onPaint event not triggered twice

itzwich1

Hallo,

I try to build my own spinBox. Now I draw my Up & Down Arrow buttons with Canvas which draw the arrows in the onPaint event.

Now the Problem

mainWindow.qml // Window where I would like to use my SpinBox
{
     OwnSpinBox{
          width: 100
          height: 20
          value: 20 //It works (Both of my Up&Down Arrows will draw with onPaint
          Component.onCompleted:{
               value: 20   //Works not (Only one of both Arrows will draw with onPaint
          }
     }
}

Component.onCompleted: value: 20

value: 20

It looks like that onPaint event works only once in ColumLayout. But only value will set in Component.onCompleted

value is a int which will checks in a cpp class if its valid. Is it valid da int will converted to a string and will write to the textInput as text.

My Cpp class inherits from QQuickItem.

Hope anybody can help me.

sierdzio

@itzwich1 said in onPaint event not triggered twice:

Component.onCompleted:{
value: 20 //Works not (Only one of both Arrows will draw with onPaint
}

This syntax is incorrect. It should be:

 Component.onCompleted:{
               value = 20
          }

itzwich1

@sierdzio sorry thats my mistake. I said (value = 20)

sierdzio

Assignment like this (with =) breaks bindings (with :). So, if you rely on some property to set the value (like value: someOtherValue), don't add override in onCompleted.

itzwich1

@sierdzio I do not use both versions at the same time. If I use the value: 20 it works fine and my up and down arrows will painted. If I use (Component.onCompleted: value = 20) instead of (value: 20) it doesn't work.

sierdzio

OK, now I begin to understand :-) Try forcing a repaint in your setter for value property (in C++).

itzwich1

@sierdzio How can I trigger onPaint event on c++ side?

sierdzio

You can call updatePaintNode(yourMainNode, nullptr); if you have the main node stored somewhere. Alternatively, mark the node as dirty https://doc.qt.io/qt-5/qsgnode.html#markDirty

itzwich1

@sierdzio I think that solves not the problem. I try to use update() which call updatePaintNode in it (according the doku). Problem is still there.

sierdzio

Verify if it's called or not with debugger or qDebug.

Maybe paste the drawing code here, perhaps there's something wrong there?

itzwich1

My colleague could help me. It looks like that the general layouting went wrong.