Updating QGraphicsEffect for QGraphicsSvgItem

S Tozer

Hi. I have a class derived from QGraphicsSvgItem, which I'd like to be able to apply graphical effects to during selection of these items in my scene.

With QGraphicsItems, I've been able to re-implement the 'paint' method, and do something during 'isSelected()' - such as changing pen or brush colours. No big deal...

With QGraphicsSvgItem, I've gotten stuck in understanding how to re-implement the paint method (I haven't been able to get my graphic to display at all once I've added this method to my class). My question is: what code do I need to add after re-implementing 'paint' in order to get the graphic to display? Am I maybe trying to go about this the wrong way?

Here's some example code:

from PyQt5.QtWidgets import *
from PyQt5.QtSvg import *
from PyQt5.QtCore import *


class MySVG(QGraphicsSvgItem):
    def __init__(self, icon):
        super().__init__(icon)

        self.setFlags(QGraphicsSvgItem.ItemIsSelectable | QGraphicsSvgItem.ItemSendsGeometryChanges)

    # when I uncomment the code below, svg image doesn't show. I'm confused about what I need to write here...

    # def paint(self, painter, option, widget=None):
    #
    #     # I want to set a graphics colorize effect when item is selected, and disable the effect when deselected
    #     if self.isSelected():
    #         self._effect = QGraphicsColorizeEffect()
    #         self._effect.setColor(Qt.red)
    #         self._effect.setStrength(.5)
    #         self.setGraphicsEffect(self._effect)
    #
    #     else:
    #         pass
    #         #self.setGraphicsEffect(0)

svg_icon_path = 'E:\\dev\\qt_aStar\\SVG\\input.svg'

app = QApplication([])
scene = QGraphicsScene()
view = QGraphicsView(scene)

svg_item = MySVG(svg_icon_path)
scene.addItem(svg_item)

view.show()
app.exec_()

Any advice would be much appreciated,
Thanks!

Stu

S Tozer

This post is deleted!

S Tozer

Thanks Denni. I'm still confused about what I need to be passing to what, unfortunately (I'm quite new to QGraphics scenes/views/and items). I've edited my code example above, simplifying it and making it a more complete (runnable) example.

S Tozer

@Denni-0 said in Updating QGraphicsEffect for QGraphicsSvgItem:

Denni, that's great! Thanks so much. :):) I had tried -

 def paint(self, painter, option, widget=None):
    self.paint(self, painter, option, widget)

Which looked kindof ridiculous (I was just calling the same method on itself, whereas I had to use the actual parent object as you tried to explain to me in previous post).

Only one thing - my code for disabling the graphicsEffect when my item is deselected doesn't appear to work -

self.setGraphicsEffect(0)

I'm sure this is no big deal and I will dig around a bit for the answer.

Thanks again for your time and help on this -

Stu

S Tozer

Thanks and apologies.

I was referring to setting the graphics effect in the 'paint' method on selection of the item, or disabling it once the item is deselected.

I ended up going with, in the constructor:

        self._colourise_effect = QGraphicsColorizeEffect()
        self.setGraphicsEffect(self._colourise_effect)
        self._colourise_effect.setEnabled(False)

and in the 'paint' method:

        if self.isSelected():
            self._colourise_effect.setEnabled(True)
        else:
            self._colourise_effect.setEnabled(False)

'self.setGraphicsEffect(0)' or 'self.setGraphicsEffect(None) was not working... (although I had seen this in other code snippets)

Cheers!