[Lazarus] A bitmap strange issue

Giuliano Colla giuliano.colla at fastwebnet.it
Sun Apr 22 12:38:26 CEST 2018

Il 21/04/2018 18:07, Vojtěch Čihák via Lazarus ha scritto:

> @ MyBitmap := Image1.Picture.Bitmap;
> This line only copies pointer, but Image1.Picture.Bitmap belongs to 
> Image1 and it should care itself.

That's what I had guessed, but this means that there's a patent 
inconsistency, as shown in the Button2Click part of my test:

> Image1.Picture.Bitmap := MyBitmap; FreeAndNil(MyBitmap); 

doesn't generate any error. If I don't free MyBitmap I see a memory 
leakage in heaptrc.


Image1.Picture.Bitmap := MyBitmap;

performs an implicit assign, creating a new Bitmap Object for Image1.

The apparently symmetrical

MyBitmap := Image1.Picture.Bitmap;

just copies the pointer. Timage.Picture.GetBitmap and 
TImage.Picture.SetBitmap do not follow the same logic.

All of this is maybe somewhat Delphi compatible. Actually Delphi (Rad 
Studio 10.1) doesn't generate a SIGSEV with the same code, but rather 
just an "Illegal Pointer Operation" warning. However IMO it still 
remains quite inconsistent.


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