Applied patch by Philippe Saint-Pierre with some changes by myself:

* Added Revert button and Revert feature. The time at which the preflet
  is started is remembered, the uptime of the preflet is calculated
  via system_time().

TODO: Better placement for the Revert button. Currently it looks like it can
only revert date changes.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@25210 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/preferences/time/DateTimeView.cpp

@@ -6,6 +6,7 @@
  *		Andrew McCall <mccall@@digitalparadise.co.uk>
  *		Mike Berg <[email protected]>
  *		Julun <[email protected]>
+ *		Philippe Saint-Pierre <[email protected]>
  */
 
 #include "DateTimeView.h"
@@ -13,8 +14,10 @@
 #include "CalendarView.h"
 #include "DateTimeEdit.h"
 #include "TimeMessages.h"
+#include "DateTime.h"
 
 
+#include <Button.h>
 #include <CheckBox.h>
 #include <Entry.h>
 #include <File.h>
@@ -25,6 +28,7 @@
 #include <String.h>
 #include <StringView.h>
 #include <Window.h>
+#include <time.h>
 
 
 #ifdef HAIKU_TARGET_PLATFORM_HAIKU
@@ -39,10 +43,14 @@ DateTimeView::DateTimeView(BRect frame)
 	: BView(frame, "dateTimeView", B_FOLLOW_NONE, B_WILL_DRAW | B_NAVIGABLE_JUMP),
 	  fGmtTime(NULL),
 	  fUseGmtTime(false),
-	  fInitialized(false)
+	  fInitialized(false),
+	  fSystemTimeAtStart(system_time())
 {
 	_ReadRTCSettings();
 	_InitView();
+
+	// record the current time to enable revert.
+	time(&fTimeAtStart);
 }
 
 
@@ -64,6 +72,7 @@ DateTimeView::AttachedToWindow()
 		fGmtTime->SetTarget(this);
 		fLocalTime->SetTarget(this);
 		fCalendarView->SetTarget(this);
+		fRevertButton->SetTarget(this);
 	}
 }
 
@@ -116,11 +125,18 @@ DateTimeView::MessageReceived(BMessage *message)
 			msg.what = H_USER_CHANGE;
 			msg.AddBool("time", false);
 			Window()->PostMessage(&msg);
-		}	break;
+			break;
+		}
 
 		case kRTCUpdate:
-			fUseGmtTime = !fUseGmtTime;
+			fUseGmtTime = fGmtTime->Value() == B_CONTROL_ON;
 			_UpdateGmtSettings();
+			CheckCanRevert();
+			break;
+
+		case kMsgRevert:
+			_Revert();
+			fRevertButton->SetEnabled(false);
 			break;
 	
 		default:
@@ -130,6 +146,62 @@ DateTimeView::MessageReceived(BMessage *message)
 }
 
 
+void
+DateTimeView::CheckCanRevert()
+{
+	// check GMT vs Local setting
+	bool enable = fUseGmtTime != fOldUseGmtTime;
+
+	// check for changed time
+	time_t unchangedNow = fTimeAtStart + _PrefletUptime();
+	time_t changedNow;
+	time(&changedNow);
+
+	enable = enable || (changedNow != unchangedNow);
+
+	fRevertButton->SetEnabled(enable);
+}
+
+
+void
+DateTimeView::_Revert()
+{
+	// Set the clock and calendar as they were at launch time + 
+	// time ellapsed since application launch.
+
+	fUseGmtTime = fOldUseGmtTime;
+	_UpdateGmtSettings();
+
+	if (fUseGmtTime)
+		fGmtTime->SetValue(B_CONTROL_ON);
+	else
+		fLocalTime->SetValue(B_CONTROL_ON);
+
+	time_t timeNow = fTimeAtStart + _PrefletUptime();
+	struct tm result;
+	struct tm* timeInfo;
+	timeInfo = localtime_r(&timeNow, &result);
+
+	BDateTime dateTime = BDateTime::CurrentDateTime(B_LOCAL_TIME);
+	BTime time = dateTime.Time();
+	BDate date = dateTime.Date();
+	time.SetTime(timeInfo->tm_hour, timeInfo->tm_min, timeInfo->tm_sec % 60);
+	date.SetDate(timeInfo->tm_year + 1900, timeInfo->tm_mon + 1,
+		timeInfo->tm_mday); 
+	dateTime.SetTime(time);
+	dateTime.SetDate(date);
+	
+	set_real_time_clock(dateTime.Time_t());
+}
+
+
+time_t
+DateTimeView::_PrefletUptime() const
+{
+	return (time_t)((system_time() - fSystemTimeAtStart) / 1000000);
+}
+
+
 void
 DateTimeView::_InitView()
 {
@@ -192,6 +264,22 @@ DateTimeView::_InitView()
 	else
 		fLocalTime->SetValue(B_CONTROL_ON);
 
+	fOldUseGmtTime = fUseGmtTime;
+
+	BRect rect = Bounds();
+
+	rect.left = 10;
+	rect.top = rect.bottom - 10;
+
+	fRevertButton = new BButton(rect, "revert", "Revert",
+		new BMessage(kMsgRevert), B_FOLLOW_LEFT | B_FOLLOW_BOTTOM, B_WILL_DRAW);
+	
+	fRevertButton->ResizeToPreferred();
+	fRevertButton->SetEnabled(false);
+	float buttonHeight = fRevertButton->Bounds().Height();
+	fRevertButton->MoveBy(0, -buttonHeight);
+	AddChild(fRevertButton);
+
 	ResizeTo(fClock->Frame().right + 10.0, fGmtTime->Frame().bottom + 10.0);
 }
 

src/preferences/time/DateTimeView.h

@@ -6,6 +6,7 @@
  *		Andrew McCall <mccall@@digitalparadise.co.uk>
  *		Mike Berg <[email protected]>
  *		Julun <[email protected]>
+ *		Philippe Saint-Pierre <[email protected]>
  */
 #ifndef DATE_TIME_VIEW_H
 #define DATE_TIME_VIEW_H
@@ -19,6 +20,7 @@ class TTimeEdit;
 class BCalendarView;
 class BRadioButton;
 class TAnalogClock;
+class BButton;
 
 
 class DateTimeView : public BView {
@@ -30,12 +32,16 @@ class DateTimeView : public BView {
 		virtual void 	Draw(BRect updaterect);
 		virtual void 	MessageReceived(BMessage *message);
 
+				void	CheckCanRevert();
+
 	private:
 		void 			_InitView();
 		void 			_ReadRTCSettings();
 		void			_WriteRTCSettings();
 		void			_UpdateGmtSettings();
 		void 			_UpdateDateTime(BMessage *message);
+		void			_Revert();
+		time_t			_PrefletUptime() const;
 
 	private:
 		BRadioButton 	*fLocalTime;
@@ -45,8 +51,14 @@ class DateTimeView : public BView {
 		BCalendarView 	*fCalendarView;
 		TAnalogClock 	*fClock;
 
+		BButton			*fRevertButton;
+
 		bool 			fUseGmtTime;
+		bool			fOldUseGmtTime;
 		bool			fInitialized;
+
+		time_t			fTimeAtStart;
+		bigtime_t		fSystemTimeAtStart;
 };
 
 #endif	// DATE_TIME_VIEW_H

src/preferences/time/TimeMessages.h

@@ -6,6 +6,7 @@
  *		Andrew McCall, [email protected]
  *		Mike Berg <[email protected]>
  *		Julun <[email protected]>
+ *		Philippe Saint-Pierre <[email protected]>
  */
 #ifndef TIME_MESSAGES_H
 #define TIME_MESSAGES_H
@@ -40,5 +41,8 @@ const uint32 kWeekStart = '_kws';
 // clicked on day in calendar
 const uint32 kDayChanged = '_kdc';
 
+// clicked on revert button
+const uint32 kMsgRevert = 'rvrt';
+
 #endif //TIME_MESSAGES_H
 

src/preferences/time/TimeWindow.cpp

@@ -43,6 +43,7 @@ TTimeWindow::MessageReceived(BMessage *message)
 	switch(message->what) {
 		case H_USER_CHANGE:
 			fBaseView->ChangeTime(message);
+			fDateTimeView->CheckCanRevert();
 			break;
 		
 		case B_ABOUT_REQUESTED: