python - 在自定义像素网格上移动 Canvas 上的矩形

Question

我编写这段代码是为了练习，它会在按下鼠标左键时移动我的标签:

def motion(self, event):
    delta_x = event.x - self._drag_data["x"]
    delta_y = event.y - self._drag_data["y"]

    self.canvas.move(self._drag_data["item"], delta_x, delta_y)

    self._drag_data["x"] = event.x
    self._drag_data["y"] = event.y

接下来，我尝试在定义的网格(假设为 5 个像素)上移动标签。因此，将标签直接“扣”在一起会更容易。

我该怎么做？有没有办法每 5 个像素移动标签一次？因此，每 5 个像素，标签就会再次在光标下方跳转。

这是我发现的提取函数的示例:

import tkinter as tk

class Example(tk.Frame):

    def __init__(self, parent):
        tk.Frame.__init__(self, parent)

        self.canvas = tk.Canvas(width=400, height=400)
        self.canvas.pack(fill="both", expand=True)

        self._drag_data = {"x": 0, "y": 0, "item": None}

        self._create_token((100, 100), "white")

        self.canvas.tag_bind("token", "<ButtonPress-1>", self.on_token_press)
        self.canvas.tag_bind("token", "<ButtonRelease-1>", self.on_token_release)
        self.canvas.tag_bind("token", "<B1-Motion>", self.on_token_motion)

    def _create_token(self, coord, color):
        (x,y) = coord
        self.canvas.create_oval(x-25, y-25, x+25, y+25, outline=color, fill=color, tags="token")

    def on_token_press(self, event):
        self._drag_data["item"] = self.canvas.find_closest(event.x, event.y)[0]
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

    def on_token_release(self, event):
        self._drag_data["item"] = None
        self._drag_data["x"] = 0
        self._drag_data["y"] = 0

    def on_token_motion(self, event):
        delta_x = event.x - self._drag_data["x"]
        delta_y = event.y - self._drag_data["y"]
        self.canvas.move(self._drag_data["item"], delta_x, delta_y)
        self._drag_data["x"] = event.x
        self._drag_data["y"] = event.y

if __name__ == "__main__":
    root = tk.Tk()
    Example(root).pack(fill="both", expand=True)
    root.mainloop()

Answer 1

这里我们将 x 和 y 的 delta 设置为 5，然后检查鼠标位置是否在我们的项目后面/下方，如果是，我们将 x 或 y 乘以 -1 以使 delta 为负，这样我们的项目就会朝我们的鼠标。

def motion(self, event):
    delta_x = 0
    delta_y = 0
    step = 5

    if abs(event.x - self._drag_data["x"]) >= step:
        delta_x = step
    if abs(event.y - self._drag_data["y"]) >= step:
        delta_y = step

    if event.x < self._drag_data["x"]:
        delta_x *= -1
    if event.y < self._drag_data["y"]:
        delta_y *= -1

    self.canvas.move(self._drag_data["item"], delta_x, delta_y)

    if delta_x != 0:
        self._drag_data["x"] = event.x
    if delta_y != 0:
        self._drag_data["y"] = event.y