[SailfishDevel] Seg fault in QML ListView when connected to SQL model

[coding]

Hi Dmitriy,

Thank you for your input!

I am building a todo list app which have projects and tasks stored in sql. These projects/tasks shall be displayed in several ListViews (on different Pages).

I have mainly two use cases for displaying the sql data:

1) A full screen ListView inside a Flickable. I use "anchors.fill: parent" to set the size for this ListView.
2) A ListView which does not cover the entire Page since I want some other QML items on that page. I use a QML Column to display the QML items including the ListView, but I have set the ListView to a fixed size to get the right proportions between the different items in the QML Column.

I have however been able to reproduce the problem for both cases above so I don't think the problem is related to the ListView having a fixed height.

My app use Silica components like SilicaFlickable and SIlicaListView but when troubleshooting I have tried to remove the Silica components to rule out any Silica related bugs. I could however not find any matching components to replace Silica ListItem and ContextMenu so I cannot completely rule out that this bug may be related to Silica components.

>From the call stack it looks like it crashes in Qt core components, but I have problems following what happens. It is #89 in the call stack which deletes the item in the model/ListView which eventually results in segmentation fault.

Regards

On Mon, 7 Sep 2015 09:42:19 +0600, Dmitriy Purgin <dpurgin at gmail.com> wrote:

> Hi,
> 
> can you tell please what are you trying to achieve, e.g. what view are you
> building? Why do you set explicit height for the ListView anyway?
> 
> Cheers
> Dmitriy
> 
> 2015-09-06 14:00 GMT+06:00 coding <coding at userspace.se>:
> 
> > Hi,
> >
> > I am developing a sailfish app using a QML ListView which is connected to
> > a model using a sqlite db. The model is based on QSqlTableModel, but
> > extended so it can be used by the QML ListView. I have found a segmentation
> > fault related to the ListView when trying to delete an element in the
> > ListView using the ContextMenu. I considered reporting this as a bug to
> > qt.io, but I decided to post it here first.
> >
> > I have tried to reproduce the problem with a short code snippet, but since
> > the bug needs the SQL model it was hard to get it very short.
> > QML code: http://pastebin.com/b5zkFm1q
> > C++ code: http://pastebin.com/5RN269kH
> > gdb trace: http://pastebin.com/4ZdCbZd6
> > app debug output: http://pastebin.com/C4N9T1tP
> >
> > How to reproduce:
> > 1. Start app (in emulator, I don't have my jolla tablet yet)
> > 2. Long press the last element in the list and select "Delete" from the
> > context menu.
> > (It can also be triggered from other elements in the list, but the code at
> > pastebin is based on the last element)
> >
> > The bug is triggered if the bottom of ContextMenu is rendered below the
> > height of the ListView.
> > When long pressing the n:th element in the ListView it will crash if:
> > listviewHeight < n*elementHeight+(n-1)*spacing + contextMenuHeight
> >
> > Example (using pastebin code):
> > ListView is 338 pixels high and have 4 items inside
> > Each item is 44 pixels high
> > Spacing is 1 pixel
> > Context menu is 160 pixels high
> >
> > When clicking on the 4:th item (starting counting from 1) the total height
> > of items + spacing + context menu will be:
> > 4*(44) + (4-1)*1 + 160 = 339 pixels
> > listviewHeight=338 => crash
> > listviewHeight=339 => not crash
> >
> > When deleting the element in the list I do two things:
> > 1. model->removeRow(index) //Everything is fine after this is executed
> > 2. model->submitAll() //Results in segmentation fault
> >
> > I have tried replacing the model with a QML ListModel, created/filled in
> > QML, but then the bug is not triggered.
> >
> > Any input would be appreciated!
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