Automatically determine the first weekday for a calendar control

If neither wxCAL_SUNDAY_FIRST or wxCAL_MONDAY_FIRST was given, use
wxDateTime::GetFirstWeekDay() to automatically determine the preferred
day.

This changes the earlier default behaviour, which was to use Sunday
if not otherwise specified. However, the wxGTK native calendar control
ignored this behaviour anyway.

include/wx/calctrl.h

@@ -27,7 +27,7 @@
 enum
 {
     // show Sunday as the first day of the week (default)
-    wxCAL_SUNDAY_FIRST               = 0x0000,
+    wxCAL_SUNDAY_FIRST               = 0x0080,
 
     // show Monday as the first day of the week
     wxCAL_MONDAY_FIRST               = 0x0001,
@@ -332,6 +332,9 @@ protected:
 
     // called by EnableHolidayDisplay()
     virtual void RefreshHolidays() { }
+
+    // does the week start on monday based on flags and OS settings?
+    bool WeekStartsOnMonday() const;
 };
 
 // ----------------------------------------------------------------------------

include/wx/generic/calctrlg.h

@@ -202,13 +202,13 @@ private:
     // get the first/last days of the week corresponding to the current style
     wxDateTime::WeekDay GetWeekStart() const
     {
-        return HasFlag(wxCAL_MONDAY_FIRST) ? wxDateTime::Mon
+        return WeekStartsOnMonday() ? wxDateTime::Mon
                                            : wxDateTime::Sun;
     }
 
     wxDateTime::WeekDay GetWeekEnd() const
     {
-        return HasFlag(wxCAL_MONDAY_FIRST) ? wxDateTime::Sun
+        return WeekStartsOnMonday() ? wxDateTime::Sun
                                            : wxDateTime::Sat;
     }
 

interface/wx/calctrl.h

@@ -8,7 +8,7 @@
 enum
 {
     // show Sunday as the first day of the week (default)
-    wxCAL_SUNDAY_FIRST               = 0x0000,
+    wxCAL_SUNDAY_FIRST               = 0x0080,
 
     // show Monday as the first day of the week
     wxCAL_MONDAY_FIRST               = 0x0001,
@@ -254,6 +254,11 @@ enum wxCalendarHitTestResult
     month is changed, so you will often want to update them in
     @c EVT_CALENDAR_PAGE_CHANGED event handler.
 
+    If neither the @c wxCAL_SUNDAY_FIRST or @c wxCAL_MONDAY_FIRST style is given,
+    the first day of the week is determined from operating system's settings,
+    if possible. The native wxGTK calendar chooses the first weekday based on
+    locale, and these styles have no effect on it.
+
     @beginStyleTable
     @style{wxCAL_SUNDAY_FIRST}
            Show Sunday as the first day in the week (not in wxGTK)

src/common/calctrlcmn.cpp

@@ -195,5 +195,26 @@ bool wxCalendarCtrlBase::SetHolidayAttrs()
     return true;
 }
 
+bool wxCalendarCtrlBase::WeekStartsOnMonday() const
+{
+    if ( HasFlag(wxCAL_MONDAY_FIRST) )
+    {
+        return true;
+    }
+    else if ( HasFlag(wxCAL_SUNDAY_FIRST) )
+    {
+        return false;
+    }
+    else
+    {
+        // Neither flag was explicitly given, let's make a best guess
+        // based on locale and/or OS settings.
+
+        wxDateTime::WeekDay firstDay;
+        wxDateTime::GetFirstWeekDay(&firstDay);
+        return firstDay == wxDateTime::Mon;
+    }
+}
+
 #endif // wxUSE_CALENDARCTRL
 

src/generic/calctrlg.cpp

@@ -245,6 +245,10 @@ void wxGenericCalendarCtrl::SetWindowStyleFlag(long style)
                     (m_windowStyle & wxCAL_SEQUENTIAL_MONTH_SELECTION),
                   wxT("wxCAL_SEQUENTIAL_MONTH_SELECTION can't be changed after creation") );
 
+    wxASSERT_MSG( !((style & wxCAL_SUNDAY_FIRST) &&
+                   (style & wxCAL_MONDAY_FIRST)),
+                 "wxCAL_SUNDAY_FIRST and wxCAL_MONDAY_FIRST cannot be both used" );
+
     wxControl::SetWindowStyleFlag(style);
 }
 
@@ -644,7 +648,7 @@ bool wxGenericCalendarCtrl::AdjustDateToRange(wxDateTime *date) const
 
 size_t wxGenericCalendarCtrl::GetWeek(const wxDateTime& date) const
 {
-    size_t retval = date.GetWeekOfMonth(HasFlag(wxCAL_MONDAY_FIRST)
+    size_t retval = date.GetWeekOfMonth(WeekStartsOnMonday()
                                    ? wxDateTime::Monday_First
                                    : wxDateTime::Sunday_First);
 
@@ -891,7 +895,7 @@ void wxGenericCalendarCtrl::OnPaint(wxPaintEvent& WXUNUSED(event))
         dc.SetPen(wxPen(m_colHeaderBg, 1, wxPENSTYLE_SOLID));
         dc.DrawRectangle(0, y, GetClientSize().x, m_heightRow);
 
-        bool startOnMonday = HasFlag(wxCAL_MONDAY_FIRST);
+        bool startOnMonday = WeekStartsOnMonday();
         for ( int wd = 0; wd < 7; wd++ )
         {
             size_t n;
@@ -1238,7 +1242,7 @@ bool wxGenericCalendarCtrl::GetDateCoord(const wxDateTime& date, int *day, int *
 
     if ( IsDateShown(date) )
     {
-        bool startOnMonday = HasFlag(wxCAL_MONDAY_FIRST);
+        bool startOnMonday = WeekStartsOnMonday();
 
         // Find day
         *day = date.GetWeekDay();
@@ -1479,7 +1483,7 @@ wxCalendarHitTestResult wxGenericCalendarCtrl::HitTest(const wxPoint& pos,
         {
             if ( wd )
             {
-                if ( HasFlag(wxCAL_MONDAY_FIRST) )
+                if ( WeekStartsOnMonday() )
                 {
                     wday = wday == 6 ? 0 : wday + 1;
                 }

src/msw/calctrl.cpp

@@ -152,11 +152,11 @@ WXDWORD wxCalendarCtrl::MSWGetStyle(long style, WXDWORD *exstyle) const
 
 void wxCalendarCtrl::SetWindowStyleFlag(long style)
 {
-    const bool hadMondayFirst = HasFlag(wxCAL_MONDAY_FIRST);
+    const bool hadMondayFirst = WeekStartsOnMonday();
 
     wxCalendarCtrlBase::SetWindowStyleFlag(style);
 
-    if ( HasFlag(wxCAL_MONDAY_FIRST) != hadMondayFirst )
+    if ( WeekStartsOnMonday() != hadMondayFirst )
         UpdateFirstDayOfWeek();
 }
 
@@ -427,7 +427,7 @@ void wxCalendarCtrl::UpdateMarks()
 void wxCalendarCtrl::UpdateFirstDayOfWeek()
 {
     MonthCal_SetFirstDayOfWeek(GetHwnd(),
-                               HasFlag(wxCAL_MONDAY_FIRST) ? MonthCal_Monday
+                               WeekStartsOnMonday() ? MonthCal_Monday
                                                            : MonthCal_Sunday);
 }
 

src/qt/calctrl.cpp

@@ -107,9 +107,9 @@ void wxCalendarCtrl::UpdateStyle()
     if ( !m_qtCalendar )
         return;
 
-    if ( m_windowStyle & wxCAL_MONDAY_FIRST )
+    if ( WeekStartsOnMOnday() )
         m_qtCalendar->setFirstDayOfWeek(Qt::Monday);
-    else // wxCAL_SUNDAY_FIRST
+    else
         m_qtCalendar->setFirstDayOfWeek(Qt::Sunday);
 
     if ( m_windowStyle & wxCAL_SHOW_WEEK_NUMBERS )