[FIXED] QGrapicsScene: Changing of QGraphicRects height only applied after second run

Issue

I am programming a stacked bar plot in QGraphicsScene using QGraphicRectItems. Everything works so far, but it seems as if I change the height of the QGraphicsRectItems straight after creating it with setRect, the height is not applied. Strangely, if I rerun the program the height is always changed to the same "random" values.

If I change the height of the QGraphicsRects once more, using the same function everything works. Is there anything I need to do after creating a QGraphicsRect to "register" it or something?

Edit:

The same happens if I change the heights again. I need to do it twice to make the bars adjust their height correctly.

Code:

In my function I change the height of the (stacked) QGraphicsRectItems with:

accH = 0
for i, h in enumerate(data):
    geo = rects[i].rect()
    print "before\t\t\t", geo
    print "target height\t\t", h
    geo.setHeight(h)
    geo.setY(accH)
    rects[i].setRect(geo)
    print "changed geometry\t", geo
    print "geometry of updated rect", rects[i].rect()
    print "___"

    accH += h
print "-----"

rects is a list of previously created QGraphicsItems.

Output of the print statements above with data = [ 98. 263. 6710. 0.]:

First run:

before                  PySide.QtCore.QRectF(0.000000, 0.000000, 1.000000, 98.000000)
target height           98.0
changed geometry        PySide.QtCore.QRectF(0.000000, 0.000000, 1.000000, 98.000000)
geometry of updated rect PySide.QtCore.QRectF(0.000000, 0.000000, 1.000000, 98.000000)
___
before                  PySide.QtCore.QRectF(0.000000, 98.000000, 1.000000, 166.000000)
target height           263.0
changed geometry        PySide.QtCore.QRectF(0.000000, 98.000000, 1.000000, 263.000000)
geometry of updated rect PySide.QtCore.QRectF(0.000000, 98.000000, 1.000000, 263.000000)
___
before                  PySide.QtCore.QRectF(0.000000, 361.000000, 1.000000, 6351.000000)
target height           6710.0
changed geometry        PySide.QtCore.QRectF(0.000000, 361.000000, 1.000000, 6710.000000)
geometry of updated rect PySide.QtCore.QRectF(0.000000, 361.000000, 1.000000, 6710.000000)
___
before                  PySide.QtCore.QRectF(0.000000, 7071.000000, 1.000000, -7068.000000)
target height           0.0
changed geometry        PySide.QtCore.QRectF(0.000000, 7071.000000, 1.000000, 0.000000)
geometry of updated rect PySide.QtCore.QRectF(0.000000, 7071.000000, 1.000000, 0.000000)
___

Second run:

before                  PySide.QtCore.QRectF(0.000000, 0.000000, 1.000000, 98.000000)
target height           98.0
changed geometry        PySide.QtCore.QRectF(0.000000, 0.000000, 1.000000, 98.000000)
geometry of updated rect PySide.QtCore.QRectF(0.000000, 0.000000, 1.000000, 98.000000)
___
before                  PySide.QtCore.QRectF(0.000000, 98.000000, 1.000000, 263.000000)
target height           263.0
changed geometry        PySide.QtCore.QRectF(0.000000, 98.000000, 1.000000, 263.000000)
geometry of updated rect PySide.QtCore.QRectF(0.000000, 98.000000, 1.000000, 263.000000)
___
before                  PySide.QtCore.QRectF(0.000000, 361.000000, 1.000000, 6710.000000)
target height           6710.0
changed geometry        PySide.QtCore.QRectF(0.000000, 361.000000, 1.000000, 6710.000000)
geometry of updated rect PySide.QtCore.QRectF(0.000000, 361.000000, 1.000000, 6710.000000)
___
before                  PySide.QtCore.QRectF(0.000000, 7071.000000, 1.000000, 0.000000)
target height           0.0
changed geometry        PySide.QtCore.QRectF(0.000000, 7071.000000, 1.000000, 0.000000)
geometry of updated rect PySide.QtCore.QRectF(0.000000, 7071.000000, 1.000000, 0.000000)
___

What I just realized just now while making this output ready for stackoverflow, the problem seems that the height of each QGraphicsRectItem is the proper height - its y value. I tried now to first do setY and then setHeight on geo above. Then the prints suggest that the geometry (rect) of the QGraphicsRects are correct. But on the QGraphicsView I do not see any change.

Solution

I found the solution to my problem eventually.

What one has to do is to call setY before setHeight on the QRect defining the geometry of the QGraphicsRect.

Answered By - P.R.