Horizontal scrolling won't activate for ttk Treeview widget

Question

I'm using the ttk Treeview widget to implement a folder/path selection dialog. It's all working as expected except that my horizontal scrollbar won't activate. No matter how wide the folder path goes horizontally, and no matter how narrow the window, the horizontal slider never appears. Vertical scrolling is working perfectly though.

I'm figuring it's either some kind of limitation when you only use one column in the treeview, or just a newbie mistake with configuring and connecting the widgets. I'd bet on the latter.

Example with dialog widened to show full folder depth:

Dialog narrowed to the point where horizontal scrolling should activate (but doesn't):

Here's my GUI layout code:

winDirSel = tk.Toplevel()
winDirSel.title('Select Test Directory...')
tvwDirSel = ttk.Treeview(winDirSel,
                         height=10,padding=3,
                         show='tree')
lblTestDir = tk.Label(winDirSel, relief=tk.SUNKEN,
                      justify=tk.LEFT, anchor=tk.W,
                      textvariable=ctrlTestDir,width=80)
scbHDirSel = ttk.Scrollbar(winDirSel,
                           orient=tk.HORIZONTAL,
                           command=tvwDirSel.xview)
scbVDirSel = ttk.Scrollbar(winDirSel,
                           orient=tk.VERTICAL,
                           command=tvwDirSel.yview)
tvwDirSel.configure(xscrollcommand=scbHDirSel.set,
                    yscrollcommand=scbVDirSel.set)
lblTestDir.grid(row=0,column=0,sticky=tk.EW)
tvwDirSel.grid(row=1,column=0,sticky=tk.NSEW)
scbVDirSel.grid(row=1,column=1,sticky=tk.NS)
scbHDirSel.grid(row=2,column=0,sticky=tk.EW)
winDirSel.rowconfigure(1,weight=1)
winDirSel.columnconfigure(0,weight=1)

Answer 1

OK, after some playing with minwidth and stretch, I think I have a better handle on it. The horizontal scrolling is triggered by the column-edge going out of the window's bounds, not the content of the column. So you can use these parameters to force the column to be wider and thus force the scrolling.

The problem though is that you then lose the automatic adjustment of the column width to suit the width of the tree itself. You either have to force it very wide to accommodate any (assumed) likely folder depth, or you live with folder names getting truncated at the right boundary of the column.

So bottom line: it's just a limitation of the widget itself. (At least with respect to its behavior on my platform, MS Windows.)

Answer 2

import tkinter as tk
import tkinter.ttk as ttk
import tkinter.font as tk_font

class TreeListBox:

    def __init__(self, master, root, dict_group):
        self.master = master
        self.root = root
        self.dict_group = dict_group
        self.level = 0
        self.setup_widget_tree()
        self.build_tree(self.root, '')

    def setup_widget_tree(self):
        container_tree = tk.Frame(self.master, width=250, height=300)
        container_tree.propagate(False)
        container_tree.pack(side="left", fill='y')
        self.tree = ttk.Treeview(container_tree, show="tree", selectmode='browse')
        fr_y = tk.Frame(container_tree)
        fr_y.pack(side='right', fill='y')
        tk.Label(fr_y, borderwidth=1, relief='raised', font="Arial 8").pack(side='bottom', fill='x')
        sb_y = tk.Scrollbar(fr_y, orient="vertical", command=self.tree.yview)
        sb_y.pack(expand='yes', fill='y')
        fr_x = tk.Frame(container_tree)
        fr_x.pack(side='bottom', fill='x')
        sb_x = tk.Scrollbar(fr_x, orient="horizontal", command=self.tree.xview)
        sb_x.pack(expand='yes', fill='x')
        self.tree.configure(yscrollcommand=sb_y.set, xscrollcommand=sb_x.set)
        self.tree.pack(fill='both', expand='yes')

    def build_tree(self, parent, id_stroki):
        self.level += 1
        id = self.tree.insert(id_stroki, 'end', text=parent)
        # -----------------
        col_w = tk_font.Font().measure(parent)
        if col_w > 1000:
            col_w -= 400
        elif col_w > 500:
            col_w -= 200
        elif col_w > 300:
            col_w -= 100
        col_w = col_w + 25 * self.level
        if col_w > self.tree.column('#0', 'width'):
            self.tree.column('#0', width=col_w)
        # -----------------
        for element in sorted(self.dict_group[parent]):
            self.build_tree(element, id)
        self.level -= 1

if __name__ == '__main__':
    dict_group = {'Nomenclature': ['ABC1', 'ABC2'],
                  'ABC1': ['ABC3', 'ABC4'],
                  'ABC2': ['ABC5'],
                  'ABC3': ['ABC______________________________________6'],
                  'ABC4': ['ABC--------------------------------------8'],
                  'ABC5': ['ABC######################################9'],
                  'ABC______________________________________6': [],
                  'ABC--------------------------------------8': [],
                  'ABC######################################9': []
                  }
    root = tk.Tk()
    myTest = TreeListBox(root, 'Nomenclature', dict_group)
    root.mainloop()