C / C++ / MFC

5-Dec-23 4:05

You should not use fgetc, fgets, or any other character based function to process binary files. You should use fread | Microsoft Learn[^] and fwrite | Microsoft Learn[^].

Re: copying a file

k50545-Dec-23 4:42

k5054

5-Dec-23 4:42

While your method may work, assuming that ch is an int, and so does not have the 255/-1 issue, your method is horribly inefficient. Richard's suggestion to use fread/fwrite produces much better performance.

For example, given an 8M file, looping through your code 100 times took about 32 seconds. Using a fread/fwrite using a 4K buffer, the same 100 lops took just under 1 second to complete. This was on a PI-3, and successive runs remained stable. I'd expect an 8M file to sit comfortably in the file cache, so the difference is totally down to the difference between extracting a single char at a time, and reading a lot of characters at a time.

"A little song, a little dance, a little seltzer down your pants"
Chuckles the clown

Myth of a Myth?

jschell4-Dec-23 3:38

jschell

4-Dec-23 3:38

From CP newsletter

The Myth of Smart Pointers – Logikal Blog[^]

Basically complaining about what unique_ptr<t> is defined as.

Myself reading it and looking at the code it seems to me that the author does not understand the difference between the C++ specification and the C++ compiler/runtime.

Which has always been a problem for some people using C/C++ pointers since C (before C++ existed.)

The author seems to be suggesting that the specification is guaranteeing that the memory will be collected. But without even reading the spec I seriously doubt it says that. I suspect it is noting that the it might be collected so one should not rely on it.

There are multiple other places where one can do similar things and it might or might not work depending on compiler, binary and even execution flow (which is really fun to debug.)

Perhaps I am mistaken in what I am reading?

Re: Myth of a Myth?

Richard MacCutchan4-Dec-23 4:57

how to add another primary menu - C + in Qt

4-Dec-23 4:57

Given the fact that he is breaking all the rules by branching off into QML (whatever that is, and by his own comments something to be avoided) and Javscript, then you cannot expect C++ to know what is happening outside.

Re: Myth of a Myth?

Mircea Neacsu4-Dec-23 5:05

Mircea Neacsu

4-Dec-23 5:05

jschell wrote:
The author seems to be suggesting that the specification is guaranteeing that the memory will be collected. But without even reading the spec I seriously doubt it says that. I suspect it is noting that the it might be collected so one should not rely on it.

Of course it doesn't guarantee. Where the memory is coming from and where it is going to, is outside the scope of the language specification. From C++11 to C++23 there was some kind of support for garbage collection using std::declare_reachable, but it was deleted[^].

Mircea

Re: Myth of a Myth?

harold aptroot6-Dec-23 19:55

harold aptroot

6-Dec-23 19:55

It was a silly article, going out of his way to create a bug and then blaming it on the thing he just intentionally broke.

But doing things with C++ that rely on platform/compiler specific details is explicitly allowed, and frequently necessary. The C++ specification alone does not make enough guarantees to result in a useful system - intentionally, so that the details can differ.

Salvatore Terress1-Dec-23 6:34

Salvatore Terress

1-Dec-23 6:34

Voluntarily removed - posted in wrong forum...

modified 3-Dec-23 14:27pm.

Re: how to add another primary menu - C + in Qt

Andre Oosthuizen1-Dec-23 22:18

Andre Oosthuizen

1-Dec-23 22:18

37 Questions asked in 2 months starts leaning towards a "Help Vampire". You have not shown us in your code above what you have tried apart from 4 lines of code, which oddly looks AI generated. Please tell us what you have researched so far on how to add second primary menus. If this errors, show the error and we will gladly assist from there.

Re: how to add another primary menu - C + in Qt

Richard MacCutchan1-Dec-23 22:22

1-Dec-23 22:22

A number of previous incarnations, one of which was at Discussions - Linux Programming Discussion Boards[^]

Invalidate rectangle

Calin Negru1-Dec-23 0:41

1-Dec-23 0:41

I’m trying to display an animated bitmap in a win32 application with GDIplus. Last time when I talked about this here I was told I should invalidate a rectangle to force the App to refresh/draw another frame. I’m trying to understand the theory for now. I will come up with code in a day or two if necessary. My question is do you create and invalidate between beginpaint and endpaint a rectangle that has no particular purpose or does it have to be a rectangle that actually does something.
I’m having a difficult time understanding the connection between a rectangle and the rendering process of a win32 api window

CPallini1-Dec-23 1:01

CPallini

1-Dec-23 1:01

Roughly speaking, the invalidated rectagle will be redrawn in the next WM_PAINT call (other parts of the client area are not redrawn). So, if you need to update a portion of the client area then invalidate the corresponding rectangle and then call UpdateWindow().
In simple scenarios you can invalidate the entire client area and then call UpdateWindow().
See, for instance: Invalidating the Client Area - Win32 apps | Microsoft Learn[^].

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Calin Negru1-Dec-23 1:40

1-Dec-23 1:40

Basically I need a rectangle taking the whole window for my game, I think I understand, I’ll post a followup if I’ll run into trouble setting things. Thank you.

CPallini1-Dec-23 1:56

CPallini

1-Dec-23 1:56

You are welcome.

"In testa che avete, Signor di Ceprano?"
-- Rigoletto

Richard MacCutchan1-Dec-23 2:13

1-Dec-23 2:13

The only things you should be doing between BeginPaint and EndPaint is redrawing/rewriting the parts of the client window that may have changed. Outside of the WM_PAINT handler, you decide which part (or all) of the window needs to be repainted. You then set those values into a call to InvalidateRect, which will post a WM_PAINT message to your message queue.

Calin Negru1-Dec-23 3:55

1-Dec-23 3:55

>The only things you should be doing between beginpaint and endpaint

I was thinking to disregard everything that was rendered in one frame, and then render things all over again. Keeping track of pieces that visually change in my game ( if that’s what you mean) seems like a burden at this point.
So far I’m only looking for a way to trigger a new paint event

modified 2-Dec-23 3:45am.

Richard MacCutchan1-Dec-23 4:28

1-Dec-23 4:28

You are welcome to do that, but it may affect the performance in certain scenarios.

Calin Negru2-Dec-23 5:02

2-Dec-23 5:02

I see

Richard MacCutchan2-Dec-23 6:47

2-Dec-23 6:47

It all seems a bit odd until you understand that everything in Windows is message driven. For each message type that you handle you need an event handler, for all the others just let Windows deal with them.