I'm new to Python and I'm trying to create a simple GUI using Tkinter.
So often in many user interfaces, hitting the tab button will change the focus from one Text widget to another. Whenever I'm in a Text widget, tab only indents the text cursor.
Does anyone know if this is configurable?
This is very easy to do with Tkinter.
There are a couple of things that have to happen to make this work. First, you need to make sure that the standard behavior doesn't happen. That is, you don't want tab to both insert a tab and move focus to the next widget. By default events are processed by a specific widget prior to where the standard behavior occurs (typically in class bindings). Tk has a simple built-in mechanism to stop events from further processing.
Second, you need to make sure you send focus to the appropriate widget. There is built-in support for determining what the next widget is.
For example:
def focus_next_window(event):
event.widget.tk_focusNext().focus()
return("break")
text_widget=Text(...)
text_widget.bind("<Tab>", focus_next_window)
Important points about this code:
The method tk_focusNext() returns the next widget in the keyboard traversal hierarchy.
the method focus() sets the focus to that widget
returning "break" is critical in that it prevents the class binding from firing. It is this class binding that inserts the tab character, which you don't want.
If you want this behavior for all text widgets in an application you can use the bind_class() method instead of bind() to make this binding affect all text widgets.
You can also have the binding send focus to a very specific widget but I recommend sticking with the default traversal order, then make sure the traversal order is correct.
It is really simple in PyQt4 simply use this one single line below and you will be able to change focus by pressing tab button:
self.textEdit.setTabChangesFocus(True)
The focus traversal is somewhat customizable, usually letting the X windows manager handle it (with focus follows mouse, or click). According to the manual it should be possible to bind an event to the key press event, for tab presses, and triggering a focusNext event in those cases.
Related
How do you overwrite a QWidget's focusOutEvent to save/submit and display the QSqlTablemodel's lastError, after losing focus? I want to inform the user if there was any problems saving the model and have him correct or discard the changes.
I tried implementing the code below on a QWidget, which is a tab in tabControl but it is not executing when I close the tab or when navigating to child/sub tabs
def focusOutEvent(self,event):
print("Losing focus now")
self.model.submitAll()
print(self.model.lastError().text())
The focusOutEvent generally requires the focusPolicy to be set to something other than the default of Qt::NoFocus in order to receive focus events.
The policy is Qt::TabFocus if the widget accepts keyboard focus by
tabbing, Qt::ClickFocus if the widget accepts focus by clicking,
Qt::StrongFocus if it accepts both, and Qt::NoFocus (the default) if
it does not accept focus at all.
Refer to http://doc.qt.io/archives/qt-4.8/qwidget.html#focusOutEvent & http://doc.qt.io/archives/qt-4.8/qwidget.html#focusPolicy-prop for more information on this.
I am currently working on a project using Python and tkinter.
The problem is that I don't know what's the proper way to display multiple windows, or screens, I don't know how to call them. Let me explain better.
When the application starts the login screen appears. After that, if I click register, I want to go to the register screen, but I don't want it to be a separate window (I don't want to have 2 windows displayed at the same time), but rather another window with different content ?!
How should I handle properly this situation? Create a second window using Toplevel and hiding the first (can I do that?) or changing the widgets of the first?
Code I've written so far
You can do that- just call window.withdraw() on the Toplevel you need to hide after creating a new Toplevel. Changing the widgets in the first is also an option- if you like, you could always try a Notebook widget and disable manual flipping or just put each "screen" in a frame and grid_ or pack_forget them to remove them from the window.
I have two windows in my application and one of these windows has no frame for design purposes.
The frame with the window has the usual toolbar with the minimize, restore, maximize and close buttons.
Is there a way i can close the window with no frame, with the framed windows close button?
Yes. You just need to save a reference to the 2nd frame. Something like this should suffice:
self.secondFrame = MySecondFrame()
Then in the first frame's close method, you can just do something like this:
self.secondFrame.Close()
However, I should note that creating a frame without the usual toolbar goes against most OS GUI guidelines and users will likely be irritated by that design decision.
EDIT: Yes, you can catch the event that occurs when the user presses the "X" button on the window via wx.EVT_CLOSE. When you do that, you need to call the main frame's Destroy() method instead of its Close method or you'll end up in an infinite loop since calling Close() fires EVT_CLOSE. You can still use Close() for the second frame though.
How to change the button decoration with wxPython, generally when the button is clicked, a dotted lines appear on the button.. any way to make that button not show the dotted lines?
Thanks
Assuming you're running your program on Windows (you didn't say which OS, but dotted lines are used by Windows Classic look), the dotted lines are called the focus rect, and they appear to mark a button or widget as focused. They are a system setting, and your program is acting as it should - wxWidgets is meant to emulate the underlying OS default behaviour as closely as possible.
Update
I don't think you can change this behaviour from inside the program. I really doubt that wxWidgets has a setting somewhere for this, as it is OS-dependent and is the standard and correct behaviour for the Classic theme. But the focus rect is shown by default only on the Classic Look which few people use.
Try switching to Luna theme (the default on XP), and you'll see that the focus rect won't appear unless you start hitting Tab while your window is in focus. By the way, the focus rect is needed exactly for when you are switching the focus using the Tab key. You need to see where the focus is, after all. That way you know when you press Enter or Space, which button is going to be pressed. Not everyone uses only the mouse.
You can use a custom button, for instance wx.lib.buttons.GenButton which is in pure python so you can overwrite the look, feel etc.
This also has a method SetUseFocusIndicator to turn off the dotted focus indicator
How to suppress end user ability to edit/add/delete text in a Text widget? (Python v3.2.. and tkinter)
The point is to suppress only the ability to change/add/delete text but not to castrate other features. Perhaps a NoEdit Text widged would be a better name.
I've tried .text['state'] = 'disabled' and it works almost OK in Windows (it still allows user to select/copy text highlights the selection, page up/down and up/down buttons work. The only thing broken seems to be the cursor made invisible.)
But on MacIntosh everything is broken. No highlights, no select/copy,... UGH
Since Tkinter has practically no documentation in Python, I've searched and found some TCL advise, to derive a new class and suppress the insert and delete functions.
So, I've tried as so:
class roText(tk.Text):
def insert(self,*args,**kwargs):
print(" Hey - Im inside roText.insert")
pass
def delete(self,*args,**twargs):
pass
def pInsert(self,*args,**twargs):
super().insert(*args,**twargs)
Unfortunately it didn't work right. Apparently tkinter does not use those insert and delete functions when end user enters/deletes code. Perhaps those TCL insert/delete are something else, and I lost something in translation from TCL and Swahili. What functions does tkinter.Text use for end user editing text? Hopefully they are not internal...
So, is there a way to modify the Text widget to suppress only end user editing?
Is there a way to do it without diving inside and overriding internal Tkinter code, so the stuff doesn't get broken by next releases of Tkinter?
Looking at the Idle shell window, I see that they've managed to suppress edits (except for the last line). So there is a way. But what is it and how costly?
Sorry for bumping an old question, but I was searching for an answer to this question also and finally found a solution. The solution I found involves overriding the key bindings when the text widget has focus and is pretty simple. Found here.
To override the bindings of a widget there is a bind function where you pass a string of what is to be overridden and the new function you want it to call.
self.txtBox.bind("<Key>", self.empty)
Somewhere else in the class you'll need to define the function to handle the event.
def empty(self, event):
return "break"
By returning the string "break" the event handler knows to stop after your function, instead of continuing with the default action.
I hope this answers your question. Cheers.
The reason the disabled state doesn't seem to work on the Mac is because it turns off the binding that gives focus to the widget. Without focus, the highlighting on a Mac doesn't show up. If you set the state to disabled but then assign a binding to <ButtonPress-1> to explicitly set focus to the disabled text widget, you can then select and copy text and the highlighting will show.
As for the cursor disappearing... arguably, that's what's supposed to happen. The cursor tells the user "this is where text will get inserted". Since no text will get inserted, having that visual clue would be confusing to the user. What you could do instead, if it was really important, is to insert a small image wherever they click to simulate the cursor.
To answer your question about whether the widget actually uses the insert and delete methods: the methods on the actual underlying widget are what the default bindings use, so overriding them in a subclass has no effect. You would need to redo all the default bindings for that to work. It's doable, but a lot of work.
Unfortunately, this is one area where programming in Tcl really shines, because you can simply disable the insert and delete commands of the widget. Of course, you can do that directly in Tkinter also since ultimately it runs tcl code to do everything, but that would involve writing some tcl code which is not a very good solution from the perspective of a Python coder.
I think the best solution is to use the disabled state, then add in just enough bindings to do what you want.
Here's a simple example that works by explicitly setting focus on a mouse button click. With this code I'm able to click and swipe to select a region, or double- or triple-click to select words and lines:
import Tkinter as tk
class SampleApp(tk.Tk):
def __init__(self, *args, **kwargs):
tk.Tk.__init__(self, *args, **kwargs)
self.text = tk.Text(width=40, height=20)
self.text.bind("<1>", self.set_focus)
self.text.insert("end", "\n".join(dir(tk.Tk)))
self.text.configure(state="disabled")
self.text.pack(fill="both", expand=True)
def set_focus(self, event):
'''Explicitly set focus, so user can select and copy text'''
self.text.focus_set()
if __name__ == "__main__":
app = SampleApp()
app.mainloop()
#BryanOakley It took me a while to test your suggestion since I have no Mac.
Unfortunately Mac implementation of Python is buggy.
I've added focus, ie my disable function which I call after creating a window and inserting text, now calls first:
self.txt['state'] = 'disabled'
and then
self.txt.focus_set()
Which is what I think you've suggested.
It "kind of" worked. Ie: when selecting text (click and drag or double-click) highlighting works most of the time. Python must have some bad memory references or such bugs: Sometimes highlighting doesn't work at first, then it starts working (in the same window) after more clicking. Sometimes when program is invoked it works right of the bat. Sometimes selecting with Shift-rightArrow key will work but selecting with the mouse will not. Then starts working again. Or it will work fine in one window but not in another one (both of the same class), then starts working in all windows...etc...
The good thing is that adding focus did not affect badly Windows (ie all works fine as without focus.
I guess at this point I will just hope that future/next release of Python for Mac will fix those bugs..
BTW, it seems that Mac is a bit of an orphan for Python. Implementation is much uglier then for Windows. I mean the fonts look worse, the buttons, etc.. Or it could be due to different screen resolutions and Python ports that poorly account for those. Not sure
Anyway. Thank you for your help and suggestion to use focus for Mac.