Tkinter 滚动条使用导致按钮不可见

import Tkinter
import ImageTk
import Image
​
class Interface(Tkinter.Tk) :
    def __init__(self, parent) :
        Tkinter.Tk.__init__(self, parent)
        self.parent = parent
        self.initialize()
​
    # Creation of the widgets
    def initialize(self) :
        # Fenetre principale
        self.minsize(437, 98)
        # Scrollbars working on principal Canvas self.c
        self.ascenseur_y = Tkinter.Scrollbar(self, orient=Tkinter.VERTICAL)
        self.ascenseur_x = Tkinter.Scrollbar(self, orient=Tkinter.HORIZONTAL)
        self.ascenseur_y.grid(row=0, column=1, sticky="ns")
        self.ascenseur_x.grid(row=1, column=0, sticky="ew")
​
        # Canvas self.c - Frame self.fr and label self.bl are in self.c
        self.c = Tkinter.Canvas(self, yscrollcommand=self.ascenseur_y.set, xscrollcommand=self.ascenseur_x.set, bg="white", highlightthickness=0)
        self.c.grid(row=0, column=0, sticky="news")
        self.c.bind('<Configure>', self.dimensionner)
​
        self.grid_rowconfigure(0, weight=1)
        self.grid_columnconfigure(0, weight=1)
​
        self.ascenseur_x.config(command=self.c.xview)
        self.ascenseur_y.config(command=self.c.yview)
​
        self.grid_rowconfigure(0, weight=1)
        self.grid_columnconfigure(0, weight=1)
​
        # Invisible Frame to bind Mousewheel event with vertical scrollbar
        self.fr = Tkinter.Frame(self.c)
        self.fr.pack(expand=True, fill="both")
        self.fr.bind_all("<MouseWheel>", self._on_mousewheel_haupt)
​
        # Def Label with background-picture. all other widgets but the scrollbars are in self.bl
        self.apercu_logo="Logo.png"
        self.photo = ImageTk.PhotoImage(Image.open(self.apercu_logo))
        self.bl = Tkinter.Label(self.c, image=self.photo, bg="white")
​
        self.image_y = self.winfo_height()/2
        self.image_x = self.winfo_width()/2
        self.c.create_window(450/2, 300/2, window=self.bl, height=500, width=800)
        self.bl.update_idletasks()
​
        # Button "start pdf2pptx"
        self.bouton_pdf2pptx = Tkinter.Button(self.bl, width=13, text=u"Pdf2pptx", command=self.ButtonPdf2pptx, anchor="center", cursor="hand2", padx=0)
        self.bouton_pdf2pptx.grid(column=0, row=0, padx=10)
        self.bouton_pdf2pptx.bind("<Return>", self.EnterPdf2pptx)
        self.bouton_pdf2pptx.focus_set()
​
        # Button "start xls2inp"
        self.bouton_xls2inp = Tkinter.Button(self.bl, width=13, text=u"xls2inp", command=self.ButtonXls2inp, anchor="center", cursor="hand2", padx=0)
        self.bouton_xls2inp.grid(column=1, row=0, padx=10)
        self.bouton_xls2inp.bind("<Return>", self.EnterXls2inp)
​
        # Button "start Zeichen ersetzer"
        self.bouton_ZeichenErsetzer = Tkinter.Button(self.bl, width=13, text=u"Zeichen ersetzer", command=self.ButtonZeichenErsetzer, anchor="center", cursor="hand2", padx=0)
        self.bouton_ZeichenErsetzer.grid(column=2, row=0, padx=10)
        self.bouton_ZeichenErsetzer.bind("<Return>", self.EnterZeichenErsetzer)
​
​
        # Configuration rows/columns - in self.bl
​
        self.bl.grid_rowconfigure(0, weight=1, pad=100, minsize=50)
​
        self.bl.grid_columnconfigure(0, weight=1, pad=30, minsize=140)
        self.bl.grid_columnconfigure(1, weight=1, pad=30, minsize=140)
        self.bl.grid_columnconfigure(2, weight=1, pad=30, minsize=140)
​
        # Logo of the main window
        self.iconbitmap("IcoKAG.ico")
​
    # Options of the main window
        # Resizable
        self.resizable(True, True)
        # Principal Canvas and config of the scrollbars
        self.image_y = self.winfo_height()/2
        self.image_x = self.winfo_width()/2
        self.c.create_window(self.image_x, self.image_y, window=self.fr)
        self.fr.update_idletasks()
​
        # Min size of main window
        self.minsize(200, 100)
​
        # Size of main window at the opening
        self.geometry("500x300")
​
        if self.winfo_width() < 437 :
            self.bl.grid_columnconfigure(0, weight=1, pad=30, minsize=self.winfo_width()/3)
            self.bl.grid_columnconfigure(1, weight=1, pad=30, minsize=self.winfo_width()/3)
            self.bl.grid_columnconfigure(2, weight=1, pad=30, minsize=self.winfo_width()/3)
        else :
            self.bl.grid_columnconfigure(0, weight=1, pad=30, minsize=140)
            self.bl.grid_columnconfigure(1, weight=1, pad=30, minsize=140)
            self.bl.grid_columnconfigure(2, weight=1, pad=30, minsize=140)
​
        if self.winfo_height() >= 300 and self.winfo_width() >= 500 :
            self.SR = (0, 0, self.photo.width(), self.photo.height())
            self.SRL = list(self.SR)
            self.SRL[2] = self.winfo_width() - 16
            self.SRL[3] = self.winfo_height() - 16
            self.c.config(scrollregion=tuple(self.SRL))
            self.update()
            self.bl.update_idletasks()
        elif self.winfo_height() < 300 and self.winfo_width() >= 500 :
            self.SR = (0, 0, self.photo.width(), self.photo.height())
            self.SRL = list(self.SR)
            self.SRL[2] = self.winfo_width() - 16
            self.SRL[3] -= 16
            self.c.config(scrollregion=tuple(self.SRL))
            self.update()
            self.bl.update_idletasks()
        elif self.winfo_height() >= 300 and self.winfo_width() < 500 :
            self.SR = (0,