Tkcalendar: Right align calendar dropdown with the DateEntry

Question

By default the calendar dropdown & DateEntry widgets are left-aligned. In one case, the calendar is getting out of the screen as shown in the pic. Can we somehow right-align the calendar dropdown with respect to the corresponding DateEntry widget.

Answer 1

It is possible to right-align the dropdown by rewriting the drop_down() method of the DateEntry. The dropdown is a Toplevel which is positioned on the screen with

self._top_cal.geometry('+%i+%i' % (x, y))

where (x, y) is the top-left corner of the dropdown. So, for a left-aligned dropdown

x = self.winfo_rootx()  # the left side of the entry 

Now to get a right-aligned dropdown, we need to change x into

x = self.winfo_rootx() + self.winfo_width() - self._top_cal.winfo_reqwidth()

namely (position of the right side of the entry) - (width of the dropdown).

Full code:

from tkcalendar import DateEntry
import tkinter as tk

class MyDateEntry(DateEntry):
    def __init__(self, master=None, align='left', **kw):
        DateEntry.__init__(self, master, **kw)
        self.align = align

    def drop_down(self):
        """Display or withdraw the drop-down calendar depending on its current state."""
        if self._calendar.winfo_ismapped():
            self._top_cal.withdraw()
        else:
            self._validate_date()
            date = self.parse_date(self.get())
            if self.align == 'left':  # usual DateEntry
                x = self.winfo_rootx()
            else:  # right aligned drop-down
                x = self.winfo_rootx() + self.winfo_width() - self._top_cal.winfo_reqwidth()
            y = self.winfo_rooty() + self.winfo_height()
            if self.winfo_toplevel().attributes('-topmost'):
                self._top_cal.attributes('-topmost', True)
            else:
                self._top_cal.attributes('-topmost', False)
            self._top_cal.geometry('+%i+%i' % (x, y))
            self._top_cal.deiconify()
            self._calendar.focus_set()
            self._calendar.selection_set(date)


root = tk.Tk()

tk.Label(root, text='left align').grid(row=0, column=0)
tk.Label(root, text='right align').grid(row=0, column=1)
MyDateEntry(root).grid(row=1, column=0)
MyDateEntry(root, align='right').grid(row=1, column=1)

root.mainloop()    

EDIT: you can also detect if the drop-down will be out of screen and automatically adjust the drop-down position to avoid that:

def drop_down(self):
    """Display or withdraw the drop-down calendar depending on its current state."""
    if self._calendar.winfo_ismapped():
        self._top_cal.withdraw()
    else:
        self._validate_date()
        date = self.parse_date(self.get())
        h = self._top_cal.winfo_reqheight()
        w = self._top_cal.winfo_reqwidth()
        x_max = self.winfo_screenwidth()
        y_max = self.winfo_screenheight()
        # default: left-aligned drop-down below the entry
        x = self.winfo_rootx()
        y = self.winfo_rooty() + self.winfo_height()
        if x + w > x_max:  # the drop-down goes out of the screen
            # right-align the drop-down
            x += self.winfo_width() - w
        if y + h > y_max:  # the drop-down goes out of the screen
            # bottom-align the drop-down
            y -= self.winfo_height() + h
        if self.winfo_toplevel().attributes('-topmost'):
            self._top_cal.attributes('-topmost', True)
        else:
            self._top_cal.attributes('-topmost', False)
        self._top_cal.geometry('+%i+%i' % (x, y))
        self._top_cal.deiconify()
        self._calendar.focus_set()
        self._calendar.selection_set(date)

Note that this solution will not work properly when using several monitors since tkinter detects only one big rectangular screen.