C / C++ / MFC

Re: Calling functions in DLL (Flash) that I didn't load

25-Jan-10 8:32

Greetings - my first question so please forgive any faux-pas I make..

My Win32 application loads a number of embedded Web browsers, each of which load and play a Flash movie.

I want to find a way to control the volume of each loaded Flash movie independently of each other. My target platform is Windows XP so I can't use the mixer APIs that I hear are available on Vista and 7.

Here is the code with error checking etc. removed (I'm using a very simple Flash API call to test)

HMODULE hFlashDLL = GetModuleHandle( "NPSWF32.dll" );
typedef void (__stdcall *flash_func)();
flash_func flash_stop_func = (flash_func)GetProcAddress( hFlashDLL, "native_ShockwaveFlash_StopPlay" );
flash_stop_func();

hFlashDLL and flash_stop_func appear to be valid but when I call the function itself I get an access violation.

Should this work and I'm missing something obvious in my code or is this sort of thing just disallowed in Win32?

Any pointers appreciated.

CODEPC25-Jan-10 11:31

CODEPC

25-Jan-10 11:31

opensoar wrote:
HMODULE hFlashDLL = GetModuleHandle( "NPSWF32.dll" );

Did you try this:
HINSTANCE hLib = LoadLibrary(_T("NPSWF32.dll"));

Re: Calling functions in DLL (Flash) that I didn't load

opensoar25-Jan-10 12:02

Re: Calling functions in DLL (Flash) that I didn't load

25-Jan-10 12:02

I did and I get the same access violation error. Even if it worked though, wouldn't that just let me control an instance of Flash that I load versus an instance loaded by the browser (which is what I want)?

I think each browser instance must load it's own version of the plugin or controlling Flash parameters in one would control them all.

Richard MacCutchan25-Jan-10 12:07

Richard MacCutchan

25-Jan-10 12:07

opensoar wrote:
HMODULE hFlashDLL = GetModuleHandle( "NPSWF32.dll" );

Are you sure that this dll is loaded into memory at this point? You don't error check the returned value hFlashDLL.

MVP 2010 - are they mad?

Re: Calling functions in DLL (Flash) that I didn't load

opensoar25-Jan-10 12:29

Re: Calling functions in DLL (Flash) that I didn't load

25-Jan-10 12:29

Yep - it's loaded. Like I said in my original message, I listed the code with error checking etc. removed and the values I get back seem ok.

Richard MacCutchan25-Jan-10 12:41

Richard MacCutchan

25-Jan-10 12:41

opensoar wrote:
hFlashDLL and flash_stop_func appear to be valid but when I call the function itself I get an access violation.

My apologies, I missed this in your original post. Is there any more information from the access violation to give any indication of what it is complaining about? Also are you sure that native_ShockwaveFlash_StopPlay does not require any parameters?

MVP 2010 - are they mad?

Re: Calling functions in DLL (Flash) that I didn't load

opensoar25-Jan-10 13:11

Re: Calling functions in DLL (Flash) that I didn't load

25-Jan-10 13:11

>> Also are you sure that native_ShockwaveFlash_StopPlay does not require any parameters?

That was my thought too Richard - docs are a bit thin on the ground and that function name doesn't match any in the the other Flash API docs I've seen so I'm thinking those calls are wrapped somehow and that my part of the problem.

Nothing more useful in the error message as far as I can tell.

Richard MacCutchan25-Jan-10 21:45

Richard MacCutchan

25-Jan-10 21:45

I just Googled native_ShockwaveFlash_StopPlay and found one hit; someone else complaining of the same issue. My only suggestion is to try and get some documentation on this library from someone else around the world.

MVP 2010 - are they mad?

Screen Capture

Member 686483925-Jan-10 6:17

25-Jan-10 6:17

Hi Members

How i get Screen capture?I am using dialog based application i want to get Screen capture and save into .dat format.
Please help me

Rajesh R Subramanian25-Jan-10 6:21

25-Jan-10 6:21

See Barry's Screen Capture[^]

I used the CodeProject "search" feature to arrive on that result.

“Follow your bliss.” – Joseph Campbell

David Crow25-Jan-10 7:07

David Crow

25-Jan-10 7:07

Member 6864839 wrote:

How i get Screen capture?

See here for an idea.

"One man's wage rise is another man's price increase." - Harold Wilson

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

"Man who follows car will be exhausted." - Confucius

Member 686483925-Jan-10 7:32

25-Jan-10 7:32

thanks both of you for reply.I use this code

HDC m_hdcMem,hdc;
HBITMAP m_Bitmap,m_OldBitmap,hMainBmp ;
//one intersting for you if you want to use of other resulition
int x=800;
int y=600;

//use of GetDC()->m_hDC and see result.
//hdc=GetDC()->m_hDC;
hdc=GetDesktopWindow()->GetDC()->m_hDC;

m_hdcMem= CreateCompatibleDC(hdc);

//one interesting for you if you want to use of other 	
m_Bitmap = CreateCompatibleBitmap(hdc,x,y);
 m_OldBitmap=(HBITMAP) SelectObject(m_hdcMem, m_Bitmap);

  BitBlt(m_hdcMem, 0,0,x,y, hdc,0,0,SRCCOPY);
 hMainBmp =(HBITMAP) SelectObject(m_hdcMem, m_OldBitmap);
///////////Now you have a hbitmap of screen hMainBmp/////

CImage m_Image;
m_Image.Attach(hMainBmp);
m_Image.Save("C:\\image.bmp");//use of jpg instead bmp but if you can zip your file its good.
m_Image.Detach();
DeleteDC(m_hdcMem);
DeleteObject(hMainBmp );
DeleteObject(m_OldBitmap);

It's working for me.
Now i want to save file in format of .DAT.
Please help me

Rajesh R Subramanian25-Jan-10 7:35

25-Jan-10 7:35

Member 6864839 wrote:
Now i want to save file in format of .DAT.

There's no such .DAT file. What you've got by capturing the screen is a bitmap, and you just save it to the disk by providing any extension you want to the filename. Or if by .DAT you want to have a file format that your app can only handle, encrypt (search the site) the bitmap and save it to ".DAT format".

“Follow your bliss.” – Joseph Campbell

Member 686483925-Jan-10 7:43

25-Jan-10 7:43

ok i use this code but file not save in my disk.

m_Image.Save("C:\\image.dat");

Rajesh R Subramanian25-Jan-10 8:38

25-Jan-10 8:38

Take a look at the example at the end of the documentation for CImage::Save()[^]. Because you said "image.dat", the call didn't know the format. You will need to explicitly specify it as bitmap format by doing it this way:

m_Image.Save("c:\\image.dat",ImageFormatBMP);

“Follow your bliss.” – Joseph Campbell

Member 686483925-Jan-10 9:07

25-Jan-10 9:07

Thanks it's working.
Thanks once again...........

Rajesh R Subramanian25-Jan-10 9:16

How to share memory between instances of dll

25-Jan-10 9:16

I'm glad I could help.

Shameless plug: May I please ask you to mark the helpful replies as "Good Answer" by clicking on the appropriate posts? Smile | :)

“Follow your bliss.” – Joseph Campbell

Sauce!25-Jan-10 2:10

Sauce!

25-Jan-10 2:10

I have a dll that needs to share data among all instances. How can I accomplish this? I've tried a multitude of compiler-specific #pragma's (visual studio 2008 for anyone who's asking) and no matter what I do, I cannot share the variables across all instances.

MSDN says memory-mapped files are one of several solutions, so any info on that too would be welcome.

CPallini25-Jan-10 2:21

CPallini

25-Jan-10 2:21

Have you read (MSDN): "How do I share data in my DLL with an application or with other DLLs"?
Smile | :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler.
-- Alfonso the Wise, 13th Century King of Castile.

This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong.
-- Iain Clarke

[My articles]

Sauce!25-Jan-10 2:39

Sauce!

25-Jan-10 2:39

I've tried that, and it didn't work Frown | :(

I remember reading somewhere (on MSDN) that the #pragma data_seg() directive should not be used with classes that require deep copy constructors. Unfortunately, the data I want to share is an std::list.

The page you linked me to goes on to say "Because of these restrictions, Microsoft does not recommend sharing C++ objects between processes."

They also don't recommend sharing pointers, so what alternative do I have?

CPallini25-Jan-10 2:58

CPallini

25-Jan-10 2:58

Sauce! wrote:
They also don't recommend sharing pointers, so what alternative do I have?

In the same page:

In general, if you want to use C++ to share data between processes, write a class
that internally uses a memory-mapped file to share data, but do not share the class instances themselves. This might require special care in developing such a class, but it enables application developers to fully control the side effects of sharing data.

Sauce!25-Jan-10 3:03

Sauce!

25-Jan-10 3:03

I guess I have a bit of reading to do, this sounds complicated Frown | :(

Cedric Moonen25-Jan-10 3:05

Cedric Moonen

25-Jan-10 3:05

BTW, why do you need to share data across several instance of the dll ?

Cédric Moonen
Software developer

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