[Interest] Seeking workaround for TableView contentX|contentY bug when hiding columns

[Patrick Stinson]

For what it's worth, emitting `modelReset` from the model does seem to reset the corruption, but then you loose any view state, scroll positions, etc.

> On May 9, 2020, at 5:50 PM, Patrick Stinson <patrickkidd at gmail.com> wrote:
> 
> I found a rather serious bug where TableView.contentX and TableView.contentY gets corrupted when you hide and reshow columns or rows (bug report here: https://bugreports.qt.io/browse/QTBUG-82535 <https://bugreports.qt.io/browse/QTBUG-82535>). I'm looking for a workaround since this makes it impossible to use overlay items.
> 
> Resizing the width of a TableView with columnWidthProvider results in the contentX property having the wrong value. The following video demonstrate how the red rectangle, which has a fixed x of zero, jumps to the right as you resize the table view:
> 
> https://youtu.be/9YEaoTUR4Eo <https://youtu.be/9YEaoTUR4Eo>
> 
> 
> import QtQuick 2.14
> import QtQml.Models 2.14
> import Qt.labs.qmlmodels 1.0
> 
> 
> TableView {
>     id: table        
> 
>     Timer {
>         // Just resize the table twice on init to programatically reproduce the bug.
>         // comment this entire item out to reproduce the bug with manual window resizing.
>         id: timer
>         interval: 1
>         running: true
>         repeat: true
>         property int count: 0
>         onTriggered: {
>             if(count == 0){
>                 table.width = 400
>             } else if(count == 2) {
>                 timer.running = false
>             }
>             count++
>         }
>     }
> 
>     // This "overlay" element doesn't stay put as it should since `x` is always zero.
>     // https://doc.qt.io/qt-5/qml-qtquick-tableview.html#overlays-and-underlays <https://doc.qt.io/qt-5/qml-qtquick-tableview.html#overlays-and-underlays>
>     Rectangle {
>         width: 20
>         height: table.contentHeight
>         color: 'red'
>     }
> 
>     onWidthChanged: {
>         table.forceLayout()
>         print('contentX', contentX) // shows that contextX does not match what is displayed.
>     }
> 
>     // Bug happens when a zero-width column changes to a positive-width column.
>     // So expand the table from less than 200 width to greater than 200 width to corrupt contentX.
>     columnWidthProvider: function(col) {
>         if(table.width > 200) {
>             return 40
>         } else {
>             return col % 2 == 0 ? 0 : 60 // change the `0` width to `1` and the bug doesn't happen
>         }
>     }
> 
>     delegate: Rectangle {
>         implicitHeight: 30
>         border {
>             width: 1
>         }
>         Text { text: display }
>     }
> 
>     model: TableModel {
>         TableModelColumn { display: 'col_1' }
>         TableModelColumn { display: 'col_2' }
>         rows: [
>             { col_1: 'cell 1', col_2: 'cell 1' },
>         ]
>     }
> }
> 
> 

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