AlexBelo

FreeAndNil() - The Great Delphi Developer Debate https://s608.t.en25.com/e/es?s=608&e=5507850&elqTrackId=65d0dc3c5cdd4756be52277591b686f0&elq=bbc2a556cfa141cc926d04a00819b81d&elqaid=44034&elqat=1 OMG. What? Again? Unbelievable! :-) The following MVPs have shared their opinion on the topic. Register now to see what they have to say! Allen Bauer, Dalija Prasnikar, Frank Lauter, Uwe Raabe, Paul TOTH, Radek Cervinka, Olaf Monien, Dr. Holger Flick, Patrick Prémartin, Boian Mitov, Matthew Vesperman, Vinicius Sanchez, Darian Miller, Juliomar Marchetti, Erik van Bilsen, and Nick Hodges

Hi all. Is this possible to select on QP only reports which I marked with "Start watching this issue"? -- Alex

Thank you, it works.

Hi all. After formatting some lines of message as code (</>) I can not find out how to edit lines in "code section". Is this possible?

Hi all. I have a problem when I try to show a bmp in TImage when Image->Stratched=true. All work as expected when any bmp dimension is less than 32767. But higher dimensions lead to garbage in Image. Is this known limitation of WinAPI (can not find any in docs and Google) or bug in Graphics unit of RAD2007? TIA. -- Alex

AFAIR, there was QC (old borland quality control system) report about 16bit API calls in VCL (in some components if memory serves).

> I don't know why you would prefer DDB when you're working with bitmaps that large. Use DIBs instead. They are backed by virtual memory. Exactly by reason of "my" virtual memory: DDB resides somewhere in GDI (out of my process); I simply has no memory to hold bmp data in my memory during subsequent operations. OK, further investigations have more academical interest because workaround (manual call of StretchBlt) is already found ...

I've found the only related question (without answer) GDI+ Bitmap size limitation? (December 1st, 2006) https://forums.codeguru.com/showthread.php?407837-GDI-Bitmap-size-limitation Also I've noticed that if I comment out Image->Picture->Bitmap->PixelFormat=pfDevice; the problem exists only when initial bmp has pfDevice or pf32bit (the same as pfDevice, AFAIUI) format. Upd: CDC Class (MFC, not very relevant, but ...) https://docs.microsoft.com/en-us/cpp/mfc/reference/cdc-class?view=msvc-160

void TForm1::AdjImage(bool stretch) { if(stretch) { ScrollBox->VertScrollBar->Visible=false; ScrollBox->HorzScrollBar->Visible=false; Image->AutoSize=false; Image->Width=ScrollBox->ClientWidth; Image->Height=ScrollBox->ClientHeight; Image->Stretch=true; } else { Image->Stretch=false; Image->AutoSize=true; ScrollBox->VertScrollBar->Visible=true; ScrollBox->HorzScrollBar->Visible=true; } } void __fastcall TForm1::btnCreateBmpClick(TObject *Sender) { AdjImage(cbStretch->Checked); // preparing Image according to desired view unsigned int w=seW->AsInteger; // test dimensions unsigned int h=seH->AsInteger; TPixelFormat pf; if(rbDevice->Checked) pf=pfDevice; else if(rb8bit->Checked) pf=pf8bit; else if(rb24bit->Checked) pf=pf24bit; else pf=pf32bit; TcppBitmap bmp; bmp->PixelFormat=pf; bmp->SetSize(w, h); TColor c; if(pf!=pf8bit) c=clRed; else c=clBlack; bmp->Canvas->Pen->Color=c; // some testing draw bmp->Canvas->Pen->Width=10; bmp->Canvas->MoveTo(5, 0); bmp->Canvas->LineTo(5, h); bmp->Canvas->MoveTo(0, 0); bmp->Canvas->LineTo(w, h); bmp->Canvas->Pen->Width=1; bmp->Canvas->MoveTo(0, 0); bmp->Canvas->LineTo(w, 0); bmp->Canvas->LineTo(w-1, 0); bmp->Canvas->LineTo(w-1, h-1); bmp->Canvas->LineTo(0, h-1); bmp->Canvas->LineTo(0, 0); Image->Picture->Assign(bmp); // show in Image Image->Picture->Bitmap->PixelFormat=pfDevice; // "move into GDI domain" (out of application's memory space) Image->Picture->Bitmap->FreeImage(); // deallocate DIB-section (if initial bmp was not pfDevice) if(pf!=pf8bit) c=clGreen; else c=clGray; // another test (on Image internal bitmap now) Image->Canvas->Pen->Color=c; Image->Canvas->Pen->Width=10; Image->Canvas->MoveTo(20, 0); Image->Canvas->LineTo(20, h); } Results: left - H<32768 (as expected), right H=32768 (usually random pieces of desktop).

> 32768 x 32768 x 24 bit ---> 3 Gb No, I mean any dimention (not both) like 1024*32768. I suspect that somewhere in VCL some "size parameter" is word (not cardinal). It would be nice to check this issue in current version.

After some experiments: - if I do StretchBlt manually into intermediate bmp the result is always correct (i.e. this API call works as expected even with huge bmp ~1Gb); - if I set Image->Stretched=true and perform Image->Picture->Assign(bmp), the resulting picture in Image on a form is totally wrong when bmp->Width or Height is >32767; tracing into Graphics unit doesn't show anything suspicious (the same call of StretchBlt with correct parameters) ... So as workaround I have to create stretched image manually...

> Graphics32 Unfortunately I can not use 32bit images due to memory limits. As I mentioned above I use RAD2007 and 32bit compiler. Even on Win64 (where 32bit app can use nearly 4 Gb of memory) I have not enough continuous memory for 32bit image (24bit bmp is still workable in my case).

Thank you for your response. Yes, I can create stretched bmp manually but for now I'd like to use a simple solution (if possible). > huge (more than a CD for a single image) Wow. Of course, you have no chance to process such picture with any thinkable API/hardware. My images are much smaller (like 2k*150k) but even them cause "Out of resourses". 🙂

Hi all. Just for your information: IDE cannot find declaration with 32-bit clang compiler https://quality.embarcadero.com/browse/RSP-29732

Hi all. Do anybody know any ready for use class for handling memory mapped files in TFileStream manner (r/w operations with emulation of continuous data stream)? TIA. -- Alex

Hmm... Good option. 🙂 As documentation states: MapViewOfFile function (memoryapi.h) Maps a view of a file mapping into the address space of a calling process. So mapped view is in "my" address space. AFAIUI, OS gives me (and others who use the same mapped file) access to some "external" pages in memory but I see these pages as array allocated in "my" memory. And big view will take big continuous piece of virtual memory in my process. About TFileStream. As documentation states: ... file views derived from any file mapping object that is backed by the same file are coherent or identical at a specific time. Coherency is guaranteed for views within a process and for views that are mapped by different processes. (Not surprising: data resides in the same pages in memory.) AFAIUI "normal" files don't have such property.

You are right in general when you say about direct manipulations with data in created view. But my main motivation here is standartization of data access with descendant of TStream.

I still use RAD2007, it is 32bit. And yes - it is not hard to implement "walking" view. (But we always have a hope that someone already did it before. 🙂) Mapping view of big size (entire file as subcase) takes a lot of memory (no miracle here) so it is not "for free" even in 64bit OS.

I don't want to expand file but operate with big file via mapped view of reasonable size; mapping view of entire file is impossible. Take a look: MapViewOfFile function https://docs.microsoft.com/en-us/windows/win32/api/memoryapi/nf-memoryapi-mapviewoffile Mapping a file makes the specified portion of a file visible in the address space of the calling process. For files that are larger than the address space, you can only map a small portion of the file data at one time. When the first view is complete, you can unmap it and map a new view.

Thank you for your responce. AFAICS both sources do not automatically process boundaries of currently mapped view during r/w operations . . . I.e. if start of r/w data block is in current view but its end is not then operation will fail. But I wish to r/w stream without thinking about boundaries of current view; Read/Write methods should move view (of predefined size) automatically. Of course, I can modify Read/Write methods myself to achieve necessary functionality.

Ah, as easy as doubleclick. Thank you.

No. 🙂 My allegation about lists of objects is not right. (I investigated this problem too long ago; memory fail me.) More accurate info: unit Graphics; { FreeMemoryContexts is called by the VCL main winproc to release memory DCs after every message is processed (garbage collection). Only memory DCs not locked by other threads will be freed. } procedure FreeMemoryContexts; var I: Integer; begin with BitmapCanvasList.LockList do try for I := Count-1 downto 0 do with TBitmapCanvas(Items[I]) do if TryLock then try FreeContext; finally Unlock; end; finally BitmapCanvasList.UnlockList; end; end; unit Controls; procedure TWinControl.MainWndProc(var Message: TMessage); begin try try WindowProc(Message); finally FreeDeviceContexts; FreeMemoryContexts; end; except Application.HandleException(Self); end; end; So main thread (where MainWndProc works) fairly often deselects unlocked memory contexts. It causes all kinds of problems in background threads which use bitmaps without locking.

GDI objects like brushes are in global list. RTL browses this list in main thread on every idle event and deletes all unused objects; locking any canvas simply disables updating of the list. If you (or some 3-d party library) somewhere do not lock a canvas in backgrownd thread it is possible that some object (brush in your case) is already deleted or/and overwritten but your code is still using old element in list. As a result you can see erratic behaviour of any kind.

If problem is not in skipped code then this is a bug. I suspect that you do something wrong with canvas(es) somewhere in your program. Locking canvas should work. BTW, Do you use TJPEGImage.Draw in your threads? This method had a bug (no canvas lock) in old versions. Also, do you copy bmps in thread(s)? I know for sure (after a lot of experiments) that both canvases must be locked in this case. Moreover, to be sure that bmp is really copied in this "safe locked" state you need to modify target bmp (assign a pixel to itself for example); this creates real copy of data in target bmp (instead of reference on source data).

🙂. But (IMHO) dropping of official forum was really wrong decision. In old days (since ~2000 year) I usually started my day from browsing of official newsgroups (in good old plain text and very handy tree format of messages) and I still have a huge collection of answers in "how to ..." style from famous specialists like Peter Below, Remy, and many others. After end of NG civilization there is no default place where I can get help from gurus and be well informed. Yes, you can say that there are many such places but "many" means "scattered" in this context ...