MWContext* pContext, XP_HUGE_CHAR_PTR pBuffer )
 }
 
 #ifdef MOZ_ENDER_MIME
+
+extern "C" {
+  void *MSG_CreateMimeRelatedStreamSaver(MWContext *, char **, char **);
+};
+
+ED_FileError
+EDT_SaveMimeToBuffer(MWContext *pContext, XP_HUGE_CHAR_PTR *pBuffer, XP_Bool async)
+{
+	ED_FileError status = ED_ERROR_NONE;
+	char *pRootPartName = 0;
+	void *fs = MSG_CreateMimeRelatedStreamSaver(pContext,
+								  &pRootPartName, (char **)pBuffer);
+
+	if (!fs)
+		return ED_ERROR_FILE_WRITE;
+
+	status = EDT_SaveFileTo(pContext, ED_FINISHED_MAIL_SEND, pRootPartName, fs,
+							TRUE, TRUE);
+
+	if (!async && status == ED_ERROR_NONE)
+	{
+		while ( pContext->edit_saving_url )
+			FEU_StayingAlive();
+	}
+
+	return status;
+}
+
 void EDT_ReadMimeFromBuffer(MWContext* pContext, XP_HUGE_CHAR_PTR pBuffer )
 {
     GET_WRITABLE_EDIT_BUF_OR_RETURN(pContext, pEditBuffer);

lib/mailto/mhtmlstm.cpp

@@ -1131,4 +1131,13 @@ MSG_MimeRelatedSaver::IsLocalPersistentFile(intn /*iFileIndex*/) {
     return FALSE;
 }
 
+extern "C" void *
+MSG_CreateMimeRelatedStreamSaver(MWContext *context,
+								 char **origRootURL, char **streamOut)
+{
+	return ((void *)new MSG_MimeRelatedStreamSaver(
+					NULL, context, NULL, FALSE, MSG_DeliverNow,
+					NULL, 0, NULL, NULL, origRootURL, streamOut));
+}
+
 //#endif