Uso de formas rellenas

En esta sección se muestra cómo usar funciones de formas rellenadas. En el ejemplo se usa el procedimiento de ventana principal de una aplicación que permite al usuario dibujar puntos suspensivos, rectángulos y rectángulos con esquinas redondeadas.

El usuario dibuja una forma rellenada seleccionando una forma determinada en el menú, colocando el cursor en la esquina superior izquierda de la forma (o el rectángulo delimitador de la forma en el caso de una elipse) y arrastrando el mouse hasta que se obtienen las dimensiones deseadas.

En la ilustración siguiente se muestran tres formas rellenadas mediante el código de ejemplo de esta sección.

Para permitir que el usuario dibuje formas rellenadas, incluya el siguiente menú emergente en la aplicación.

   POPUP "Filled &Shapes"
   {
      MENUITEM "&Ellipse",   IDM_ELLIPSE
      MENUITEM "&Rectangle", IDM_RECTANGLE
      MENUITEM "R&oundRect", IDM_ROUNDRECT
   }

Los valores del elemento de menú de la plantilla de menú son constantes que debe definir como se indica a continuación en el archivo de encabezado de la aplicación.

#define IDM_ELLIPSE    1100
#define IDM_RECTANGLE  1200
#define IDM_ROUNDRECT  1300

Por último, incluya el siguiente procedimiento de ventana en la aplicación.

BOOL CALLBACK MainWndProc(HWND hwnd, UINT uMsg, WPARAM wParam, 
                          LPARAM lParam) 
{ 
    HDC hdc;          // handle to device context (DC)  
    PAINTSTRUCT ps;   // paint data for Begin/EndPaint  
    POINT ptClientUL; // client area upper left corner  
    POINT ptClientLR; // client area lower right corner  
    static HDC hdcCompat; // handle to DC for bitmap  
    static POINT pt;      // x- and y-coordinates of cursor  
    static RECT rcTarget; // rect to receive filled shape  
    static RECT rcClient; // client area rectangle  
    static BOOL fSizeEllipse; // TRUE if ellipse is sized  
    static BOOL fDrawEllipse;   // TRUE if ellipse is drawn  
    static BOOL fDrawRectangle; // TRUE if rectangle is drawn  
    static BOOL fSizeRectangle; // TRUE if rectangle is sized  
    static BOOL fSizeRoundRect; // TRUE if rounded rect is sized  
    static BOOL fDrawRoundRect; // TRUE if rounded rect is drawn  
    static int nEllipseWidth;   // width for round corners  
    static int nEllipseHeight;  // height for round corners  
 
    switch (uMsg) 
    { 
        case WM_COMMAND: 
            switch (wParam) 
            { 

                // Set the appropriate flag to indicate which  
                // filled shape the user is drawing.  

                case IDM_ELLIPSE: 
                    fSizeEllipse = TRUE; 
                break; 
 
                case IDM_RECTANGLE: 
                    fSizeRectangle = TRUE; 
                break; 
 
                case IDM_ROUNDRECT: 
                    fSizeRoundRect = TRUE; 
                break; 
 
                default: 
                    return DefWindowProc(hwnd, uMsg, wParam, 
                         lParam); 
            } 
            break; 
 
 
        case WM_CREATE: 
            nEllipseWidth = 20; 
            nEllipseHeight = 20; 
 
            return 0; 
 
        case WM_PAINT: 
 
 
            BeginPaint(hwnd, &ps); 
 
            // Because the default brush is white, select  
            // a different brush into the device context  
            // to demonstrate the painting of filled shapes.  
 
            SelectObject(ps.hdc, GetStockObject(GRAY_BRUSH)); 
 
            // If one of the filled shape "draw" flags is TRUE,  
            // draw the corresponding shape.  
 
            if (fDrawEllipse) 
            {
                Ellipse(ps.hdc, rcTarget.left, rcTarget.top, 
                    rcTarget.right, rcTarget.bottom); 
                fDrawEllipse = FALSE; 
                rcTarget.left = rcTarget.right = 0; 
                rcTarget.top = rcTarget.bottom = 0; 
            } 
 
            if (fDrawRectangle) 
            {
                Rectangle(ps.hdc, rcTarget.left, rcTarget.top, 
                    rcTarget.right, rcTarget.bottom); 
                fDrawRectangle = FALSE; 
                rcTarget.left = rcTarget.right = 0; 
                rcTarget.top = rcTarget.bottom = 0; 
            } 
 
            if (fDrawRoundRect) 
            {
                RoundRect(ps.hdc, rcTarget.left, rcTarget.top, 
                    rcTarget.right, rcTarget.bottom, 
                    nEllipseWidth, nEllipseHeight); 
                fDrawRectangle = FALSE; 
                rcTarget.left = rcTarget.right = 0; 
                rcTarget.top = rcTarget.bottom = 0; 
            } 
 
            EndPaint(hwnd, &ps); 
            break; 
 
        case WM_SIZE: 
 
            // Convert the client coordinates of the client area  
            // rectangle to screen coordinates and save them in a  
            // rectangle. The rectangle is passed to the ClipCursor  
            // function during WM_LBUTTONDOWN processing.  
 
            GetClientRect(hwnd, &rcClient); 
            ptClientUL.x = rcClient.left; 
            ptClientUL.y = rcClient.top; 
            ptClientLR.x = rcClient.right; 
            ptClientLR.y = rcClient.bottom; 
            ClientToScreen(hwnd, &ptClientUL); 
            ClientToScreen(hwnd, &ptClientLR); 
            SetRect(&rcClient, ptClientUL.x, ptClientUL.y, 
                ptClientLR.x, ptClientLR.y); 
            return 0; 
 
        case WM_LBUTTONDOWN: 
 
            // Restrict the cursor to the client area.  
            // This ensures that the window receives a matching  
            // WM_LBUTTONUP message.  
 
            ClipCursor(&rcClient); 
 
            // Save the coordinates of the cursor.  
 
            pt.x = (LONG) LOWORD(lParam); 
            pt.y = (LONG) HIWORD(lParam); 
 
            // If the user chooses one of the filled shapes,  
            // set the appropriate flag to indicate that the  
            // shape is being sized.  
 
             if (fDrawEllipse) 
                fSizeEllipse = TRUE; 
 
            return 0; 
 
        case WM_MOUSEMOVE: 
 
            // If one of the "size" flags is set, draw  
            // the target rectangle as the user drags  
            // the mouse.  
 
            if ((wParam && MK_LBUTTON) 
                    && (fSizeEllipse || fSizeRectangle 
                    || fSizeRoundRect)) 
            {  
 
                // Set the mixing mode so that the pen color is the  
                // inverse of the background color. The previous  
                // rectangle can then be erased by drawing  
                // another rectangle on top of it.  
 
                hdc = GetDC(hwnd); 
                SetROP2(hdc, R2_NOTXORPEN); 
 
                // If a previous target rectangle exists, erase  
                // it by drawing another rectangle on top.  
 
                if (!IsRectEmpty(&rcTarget)) 
                {
                    Rectangle(hdc, rcTarget.left, rcTarget.top, 
                        rcTarget.right, rcTarget.bottom); 
                }

                // Save the coordinates of the target rectangle.  
                // Avoid invalid rectangles by ensuring that the  
                // value of the left coordinate is greater than  
                // that of the right, and that the value of the  
                // bottom coordinate is greater than that of  
                // the top.  
 
                if ((pt.x < (LONG) LOWORD(lParam)) && 
                        (pt.y > (LONG) HIWORD(lParam))) 
                {
                    SetRect(&rcTarget, pt.x, HIWORD(lParam), 
                        LOWORD(lParam), pt.y); 
                } 
 
                else if ((pt.x > (LONG) LOWORD(lParam)) && 
                        (pt.y > (LONG) HIWORD(lParam))) 
                {
                    SetRect(&rcTarget, LOWORD(lParam), 
                        HIWORD(lParam), pt.x, pt.y); 
                }
 
                else if ((pt.x > (LONG) LOWORD(lParam)) && 
                        (pt.y < (LONG) HIWORD(lParam))) 
                {
                    SetRect(&rcTarget, LOWORD(lParam), pt.y, 
                        pt.x, HIWORD(lParam)); 
                }
                else 
                {
                    SetRect(&rcTarget, pt.x, pt.y, LOWORD(lParam), 
                        HIWORD(lParam)); 
                }
 
                // Draw the new target rectangle.  
 
                Rectangle(hdc, rcTarget.left, rcTarget.top, 
                    rcTarget.right, rcTarget.bottom); 
                ReleaseDC(hwnd, hdc); 
            } 
            return 0; 
 
        case WM_LBUTTONUP: 
 
            // If one of the "size" flags is TRUE, reset it to FALSE,  
            // and then set the corresponding "draw" flag. Invalidate  
            // the appropriate rectangle and issue a WM_PAINT message.  
 
            if (fSizeEllipse) 
            { 
                fSizeEllipse = FALSE; 
                fDrawEllipse = TRUE; 
            } 
 
            if (fSizeRectangle) 
            { 
                fSizeRectangle = FALSE; 
                fDrawRectangle = TRUE; 
            } 
 
            if (fSizeRoundRect) 
            { 
                fSizeRoundRect = FALSE; 
                fDrawRoundRect = TRUE; 
            } 
 
            if (fDrawEllipse || fDrawRectangle || fDrawRoundRect) 
            { 
                InvalidateRect(hwnd, &rcTarget, TRUE); 
                UpdateWindow(hwnd); 
            } 
 
            // Release the cursor.  
 
            ClipCursor((LPRECT) NULL); 
            return 0; 
 
        case WM_DESTROY: 
 
            // Destroy the background brush, compatible bitmap,  
            // and bitmap.  
 
            DeleteDC(hdcCompat); 
            PostQuitMessage(0); 
            break; 
 
        default: 
            return DefWindowProc(hwnd, uMsg, wParam, lParam); 
    } 
    return (LRESULT) NULL; 
}