如何在C++中在win32中创建自定义滑块控件

Question

我正在学习C/C++中的WIN32 API，想知道如何使用自定义形状的拇指(对话框的子项(创建自定义滑块/轨迹条控件。一个例子将有利于如何做到这一点，因为互联网上关于WIN32编程的信息非常少，尤其是对于自定义自己的儿童控件。请不要发布MFC示例。

以下是我试图完成的代码示例：

#pragma comment(linker,""/manifestdependency:type='win32' name='Microsoft.Windows.Common-Controls' version='6.0.0.0' processorArchitecture='*' publicKeyToken='6595b64144ccf1df' language='*'"")
#include <string>
#include <Windows.h>
#include <CommCtrl.h>
using namespace std;
HWND window = nullptr;
HWND trackBar = nullptr;
HWND progressBar = nullptr;
HWND staticText = nullptr;
WNDPROC defWndProc = nullptr;
static HBITMAP hBitmapThumb, hBitmapBar;
static BITMAP bm;
LRESULT OnWindowClose(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
PostQuitMessage(0);
return CallWindowProc(defWndProc, hwnd, message, wParam, lParam);
}
LRESULT OnTrackBarChanged(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
LRESULT value = SendMessage(trackBar, TBM_GETPOS, 0, 0);
SendMessage(progressBar, PBM_SETPOS, value, 0);
SendMessage(staticText, WM_SETTEXT, 0, reinterpret_cast<LPARAM>(to_wstring(value).c_str()));
return CallWindowProc(defWndProc, hwnd, message, wParam, lParam);
}
void DrawBitmapTransparent(HDC hDCDest, int nXDest, int nYDest, int nBitmapWidth, int nBitmapHeight, HBITMAP hBitmap, int nXSrc, int nYSrc, int nTransparentColor)
{
HDC hDCSrc;
HBITMAP hBitmapOld;
HDC hDCMask;
HBITMAP hBitmapMask;
HBITMAP hBitmapMaskOld;
HDC hDCMem;
HBITMAP hBitmapMem;
HBITMAP hBitmapMemOld;
int nBkColorOld;
int nTextColorOld;
BITMAP bm;
GetObject( hBitmap, sizeof( BITMAP ), &bm );
if (!nBitmapWidth) {
nBitmapWidth = bm.bmWidth;
}
if (!nBitmapHeight) {
nBitmapHeight = bm.bmHeight;
}
hDCSrc = CreateCompatibleDC( hDCDest );
hBitmapOld = reinterpret_cast<HBITMAP>(SelectObject( hDCSrc, hBitmap ));
hDCMask = CreateCompatibleDC( hDCDest );
hBitmapMask = CreateBitmap( nBitmapWidth, nBitmapHeight, 1, 1, 0 );
hBitmapMaskOld = reinterpret_cast<HBITMAP>(SelectObject( hDCMask, hBitmapMask ));
hDCMem = CreateCompatibleDC( hDCDest );
hBitmapMem = CreateCompatibleBitmap( hDCDest, nBitmapWidth, nBitmapHeight );
hBitmapMemOld = reinterpret_cast<HBITMAP>(SelectObject( hDCMem, hBitmapMem ));
nBkColorOld = SetBkColor( hDCSrc, nTransparentColor );
BitBlt( hDCMask, 0, 0, nBitmapWidth, nBitmapHeight, hDCSrc, nXSrc, nYSrc, SRCCOPY );
SetBkColor( hDCSrc, nBkColorOld );
nBkColorOld = SetBkColor( hDCDest, RGB(255,255,255) );
nTextColorOld = SetTextColor( hDCDest, RGB(0,0,0) );
BitBlt( hDCMem, 0, 0, nBitmapWidth, nBitmapHeight, hDCDest, nXDest, nYDest, SRCCOPY );
BitBlt( hDCMem, 0, 0, nBitmapWidth, nBitmapHeight, hDCSrc, nXSrc, nYSrc, SRCINVERT );
BitBlt( hDCMem, 0, 0, nBitmapWidth, nBitmapHeight, hDCMask, 0, 0, SRCAND );
BitBlt( hDCMem, 0, 0, nBitmapWidth, nBitmapHeight, hDCSrc, nXSrc, nYSrc, SRCINVERT );
BitBlt( hDCDest, nXDest, nYDest, nBitmapWidth, nBitmapHeight, hDCMem, 0, 0, SRCCOPY );
SetBkColor( hDCDest, nBkColorOld );
SetTextColor( hDCDest, nTextColorOld );
SelectObject( hDCMem, hBitmapMemOld );
DeleteDC( hDCMem );
DeleteObject( hBitmapMem );
SelectObject( hDCMask, hBitmapMaskOld );
DeleteDC( hDCMask );
DeleteObject( hBitmapMask );
SelectObject( hDCSrc, hBitmapOld );
DeleteDC( hDCSrc );
}
LRESULT CALLBACK WndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam) {
switch(message) {
case WM_NOTIFY :
{
LPNMHDR lpNmhdr = reinterpret_cast<LPNMHDR>(lParam);
if (lpNmhdr->code == NM_CUSTOMDRAW)
{
LPNMCUSTOMDRAW lpNMCustomDraw = reinterpret_cast<LPNMCUSTOMDRAW>(lParam);
if (lpNMCustomDraw->dwDrawStage == CDDS_PREPAINT) {
return CDRF_NOTIFYITEMDRAW;
}
else if (lpNMCustomDraw->dwDrawStage == CDDS_ITEMPREPAINT)
{
long nLeft = lpNMCustomDraw->rc.left;
long nTop = lpNMCustomDraw->rc.top;
long nRight = lpNMCustomDraw->rc.right;
long nBottom = lpNMCustomDraw->rc.bottom;
if (lpNMCustomDraw->dwItemSpec == TBCD_THUMB && hBitmapThumb)
{
long nWidth = nRight - nLeft;
long nHeight = nBottom - nTop;
if (nWidth - bm.bmWidth > 0)
{
nLeft += (nWidth - bm.bmWidth)/2;
nWidth = bm.bmWidth;
}
if (nHeight - bm.bmHeight > 0)
{
nTop += (nHeight - bm.bmHeight) / 2;
nHeight = bm.bmHeight;
}
DrawBitmapTransparent(lpNMCustomDraw->hdc , nLeft, nTop, nWidth, nHeight, hBitmapThumb, 0, 0, RGB( 255, 0, 255 ));
return CDRF_SKIPDEFAULT ;
}
}
}
}
break;
}
if (message == WM_CLOSE && hwnd == window) return OnWindowClose(hwnd, message, wParam, lParam);
if (message == WM_HSCROLL && hwnd == window && reinterpret_cast<HWND>(lParam) == trackBar) return OnTrackBarChanged(hwnd, message, wParam, lParam);
return CallWindowProc(defWndProc, hwnd, message, wParam, lParam);
}
int main() {
window = CreateWindowEx(0, WC_DIALOG, L"TrackBar example", WS_OVERLAPPEDWINDOW, CW_USEDEFAULT, CW_USEDEFAULT, 300, 300, nullptr, nullptr, nullptr, nullptr);
trackBar = CreateWindowEx(0, TRACKBAR_CLASS, nullptr, WS_CHILD | TBS_HORZ | TBS_BOTTOM | WS_VISIBLE | TBS_FIXEDLENGTH, 150, 10, 250, 70, window, nullptr, nullptr, nullptr);
progressBar = CreateWindowEx(0, PROGRESS_CLASS, nullptr, WS_CHILD | PBS_SMOOTH | WS_VISIBLE, 20, 100, 200, 23, window, nullptr, nullptr, nullptr);
staticText = CreateWindowEx(0, WC_STATIC, L"100", WS_CHILD | WS_VISIBLE, 20, 150, 100, 23, window, nullptr, nullptr, nullptr);
defWndProc = reinterpret_cast<WNDPROC>(SetWindowLongPtr(window, GWLP_WNDPROC, reinterpret_cast<LONG_PTR>(WndProc)));
hBitmapThumb = reinterpret_cast<HBITMAP>(LoadImage(NULL, reinterpret_cast<LPCWSTR>("pink.bmp"), IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE));
GetObject( hBitmapThumb, sizeof( BITMAP ), &bm );
SendMessage(trackBar, TBM_SETRANGEMIN, 1, 0);
SendMessage(trackBar, TBM_SETRANGEMAX, 1, 200);
SendMessage(trackBar, TBM_SETTHUMBLENGTH, bm.bmWidth*2, 0);
SendMessage(progressBar, PBM_SETRANGE32, 0, 200);
SendMessage(progressBar, PBM_SETPOS, 100, 0);
ShowWindow(window, SW_SHOW);
MSG message = { 0 };
while (GetMessage(&message, nullptr, 0, 0))
DispatchMessage(&message);
}

在这个例子中，我试图用位图图像替换轨迹条拇指，但显然什么都没发生，它编译了，但轨迹条很小，没有被图像替换。请告诉我如何解决这个问题。

Answer 1

我复制/粘贴了您的代码并运行了它，还发现了丢失的拇指。开始跟踪它，发现hbitmapThumb为null。。。。当然，因为我没有pink.bmp！我改变了它从一个绝对路径加载。。。注意到你错过了上的L

hBitmapThumb = reinterpret_cast<HBITMAP>(LoadImage(NULL, reinterpret_cast<LPCWSTR>(L"c:\users\me\Documents\pink.bmp"), IMAGE_BITMAP, 0, 0, LR_LOADFROMFILE));

您可能不需要绝对路径，这取决于您计算机上文件的位置。

但你绝对需要在引号前加L，否则你会重新解释将窄字符串转换为宽字符串，这将是一个无效的文件名！

所以，是的，我认为你做了更难的部分，把自定义绘图等做好了，但只是犯了一个char对w_char的错误。如果修复L也为您修复了问题，请告诉我。