Question

Does anyone have any idea why I get different line widths on the canvas in the following example?

from Tkinter import *
bigBoxSize = 150

class cFrame(Frame):
    def __init__(self, master, cwidth=450, cheight=450):
        Frame.__init__(self, master, relief=RAISED, height=550, width=600, bg = "grey")
        self.canvasWidth = cwidth
        self.canvasHeight = cheight
        self.canvas = Canvas(self, bg="white", width=cwidth, height=cheight, border =0)
        self.drawGridLines()
        self.canvas.pack(side=TOP, pady=20, padx=20)

    def drawGridLines(self, linewidth = 10):
        self.canvas.create_line(0, 0, self.canvasWidth, 0, width= linewidth )
        self.canvas.create_line(0, 0, 0, self.canvasHeight, width= linewidth )

        self.canvas.create_line(0, self.canvasHeight, self.canvasWidth + 2, self.canvasHeight, width= linewidth )
        self.canvas.create_line(self.canvasWidth, self.canvasHeight, self.canvasWidth, 1, width= linewidth )

        self.canvas.create_line(0, bigBoxSize, self.canvasWidth, bigBoxSize, width= linewidth )
        self.canvas.create_line(0, bigBoxSize * 2, self.canvasWidth, bigBoxSize * 2, width= linewidth)


root = Tk()
C = cFrame(root)
C.pack()
root.mainloop()

It’s really frustrating me as I have no idea what’s happening. If anyone can help me out then that’d be fantastic. Thanks!

Answer 1

When you draw a line with a width greater than 1, the extra pixels have to be drawn somewhere. As you observed in your own followup post, some of those pixels are being drawn off screen. All you need to do is adjust your original coordinates to take into account the width of the line.