Question

下面的线条绘制代码有什么错误？

line1正确绘制垂直线
line2正确绘制水平线
line3和line4绘制对角线而不是水平线，并且垂直线

void GxDrawLine(HWND wnd, INT x0, INT y0, INT x1, INT y1, UINT line_thickness, UINT col) {
    COLORREF color = (COLORREF) col;
    HPEN pen = NULL;
    if (line_thickness == 1) {
        SetDCPenColor(GetDC(wnd), color);
    } else {
        pen = CreatePen(PS_SOLID, line_thickness, color);
        SelectObject(GetDC(wnd), pen);
    }
    MoveToEx(GetDC(wnd), x0, y0, NULL);
    LineTo(GetDC(wnd), x1, y1);
    if (pen) {
        SelectObject(GetDC(wnd), GetStockObject(DC_PEN));
        DeleteObject(pen);
    }
}
HWND wnd1 = CreateWindowExW(0, wc1.lpszClassName, L "Button",
    WS_TABSTOP | WS_CHILD | WS_VISIBLE, 10, 10,
    60, 60, wnd, NULL, wc.hInstance, & a); //NULL);
GxDrawLine(wnd1, 0, 0, 0, 48, 1, 0xf5f5f5);
GxDrawLine(wnd1, 0, 0, 48, 0, 1, 0xf5f5f5);
GxDrawLine(wnd1, 48, 0, 48, 48, 1, 0xf5f5f5);
GxDrawLine(wnd1, 0, 48, 48, 48, 1, 0xf5f5f5);

Answer 1

在未释放DC =>内存泄漏

的情况下，您不得调用 GetDC（wnd） n次。

固定代码=>

void GxDrawLine(HWND wnd, INT x0, INT y0, INT x1, INT y1, UINT line_thickness, UINT col)
{
    HPEN hPenOld = NULL ;
    COLORREF crColorOld = NULL;
    HDC hDC = GetDC(wnd);
    HPEN pen = NULL;
    if (line_thickness == 1)
    {
        hPenOld = (HPEN)SelectObject(hDC, (HGDIOBJ)GetStockObject(DC_PEN));
        COLORREF crColorOld = SetDCPenColor(hDC, col);
    }
    else
    {
        pen = CreatePen(PS_SOLID, line_thickness, col);
        hPenOld = (HPEN)SelectObject(hDC, pen);
    }
    MoveToEx(hDC, x0, y0, NULL);
    LineTo(hDC, x1, y1);
    SetDCPenColor(hDC, crColorOld);
    SelectObject(hDC, hPenOld);
    if (pen)
        DeleteObject(pen);
    ReleaseDC(wnd, hDC);
}

无法以适当的形式绘制线条

1 个答案: