Das Beispiel in diesem Abschnitt wird ein einfaches Textverarbeitungsprogramm entnommen. Es enthält Code, der den Benutzer die Position der Einfügemarke festlegen, indem Sie an einer beliebigen Stelle auf einer Textzeile, und wählen (hervorheben) ermöglicht eine Textzeile durch Doppelklicken auf eine beliebige Stelle auf der Linie.
LRESULT APIENTRY MainWndProc(HWND hwndMain, UINT uMsg, WPARAM wParam, LPARAM lParam)
{
HDC hdc; // handle of device context
TEXTMETRIC tm; // font size data
int i, j; // loop counters
int cCR = 0; // count of carriage returns
char ch; // character from input buffer
static int nBegLine; // beginning of selected line
static int nCurrentLine = 0; // currently selected line
static int nLastLine = 0; // last text line
static int nCaretPosX = 0; // x-coordinate of caret
static int cch = 0; // number of characters entered
static int nCharWidth = 0; // exact width of a character
static char szHilite[128]; // text string to highlight
static DWORD dwCharX; // average width of characters
static DWORD dwLineHeight; // line height
static POINTS ptsCursor; // coordinates of mouse cursor
static COLORREF crPrevText; // previous text color
static COLORREF crPrevBk; // previous background color
static PTCHAR pchInputBuf; // address of input buffer
static BOOL fTextSelected = FALSE; // text-selection flag
switch (uMsg)
{
case WM_CREATE:
// Get the metrics of the current font.
hdc = GetDC(hwndMain);
GetTextMetrics(hdc, &tm);
ReleaseDC(hwndMain, hdc);
// Save the average character width and height.
dwCharX = tm.tmAveCharWidth;
dwLineHeight = tm.tmHeight;
// Allocate a buffer to store keyboard input.
pchInputBuf = (LPSTR) GlobalAlloc(GPTR,
BUFSIZE * sizeof(TCHAR));
return 0;
case WM_CHAR:
switch (wParam)
{
case 0x08: // backspace
case 0x0A: // linefeed
case 0x1B: // escape
MessageBeep(0xFFFFFFFF);
return 0;
case 0x09: // tab
// Convert tabs to four consecutive spaces.
for (i = 0; i < 4; i++)
SendMessage(hwndMain, WM_CHAR, 0x20, 0);
return 0;
case 0x0D: // carriage return
// Record the carriage return, and position the
// caret at the beginning of the new line.
pchInputBuf[cch++] = 0x0D;
nCaretPosX = 0;
nCurrentLine += 1;
break;
default: / displayable character
ch = (char) wParam;
HideCaret(hwndMain);
// Retrieve the character's width, and display the
// character.
hdc = GetDC(hwndMain);
GetCharWidth32(hdc, (UINT) wParam, (UINT) wParam,
&nCharWidth);
TextOut(hdc, nCaretPosX,
nCurrentLine * dwLineHeight, &ch, 1);
ReleaseDC(hwndMain, hdc);
// Store the character in the buffer.
pchInputBuf[cch++] = ch;
// Calculate the new horizontal position of the
// caret. If the new position exceeds the maximum,
// insert a carriage return and reposition the
// caret at the beginning of the next line.
nCaretPosX += nCharWidth;
if ((DWORD) nCaretPosX > dwMaxCharX)
{
nCaretPosX = 0;
pchInputBuf[cch++] = 0x0D;
++nCurrentLine;
}
ShowCaret(hwndMain);
break;
}
SetCaretPos(nCaretPosX, nCurrentLine * dwLineHeight);
nLastLine = max(nLastLine, nCurrentLine);
break;
// Process other messages.
case WM_LBUTTONDOWN:
// If a line of text is currently highlighted, redraw
// the text to remove the highlighting.
if (fTextSelected)
{
hdc = GetDC(hwndMain);
SetTextColor(hdc, crPrevText);
SetBkColor(hdc, crPrevBk);
TextOut(hdc, 0, nCurrentLine * dwLineHeight,
szHilite, lstrlen(szHilite));
ReleaseDC(hwndMain, hdc);
ShowCaret(hwndMain);
fTextSelected = FALSE;
}
// Save the current mouse-cursor coordinates.
ptsCursor = MAKEPOINTS(lParam);
// Determine which line the cursor is on, and save
// the line number. Do not allow line numbers greater
// than the number of the last line of text. The
// line number is later multiplied by the average height
// of the current font. The result is used to set the
// y-coordinate of the caret.
nCurrentLine = min((int)(ptsCursor.y / dwLineHeight),
nLastLine);
// Parse the text input buffer to find the first
// character in the selected line of text. Each
// line ends with a carriage return, so it is possible
// to count the carriage returns to find the selected
// line.
cCR = 0;
nBegLine = 0;
if (nCurrentLine != 0)
{
for (i = 0; (i < cch) &&
(cCR < nCurrentLine); i++)
{
if (pchInputBuf[i] == 0x0D)
++cCR;
}
nBegLine = i;
}
// Starting at the beginning of the selected line,
// measure the width of each character, summing the
// width with each character measured. Stop when the
// sum is greater than the x-coordinate of the cursor.
// The sum is used to set the x-coordinate of the caret.
hdc = GetDC(hwndMain);
nCaretPosX = 0;
for (i = nBegLine;
(pchInputBuf[i] != 0x0D) && (i < cch); i++)
{
ch = pchInputBuf[i];
GetCharWidth32(hdc, (int) ch, (int) ch, &nCharWidth);
if ((nCaretPosX + nCharWidth) > ptsCursor.x) break;
else nCaretPosX += nCharWidth;
}
ReleaseDC(hwndMain, hdc);
// Set the caret to the user-selected position.
SetCaretPos(nCaretPosX, nCurrentLine * dwLineHeight);
break;
case WM_LBUTTONDBLCLK:
// Copy the selected line of text to a buffer.
for (i = nBegLine, j = 0; (pchInputBuf[i] != 0x0D) &&
(i < cch); i++)
{
szHilite[j++] = pchInputBuf[i];
}
szHilite[j] = '\0';
// Hide the caret, invert the background and foreground
// colors, and then redraw the selected line.
HideCaret(hwndMain);
hdc = GetDC(hwndMain);
crPrevText = SetTextColor(hdc, RGB(255, 255, 255));
crPrevBk = SetBkColor(hdc, RGB(0, 0, 0));
TextOut(hdc, 0, nCurrentLine * dwLineHeight, szHilite,
lstrlen(szHilite));
SetTextColor(hdc, crPrevText);
SetBkColor(hdc, crPrevBk);
ReleaseDC(hwndMain, hdc);
fTextSelected = TRUE;
break;
// Process other messages.
default:
return DefWindowProc(hwndMain, uMsg, wParam, lParam);
}
return NULL;
}