Question

I would like to use raw winapi32 to check button style whether it is a checkbox button or a pushbutton.

bool isPushBtn(HWND hBtn, DWORD dwStyle)
{
   return (0!=dwStyle | GetWindowLong(hBtn,GWL_STYLE));
}

But this always returns false. Do you know a way to check this ? Thank you.

Answer 1

In order to understand how button styles work we need to look at the values used by the style constants:

#define BS_PUSHBUTTON       0x00000000L
#define BS_DEFPUSHBUTTON    0x00000001L
#define BS_CHECKBOX         0x00000002L
#define BS_AUTOCHECKBOX     0x00000003L
#define BS_RADIOBUTTON      0x00000004L
#define BS_3STATE           0x00000005L
#define BS_AUTO3STATE       0x00000006L
#define BS_GROUPBOX         0x00000007L
#define BS_USERBUTTON       0x00000008L
#define BS_AUTORADIOBUTTON  0x00000009L
#define BS_PUSHBOX          0x0000000AL
#define BS_OWNERDRAW        0x0000000BL
#define BS_TYPEMASK         0x0000000FL
#define BS_LEFTTEXT         0x00000020L

#define BS_TEXT             0x00000000L
#define BS_ICON             0x00000040L
#define BS_BITMAP           0x00000080L
#define BS_LEFT             0x00000100L
#define BS_RIGHT            0x00000200L
#define BS_CENTER           0x00000300L
#define BS_TOP              0x00000400L
#define BS_BOTTOM           0x00000800L
#define BS_VCENTER          0x00000C00L
#define BS_PUSHLIKE         0x00001000L
#define BS_MULTILINE        0x00002000L
#define BS_NOTIFY           0x00004000L
#define BS_FLAT             0x00008000L
#define BS_RIGHTBUTTON      BS_LEFTTEXT

The other essential reference is the Button Styles topic at MSDN. However, what that document does not explain is that the BS_PUSHBUTTON to BS_OWNERDRAW flags, the type flags, are mutually exclusive. The other flags can be used in combination with one of the type flags. This can be inferred from the bit patterns of the values.

The documentation for BS_TYPEMASK states:

Windows 2000: A composite style bit that results from using the OR operator on BS_* style bits. It can be used to mask out valid BS_* bits from a given bitmask. Note that this is out of date and does not correctly include all valid styles. Thus, you should not use this style.

However I think this is misleading and endorse what ybungalobill said in his answer. No harm can come of following that advice.

In other words you should mask the style with BS_TYPEMASK and then test for a particular button type.

bool isButtonType(HWND hBtn, DWORD dwType)
{
     assert(dwType<=BS_TYPEMASK);
     return (GetWindowLong(hBtn, GWL_STYLE) & BS_TYPEMASK) == dwType;
}