tkinter touchscreen scrolling - button press makes unwanted scrolling - Printable Version +- Python Forum (https://python-forum.io) +-- Forum: Python Coding (https://python-forum.io/forum-7.html) +--- Forum: GUI (https://python-forum.io/forum-10.html) +--- Thread: tkinter touchscreen scrolling - button press makes unwanted scrolling (/thread-31703.html) |
tkinter touchscreen scrolling - button press makes unwanted scrolling - nanok66 - Dec-28-2020 Hi all, I have a python tkinter GUI that I am using with a touchscreen. One page on my GUI has more buttons than can fit in one screen, so I found some excellent code that creates a vertical scrolled frame. With this frame I can drag my finger on the touchscreen and the frame will move accordingly. My issue is when I press a button, the scrolling happens too. I basically have to "chase the button" up or down the screen (depending on if the button is located in the top or bottom half of the screen). I wish this was easily reproduceable but this issue only occurs when I am using my finger on the touchscreen, it does not happen when I am using the mouse. I tried using a stylus pen (maybe my fingers are too fat) but the issue is the same. I tried reducing the speed of the scroll, and I even commented out 2 lines at the very bottom of the code. Commenting out the 2 lines actually seemed to do nothing, I wonder what those lines are for?? Below is the code for the frame. My python app is too complex to give you a full working page to actually play with, so sorry about that. Perhaps someone can tell just by looking at my class. Any help is appreciated!! class VerticalScrolledFrame(tk.Frame): def __init__(self, parent, bg, *args, **kw): tk.Frame.__init__(self, parent, *args, **kw) # create a canvas object and a vertical scrollbar for scrolling it canvas = tk.Canvas(self, bd=0, highlightthickness=0, bg=bg) canvas.pack(side=tk.LEFT, fill=tk.BOTH, expand=True) # reset the view canvas.xview_moveto(0) canvas.yview_moveto(0) self.canvasheight = 2000 # create a frame inside the canvas which will be scrolled with it self.interior = interior = tk.Frame(canvas, height=self.canvasheight, bg=bg) interior_id = canvas.create_window(0, 0, window=interior, anchor=tk.NW) # track changes to the canvas and frame width and sync them, # also updating the scrollbar def _configure_interior(event): # update the scrollbars to match the size of the inner frame size = (interior.winfo_reqwidth(), interior.winfo_reqheight()) canvas.config(scrollregion="0 0 %s %s" % size) if interior.winfo_reqwidth() != canvas.winfo_width(): # update the canvas's width to fit the inner frame canvas.config(width=interior.winfo_reqwidth()) interior.bind('<Configure>', _configure_interior) def _configure_canvas(event): if interior.winfo_reqwidth() != canvas.winfo_width(): # update the inner frame's width to fill the canvas canvas.itemconfigure(interior_id, width=canvas.winfo_width()) canvas.bind('<Configure>', _configure_canvas) self.offset_y = 0 self.prevy = 0 self.scrollposition = 1 def on_press(event): self.offset_y = event.y_root #if self.scrollposition < 1: #commenting out these 2 lines fixed an old scrolling issue that kept resetting the position #self.scrollposition = 1 if self.scrollposition > self.canvasheight: self.scrollposition = self.canvasheight canvas.yview_moveto(self.scrollposition / self.canvasheight) def on_touch_scroll(event): nowy = event.y_root sectionmoved = 11 # speed of scroll if nowy > self.prevy: event.delta = -sectionmoved elif nowy < self.prevy: event.delta = sectionmoved else: event.delta = 0 self.prevy= nowy self.scrollposition += event.delta canvas.yview_moveto(self.scrollposition/ self.canvasheight) #self.bind("<Enter>", lambda _: self.bind_all('<Button-1>', on_press), '+') #what does this line do? apparently not needed #self.bind("<Leave>", lambda _: self.unbind_all('<Button-1>'), '+') ##what does this line do? apparently not needed self.bind("<Enter>", lambda _: self.bind_all('<B1-Motion>', on_touch_scroll), '+') self.bind("<Leave>", lambda _: self.unbind_all('<B1-Motion>'), '+') RE: tkinter touchscreen scrolling - button press makes unwanted scrolling - nanok66 - Dec-28-2020 Ok, I entirely commented out the on_press function and it seems to work fine. Also I added some code to on_touch_scroll. Pushing the buttons now does not make the screen jump! But I cannot slowly scroll the screen, only can scroll with fast finger flicks now. I guess I can live with that compromise (lost the ability to slow scroll). But there is another issue that persists - if my last touch was far from the newest touch, the screen will scroll a tiny amount towards the new touch. I would definitely like to know how to deactivate that effect. def on_touch_scroll(event): nowy = event.y_root sectionmoved = 11 # speed of scroll if nowy > (self.prevy + 20): # to limit the minimum threshold to scroll event.delta = -sectionmoved elif nowy < (self.prevy - 20): # to limit the minimum threshold to scroll event.delta = sectionmoved else: event.delta = 0 self.prevy= nowy self.scrollposition += event.delta canvas.yview_moveto(self.scrollposition/ self.canvasheight) |