mfc slider 控件中是否有一种方法，当我移动拇指时，它会在默认背景颜色上填充 slider 的背景颜色

Question

I am trying to make a customised slider in mfc.Is there a way so that as I move the slider, the background color changes according to the position of the thumb of the slider over the default background color, just like the default .net slider in .net。

void rogreen::OnPaint()
{
    CPaintDC dc(this); // device context for painting
                       // TODO: Add your message handler code here
                       // Do not call CStatic::OnPaint() for painting messages

    CRect rectWindow;
    GetClientRect(&rectWindow);


    CRect rect;
    GetClientRect(&rect);

    int r1 = { 0 }, g1 = { 255 }, b1 = { 0 }; //Any start color
    int r2 = { 0 }, g2 = { 0 }, b2 = { 0 }; //Any stop color

    for (int i = 0;i < rect.Height();i++)
    {
        int r, g, b;
        r = r1 + (i * (r2 - r1) / rect.Height());
        g = g1 + (i * (g2 - g1) / rect.Height());
        b = b1 + (i * (b2 - b1) / rect.Height());
        dc.FillSolidRect(0, i, rect.Width(), 1, RGB(r, g, b));
    }
}

Answer 1

使用https://docs.microsoft.com/en-us/windows/win32/gdi/drawing-a-shaded-rectangle中的示例，您可以像这样处理WM_CTLCOLORSTATIC消息：

case WM_CTLCOLORSTATIC:
{
    if (::GetDlgItem(hDlg, IDC_SLIDER) == (HWND)lParam) {
        HDC hdc = (HDC)wParam;
        RECT r = {};
        ::GetClientRect((HWND)lParam, &r);
        
        // Create an array of TRIVERTEX structures that describe 
        // positional and color values for each vertex. For a rectangle, 
        // only two vertices need to be defined: upper-left and lower-right. 
        TRIVERTEX vertex[2];
        vertex[0].x = 0;
        vertex[0].y = 0;
        vertex[0].Red = 0x0000;
        vertex[0].Green = 0x8000;
        vertex[0].Blue = 0x8000;
        vertex[0].Alpha = 0x0000;

        vertex[1].x = r.right; // 400;
        vertex[1].y = r.bottom; // 40;
        vertex[1].Red = 0x0000;
        vertex[1].Green = 0xd000;
        vertex[1].Blue = 0xd000;
        vertex[1].Alpha = 0x0000;

        // Create a GRADIENT_RECT structure that 
        // references the TRIVERTEX vertices. 
        GRADIENT_RECT gRect;
        gRect.UpperLeft = 0;
        gRect.LowerRight = 1;
        // Draw a shaded rectangle. 
        GradientFill(hdc, vertex, 2, &gRect, 1, GRADIENT_FILL_RECT_V);
        return (INT_PTR)::GetStockObject(NULL_BRUSH);
    }
}

您可以使用滑块的 position 来计算所需的颜色值。

Answer 2

我无法提供答案，因为我自己没有尝试过您想要的，但您应该查看“所有者绘制”控制选项。 我用它来创建不同颜色的按钮。 我没有尝试在 slider 移动时改变颜色。

（我假设您在上面发布的代码不符合您的要求？）