我遇到了使用 WinAPI 无效绘制 ComboBox 的问题。当您最小化应用程序并在未隐藏 ComboBox 控件的选择后恢复它时,它看起来像这样:
如您所见,OK 按钮获得了焦点,但 ComboBox 的选择仍未隐藏。当控件失去输入焦点时,ComboBox 的正常行为会隐藏选择。
代码:
#define WIN32_MEAN_AND_LEAN
#include <SDKDDKVer.h>
#include <Windows.h>
#include <Windowsx.h>
#include <CommCtrl.h>
#include <assert.h>
struct window_context {
HINSTANCE _instance;
HWND _window;
HWND _combo_box2;
HWND _ok_button;
window_context(HINSTANCE instance) noexcept : _instance{ instance }
{
}
};
static BOOL on_create(HWND hwnd, LPCREATESTRUCT lpCreateStruct) noexcept
{
auto context = reinterpret_cast<window_context*>(lpCreateStruct->lpCreateParams);
context->_combo_box2 = CreateWindowW(WC_COMBOBOXW,
L"",
CBS_DROPDOWN | CBS_AUTOHSCROLL | WS_TABSTOP | WS_VSCROLL | WS_VISIBLE | WS_CHILD,
0, 0, 0, 0,
hwnd,
(HMENU)44,
nullptr,
nullptr);
ComboBox_AddString(context->_combo_box2, L"select me");
context->_ok_button = CreateWindowW(WC_BUTTONW,
L"OK",
BS_DEFPUSHBUTTON | BS_NOTIFY | WS_TABSTOP | WS_VISIBLE | WS_CHILD,
0, 0, 0, 0,
hwnd,
nullptr,
nullptr,
nullptr);
return true;
}
static void on_destroy(HWND hwnd) noexcept
{
PostQuitMessage(0);
}
static void on_size(HWND hwnd, UINT state, int cx, int cy) noexcept
{
auto context = reinterpret_cast<window_context*>(GetWindowLongPtrW(hwnd, GWLP_USERDATA));
MoveWindow(context->_combo_box2,
10,
10,
100,
100,
true); // causes the weird behaviour to occur
// using SetWindowPos doesn't help
// using SetWindowPos with SWP_NOSIZE prevents the bug from occuring
// but also locks it into size which is not acceptable
// since I use this to deal with DPI scaling changes
MoveWindow(context->_ok_button,
10,
110,
100,
50,
true);
}
static void on_activate(HWND hwnd, UINT state, HWND hwndActDeact, BOOL fMinimized) noexcept
{
auto context = reinterpret_cast<window_context*>(GetWindowLongPtrW(hwnd, GWLP_USERDATA));
if (state)
SetFocus(context->_ok_button);
}
static BOOL on_nc_create(HWND hwnd, LPCREATESTRUCT lpCreateStruct) noexcept
{
auto context = reinterpret_cast<window_context*>(lpCreateStruct->lpCreateParams);
context->_window = hwnd;
SetWindowLongPtrW(hwnd, GWLP_USERDATA, reinterpret_cast<LONG_PTR>(context));
return FORWARD_WM_NCCREATE(hwnd, lpCreateStruct, DefWindowProcW);
}
static LRESULT CALLBACK wnd_proc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam) noexcept
{
switch (uMsg) {
HANDLE_MSG(hwnd, WM_CREATE, on_create);
HANDLE_MSG(hwnd, WM_DESTROY, on_destroy);
HANDLE_MSG(hwnd, WM_SIZE, on_size);
HANDLE_MSG(hwnd, WM_ACTIVATE, on_activate);
HANDLE_MSG(hwnd, WM_NCCREATE, on_nc_create);
}
return DefWindowProcW(hwnd, uMsg, wParam, lParam);
}
static bool register_class(HINSTANCE hInstance) noexcept
{
WNDCLASSEXW wcex;
wcex.cbSize = sizeof(wcex);
wcex.style = CS_HREDRAW | CS_VREDRAW;
wcex.lpfnWndProc = &wnd_proc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = nullptr;
wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW + 1);
wcex.lpszMenuName = nullptr;
wcex.lpszClassName = L"test";
wcex.hIconSm = nullptr;
return RegisterClassExW(&wcex) != 0;
}
static bool create_window(window_context& context) noexcept
{
return CreateWindowExW(0,
L"test",
L"Win32 Program",
WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT,
CW_USEDEFAULT,
800,
600,
nullptr,
nullptr,
context._instance,
&context);
}
int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPWSTR lpCmdLine,
_In_ int nCmdShow)
{
if (!register_class(hInstance))
return false;
window_context context{ hInstance };
if (!create_window(context))
return false;
ShowWindow(context._window, nCmdShow);
MSG msg;
BOOL got_message;
while ((got_message = GetMessageW(&msg, nullptr, 0, 0)) && got_message != -1) {
if (IsDialogMessageW(context._window, &msg))
continue;
TranslateMessage(&msg);
DispatchMessageW(&msg);
}
return static_cast<int>(msg.wParam);
}
重现问题的步骤:
- 从组合框中选择
选择我
- 最小化窗口
- 恢复窗口
ComboBox 现在应该显示为选中状态,即使它并未选中。
解决问题的步骤:
- 使 ComboBox 的区域无效无济于事,重绘 Combobox 仍然无法解决问题
- 只在指定位置创建 ComboBox 且不移动其位置或更改其大小时不会出现此问题
- 当您使用
SetWindowPos
只是移动 ComboBox 的位置时,问题不会出现
- 一旦更改 ComboBox 的大小,就会出现这种奇怪的行为。
- 对话框以某种方式正确地处理了这个问题
- WinForms 也能正确处理这个问题,但我没能找到他们如何防止它发生
- 只有当您从下拉列表中选择一个项目时才会出现错误,当您输入自定义文本时错误会消失
这确实是一个非常奇特的问题,我非常感谢您的帮助。
最佳答案
您可以通过调用 ComboBox_SetEditSel(context->_combo_box2, -1, -1);
解决这个问题(参见 CB_SETEDITSEL
)或者在调整大小之前在组合框的编辑控件中找到选定的字符,然后在调整大小后恢复这些值。
static void on_size(HWND hwnd, UINT, int, int) noexcept
{
auto context=reinterpret_cast<window_context*>(GetWindowLongPtr(hwnd,GWLP_USERDATA));
DWORD range = ComboBox_GetEditSel(context->_combo_box2);
DWORD start = LOWORD(range);
DWORD end = HIWORD(range);
MoveWindow(context->_combo_box2, 10, 10, 150, 100, true);
MoveWindow(context->_ok_button, 10, 110, 100, 50, true);
ComboBox_SetEditSel(context->_combo_box2, start, end);
}
但是您可能会发现在使用其他控件时会遇到类似的问题,很难找到解决所有问题的方法。考虑使用 DialogBox
相反。
关于c++ - 如何处理 win32 winapi 中无效绘制的 ComboBox 控件?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/49603893/