Thread: 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:

#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

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