BEmailMessage: added missing const, Date() returns time_t.

* Added missing const to some getter methods.
* Date() now tries to parse the date of the mail, and return it as
  a time_t; you can still retrieve the actual string via
  HeaderField("Date") if you have to.
* Mail now shows the time in the local time zone, and with the
  current locale.

headers/os/mail/MailMessage.h

@@ -55,13 +55,13 @@ public:
 				// addresses the message appropriately, but ForwardMessage()
 				// leaves it unaddressed.
 
-			const char*			To();
-			const char*			From();
-			const char*			ReplyTo();
-			const char*			CC();
-			const char*			Subject();
-			const char*			Date();
-			int					Priority();
+			const char*			To() const;
+			const char*			From() const;
+			const char*			ReplyTo() const;
+			const char*			CC() const;
+			const char*			Subject() const;
+			time_t				Date() const;
+			int					Priority() const;
 
 			void				SetSubject(const char* to,
 									uint32 charset = B_MAIL_NULL_CONVERSION,

src/apps/mail/Header.cpp

@@ -38,6 +38,7 @@ of their respective holders. All rights reserved.
 #include <stdio.h>
 
 #include <ControlLook.h>
+#include <DateTimeFormat.h>
 #include <E-mail.h>
 #include <LayoutBuilder.h>
 #include <Locale.h>
@@ -429,6 +430,22 @@ THeaderView::Date() const
 }
 
 
+void
+THeaderView::SetDate(time_t date)
+{
+	fDate = date;
+
+	if (fDateView != NULL) {
+		BDateTimeFormat formatter;
+
+		BString string;
+		formatter.Format(string, date, B_FULL_DATE_FORMAT,
+			B_MEDIUM_TIME_FORMAT);
+		SetDate(string);
+	}
+}
+
+
 void
 THeaderView::SetDate(const char* date)
 {
@@ -505,8 +522,12 @@ THeaderView::SetFromMessage(BEmailMessage* mail)
 		SetAccount(accountName);
 
 	// Set the date on this message
-	const char* dateField = mail->Date();
-	SetDate(dateField != NULL ? dateField : B_TRANSLATE("Unknown"));
+	time_t date = mail->Date();
+	if (date <= 0) {
+		const char* dateField = mail->HeaderField("Date");
+		SetDate(dateField != NULL ? dateField : B_TRANSLATE("Unknown"));
+	} else
+		SetDate(date);
 
 	return B_OK;
 }

src/apps/mail/Header.h

@@ -79,6 +79,7 @@ public:
 
 			bool				IsDateEmpty() const;
 			const char*			Date() const;
+			void				SetDate(time_t date);
 			void				SetDate(const char* date);
 
 			int32				AccountID() const;
@@ -102,6 +103,7 @@ private:
 			AddressTextControl*	fBccControl;
 			BTextControl*		fSubjectControl;
 			BStringView*		fDateView;
+			time_t				fDate;
 			bool				fIncoming;
 			bool				fResending;
 };

src/apps/mail/MailWindow.cpp

@@ -2177,7 +2177,7 @@ TMailWindow::Reply(entry_ref* ref, TMailWindow* window, uint32 type)
 	if (address.Length() <= 0)
 		address = B_TRANSLATE("(Address unavailable)");
 
-	BString date(mail->Date());
+	BString date(mail->HeaderField("Date"));
 	if (date.Length() <= 0)
 		date = B_TRANSLATE("(Date unavailable)");
 

src/kits/mail/MailMessage.cpp

@@ -226,28 +226,28 @@ BEmailMessage::ForwardMessage(bool accountFromMail, bool includeAttachments)
 
 
 const char*
-BEmailMessage::To()
+BEmailMessage::To() const
 {
 	return HeaderField("To");
 }
 
 
 const char*
-BEmailMessage::From()
+BEmailMessage::From() const
 {
 	return HeaderField("From");
 }
 
 
 const char*
-BEmailMessage::ReplyTo()
+BEmailMessage::ReplyTo() const
 {
 	return HeaderField("Reply-To");
 }
 
 
 const char*
-BEmailMessage::CC()
+BEmailMessage::CC() const
 {
 	return HeaderField("Cc");
 		// Note case of CC is "Cc" in our internal headers.
@@ -255,21 +255,25 @@ BEmailMessage::CC()
 
 
 const char*
-BEmailMessage::Subject()
+BEmailMessage::Subject() const
 {
 	return HeaderField("Subject");
 }
 
 
-const char*
-BEmailMessage::Date()
+time_t
+BEmailMessage::Date() const
 {
-	return HeaderField("Date");
+	const char* dateField = HeaderField("Date");
+	if (dateField == NULL)
+		return -1;
+
+	return ParseDateWithTimeZone(dateField);
 }
 
 
 int
-BEmailMessage::Priority()
+BEmailMessage::Priority() const
 {
 	int priorityNumber;
 	const char* priorityString;