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I am trying to use the rendered output of a video player in my C# code. The program (which is the VLC media player) is written in plain C and is wrapped in a DLL.
I should pass pointers to two callback functions (dolock and unlock ) as string arguments (argv ) to the player when it is instantiated through a DLL call. here is the function signatures in C:
void *dolock (void *struct)
void unlock(void * struct)
(the struct arguments are not used in my case).
they appear in my C# code as:
public static IntPtr dolock(IntPtr ctx)
public static void unlock(IntPtr ctx)
I use delegates and Marshal.GetFunctionPointerForDelegate to obtain the function pointers.
This works perfect and I can see in the debugger that the player successfully invokes my dolock function. But, an exception is raised after the function invocation, when the dolock function returns with a pointer to a buffer. I can not understand if it is because the player is not allowed to write in the memory which is allocated in my program or I am returning a wrong pointer. The error is a famous one:
The instruction at ... referenced memory at "0x000000". The memory could not be "written" .
I have tried different ways to allocate the memory buffer (which I should return its pointer in dolock), all failed with the same error.
* Allocating space in the unmanaged section of the program memory using AllocHGlobal.
* using stackalloc to allocate the buffer in stack (unmovable by GC).
* using Bitmap and BitmapData GDI+ classes and returning the bitmapdata.scan0 pointer after locking the bitmap.
Any idea what might be the cause?
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Is ctx, actually a struct? It might be that vlc is attempting to write to the struct it was expecting. If you are passing IntPtr.Zero it will try to write to memory location 0x000000.
Henry Minute
Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”
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No, as I said, dolock and unlock are callback functions and it is the vlc which is actually passing these arguments to my program.
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The problem is fixed.
I should use [UnmanagedFunctionPointer(CallingConvention.Cdecl)] attribute before my dolock/unlock functions.
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i am using windows media player control axWindowsMediaPlayer1
i want to be able to adjust the balance for channel a and b volume in a stereo audio
pleas help
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Have you Googled for this?
Henry Minute
Do not read medical books! You could die of a misprint. - Mark Twain
Girl: (staring) "Why do you need an icy cucumber?"
“I want to report a fraud. The government is lying to us all.”
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public void OnDocumentComplete(object pDisp, ref object URL)
{
// second time control goes upto here but doesnot go into if statements
if (URL.ToString().EndsWith(".pdf")&& (!URL.ToString().StartsWith("file:///")))
{
object obj = System.Reflection.Missing.Value;
webBrowser.Navigate("C:\\BHO.pdf", ref obj, ref obj, ref obj, ref obj);
}
}
open Internet Explorer which has PDF links.
click a PDF link such that the corresponding PDF file is opened in new window
Instead of original PDF file, C:\BHO.pdf is opened on new window
close that new window in which C:\BHO.pdf is opened.
Again click on same link, event gets fired but instead of C:\BHO.pdf, original pdf is opened on browser.
Why does if condition statements doesn't execute when I do the same thing second time.
In Navigate("C:\\BHO.pdf", ref obj, ref obj, ref obj, ref obj) why we are passing
System.Reflection.Missing.Value
Is my problem is due to this or due to some other thing?
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Wrong forum for a start.. but have you stepped through the code? What are you trying to achieve here? It looks like you want BHO.PDF to open no matter what PDF file is clicked on?!
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Hi,
I have a question about UI design in NET.
I am creating a scientific application with C# and VS2008. Currently I am using a tab conrol were till now I have 3 level tab depth (eg tab inside tab etc) which is not very convenient, nor user friendly.
I am thinking to switch to an outlook UI style were the general tabs will be moved to left panel with the form of buttons. While the right panel will have the detail form again with tabs but lesser depth.
So my question is what is the best approach of doing this?
Should I move to a MDI where in the right panel will load detail form's in full mode?
Or should I search for some specific tab component?
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We use Infragistics Listbar, one of the few controls of theirs I like. It gives an excellent outlook style listbar, relatively easy to use which is a huge bonus from them.
The only trouble with the ui design like you are proposing (I use it also) is when there is a large amount of detail to be displayed. I have a standard toolbar somewhere with alphabet buttons for filtering large sets. Use a DGV for detail, it's faster than a listview and easier to format.
Never underestimate the power of human stupidity
RAH
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In my situation, I don't have large amount of detail to be displayed, rather data grouped in distinct way...
I saw (don't remember where) an approach where instead of MDI the SDI is used with custom controls. A custom control in my situation would be a detail form which could show or hide depended on which button is clicked.
Not quite sure if this approach is best.
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I let the listbar do the grouping, content is database driven. The details are only available in lists in the main form and any further information/work is done via dialogs. No data is manipulated in the main form. Dialogs of course are customised for each data type.
I dislike the disappearing control paradign as I find it difficult to support and the main form becomes very bloated.
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I see,
However I am busting my head know how to implement the outlook approach... I mean is it MDI app and show/hide each time new form? Or do they use other pattern?
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I can see only 2 types of data, list and calendar. Outlook may treat the sections differently but that is their choice, I suspect there are a number of user controls and a datalist tool. In my corporate CRUD life there is basically 1 type of data, lists, how you display them is just candy, can be very important but still candy.
Where you do your data manipulation is more important to me as that is where the nasty bits like validation come into play. I never do this in the main form.
Never underestimate the power of human stupidity
RAH
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Net nazi stops me on the wordpress link but I understand the reply from JRQ I just don't have a requirement for that many disparate data types. I have not used MDI for many years, always was a kludge, so I can't compare, I like SDI.
B/c I have only 1 basic type of data and 1 presentation style I have very limited need to communicate between controls. Mine is mainform calls dialog with an ID for the data required. Dialog return a dialogresult to the main form which updates the list from the database if required.
I must admit my UI is VERY BORING for the users but then my environment is corporate CRUD where they are interested in the DATA not the eye candy. Whenever I have time I like to play with the UI a little but there is not a lot of time for pretties.
Never underestimate the power of human stupidity
RAH
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DevEx do some nice stuff and have a good rep here on CP.
Never underestimate the power of human stupidity
RAH
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Do you mean commercial components?
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Hi.
How can i open page of a specific tab when a condition achieved without click this tab using c#?
modified on Wednesday, April 29, 2009 5:55 AM
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You can programmatically change the current TabPage by using one of the following TabControl properties
SelectedIndex[^]
SelectedTab[^]
If the control is not loaded properly, use the help of ResumeLayout and Refresh methods.
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I have this project that make use of the window media player control axWindowsMediaPlayer to play back a stream coming for a streaming server.
what i need to do is to be able to sample the waveform and draw it as the audio is being played.
would Microsoft.DirectX.DirectSound be usefull?
in C# or VB please...
thank you
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hi , I created a fullscreen form, setting its topmost prperty to true and provide 2 textboxes in it (for username and password)
so i create a lock screen program usin this way.
i use a Timer that ticks every 500msec:
it causes the form stays on top even if user press ALT-CNTRL-DLT
void aTimer_Tick(object sender, EventArgs e )
{
try
{
this.Activate();
this.Select();
this.BringToFront();
}
catch
{
}
}
then i put the address of my program as a startup program, and it will run each time i login
but the problem is when i log in!! if i quicly run a program(beform my (Lock)form open) then i can hack the lock screen and it won't come to top,unless i click it!
it seems that
this.Activate();
this.Select();
this.BringToFront();
doesn't work when first the form is not active!
any suggestions?
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Set the lock screen always on top.
 *12Code
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