[Bug] Gtk: Shapes-based rendering disappears when coming back from navigation page

[knocte]

Description

When using navigation pages, we found an edge case in which, if going 2 levels deep through navigation, and coming back, to the initial page, a Shapes-API-based rendering disappears (when using GTK; in other platforms the rendering doesn't disappear).

Steps to Reproduce

1. Run the minimal testcase provided: you will see a black circle and a button "Next".
2. Click on Next: new page gets shown (called SecondPage).
3. Click on Next again: new page gets shown (called ThirdPage).
4. Click the back button on the navigation bar.

Expected Behavior

The initial page is shown again, so the black circle shows again (this happens in Android).

Actual Behavior

The initial page should be shown again, but the black circle is not shown (this happens in Gtk).

Basic Information

• Version with issue: 5.0.0.2012
• Last known good version: N/A
• Platform Target Frameworks:
  • Gtk
• NuGet Packages:
• Affected Devices:

Reproduction Link

(Testcase.zip attached, or clone this branch:
https://github.com/nblockchain/geewallet/tree/bugreport/shapesDisappearingDuringNav )

Workaround

Force a Redraw of the Shapes-based rendering in the OnAppearing() event of the initial page.