Pure Python gestures

[mikael]

Python gesture implementation on Github for those situations where you cannot or do not want to use the ObjC gestures.

Simple usage example:

import pygestures

class MyTouchableView(pygestures.GestureView):
  
  def on_swipe(self, data):
    if data.direction in (data.UP, data.DOWN):
      print('I was swiped vertically')

Run the file as-is to play around with the gestures. (Green circles track your touches, crosshairs show the centroid, red circle reflects pan, pinch and rotation.)

In your subclass, implement any or all the methods below to handle gestures. All methods get an information object with attributes including:

• state - one of BEGAN, CHANGED, ENDED
• location - location of the touch, or the centroid of all touches, as a scene.Point
• no_of_touches - use this if you want to filter for e.g. only taps with 2 fingers

Methods:

• on_tap
• on_long_press
• on_swipe - data includes direction, one of UP, DOWN, LEFT, RIGHT
• on_swipe_up, on_swipe_down, on_swipe_left, on_swipe_right
• on_pan - data includes translation, the distance from the start of the gesture, as a scene.Point. For most purposes this is better than location, as it does not jump around if you add more fingers.
• on_pinch - data includes scale
• on_rotate - data includes rotation in degrees, negative for counterclockwise rotation

There are also prev_translation, prev_scale and prev_rotation, if you need them.

If it is more convenient to you, you can inherit GestureMixin together with ui.View or some other custom view class. In that case, if you want to use e.g. rotate, you need to make sure you have set multitouch_enabled = True.

[mikael]

@Anxietier, and a version with a revealed label and a refresh trigger:

import ui
import scripter

v = ui.View(background_color='black')

class Pulled(ui.View):
    
    straight_pull = 30
    slowing_pull = 80
    
    def touch_began(self, t):
        self.start_y = ui.convert_point(t.location, from_view=self).y
        
    def touch_moved(self, t):
        delta_y = (
            ui.convert_point(t.location, from_view=self).y - 
            ui.convert_point(t.prev_location, from_view=self).y)
        if self.y < self.straight_pull:
            self.y += delta_y
            return
        if self.y < (self.straight_pull + self.slowing_pull):
            diff = self.y-self.straight_pull
            diff_fraction = diff/self.slowing_pull
            try:
                self.reveal_func(diff_fraction)
            except AttributeError: pass
            effective = 1 - min(1, diff_fraction) ** 2
            self.y += delta_y * effective
            
        
    def touch_ended(self, t):
        scripter.y(self, 0, ease_func=scripter.ease_out)
        try:
            self.reveal_func(0)
        except AttributeError: pass
        if self.y > self.straight_pull:
            self.trigger_func()

label = ui.Label(text='Release to refresh',
    text_color='white',
    flex='LBR',
    alpha=0,
)
label.size_to_fit()
label.center = v.bounds.center()
label.y = 8
v.add_subview(label)

def reveal(fraction):
    label.alpha = fraction
    
def trigger():
    scripter.hide(label)
    print('refresh')

v.add_subview(Pulled(
    reveal_func=reveal,
    trigger_func=trigger,
    frame=v.bounds,
    flex='WH',
    background_color='green'))

v.present('fullscreen')

[mikael]

@Anxietier, oh, you can throw away the touch_began method, it’s from an earlier version.

[Anxietier]

@mikael thank you
and if i want to bind it with gestures, what should i do
i mean is there any conflict between gestures and touch
what i want to make is, i can use twin fingers to zoom and move picture(imageview or subclass zoompanview, later is better i guess), and when i move picture, move space and scale would be limited, as i leave my fingers, picture's edge should be forced move to superview's edge

[Anxietier]

@mikael ah, dont bother
i didnt read doc carefully(perhaps wrong word :P), now i can bind them together, thanks for ur help, ur codes are really amazing and helpful :D

[mikael]

@Anxietier, little optimization of the ”feel” and code simplification.

import ui
import scripter

v = ui.View(background_color='black')

class Pulled(ui.View):
    
    trigger_distance = 30
    pull_distance = 80
    
    def touch_moved(self, t):
        delta_y = (
            ui.convert_point(t.location, from_view=self).y - 
            ui.convert_point(t.prev_location, from_view=self).y)
        diff_fraction = self.y/self.pull_distance
        try:
            self.reveal_func(diff_fraction)
        except AttributeError: pass
        self.y += delta_y * (1 - min(0.9, diff_fraction) ** 2)
        self.y = max(0, self.y)
        
    def touch_ended(self, t):
        scripter.y(self, 0, ease_func=scripter.ease_out)
        try:
            self.reveal_func(0)
        except AttributeError: pass
        if self.y > self.trigger_distance:
            self.trigger_func()

label = ui.Label(text='Release to refresh',
    text_color='white',
    flex='LBR',
    alpha=0,
)
label.size_to_fit()
label.center = v.bounds.center()
label.y = 8
v.add_subview(label)

def reveal(fraction):
    label.alpha = fraction
    
def trigger():
    scripter.hide(label)
    print('refresh')

v.add_subview(Pulled(
    reveal_func=reveal,
    trigger_func=trigger,
    frame=v.bounds,
    flex='WH',
    background_color='green'))

v.present('fullscreen')

[stephen]

!!! Removed by poster to not confuse future readers with incorrect Code Examples.. 🤓😉

[Anxietier]

@mikael
thanks for help, i make it
but there's another problem showed up:
i make a main view, then i subclass zoomPanView and add to mainView , after that i add imageView as zoomPanView's subVIew, like what zoomPanDemo did, when i overwrite on_pan method and test it, data.began and data.changed can give me right value, but data.ended not, i dont know why

[Anxietier]

@stephen thanks for help!
im would try to understand ur code, im not good in math though :(
btw, i tried mikael's code, and it works fine to me :P

[Anxietier]

@Anxietier said:

@mikael
thanks for help, i make it
but there's another problem showed up:
i make a main view, then i subclass zoomPanView and add to mainView , after that i add imageView as zoomPanView's subVIew, like what zoomPanDemo did, when i overwrite on_pan method and test it, data.began and data.changed can give me right value, but data.ended not, i dont know why

one more thing, i overwrote on_pinch too, and i printed data.ended, and got right value, maybe two gesture's ended flag conflict ?

[mikael]

@Anxietier, thanks for catching this. Pan end event was not properly handled, fixed now in the version on the repo.

[Anxietier]

@Anxietier said:

@Anxietier said:

@mikael
thanks for help, i make it
but there's another problem showed up:
i make a main view, then i subclass zoomPanView and add to mainView , after that i add imageView as zoomPanView's subVIew, like what zoomPanDemo did, when i overwrite on_pan method and test it, data.began and data.changed can give me right value, but data.ended not, i dont know why

one more thing, i overwrote on_pinch too, and i printed data.ended, and got right value, maybe two gesture's ended flag conflict ?

i resolved this issue
i subclass both view and GestureMixin as new ZoomPanView, then i overwrite touch_ended, so that when i subclass new ZoomPanView i can edit touch_ended,
high encapsulation not always convenient XD

[Anxietier]

@mikael said:

@Anxietier, thanks for catching this. Pan end event was not properly handled, fixed now in the version on the repo.

expecting for new version (👍 ͡❛ ͜ʖ ͡❛)👍

[mikael]

@Anxietier, is there a specific reason why you are using the Python version instead of the native iOS gestures? Just curious, because I no longer remember why I wrote pygestures. 😁 ... Probably just because I wanted to see if I could do it.

[Anxietier]

@mikael
well, im not good at math, i tried use touch_began\move\ended, and surely i can make simple function, but as it became complex, my brain be in chaos, XD

[mikael]

@Anxietier, I meant choosing between gestures.py (wrapper around iOS native gestures) and pygestures.py (pure Python gestures built on top of the ui.View.touch_x method ”primitives”.

Your answer leads me to guess you might not have been aware of the first option.

[Anxietier]

@mikael oh, i did try gesture.py, got some problems, and you suggested me subclass ZoomPanView instead for my need, then i did and i find it's interesting, so ~~ :))

@mikael said:

@Anxietier, can you subclass ZoomPanView instead?

If you run pygestures.py and swipe from the right, you get the demo picture that you can pan and zoom, and that seems to work ok.

The code for it is at the end of the file.

[mikael]

@Anxietier, oh, and I thought you were already using the python version, given the title of this discussion thread... 😄

[stephen]

@Anxietier

do you still need help with drag/friction algorithm ?

[Anxietier]

@stephen
thank you, maybe not, i did solve this problem (probably not yet)
thanks for your help :)

[Anxietier]

@mikael
haha, I was trying to make a zoom demo, but the effect is not good, so I googled key words "pythonista 2 finger zoom", then luckily found this XD