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Pointer to WndProc in a class


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#1 Patbert   Members   -  Reputation: 462

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Posted 28 February 2005 - 06:46 AM

Hi I'm trying to move all my functions for creating OpenGL windows into one class, but I've hit a problem. In the function CreateGLWindow it has the line: wc.lpfnWndProc = (WNDPROC) WndProc; // WndProc Handles Messages Which used to point to: LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM) in the same file but as I've moved them all to a class I need it to point to: LRESULT CBaseCode::CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM); With the current code the compiler gives me the error: CBaseCode.cpp: In member function `BOOL CBaseCode::CreateGLWindow(char*, int, int, int, bool)': CBaseCode.cpp:38: no matches converting function `WndProc' to type `LRESULT (*)(struct HWND__*, unsigned int, unsigned int, long int)' CbaseCode.h:13: candidates are: LRESULT CBaseCode::WndProc(HWND__*, unsigned int, unsigned int, long int) Any help would be greatly appreciated. [smile]

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#2 nmi   Members   -  Reputation: 978

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Posted 28 February 2005 - 06:51 AM

Did you make the function static ?

Example:

class C
{
LRESULT CALLBACK WndProc1(HWND, UINT, WPARAM, LPARAM);
static LRESULT CALLBACK WndProc2(HWND, UINT, WPARAM, LPARAM);
};

Here WndProc1 won't work because of the implicit this parameter,
but WndProc2 will work.

#3 Evil Steve   Members   -  Reputation: 1982

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Posted 28 February 2005 - 07:00 AM

And if you make it static, you won't be able to access any member variables.

Usually you use a static function, and store your class pointer in the HWND's 32-bit user data area like so:

//
// Header
//
class Window
{
public:
//...

protected:
static LRESULT CALLBACK StaticWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
LRESULT WndProc(UINT uMsg, WPARAM wParam, LPARAM lParam);

protected:
HWND m_hWnd;
};

//
// Source
//
// When you register the window class, pass CWindow::StaticWndProc as the window message procedure pointer

// When you create the window, pass "this" as the extra parameter
m_hWnd = CreateWindowEx(0,"Classname","Title",WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,CW_USEDEFAULT,320,200,NULL,NULL,hInstance,this);

// Now for the real code:
LRESULT CALLBACK CWindow::StaticWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
CWindow* pParent;

// Get pointer to window
if(uMsg == WM_CREATE)
{
pParent = (CWindow*)((LPCREATESTRUCT)lParam)->lpCreateParams;
SetWindowLongPtr(hWnd,GWL_USERDATA,(LONG_PTR)pParent);
}
else
{
pParent = (CWindow*)GetWindowLongPtr(hWnd,GWL_USERDATA);
if(!pParent) return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

pParent->m_hWnd = hWnd;
return pParent->WndProc(uMsg,wParam,lParam);
}

LRESULT CWindow::WndProc(UINT uMsg, WPARAM wParam, LPARAM lParam)
{
switch(uMsg)
{
// Normal code here
}

// Call default window proc if we haven't handled the message
return DefWindowProc(m_hWnd,uMsg,wParam,lParam);
}




Hope this helps,
Steve

#4 Patbert   Members   -  Reputation: 462

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Posted 28 February 2005 - 08:55 AM

Cheers, it works!

Here's the resulting code if anyones interested. (some parts are from NeHe)


// CWindow.h:

#ifndef INC_CWindow_H
#define INC_CWindow_H

#include <windows.h> // Header File For Windows
#include <gl\gl.h> // Header File For The OpenGL32 Library
#include <gl\glu.h> // Header File For The GLu32 Library

class CWindow {
public:
CWindow();
BOOL CWindow::CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag);
GLvoid KillGLWindow(GLvoid);
static LRESULT CALLBACK StaticWndProc(HWND, UINT, WPARAM, LPARAM); // Declaration For WndProc
LRESULT WndProc( UINT, WPARAM, LPARAM);
int InitGL(GLvoid);

HDC gethDC() { return hDC; };
private:
HDC hDC; // Private GDI Device Context
HGLRC hRC; // Permanent Rendering Context
HWND hWnd; // Holds Our Window Handle
HINSTANCE hInstance; // Holds The Instance Of The Application
static void ReSizeGLScene(GLsizei width, GLsizei height);
};

#endif

//CWindow.cpp:

#include "CWindow.h"
#include <gl\gl.h> // Header File For The OpenGL32 Library
#include <gl\glu.h> // Header File For The GLu32 Library

/* This Code Creates Our OpenGL Window. Parameters Are: *
* title - Title To Appear At The Top Of The Window *
* width - Width Of The GL Window Or Fullscreen Mode *
* height - Height Of The GL Window Or Fullscreen Mode *
* bits - Number Of Bits To Use For Color (8/16/24/32) *
* fullscreenflag - Use Fullscreen Mode (TRUE) Or Windowed Mode (FALSE) */


CWindow::CWindow() {
hDC=NULL; // Private GDI Device Context
hRC=NULL; // Permanent Rendering Context
hWnd=NULL; // Holds Our Window Handle
//hInstance; // Holds The Instance Of The Application
}


BOOL CWindow::CreateGLWindow(char* title, int width, int height, int bits, bool fullscreenflag)
{
GLuint PixelFormat; // Holds The Results After Searching For A Match
WNDCLASS wc; // Windows Class Structure
DWORD dwExStyle; // Window Extended Style
DWORD dwStyle; // Window Style
RECT WindowRect; // Grabs Rectangle Upper Left / Lower Right Values
WindowRect.left=(long)0; // Set Left Value To 0
WindowRect.right=(long)width; // Set Right Value To Requested Width
WindowRect.top=(long)0; // Set Top Value To 0
WindowRect.bottom=(long)height; // Set Bottom Value To Requested Height

fullscreen=fullscreenflag; // Set The Global Fullscreen Flag

hInstance = GetModuleHandle(NULL); // Grab An Instance For Our Window
wc.style = CS_HREDRAW | CS_VREDRAW | CS_OWNDC; // Redraw On Size, And Own DC For Window.
wc.lpfnWndProc = (WNDPROC) StaticWndProc; // WndProc Handles Messages
wc.cbClsExtra = 0; // No Extra Window Data
wc.cbWndExtra = 0; // No Extra Window Data
wc.hInstance = hInstance; // Set The Instance
wc.hIcon = LoadIcon(NULL, IDI_WINLOGO); // Load The Default Icon
wc.hCursor = LoadCursor(NULL, IDC_ARROW); // Load The Arrow Pointer
wc.hbrBackground = NULL; // No Background Required For GL
wc.lpszMenuName = NULL; // We Don't Want A Menu
wc.lpszClassName = "OpenGL"; // Set The Class Name

if (!RegisterClass(&wc)) // Attempt To Register The Window Class
{
MessageBox(NULL,"Failed To Register The Window Class.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}

if (fullscreen) // Attempt Fullscreen Mode?
{
DEVMODE dmScreenSettings; // Device Mode
memset(&dmScreenSettings,0,sizeof(dmScreenSettings)); // Makes Sure Memory's Cleared
dmScreenSettings.dmSize=sizeof(dmScreenSettings); // Size Of The Devmode Structure
dmScreenSettings.dmPelsWidth = width; // Selected Screen Width
dmScreenSettings.dmPelsHeight = height; // Selected Screen Height
dmScreenSettings.dmBitsPerPel = bits; // Selected Bits Per Pixel
dmScreenSettings.dmFields=DM_BITSPERPEL|DM_PELSWIDTH|DM_PELSHEIGHT;

// Try To Set Selected Mode And Get Results. NOTE: CDS_FULLSCREEN Gets Rid Of Start Bar.
if (ChangeDisplaySettings(&dmScreenSettings,CDS_FULLSCREEN)!=DISP_CHANGE_SUCCESSFUL)
{
// If The Mode Fails, Offer Two Options. Quit Or Use Windowed Mode.
if (MessageBox(NULL,"The Requested Fullscreen Mode Is Not Supported By\nYour Video Card. Use Windowed Mode Instead?","NeHe GL",MB_YESNO|MB_ICONEXCLAMATION)==IDYES)
{
fullscreen=FALSE; // Windowed Mode Selected. Fullscreen = FALSE
}
else
{
// Pop Up A Message Box Letting User Know The Program Is Closing.
MessageBox(NULL,"Program Will Now Close.","ERROR",MB_OK|MB_ICONSTOP);
return FALSE; // Return FALSE
}
}
}

if (fullscreen) // Are We Still In Fullscreen Mode?
{
dwExStyle=WS_EX_APPWINDOW; // Window Extended Style
dwStyle=WS_POPUP; // Windows Style
ShowCursor(FALSE); // Hide Mouse Pointer
}
else
{
dwExStyle=WS_EX_APPWINDOW | WS_EX_WINDOWEDGE; // Window Extended Style
dwStyle=WS_OVERLAPPEDWINDOW; // Windows Style
}

AdjustWindowRectEx(&WindowRect, dwStyle, FALSE, dwExStyle); // Adjust Window To True Requested Size

// Create The Window
if (!(hWnd=CreateWindowEx( dwExStyle, // Extended Style For The Window
"OpenGL", // Class Name
title, // Window Title
dwStyle | // Defined Window Style
WS_CLIPSIBLINGS | // Required Window Style
WS_CLIPCHILDREN, // Required Window Style
0, 0, // Window Position
WindowRect.right-WindowRect.left, // Calculate Window Width
WindowRect.bottom-WindowRect.top, // Calculate Window Height
NULL, // No Parent Window
NULL, // No Menu
hInstance, // Instance
this))) // Pass this class To WM_CREATE

{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Window Creation Error.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}

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
bits, // 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
};

if (!(hDC=GetDC(hWnd))) // Did We Get A Device Context?
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Create A GL Device Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}

if (!(PixelFormat=ChoosePixelFormat(hDC,&pfd))) // Did Windows Find A Matching Pixel Format?
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Find A Suitable PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}

if(!SetPixelFormat(hDC,PixelFormat,&pfd)) // Are We Able To Set The Pixel Format?
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Set The PixelFormat.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}

if (!(hRC=wglCreateContext(hDC))) // Are We Able To Get A Rendering Context?
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Create A GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}

if(!wglMakeCurrent(hDC,hRC)) // Try To Activate The Rendering Context
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Can't Activate The GL Rendering Context.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}

ShowWindow(hWnd,SW_SHOW); // Show The Window
SetForegroundWindow(hWnd); // Slightly Higher Priority
SetFocus(hWnd); // Sets Keyboard Focus To The Window
ReSizeGLScene(width, height); // Set Up Our Perspective GL Screen

if (!InitGL()) // Initialize Our Newly Created GL Window
{
KillGLWindow(); // Reset The Display
MessageBox(NULL,"Initialization Failed.","ERROR",MB_OK|MB_ICONEXCLAMATION);
return FALSE; // Return FALSE
}

return TRUE; // Success
}

LRESULT CALLBACK CWindow::StaticWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
CWindow* pParent;

// Get pointer to window
if(uMsg == WM_CREATE)
{
pParent = (CWindow*)((LPCREATESTRUCT)lParam)->lpCreateParams;
SetWindowLongPtr(hWnd,GWL_USERDATA,(LONG_PTR)pParent);
}
else
{
pParent = (CWindow*)GetWindowLongPtr(hWnd,GWL_USERDATA);
if(!pParent) return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

pParent->hWnd = hWnd;
return pParent->WndProc(uMsg,wParam,lParam);
}

GLvoid CWindow::KillGLWindow(GLvoid) // Properly Kill The Window
{
if (fullscreen) // Are We In Fullscreen Mode?
{
ChangeDisplaySettings(NULL,0); // If So Switch Back To The Desktop
ShowCursor(TRUE); // Show Mouse Pointer
}

if (hRC) // Do We Have A Rendering Context?
{
if (!wglMakeCurrent(NULL,NULL)) // Are We Able To Release The DC And RC Contexts?
{
MessageBox(NULL,"Release Of DC And RC Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
}

if (!wglDeleteContext(hRC)) // Are We Able To Delete The RC?
{
MessageBox(NULL,"Release Rendering Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
}
hRC=NULL; // Set RC To NULL
}

if (hDC && !ReleaseDC(hWnd,hDC)) // Are We Able To Release The DC
{
MessageBox(NULL,"Release Device Context Failed.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
hDC=NULL; // Set DC To NULL
}

if (hWnd && !DestroyWindow(hWnd)) // Are We Able To Destroy The Window?
{
MessageBox(NULL,"Could Not Release hWnd.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
hWnd=NULL; // Set hWnd To NULL
}

if (!UnregisterClass("OpenGL",hInstance)) // Are We Able To Unregister Class
{
MessageBox(NULL,"Could Not Unregister Class.","SHUTDOWN ERROR",MB_OK | MB_ICONINFORMATION);
hInstance=NULL; // Set hInstance To NULL
}

//standardFont.KillFont(); // Destroy The Font

}


LRESULT CWindow::WndProc( // Handle For This Window
UINT uMsg, // Message For This Window
WPARAM wParam, // Additional Message Information
LPARAM lParam) // Additional Message Information
{

switch (uMsg) // Check For Windows Messages
{
case WM_ACTIVATE: // Watch For Window Activate Message
{
if (!HIWORD(wParam)) // Check Minimization State
{
active=TRUE; // Program Is Active
}
else
{
active=FALSE; // Program Is No Longer Active
}

return 0; // Return To The Message Loop
}

case WM_SYSCOMMAND: // Intercept System Commands
{
switch (wParam) // Check System Calls
{
case SC_SCREENSAVE: // Screensaver Trying To Start?
case SC_MONITORPOWER: // Monitor Trying To Enter Powersave?
return 0; // Prevent From Happening
}
break; // Exit
}

case WM_CLOSE: // Did We Receive A Close Message?
{
PostQuitMessage(0); // Send A Quit Message
return 0; // Jump Back
}

case WM_KEYDOWN: // Is A Key Being Held Down?
{
keys[wParam] = TRUE; // If So, Mark It As TRUE
return 0; // Jump Back
}

case WM_KEYUP: // Has A Key Been Released?
{
keys[wParam] = FALSE; // If So, Mark It As FALSE
return 0; // Jump Back
}

case WM_SIZE: // Resize The OpenGL Window
{
ReSizeGLScene(LOWORD(lParam),HIWORD(lParam)); // LoWord=Width, HiWord=Height
return 0; // Jump Back
}
}

// Pass All Unhandled Messages To DefWindowProc
return DefWindowProc(hWnd,uMsg,wParam,lParam);
}

int CWindow::InitGL(GLvoid) // All Setup For OpenGL Goes Here
{

glEnable(GL_TEXTURE_2D); // Enable Texture Mapping ( NEW )
//glShadeModel(GL_SMOOTH); // Enable Smooth Shading

glClearColor(0.0f, 0.0f, 0.5f, 0.0f); // 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

quadratic=gluNewQuadric(); // Create A Pointer To The Quadric Object (Return 0 If No Memory)
gluQuadricNormals(quadratic, GLU_SMOOTH); // Create Smooth Normals
gluQuadricTexture(quadratic, GL_TRUE); // Create Texture Coords
/* glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Clear The Screen And The Depth Buffer
glLoadIdentity();
glTranslatef(0,0,-1);
glRasterPos2f(-0.2,0);
glPrint("LOADING..."); */

return TRUE;
}

void CWindow::ReSizeGLScene(GLsizei width, GLsizei height) // Resize And Initialize 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
}






#5 Stompy9999   Members   -  Reputation: 792

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Posted 28 February 2005 - 09:30 AM

Couldn't you also make the Proc outside the class and pass it to the Init function as a function pointer? This thread is really helpful for me because I am doing the same thing.
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#6 Stompy9999   Members   -  Reputation: 792

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Posted 28 February 2005 - 10:06 AM

I just started working on my window class. Instead of making the winproc a method of the class, I am passing it into the init function as a function pointer. My question is, is this a valid function pointer to a Winproc?:



LRESULT CALLBACK (*WndProc)(HWND, UINT, WPARAM, LPARAM);



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#7 JimPrice   Members   -  Reputation: 815

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Posted 28 February 2005 - 10:28 AM

Quote:

Couldn't you also make the Proc outside the class and pass it to the Init function as a function pointer?


This is what I ended up doing. I played around with SetWindowLong and all that malarky - then I ended up thinking:

Hang on, this is C++ - no-one's forcing me to encapsulate everything in classes.

So - I have a windowmanager class, but I use a global callback function. In your WNDCLASSEX structure, you don't even need to pass in a function pointer - just the name of the function.

Woo-hoo!

Jim.




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