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This is a Visual C++ question, not a managed C++ question. Ask in the right forum, and you'll get lots of help./
Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog
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Hi,
I want to obtain the pixel value of any pixel on the form (dialog) during mouse move.
In MFC, i can get the pixel value using
CDC *pDC = this->GetDC();<br />
COLORREF clr = pDC->GetPixel(x,y);
ReleaseDC(pDC);
How do i do the same using managed C++.
I added an event OnMouseMove, and i can get the pixel coordinate using
e->X and e->Y;
How do i get the pixel value? I tried this
Graphics ^g = this->CreateGraphics();
then i do not know what else to do...
Usman
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You can still use the old code in managed C++, it's still C++.
In GDI+, the graphics object doesn't offer a get pixel method, the Bitmap class does instead. I'm not sure how to get a bitmap that represents the current screen, without doing a screen capture ( by which time, you've had the screen in a DC and could have just called GetPixel )
Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog
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I need to get the pixel value each time the mouse is moved. Taking a full screen capture will be slow. Thus, as you have suggested, i used the unmanaged C++ code. It works, but what i'm afraid of is that the transition to and from unmanaged code will cause performance degradation. That's why i needed a pure managed solution. Anyway, since there is no managed way of doing it, i'm using the unmanaged way;
Graphics ^g = this->CreateGraphics();<br />
System::IntPtr p = g->GetHdc();<br />
HDC hdc = (HDC) p.ToPointer();<br />
<br />
COLORREF clr = GetPixel(hdc,x,y);
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Oh, thanks by the way 
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I have 2 pairs of ODE that resulted from the mathematical modelling of a 2-link robotic system. My problem is in setting the intial conditions and printing to files.
I could have attached the equations but they are not showing when I tried to copy and paste.
Anyone interested in helping me out could send me his/her email and i will send the equation with other information to him/her. I will really appreciate your assistance.
Thank you.
Regards,
Sahoong.
skg
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If you click 'Ignore HTML tags', you can paste equations without any hassles.
But, this looks like it might be a C++ and not managed C++ question.
Christian Graus - Microsoft MVP - C++
Metal Musings - Rex and my new metal blog
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Dear Chris,
Million thanks for your response.
Unfortunately, I still cannot paste the equation. It was typed with Microsoft equation editor.
The codes that I have written so far is below:
// Simulation of the Dynamics of a 2-Link Pan-Tilt Robotic Manipulator
/* This programme calculates the Velocity, Acceleration and the angles of inclination
of the two links of the Spherical Pointing Motor, which is essentially a Two-Link Robotic
Manipulator*/
//#include <basis.h>
//#include <assert.h>
//#include <string.h>
//#include <iostream.h>
//#include <iomanip.h>
//#include <fstream.h>
// Precompiler Directives
#include <math.h>
#include <stdlib.h>
// Constants Declaration
#define n (int) 2
#define m1 (float) 0.05
#define m2 (float) 0.03
#define r1 (float) 0.04
#define r2 (float) 0.06
#define ra (float) 0.04
#define rb (float) 0.06
#define l (float) 0.05
#define d (float) 0.02
#define acc_due_gravity (float) 9.81
class AngVel1
{
public:
};
class AngAccln1
{
public:
};
class AngVel2
{
public:
};
class AngAccln2
{
public:
}
/*
n = Number of Links = 2
m1 = Mass of the First Link (The Annulus)
m2 = Mass of the Second Link
r1 = Inner Radius of Link 1 (The Annulus)
r2 = Outer Radius of Link 1 (The Annulus)
ra = Outer Radius of the Annulus
rb = Inner Radius of the Annulus
l = Half the Lenght of Link 1
d = Displacement from the Centre of Mass
g = Acceleration due to gravity = 9.81
t = time in seconds
*/
// Declaration of variables (Robot Parameters)
float t;
// Prototypes
float TorqueVal(float t);
double Runge_Kutta ();
double AngVel1 (double om1){
return om1;
}
double AngAccln1 (double t, double om1, double tetha1, double tetha2){
t = 0.1;
return (tau1 - 2*m2(r2*r2/4 -h2*h2/3 -d*d) * om1*om2*sintetha2*costetha2 - m2*g*d*costetha1*costetha2)/
om1*(m1(ra*ra + rb*rb)/4 + m1(h1*h1)/3 + m2((r2*r2)(1+sinsqtetha2)/4 + m2*h2*h2*cossqtetha2/3 + m2*d*d*cossqtetha2);
}
double AngVel2 (double om2){
return om2;
}
double AngAccln2 (double t, double om1, double om2, double tetha1, double tetha2){
t=0.4;
return (tau2 + (m2(r2*r2/4 -h2*h2/3 -d*d)*om1*om1*sintetha2*costetha2) - m2*g*d*sintetha1*sintetha2)/
om2*m2(r2*r2/4 + h2*h2/3 + d*d;
double RK(double y){
double k1,k2,k3,k4;
k1=h*fn(y);
k2=h*fn(y+(k1/2.0));
k3=h*fn(y+(k2/2.0));
k4=h*fn(y+k3);
return y+(k1/6.0)+(k2/3.0)+(k3/3.0)+(k4/6.0);
}
// The Main Routine
int main()
{
// Torque Function
float TorqueVal1(float t)
{
t = 0.1;
return t;
}
// Runge-Kutta Function
double RK(double y){
double k1,k2,k3,k4;
k1=h*fn(y);
k2=h*fn(y+(k1/2.0));
k3=h*fn(y+(k2/2.0));
k4=h*fn(y+k3);
return y+(k1/6.0)+(k2/3.0)+(k3/3.0)+(k4/6.0);
}
double RK(double l){
double v1,v2,v3,v4;
v1=h*fn(l);
v2=h*fn(l+(k1/2.0));
v3=h*fn(l+(k2/2.0));
v4=h*fn(l+k3);
return l+(v1/6.0)+(v2/3.0)+(v3/3.0)+(v4/6.0);
}
}
I was not using a class before and I just started packing the four equation into classes.
You could me to olaskg@yahoo.ie.
Thank you.
skg
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I'm trying to develop a WM visualization but i cannot seem to to find any examples or tutorials on the subject. I have the wm sdk and have read the documentation, but the example in it is far from impressive. Any help would be great.
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Hi,
I posted this on MS's "Visual C++ Language" forum a few days ago without getting a useful answer. I'm hoping somebody (Nish??) here can help. I'm pretty desperately needing a solution at this point.
We are doing a transition project where we are wrapping unmanaged C++ code with C++/CLI (VS 2005) managed classes. The various methods and properties on a given managed wrapper class are mostly just pass-through calls to the wrapped C++ class.
Mostly this works fine. Sometimes, however, the call from the managed code ends up in the wrong C++ function. IOW:
void ManagedMethod1( void )
{
m_pUnmanagedObject->Func1();
}
actually calls m_pUnmanagedObject->Func20().
So far, it seems that every time this happens, the called method on the UNmanaged C++ class is declared "virtual"; it also seems that the incorrect method that is actually called is also declared virtual. I have tried in one or two situations to change the legacy class method to non-virtual and it fixed the problem. However, that isn't a very general or useful solution.
The unmanaged code is in a DLL, and the managed wrappers are in an assembly DLL. I've cleaned and rebuilt both multiple times, as well as the C# test driver program.
There is another problem that is probably related that I've found with another virtual function, this one taking a parameter (the first problems above were with virtual functions taking no parameters). Tracing in the managed wrapper code in Disassembly mode, there is what looks like a call to something called MarshalCopy, which calls the copy c'tor for the class of the passed parameter. This call appears to execute without error; however, when execution returns from that function, it returns to a completely different place than it was called from, which needless to say, is fatal pretty quickly.
I'm sure I'm doing something wrong and/or stupid; perhaps I need some kind of explicit marshalling (though I thought you didn't need this with C++ interop), or some compiler switch or something. But I've looked and looked, and can't find anything.
I would GREATLY appreciate any help or suggestions.
Thanks.
Doug
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Well, embarrassingly enough, I was doing something pretty stupid - trusting the compiler to rebuild everything necessary automatically.
Apparently I never first "Cleaned" then "REbuilt" both projects at the same time. When I did that, the problem went away.
So, I was stupid for not doing this right away, but... it seems the compiler is somehow defective, since I did "Build" both projects many times. 
I guess this is better than an actual compiler bug that MS wouldn't fix for a year!
Doug
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now i have a CString variable contain an integer value
i wanna convert the CString to int so i used atoi() function
<br />
CString strNumber = "00123"<br />
int nNumber = atoi(strNumber);<br />
then nNumber will contain (123)and it ignore the Zeros
so what if i need these Zeros, what should i do
also if i wrote
int x = 0110;
x will result into (72)
could anybody explain that
thnx 4 ur time and concern
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hello,
In a integer you can't keep the zeros, so if you want the zeros at the left you have to use string and so on,
About the second problem, if you put 0 at the left, you are using octal system so,
0110 = 0*8^3+1*8^2+1*8+0 = 72
Regards
-- modified at 10:03 Wednesday 11th October, 2006
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singersinger wrote: so what if i need these Zeros, what should i do
padding zeros is a display formatting operation and has nothing to do with the value of the intrinsice numeric type (int, long, etc.)
singersinger wrote: x will result into (72)
if you want x = 110 write:
int x = 110;
otherwise the leading zero is interpreted by the compiler to mean "octal" just as leading 0x means hexadecimal.
led mike
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note: int x;
x= 0110; //oct value 0"number", base 8
x= 0x110; //hex value 0x"number", base 16
x= 110; //dec value, base 10
so a 0110(base 8) number is 72(base 10)
* use Windows calculator to check the above values
you can NOT keep the zeros if you use a "int" type
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Hello,
To convert from CStrin to String^ I have done it like this:
CString TextAuxStr;
String^ TextCLR;
TextAuxStr = "Test";
TextCLR = gcnew String(TextAuxStr.GetBuffer());
Is there any other way to do it??
Thank you
Regards
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The method you've used is the best way to do it (though there are other ways too).
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Hello,
I'm using treeview with Windows forms, and I would like to select an ITEM of the tree when and event occurs, How can I do this??? I have been trying to use the TreeView.Select()  , but I don't manage to make it work.
Thank you
Regards
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From my View class, I select an Item like this:
CPoint PointOnClient( currentMousePointinScreenCoordinates);
ScreenToClient( &PointOnClient);
UINT uFlags;
HTREEITEM hItem = GetTreeCtrl().HitTest( PointOnClient, &uFlags);
GetTreeCtrl().Select( hItem, TVGN_CARET);
It would help to see what you are doing in your code.
"We trained hard, but it seemed that every time we were beginning to form up into teams we would be reorganised. I was to learn later in life that we tend to meet any new situation by reorganising: and a wonderful method it can be for creating the illusion of progress, while producing confusion, inefficiency and demoralisation."
-- Caius Petronius, Roman Consul, 66 A.D.
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I am using a treeView
private: System::Windows::Forms::TreeView^ TreePOver;
I created
this->TreePOver = (gcnew System::Windows::Forms::TreeView());
It is easy to now which node have you selected
String^ NodoStr;
NodoStr = "";
NodoStr = TreePOver->SelectedNode->Text::get();
And after I make a case...
But now I want to select a specific node of the treeView
In my tree for example:
this->TreePOver->Name = L"TreePOver";
treeNode1->Name = L"Node1";
treeNode1->Text = L"Node1";
treeNode2->Name = L"Node2";
treeNode2->Text = L"Node2";
treeNode3->Name = L"Node3";
treeNode3->Text = L"Node3";
If I make:
NodoStr = TreePOver->SelectedNode->Text::get();
I will get Node1, Node2, Node3 in each case, but now I want to select one of the nodes in the tree.
Thank you
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I am working with the .NET SerialPort class and I want to output some text on a textbox when a data received event occurs on the serial port. However i get this exception.
"An unhandled exception of type 'System.InvalidOperationException' occurred in System.Windows.Forms.dll
Additional information: Cross-thread operation not valid: Control 'richTextBox1' accessed from a thread other than the thread it was created on."
So to solve this I found out calling the invoke method is the right way to go. I found some C# code which is a good example, I was wondering if anyone can please convert it to C++/CLI code for me.
private void Log(LogMsgType msgtype, string msg)
{
rtfTerminal.Invoke(new EventHandler(delegate
{
rtfTerminal.SelectedText = string.Empty;
rtfTerminal.SelectionFont = new Font(rtfTerminal.SelectionFont, FontStyle.Bold);
rtfTerminal.SelectionColor = LogMsgTypeColor[(int)msgtype];
rtfTerminal.AppendText(msg);
rtfTerminal.ScrollToCaret();
}));
}
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Namespaces are great - but there are rather many of them in .net, even just in the framework.
So I've been wondering how to deal with them in a safe yet readable way. I don't want to write System::Windows::Forms::DialogResult::OK everytime a use a dialogue box. Neither do I want to simply make every class inside System::Windows::Forms part of the global namespace via a using directive. This question is replicated for the other nested .net namespaces which need to be used.
So the solution I'm considering is this:
<br />
<br />
<br />
namespace Rclsoftware
{<br />
namespace Forms = System::Windows::Forms;<br />
}<br />
<br />
<br />
if(Forms::DialogResult::OK == dlg.ShowDialog(this))<br />
{<br />
}<br />
I'd be interested to hear what people think of this approach, and if there are any potential problems I may have overlooked.
www.rclsoftware.org.uk
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You can do this:
using System::Windows::Forms::DialogResult;
to move just that object into the current scope (note it's using, not using namespace). That's a C++ rule, though, so I don't know if/how well it works with .Net namespaces/types.
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Mike,
Yes, it does work with C++/CLI.
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Really? I didn't know that.
That would actually make things worse from my point of view, because OK would effectively be in the global namespace.
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