在tkinter画布对象的查看区域周围创建“屏障”

Question

好吧，我这里有一种特殊的情况，所以请容忍我。我希望能够在tkinter画布对象的查看区域周围创建所谓的“屏障”（用户可以看到画布的部分）。例如，看看下面的截图（基于最后的MCVE）：

正如您在上面的图像中看到的，当用户到达最后一行时，该行当前位于画布的查看区域之外。但是，这不是我想要的。相反，我希望每当用户到达画布可见区域的末端时，一个“屏障”会变热，一旦接触，回车就会发生，然后一行又一行从那里继续。所以，我真正想要的不是以上这些，而是：

下面是我用来拍摄上述截图的MCVE：

import tkinter as TK

xold = None
yold = None

class canvas(TK.Frame):
    def __init__(self, root, *args, **kwargs):
        # Initialize a tkinter frame widget
        TK.Frame.__init__(self, root, width = 800, height = 850, *args, **kwargs)
        self.root = self.winfo_toplevel()
        self.bg = "white"
        self.width, self.height = 850, 800
        self.canvwidth, self.canvheight = 10000, 10000
        # Set up the canvas and its corresponding scrollbars
        self.canvas = TK.Canvas(root, width=850, height=800,
                                 bg=self.bg, borderwidth=0, highlightthickness = 5, highlightbackground = 'brown', highlightcolor = 'brown')
        self.hscroll = TK.Scrollbar(root, command=self.canvas.xview,
                                    orient=TK.HORIZONTAL)
        self.vscroll = TK.Scrollbar(root, command=self.canvas.yview)
        self.canvas.configure(xscrollcommand=self.hscroll.set,
                               yscrollcommand=self.vscroll.set)
        self.rowconfigure(0, weight=1, minsize=0)
        self.columnconfigure(0, weight=1, minsize=0)
        # Add the scrollbars into the root window
        self.canvas.grid(padx=1, pady=1, row=0,
                column=0, rowspan=1, columnspan=1, sticky = 'news')
        self.vscroll.grid(padx=1, pady=1, row=0,
                column=1, rowspan=1, columnspan=1, sticky='news')
        self.hscroll.grid(padx=1, pady=1, row=1,
                column=0, rowspan=1, columnspan=1, sticky='news')
        # Call the `reset` method of the canvas class
        self.reset()
        # Bind the `line` method to the 'l' key of the users keyboard (as an example of what I want)
        self.root.bind('<l>', self.line)

    def reset(self, canvwidth=None, canvheight=None, bg = None):
        ###############################################################################################################################
        # This adds the scrollbars themselves to the canvas and adapts them to the canvas's size (in this case, 10000 x 10000 pixels) #
        ###############################################################################################################################

        if canvwidth:
            self.canvwidth = canvwidth
        if canvheight:
            self.canvheight = canvheight
        if bg:
            self.bg = bg
        self.canvas.config(bg=bg,
                        scrollregion=(-self.canvwidth//2, -self.canvheight//2,
                                       self.canvwidth//2, self.canvheight//2))
        self.canvas.xview_moveto(0.5*(self.canvwidth - self.width + 30) /
                                                               self.canvwidth)
        self.canvas.yview_moveto(0.5*(self.canvheight- self.height + 30) /
                                                              self.canvheight)

    def line(self, event):
        ########################################################################################################
        # Create a short, horizontal, black line on every press of the user's 'l' key (as an example to go by) #
        ########################################################################################################
        global xold, yold
        if xold != None and yold != None:
            pass
        else:     
            xold, yold = 0, 0
        self.canvas.create_line(xold, yold, xold+30, yold, smooth = TK.TRUE, width = 1, capstyle = TK.ROUND, joinstyle = TK.ROUND, fill = 'black')
        xold = xold+30
        yold = yold

if __name__ == '__main__':
    # Create a window, and provide that window to the canvas class as the root window
    root = TK.Tk()
    root.geometry('900x850')
    canvas(root)
    root.mainloop()

是否可以使用tkinter将此能力添加到上面的MCVE中？如果是这样，我如何开始尝试实施它？

Answer 1

我不知道你到底想做什么（尤其是当你提供一个很大的带有滚动条的画布时，试图在显示区域中约束绘图）。在

对于最简单的情况，您只需要一个绑定值，并根据它测试xold

if xold > 440:
    xold = -410
    yold += 30

如果要考虑当前显示的区域，则必须组合来自canvasscrollregion和xview方法的信息。第一个返回画布的边界，并显示aera在滚动区域中的相对位置。在

^{pr2}$