CODEWITHSUNDEEP
pythonkivy
MASTER OF CODE
MASTER OF CODE

Reputation: 302

Kivy using Canvas: How to limit painting area?

I'm learning kivy and I want to create basic painting app. There's very nice example on kivy's main site. It allows to paint and clear the screen. I just want to add one new thing. I don't want to be allowed to paint "under the button". What I mean by that is I want to limit space on which I'm allowed to paint.

There's documentation code:

from random import random
from kivy.app import App
from kivy.uix.widget import Widget
from kivy.uix.button import Button
from kivy.graphics import Color, Ellipse, Line


class MyPaintWidget(Widget):

    def on_touch_down(self, touch):
        color = (random(), 1, 1)
        with self.canvas:
            Color(*color, mode='hsv')
            d = 30.
            Ellipse(pos=(touch.x - d / 2, touch.y - d / 2), size=(d, d))
            touch.ud['line'] = Line(points=(touch.x, touch.y))

    def on_touch_move(self, touch):
        touch.ud['line'].points += [touch.x, touch.y]


class MyPaintApp(App):

    def build(self):
        parent = Widget()
        self.painter = MyPaintWidget()
        clearbtn = Button(text='Clear')
        clearbtn.bind(on_release=self.clear_canvas)
        parent.add_widget(self.painter)
        parent.add_widget(clearbtn)
        return parent

    def clear_canvas(self, obj):
        self.painter.canvas.clear()


if __name__ == '__main__':
    MyPaintApp().run()

It doesn't use .kv file, maybe that is way to go. Thanks for any help.

EDIT: Link to documentation: https://kivy.org/doc/stable/tutorials/firstwidget.html

Upvotes: 0

Views: 428

Answers (1)

inclement
inclement

Reputation: 29488

Ignore touch input that isn't within the bounds you want. For instance, with something like if not self.collide_point(*touch.pos)): return in your touch handling methods.

You may also want to do something like treat touches as released once they leave the bounds of the drawing area, but that's up to you.

You might also want to use a StencilView to ensure that no drawing can actually appear outside the widget bounds.

Upvotes: 2

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