GDI Drawing Help

Trying to make a function to draw a simple rectangle.. if successful, I would like to use a series of rectangles to draw a grid.. Just wondering if anyone could take a look at my DrawGrid( ) function and tell me what I missing/overlooking..

Code:

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#include <windows.h>

HINSTANCE hInstGlobal;
HWND hButton, hEdit;

void DrawGrid(HWND, int rows, int column);

/*  Declare Windows procedure  */
LRESULT CALLBACK WindowProcedure (HWND, UINT, WPARAM, LPARAM);

/*  Make the class name into a global variable  */
char szClassName[ ] = "Cable Splicer";

int WINAPI WinMain (HINSTANCE hThisInstance,
                    HINSTANCE hPrevInstance,
                    LPSTR lpszArgument,
                    int nCmdShow)

{
  hInstGlobal = hThisInstance;
                   
                   
    HWND hwnd;              /* This is the handle for our window */
    MSG messages;            /* Here messages to the application are saved */
    WNDCLASSEX wincl;        /* Data structure for the windowclass */
   
 

    /* The Window structure */
    wincl.hInstance = hThisInstance;
    wincl.lpszClassName = szClassName;
    wincl.lpfnWndProc = WindowProcedure;      /* This function is called by windows */
    wincl.style = CS_DBLCLKS;                /* Catch double-clicks */
    wincl.cbSize = sizeof (WNDCLASSEX);

    /* Use default icon and mouse-pointer */
    wincl.hIcon = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hIconSm = LoadIcon (NULL, IDI_APPLICATION);
    wincl.hCursor = LoadCursor (NULL, IDC_ARROW);
    wincl.lpszMenuName = NULL;                /* No menu */
    wincl.cbClsExtra = 0;                      /* No extra bytes after the window class */
    wincl.cbWndExtra = 0;                      /* structure or the window instance */
    /* Use Windows's default color as the background of the window */
    wincl.hbrBackground = (HBRUSH) GetStockObject (WHITE_BRUSH) ;

    /* Register the window class, and if it fails quit the program */
    if (!RegisterClassEx (&wincl))
        return 0;

    /* The class is registered, let's create the program*/
    hwnd = CreateWindowEx (
          0,                  /* Extended possibilites for variation */
          szClassName,        /* Classname */
          "Cable Splice Calculator",      /* Title Text */
          WS_OVERLAPPEDWINDOW, /* default window */
          CW_USEDEFAULT,      /* Windows decides the position */
          CW_USEDEFAULT,      /* where the window ends up on the screen */
          544,                /* The programs width */
          375,                /* and height in pixels */
          HWND_DESKTOP,        /* The window is a child-window to desktop */
          NULL,                /* No menu */
          hThisInstance,      /* Program Instance handler */
          NULL                /* No Window Creation data */
          );

    /* Make the window visible on the screen */
    ShowWindow (hwnd, nCmdShow); 

    /* Run the message loop. It will run until GetMessage() returns 0 */
    while (GetMessage (&messages, NULL, 0, 0))
    {
        /* Translate virtual-key messages into character messages */
        TranslateMessage(&messages);
        /* Send message to WindowProcedure */
        DispatchMessage(&messages);
    }

    /* The program return-value is 0 - The value that PostQuitMessage() gave */
    return messages.wParam;
}


/*  This function is called by the Windows function DispatchMessage()  */

LRESULT CALLBACK WindowProcedure (HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam)
{
    switch (message)                  /* handle the messages */
    {
        case WM_CREATE:
           
            hButton = CreateWindow("BUTTON", "ADD", WS_CHILD|WS_VISIBLE|
                                    BS_DEFPUSHBUTTON, 150, 10, 140, 40,
                                    hwnd, (HMENU) 1, hInstGlobal, NULL);
                                   
            hEdit = CreateWindow("EDIT", NULL, WS_CHILD|WS_VISIBLE|
                                  WS_BORDER|ES_AUTOHSCROLL, 10, 30, 120, 20,
                                  hwnd, (HMENU) 2, hInstGlobal, NULL); 
                                 
            DrawGrid(hwnd,1,1);   
           
            break;
           
        case WM_PAINT:
           
            HDC hdc;
            PAINTSTRUCT ps;
               
            hdc = BeginPaint(hwnd, &ps);
            TextOut(hdc, 10, 10, "Enter Cable Count:", 18);
            EndPaint(hwnd, &ps);     
           
            break;         
         
        case WM_DESTROY:
            PostQuitMessage (0);      /* send a WM_QUIT to the message queue */
            break;
        default:                      /* for messages that we don't deal with */
            return DefWindowProc (hwnd, message, wParam, lParam);
    }

    return 0;
}



//Function Definitions

void DrawGrid(HWND hwnd, int rows, int column)
{
           
    HDC hdc;
    HPEN hPen;
    PAINTSTRUCT ps;
   
    hPen = CreatePen(PS_SOLID, 2, RGB(200,100,50));
   
    hdc = BeginPaint(hwnd, &ps);
   
    SelectObject(hdc, hPen);
   
    Rectangle(hdc, 10, 100, 40, 10);
   
    DeleteObject(hPen);
   
    EndPaint(hwnd, &ps);
}

---

using dev-cpp

The problem is your DrawGrid() function is only called once. You need that function to be called from the WM_PAINT handler so it gets redrawn when it needs to be.

You can't call BeginPaint() except in response to a WM_PAINT msg and you can't call it more than once in a WM_PAINT msg.

If the update area is empty then BeginPaint() won't work. Use GetUpdateRect() to check it BEFORE you call BeginPaint() or check the rect in the PAINTSTRUCT.

Trigger a WM_PAINT msg with
InvalidateRect() //use client rect
UpdateWindow()


You also have a GDI leak.
use

HPEN hOrigPen = SelectObject(hdc, hPen);

//use pen

//clean up
SelectObject(hdc, hOrigPen );
DeleteObject(hPen);


I also suggest you 'clear' the entire area by Rectangle() with the client rect.
That is,
draw over the current screen with a solid colour,
redraw the text and grid.

Got it to work.. you guys are awesome...

thanks :cool: