Using Clipping

This section contains example code that shows how to generate a clip path consisting of a character string. The example creates a logical font and uses it to draw a string within a clip path, then fills the path by drawing horizontal and vertical lines.

// DoClipPat - Draws a clip path using the specified string 
// Return value - TRUE if successful; FALSE otherwise 
// lplf - address of a LOGFONT structure that defines the font to 
// use to draw the clip path 
// lpsz - address of a string to use for the clip path 
 
BOOL DoClipPath(LPLOGFONT lplf, LPSTR lpsz) 
{ 
 LOGFONT lf; // logical font structure 
 HFONT hfont; // new logical font handle 
 HFONT hfontOld; // original logical font handle 
 HDC hdc; // display DC handle 
 int nXStart, nYStart; // drawing coordinates 
 RECT rc; // rectangle structure for painting window 
 SIZE sz; // size structure that receives text extents 
 int nStrLen; // length of the string 
 int i; // loop counter 
 HRESULT hr;
 size_t * pcch;
 
 // Retrieve a cached DC for the window. 
 
 hdc = GetDC(hwnd); 
 
 // Erase the current window contents. 
 
 GetClientRect(hwnd, &rc); 
 FillRect(hdc, &rc, GetStockObject(WHITE_BRUSH)); 
 
 // Use the specified font to create a logical font and select it 
 // into the DC. 
 
 hfont = CreateFontIndirect(lplf); 
 if (hfont == NULL) 
 return FALSE; 
 hfontOld = SelectObject(hdc, hfont); 
 
 // Create a clip path. 
 
 hr = StringCchLength(lpsz, STRSAFE_MAX_CCH, pcch);
 if (FAILED(hr))
 {
 // TODO: write error handler 
 }
 nStrLen = *pcch 
 BeginPath(hdc); 
 TextOut(hdc, nXStart, nYStart, lpsz, nStrLen); 
 EndPath(hdc); 
 SelectClipPath(hdc, RGN_DIFF); 
 
 // Retrieve the dimensions of the rectangle surrounding 
 // the text. 
 
 GetTextExtentPoint32(hdc, lpsz, nStrLen, &sz); 
 
 // Draw horizontal lines through the clip path. 
 
 for (i = nYStart + 1; i < (nYStart + sz.cy); i += 3) 
 { 
 MoveToEx(hdc, nXStart, i, (LPPOINT) NULL); 
 LineTo(hdc, (nXStart + sz.cx), i); 
 } 
 
 // Draw vertical lines through the clip path. 
 
 for (i = nXStart + 1; i < (nXStart + sz.cx); i += 3)
 { 
 MoveToEx(hdc, i, nYStart, (LPPOINT) NULL); 
 LineTo(hdc, i, (nYStart + sz.cy)); 
 } 
 
 // Select the original font into the DC and release the DC. 
 
 SelectObject(hdc, hfontOld); 
 DeleteObject(hfont); 
 ReleaseDC(hwnd, hdc); 
 
 return TRUE; 
} 

For an example that demonstrates how an application creates a rectangular clipping region, see Regions.