SkiaLayout(column) to auto adjust in height when items are invisible

[DarthDeville]

Hi - in Maui i can create a VerticalStackLayout, add child views to Stack and then if i make any of them InVisible(false) the stack collapses to the new height of the views contained. When using SkiaLayout = Column and try the same thing the stack does not collapse/adjust in height but leaves a blank placeholder of the previous view. Does the canvas need a redraw to see the change or something else i maybe missing? Ad

[taublast]

Hi, there are 2 possibilities:
1 in the current nuget we have an issue, it should not behaive this way. I cannot repro such issue with my current code i use but it's a bit ahead of the latest nuget. If this is the case ill just publish the current code i have as a new nuget..
2 If your skialayout (Type="Column") has verticaloptions Fill that might create an issue too. Could you kindly paste your xaml so i could make a 100% fix? Again your are describing something that shouldn't happen, thank you for finding this out!

[DarthDeville]

hey no problemo - heres my xaml pretty simple really but hope it helps!
<draw:SkiaLayout Type="Column" Spacing="0" HorizontalOptions="End" VerticalOptions="Start">
<draw:SkiaImage Source="Pics/pic1.png" HeightRequest="100" WidthRequest="100" HorizontalOptions="Center" IsVisible="true"/>
<draw:SkiaImage Source="Pics/pic2.png" HeightRequest="100" WidthRequest="100" HorizontalOptions="Center"/>
<draw:SkiaImage Source="Pics/pic3.png" HeightRequest="50" WidthRequest="50" Aspect="AspectFit" HorizontalOptions="Center"
</draw:SkiaLayout>

[taublast]

Thanks, will check it now.
Until we fix it you can call Parent.Invalidate() to cause it to recalc the layout to remove this placeholder. Sounds silly that shouldn't happen at all, it's just until we fix your case.
For info, a simple redraw with erasing control cache is Update(). And Repaint() is to redraw the control Parent without invalidating the current control, for example to apply transfroms to existing cache.

[taublast]

Hmm so i pasted your code inside the MainPageGif.xaml of the Sandbox project that is inside drawnui repo, and it looks to work as intended. I can push a preview nuget for you to test if you want? The point is i have a slight feeling maybe this comes from something else inside your specific layout and the code.. Not convinced this comes from existing nuget, but still, if you could try use preview one to check if it changes something would be cool.

[taublast]

preview nuget will be here for some time:
https://github.com/taublast/DrawnUi/tree/2-A/dev/preview

Please let me know if this fixes what you have found, if not would need more of your code to replicate context. Thank you so much for helping to make it better.

[taublast]

Hey just catched this mess you described myself inside a templated stack. Was yours stack with itemtemplate too?

Point is for such case you would need to call Parent.Invalidate(); inside the cell, when you want the stack to remeasure.

Reason is templated cells have always IsParentIndependent set by stack to true, so they never invalidate the parent in order not to create lags when scrolling cells of different height.

I would think on how to implement the logic "invalidate parent if already on screen". Actualy templated stack is full of hacks for smooth scrolling inside scroll, my bet that would all change into a more clean solution.

[taublast]

in my case inside the cell i did:

   if (ShowDate)
   {
       var wasInvisible = !LabelFirstDate.IsVisible;
       LabelFirstDate.Text = item.WhenDesc;
       LabelFirstDate.IsVisible = true;
       if (wasInvisible && WasMeasured)
           Parent.Invalidate();
   }
   else
   {
       var wasVisible = LabelFirstDate.IsVisible;
       LabelFirstDate.IsVisible = false;
       if (wasVisible && WasMeasured)
           Parent.Invalidate();
   }

if ShowDate dinamically changes (your case like you click on something and it changes height) it invalidates the stack.

[DarthDeville]

Thank you for your advice and direction as always!

[taublast]

That Parent.Invalidate(); is rather costly, ill put very soon a new nuget, there you could call cell.Parent.InvalidateByChild(cell); after cell wants to rebuild self in real-time, i mean when already on the screen, and it would fast remeasure only this 1 cell, works fine for my chat messages scroll im currently working at. :)