How to properly clear and change layouts?
(Qt 4.7.3)
I am using QGraphicsGridLayout to lay out several QGraphicsWidgets.
On occasion, I want to re-arrange the items, and remove or add some items to the layout. I found that the methods provided don’t exactly make this a piece of cake:
-) No clear() ? Seriously?
-) removeAt, but only with an index? What is this index supposed to mean? I didn’t find it anywhere else.
-) How can I reset a row’s fixed height, once I have set it?
-) Will now-unused rows and columns be removed automagically? Or will they remain as artifacts, and possibly use up space?
Here is what I tried so far:
I have written my own clear():
- {
- if ( ! pLayout)
- {
- return;
- }
- for (int i = pLayout->count()-1; i >= 0; --i)
- {
- pLayout->removeAt(i);
- }
- }
I have pointers to all my widgets as members, so I can temporarily handle the fact they are no longer “owned” by the layout.
Then, I have two possible layouts I want to be able to switch between:
- void CCvui_WidgetManager::arrangeLayoutForAnalogAndBinary()
- {
- clearLayout(m_pComponentLayout);
- // All items are visible in this layout variant
- m_pComponentLayout->addItem(m_pAnalogLegend,0,0,
- m_pComponentLayout->addItem(m_pDateLabel,1,0,
- m_pComponentLayout->addItem(m_pBinaryLegend,2,0,1,2);
- m_pComponentLayout->addItem(m_pValueScale,0,1);
- m_pComponentLayout->addItem(m_pAnalogCurveCanvas,0,2);
- m_pComponentLayout->addItem(m_pTimeScale,1,2,1,1);
- m_pComponentLayout->addItem(m_pBinaryCurveCanvas,2,2,1,1);
- }
- void CCvui_WidgetManager::arrangeLayoutForBinaryOnly()
- {
- clearLayout(m_pComponentLayout);
- m_pComponentLayout->addItem(m_pBinaryLegend,0,0,1,2);
- m_pComponentLayout->addItem(m_pBinaryCurveCanvas,0,2,1,1);
- m_pComponentLayout->addItem(m_pTimeScale,1,2,1,1);
- m_pComponentLayout->addItem(m_pDateLabel,1,0,
- // The following items are invisible, and therefore not added
- // to the layout:
- m_pAnalogLegend->setParentItem(m_pSpareComponents);
- m_pAnalogCurveCanvas->setParentItem(m_pSpareComponents);
- m_pValueScale->setParentItem(m_pSpareComponents);
- // Set a parent so they are deleted correctly.
- }
As you can see, I use the same layout, the same cells, and the same items, but I arrange them differently. In addition, in layout variant “binaryOnly”, I have a few invisible items, which I must “park” in an invisible item in order to keep the ownership clear.
The only solution that looks promising I have found so far is to
-) Remove all items from the layout
-) delete the layout
-) re-create the layout
-) re-add the items to the layout
-) re-add the layout to its parent
Is there any simpler, reliable way to re-arrange my items within the layout?
0 replies
You must log in to post a reply. Not a member yet? Register here!