Destroy Direct2D bitmap?

0
votes

I'm using C++ Builder XE7. Whenever a form resizes I need to rebuild a D2D bitmap, which I create with CreateBitmap(). As this will quickly eat up all video memory, I want to destroy the previous bitmap before creating a new one. Oddly enough I cannot find any information how to destroy this _di_ID2D1Bitmap. I tried the Release() method but that just gives me an AV in line 291 of systobj.h.

What is the proper way to destroy a _di_ID2D1Bitmap?

Thanks.

1
bitmapdirect2dc++builder-xe7
If _di_ID2D1Bitmap is the ID2D1Bitmap interface, just remove all references to it (eg. mySavedBMPRef = null). – Peter Kostov
Thanks @PeterKostov. Is it that simple? My confusion comes from the fact I look at this like a pointer, which I now understand it isn't. I assume not nilling it but replacing it to "point" to the new bitmap works just as well? – Mike Versteeg
_di_ID2D1Bitmap is a DelphiInterface. A variable of that type is a pointer. You don't have to free it manually, because there is an automatic reference counting - ie - when there are no references left, it will be freed automatically. In short, if you have a pointer P holding just one reference to your ID2D1Bitmap, when you pass it to the CreateBitmap() it will acquire a ref to the new bitmap while the old one will became with 0 references and will be freed. – Peter Kostov
Cool, thanks. Not familiar with Delphi so did not know that (nor is it documented). If you post that as answer I'll give you proper credits. – Mike Versteeg

1 Answers

2
votes

_di_ID2D1Bitmap is a DelphiInterface. An interface reference in Delphi is a pointer to pointer to an IMT. So, a variable of _di_ID2D1Bitmap type is a pointer.

You don't have to free it manually, because there is an automatic reference counting - ie - when there are no references left, it will be freed automatically. You may check the IInterface._AddRef and IInterface._Release methods.

In short, if you have a pointer P holding just one reference to your ID2D1Bitmap (ie _di_ID2D1Bitmap), when you pass it to the CreateBitmap() it will acquire a ref to the new bitmap while the old one will became with 0 references and will be freed.

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