tags: python qt widget
title: Simple Number Spinner 1

A **warning**: adding signals and slots to this was my first experience of why you shouldn't
do the lazy `from X import *` thing: it causes a very obscure error when you try to connect.
In particular, if I put the `NumberSpinner` class below in its own file `number_spinner.py`
in which I do the `import *`, and then in another file I also do `from PySide6.... import *`
and then `import number_spinner`, then trying to connect the number spinner to something
causes an exception, which doesn't happen with the `NumberSpinner` class is declared in
the same file. If instead we do the proper thing of not `import *`ing, the problem goes away.

That said, I failed to reproduce the exception when I went back to check the above, so that
might be the problem, or it might be something else. For reference, the exception looked like:
```
shibokensupport/signature/parser.py:270: RuntimeWarning: pyside_type_init:_resolve_value

        UNRECOGNIZED:   'PySide6.QtCore.QMetaObject.Connection'
        OFFENDING LINE: '6:PySide6.QtCore.QObject.connect(self,sender:PySide6.QtCore.QObject,signal:char*,member:char*,type:PySide6.QtCore.Qt.ConnectionType=Qt.AutoConnection)->PySide6.QtCore.QMetaObject.Connection'
     ...
        
Traceback (most recent call last):
  File "/home/john/qt/widgets/signals/a.py", line 42, in <module>
    a = A()
        ^^^
  File "/home/john/qt/widgets/signals/a.py", line 35, in __init__
    self.spinner.boing.connect(self.spinnerChanged)
TypeError: 'PySide6.QtCore.QObject.connect' called with wrong argument types:
  PySide6.QtCore.QObject.connect(NumberSpinner, str, method)
Supported signatures:
  PySide6.QtCore.QObject.connect(PySide6.QtCore.QObject, Union[bytes, bytearray, memoryview], Union[bytes, bytearray, memoryview], PySide6.QtCore.Qt.ConnectionType = Instance(Qt.AutoConnection))
  PySide6.QtCore.QObject.connect(Union[bytes, bytearray, memoryview], Callable, PySide6.QtCore.Qt.ConnectionType = Instance(Qt.AutoConnection))
  PySide6.QtCore.QObject.connect(Union[bytes, bytearray, memoryview], PySide6.QtCore.QObject, Union[bytes, bytearray, memoryview], PySide6.QtCore.Qt.ConnectionType = Instance(Qt.AutoConnection))
  PySide6.QtCore.QObject.connect(PySide6.QtCore.QObject, PySide6.QtCore.QMetaMethod, PySide6.QtCore.QObject, PySide6.QtCore.QMetaMethod, PySide6.QtCore.Qt.ConnectionType = Instance(Qt.AutoConnection))
  PySide6.QtCore.QObject.connect(PySide6.QtCore.QObject, Union[bytes, bytearray, memoryview], PySide6.QtCore.QObject, Callable, PySide6.QtCore.Qt.ConnectionType = Instance(Qt.AutoConnection))
  PySide6.QtCore.QObject.connect(PySide6.QtCore.QObject, Union[bytes, bytearray, memoryview], Callable, PySide6.QtCore.Qt.ConnectionType = Instance(Qt.AutoConnection))
  PySide6.QtCore.QObject.connect(PySide6.QtCore.QObject, Union[bytes, bytearray, memoryview], PySide6.QtCore.QObject, Union[bytes, bytearray, memoryview], PySide6.QtCore.Qt.ConnectionType = Instance(Qt.AutoConnection))
```

Thus, instead of this:
```py
#!/usr/bin/env python

from PySide6.QtCore import *
from PySide6.QtGui import *
from PySide6.QtWidgets import *
from PySide6.QtNetwork import *
app = QApplication()

# this allows us to remove keyword arguments that exist that we are interested in
# and return defaults for those not specified, so that the resulting dictionary
# can be passed to super() with those keyword arguments removed.
def gd(dictionary,key,default,delete=True):
  if key in dictionary:
    v = dictionary[key]
    if delete:
      del(dictionary[key])
    return v
  else:
    return default

class NumberSpinner(QLabel):
  def __init__(self,*xs,**kw):
    gran = int(gd(kw,"gran",10))
    gran = max(1,gran)
    vmax = int(gd(kw,"vmax",100))
    vmin = int(gd(kw,"vmin",0))
    value = int(gd(kw,"init",vmin))
    if vmax <= vmin:
      raise ValueError(f"Invalid range {vmin}..{vmax}")
    roll = int(gd(kw,"roll",False))
    super().__init__(*xs,**kw)
    self.value = value
    self.gran = gran
    self.vmax = vmax
    self.vmin = vmin
    self.roll = roll
    self.drag = False
    self.x0 = 0
    self.y0 = 0
    self.v0 = 0
    self.update()
  def update(self):
    self.setText(str(self.value))
    return super().update()
  def mousePressEvent(self,e):
    pos = e.position()
    self.x0 = pos.x()
    self.y0 = pos.y()
    self.v0 = self.value
  def mouseMoveEvent(self,e):
    pos = e.position()
    x = pos.x()
    y = pos.y()
    dy = y - self.y0
    dv = int(-dy/self.gran)
    v = self.v0 + dv
    vmx = self.vmax + 1 # so that we can attain the maximum bound
    if self.roll:
      v = self.vmin + ( (v - self.vmin) % (vmx - self.vmin) )
    else:
      v = max(self.vmin,min(self.vmax,v))
    self.value = v
    self.update()

ns = NumberSpinner(vmin=1,vmax=16,roll=False)
ns.resize(100,50)
ns.setStyleSheet("font-size: 24px")
ns.setAlignment(Qt.AlignCenter)
ns.show()
app.exec()
```
if we want a reusable spinner widget, do this
```py
import PySide6.QtWidgets
import PySide6.QtGui
import PySide6.QtCore

from jdautil import gd

class NumberSpinner(PySide6.QtWidgets.QLabel):
  changed = PySide6.QtCore.Signal(int)
  def __init__(self,*xs,**kw):
    gran = int(gd(kw,"gran",10))
    gran = max(1,gran)
    vmax = int(gd(kw,"vmax",100))
    vmin = int(gd(kw,"vmin",0))
    value = int(gd(kw,"init",vmin))
    if vmax <= vmin:
      raise ValueError(f"Invalid range {vmin}..{vmax}")
    roll = int(gd(kw,"roll",False))
    super().__init__(*xs,**kw)
    self.value = value
    self.gran = gran
    self.vmax = vmax
    self.vmin = vmin
    self.roll = roll
    self.drag = False
    self.x0 = 0
    self.y0 = 0
    self.v0 = 0
    self.update()

  def update(self):
    self.setText(str(self.value))
    return super().update()

  def mousePressEvent(self,e):
    pos = e.position()
    self.x0 = pos.x()
    self.y0 = pos.y()
    self.v0 = self.value

  def mouseMoveEvent(self,e):
    pos = e.position()
    x = pos.x()
    y = pos.y()
    dy = y - self.y0
    dv = int(-dy/self.gran)
    v = self.v0 + dv
    vmx = self.vmax + 1 # so that we can attain the maximum bound
    if self.roll:
      v = self.vmin + ( (v - self.vmin) % (vmx - self.vmin) )
    else:
      v = max(self.vmin,min(self.vmax,v))
    self.value = v
    self.changed.emit(v)
    self.update()
```
It's probably also a good idea not to be lazy and terse with variable names,
but old habits die hard.