OpenGL in Windows Forms (c++) - Buffer overflows? - winforms

Question

I wrote a program in c++ using Windows forms. I use two Forms. The first form only contains a button. When it is pressed, a second form opens. This form contains a panel where a simple OpenGL simulation is played (rotated with the help of a timer provided by windows forms). The second form can be closed and opend again by pressing the botton in the first Form. The more often this is done, the slower the 3D-OpenGL-object rotates. After doing this for about 6 times the 3D-OpenGL-object starts to flicker totally crazy. I think it has to do with the fact, that the OpenGL-Object I construct is not destroyed properly and at a certain point the memory is full (in a more complicated version of the project it was flickering between the current 3D-object and a 3D object that should have been destroyed after the window was closed).
Here is a video of the Problem.
here is the code of OpenGL:
namespace OpenGLForm
{
public ref class COpenGL: public System::Windows::Forms::NativeWindow
{
public:
// Position/Orientation of 3D Mesh in Mesh-Viewer Window
float meshPos_x;
float meshPos_y;
float meshPos_z;
float meshOri_x;
float meshOri_y;
float meshOri_z;
COpenGL(System::Windows::Forms::Panel ^ parentForm, GLsizei iWidth, GLsizei iHeight)
{
// initialize all parameter / set pointers (for pointers of type MAT)
meshPos_x = 0.0;
meshPos_y = 0.0;
meshPos_z = -2.0;
meshOri_x = -63.0;
meshOri_y = 0.0;
meshOri_z = 0.0;
CreateParams^ cp = gcnew CreateParams;
m_hDC = GetDC((HWND)parentForm->Handle.ToPointer());
System::String^ filename = "C:/Advantech/Desktop/Const.txt";
System::IO::StreamWriter^ csvWriter = gcnew System::IO::StreamWriter(filename, false, System::Text::Encoding::UTF8);
csvWriter->Write("Const");
csvWriter->Close();
if(m_hDC)
{
MySetPixelFormat(m_hDC);
ReSizeGLScene(iWidth, iHeight);
InitGL();
}
}
//custom function for transformations
System::Void Transform(float xTrans, float yTrans, float zTrans, float xRot, float yRot, float zRot)
{
//translate object
glTranslatef(xTrans, yTrans, zTrans);
//rotate along x-axis
glRotatef(xRot,1.0f,0.0f,0.0f);
//rotate along y-axis
glRotatef(yRot,0.0f,1.0f,0.0f);
//rotate along z-axis
glRotatef(zRot,0.0f,0.0f,1.0f);
}
System::Void Render(System::Void)
{
// Initial Settings
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear screen and depth buffer
glLoadIdentity();
meshOri_z = meshOri_z + 1;
// Set position and orientation of 3D mesh
Transform( meshPos_x,
meshPos_y,
meshPos_z,
meshOri_x,
meshOri_y,
meshOri_z );
glScalef( 0.05, 0.05, 0.05 );
int meshSize = 200;
// create 3D mesh Toplayer
for (int x = 1; x < meshSize; x++) {
for (int z = 1; z < meshSize; z++) {
glBegin(GL_QUADS);
int dm = 1;
glColor3f(dm,dm,dm);
glVertex3f( x, z, dm );
glVertex3f( (x+1), z, dm );
glVertex3f( (x+1), (z+1), dm );
glVertex3f( x, (z+1), dm );
glEnd();
}
}
}
System::Void SwapOpenGLBuffers(System::Void)
{
SwapBuffers(m_hDC) ;
}
private:
HDC m_hDC;
HGLRC m_hglrc;
protected:
~COpenGL(System::Void)
{
System::String^ filename = "C:/Advantech/Desktop/Dest.txt";
System::IO::StreamWriter^ csvWriter = gcnew System::IO::StreamWriter(filename, false, System::Text::Encoding::UTF8);
csvWriter->Write("Dest");
csvWriter->Close();
wglDeleteContext(m_hglrc);
DeleteDC(m_hDC);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
this->DestroyHandle();
}
GLint MySetPixelFormat(HDC hdc)
{
static PIXELFORMATDESCRIPTOR pfd= // pfd Tells Windows How We Want Things To Be
{
sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor
1, // Version Number
PFD_DRAW_TO_WINDOW | // Format Must Support Window
PFD_SUPPORT_OPENGL | // Format Must Support OpenGL
PFD_DOUBLEBUFFER, // Must Support Double Buffering
PFD_TYPE_RGBA, // Request An RGBA Format
16, // Select Our Color Depth
0, 0, 0, 0, 0, 0, // Color Bits Ignored
0, // No Alpha Buffer
0, // Shift Bit Ignored
0, // No Accumulation Buffer
0, 0, 0, 0, // Accumulation Bits Ignored
16, // 16Bit Z-Buffer (Depth Buffer)
0, // No Stencil Buffer
0, // No Auxiliary Buffer
PFD_MAIN_PLANE, // Main Drawing Layer
0, // Reserved
0, 0, 0 // Layer Masks Ignored
};
GLint iPixelFormat;
// get the device context's best, available pixel format match
if((iPixelFormat = ChoosePixelFormat(hdc, &pfd)) == 0)
{
MessageBox::Show("ChoosePixelFormat Failed");
return 0;
}
// make that match the device context's current pixel format
if(SetPixelFormat(hdc, iPixelFormat, &pfd) == FALSE)
{
MessageBox::Show("SetPixelFormat Failed");
return 0;
}
if((m_hglrc = wglCreateContext(m_hDC)) == NULL)
{
MessageBox::Show("wglCreateContext Failed");
return 0;
}
if((wglMakeCurrent(m_hDC, m_hglrc)) == NULL)
{
MessageBox::Show("wglMakeCurrent Failed");
return 0;
}
return 1;
}
bool InitGL(GLvoid) // All setup for opengl goes here
{
glShadeModel(GL_SMOOTH); // Enable smooth shading
glClearColor(0.0f, 0.0f, 0.0f, 0.5f); // Black background
glClearDepth(1.0f); // Depth buffer setup
glEnable(GL_DEPTH_TEST); // Enables depth testing
glDepthFunc(GL_LEQUAL); // The type of depth testing to do
glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST); // Really nice perspective calculations
return TRUE; // Initialisation went ok
}
GLvoid ReSizeGLScene(GLsizei width, GLsizei height) // Resize and initialise the gl window
{
if (height==0) // Prevent A Divide By Zero By
{
height=1; // Making Height Equal One
}
glViewport(0,0,width,height); // Reset The Current Viewport
glMatrixMode(GL_PROJECTION); // Select The Projection Matrix
glLoadIdentity(); // Reset The Projection Matrix
// Calculate The Aspect Ratio Of The Window
gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);
glMatrixMode(GL_MODELVIEW); // Select The Modelview Matrix
glLoadIdentity(); // Reset The Modelview Matrix
}
System::Void detectBlack(){
}
};
}
the first form only contains a button to open the second form
private: System::Void button2_Click(System::Object^ sender, System::EventArgs^ e) {
Form1^ freaker = gcnew Form1();
freaker->ShowDialog();
}
and here is the code of the second form:
private: System::Void Form1_Load(System::Object^ sender, System::EventArgs^ e) {
}
void Form1_Closing( Object^ /*sender*/, System::ComponentModel::CancelEventArgs^ e )
{
this->OpenGL->~COpenGL();
}
//Time tick for play button option
private: System::Void timer1_Tick(System::Object^ sender, System::EventArgs^ e){
UNREFERENCED_PARAMETER(sender);
UNREFERENCED_PARAMETER(e);
OpenGL->Render();
OpenGL->SwapOpenGLBuffers();
}

Answer 1

After one week of searching and trying around here the answer:
I found a class to destroy openGL objects in Windows (wgl). This class alone did not solve the problem. I had to call all the commands, then switch buffers by calling SwapBuffers(m_hDC); and call all the commands again. Later on I recognized that it is enough only to call the commands g_hDC=NULL; and g_hWnd=NULL;. So this is how my destructor looks like now:
~COpenGL(System::Void){
if (g_bFullscreen) // Are We In Fullscreen Mode?
{
ChangeDisplaySettings(NULL,0); // If So Switch Back To The Desktop
ShowCursor(TRUE); // Show Mouse Pointer
}
if (g_hRC) // Do We Have A Rendering Context?
{
if (!wglMakeCurrent(NULL,NULL)) // Are We Able To Release The DC And RC Contexts?
{
MessageBox(NULL,TEXT("Release Of DC And RC Failed."),TEXT("SHUTDOWN ERROR"),MB_OK | MB_ICONINFORMATION);
}
if (!wglDeleteContext(g_hRC)) // Are We Able To Delete The RC?
{
MessageBox(NULL,TEXT("Release Rendering Context Failed."),TEXT("SHUTDOWN ERROR"),MB_OK | MB_ICONINFORMATION);
}
g_hRC=NULL; // Set RC To NULL
}
if (g_hDC && !ReleaseDC(g_hWnd,g_hDC)) // Are We Able To Release The DC
{
MessageBox(NULL,TEXT("Release Device Context Failed."),TEXT("SHUTDOWN ERROR"),MB_OK | MB_ICONINFORMATION);
g_hDC=NULL; // Set DC To NULL
}
if (g_hWnd && !DestroyWindow(g_hWnd)) // Are We Able To Destroy The Window?
{
MessageBox(NULL,TEXT("Could Not Release hWnd."),TEXT("SHUTDOWN ERROR"),MB_OK | MB_ICONINFORMATION);
g_hWnd=NULL; // Set hWnd To NULL
}
if (!UnregisterClass(TEXT("OpenGL"),g_hInstance)) // Are We Able To Unregister Class
{
MessageBox(NULL,TEXT("Could Not Unregister Class."),TEXT("SHUTDOWN ERROR"),MB_OK | MB_ICONINFORMATION);
g_hInstance=NULL; // Set hInstance To NULL
}
SwapBuffers(g_hDC);
g_hDC=NULL;
g_hWnd=NULL;
}