Il 22/04/2018 13:22, Michael Van Canneyt via Lazarus ha scritto:
This is how all properties that are TPersistent descendents work, so
this
behaviour should not come as a surprise.
I wouldn't say so.
E.g. TCanvas is a TPersistent descendent, but the Canvas property of a
TCustomControl is declared like that:
property Canvas: TCanvas read FCanvas write FCanvas;
This means that after a
SomeControl.Canvas := MyCanvas;
or
MyCanvas := SomeControl.Canvas;
SomeControl.Canvas and MyCanvas will be the same object. Only a pointer
is copied.
On the contrary, the property Bitmap of a TPicture is declare like that:
property Bitmap: TBitmap read GetBitmap write SetBitmap;
where GetBitmap actually returns the TPicture.Bitmap Object, while
SetBitmap creates a different Bitmap Object, and assigns it the content
of the supplied bitmap (see TPicture.SetGraphic, called by
TPicture.SetBitmap).
This means that after a
MyBitmap := SomePicture.Bitmap;
MyBitmap and SomePicture.Bitmap will represent the same Object, while
after a
SomePicture.Bitmap := MyBitmap;
MyBitmap and SomePicture.Bitmap will represent different Objects.
This is IMHO a TPicture specific inconsistency.
Giuliano
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