I have a simple Win32 application that creates a button. Right after the button is created i disabled it using the EnableWindow(FALSE) function from the <windows.h>. It works normal when the button size is greater than the text applied.
But when the button size is smaller that the text of the button the client area of the entire window seems to copy the contents of the screen.
Code that causes the bug:
#include <Windows.h>
LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);
int APIENTRY wWinMain(_In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPWSTR lpCmdLine, _In_ int nCmdShow)
{
WNDCLASSEX wcex = { 0 };
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.lpfnWndProc = WndProc;
wcex.hInstance = hInstance;
wcex.hCursor = LoadCursor(nullptr, IDC_ARROW);
wcex.lpszClassName = L"MYWINDOWCLASS";
if (RegisterClassExW(&wcex) == 0)
return -1;
HWND hWnd = CreateWindowW(L"MYWINDOWCLASS", L"MYWINDOW", WS_OVERLAPPEDWINDOW,
CW_USEDEFAULT, 0, CW_USEDEFAULT, 0, nullptr, nullptr, hInstance, nullptr);
if (!hWnd)
return -1;
HWND buttonHWnd = CreateWindowW(L"BUTTON", L"MYWINDOW", WS_TABSTOP | WS_VISIBLE | WS_CHILD | BS_DEFPUSHBUTTON,
100, 100, 40, 30, hWnd, nullptr, hInstance, nullptr);
if (!buttonHWnd)
return -1;
EnableWindow(buttonHWnd, FALSE);
ShowWindow(hWnd, nCmdShow);
UpdateWindow(hWnd);
MSG msg;
while (GetMessage(&msg, nullptr, 0, 0))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
return 0;
}
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
}
return 0;
}
2
This issue you’re encountering with your Win32 application where the button’s text is larger than the button itself, leading to unexpected screen copying, is quite intriguing and likely involves some nuances of how Windows handles disabled controls and their painting. Here’s a breakdown of what might be happening and some steps to potentially resolve or understand the issue:
Possible Causes:
-
Painting Issues with Disabled Controls:
- When a control like a button is disabled, Windows might not redraw the control’s background properly, especially if the control’s size is smaller than its content. This can lead to artifacts from the underlying screen or window content showing through.
-
Text Overflow:
- If the button’s text is longer than the button’s width, Windows might be handling the overflow in an unexpected way, especially when the button is disabled. Normally, the text should be truncated or not fully displayed, but with a disabled state, the behavior might differ.
-
Window Redraw:
- The
EnableWindow(FALSE)function might not trigger a full redraw of the control or its parent window, leading to these visual anomalies.
- The
Potential Solutions:
-
Redraw the Window:
- After disabling the button, force a redraw of the window or the button itself:
InvalidateRect(hWndButton, NULL, TRUE); UpdateWindow(hWndButton);
- After disabling the button, force a redraw of the window or the button itself:
-
Adjust Button Size:
- Ensure that the button size is dynamically adjusted to fit its text or at least not smaller than the text. You could use
GetTextExtentPoint32to calculate the text size and adjust the button dimensions accordingly.
- Ensure that the button size is dynamically adjusted to fit its text or at least not smaller than the text. You could use
-
Custom Drawing:
- Override the
WM_CTLCOLORBTNmessage in your window procedure to handle the button’s painting yourself when it’s disabled. This would give you control over how the button looks when disabled:case WM_CTLCOLORBTN: if ((HWND)lParam == hWndButton) { SetBkMode((HDC)wParam, TRANSPARENT); SetTextColor((HDC)wParam, GetSysColor(COLOR_GRAYTEXT)); return (LRESULT)GetSysColorBrush(COLOR_BTNFACE); } break;
- Override the
-
Check for Overlapping Windows:
- Ensure that no other windows or parts of the desktop are overlapping or being copied onto your application’s client area. This might be less likely but worth checking.
-
Debugging:
- Use tools like Spy++ to watch the messages being sent to your window and the button when it’s disabled. This might give clues on why the screen content is being copied.
Additional Tips:
-
Testing: Test with different themes and visual styles to see if the issue persists. Sometimes, this can be theme-specific.
-
Documentation: Review MSDN documentation or any updates regarding how disabled controls should behave in different versions of Windows.
If these solutions don’t resolve the issue, it might be worth exploring deeper into how Windows handles disabled controls, possibly looking into the source code of similar applications or diving into the Windows API documentation for more specific control over the button’s appearance when disabled.