[Lazarus] RegisterWSComponent documentation?

[Zoë Peterson]

Juha,

On 11/11/20 3:48 AM, Juha Manninen via lazarus wrote:
> FYI, the TTreeView in LCL is custom drawn. It does not map to a native 
> widget unlike LCL controls typically do.

See my reply to Dmitry for the details, but the short answer is that I 
already have everything working.  It's just all in our own classes that 
descend from the widgetset ones.

I don't know if/when the behavior changed, but modern versions of macOS 
do not treat NSView (aka HWND) as opaque.  If you don't draw anything, 
the parent shows through without you having to tell it to.  In dark 
mode, even things like TEdit are translucent.  As long as the TTreeView 
doesn't do a fillRect(ClientRect), everything is drawn correctly.

NSVisualEffectView itself isn't transparent.  It's a hardware 
accelerated surface that takes advantage of the GPU compositing to draw. 
  You can put one on top of a bunch of other opaque controls, tell it to 
show what's behind the window, and it will make it seem like the desktop 
is peaking through without the opaque controls being visible.  There's 
actually a flag for "Show what's behind the window" or "Show what's 
behind the view" that controls that.

-- 
Zoë Peterson
Scooter Software