WM_NCXBUTTONUP message
Posted when the user releases either XBUTTON1 or XBUTTON2 while the cursor is in the nonclient area of a window. This message is posted to the window that contains the cursor. If a window has captured the mouse, this message is not posted.
A window receives this message through its WindowProc function.
#define WM_NCXBUTTONUP 0x00AC
Parameters
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wParam
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The low-order word specifies the hit-test value returned by the DefWindowProc function from processing the WM_NCHITTEST message. For a list of hit-test values, see WM_NCHITTEST.
The high-order word indicates which button was released. It can be one of the following values.
Value Meaning - XBUTTON1
- 0x0001
The XBUTTON1 was released. - XBUTTON2
- 0x0002
The XBUTTON2 was released. -
lParam
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A pointer to a POINTS structure that contains the x- and y-coordinates of the cursor. The coordinates are relative to the upper-left corner of the screen.
Return value
If an application processes this message, it should return TRUE. For more information about processing the return value, see the Remarks section.
Remarks
Windows supports mice with up to five buttons: left, middle, and right, plus two additional buttons called XBUTTON1 and XBUTTON2. The XBUTTON1 and XBUTTON2 buttons are often located on the sides of the mouse, near the base. These extra buttons are not present on all mice. If present, the XBUTTON1 and XBUTTON2 buttons are often mapped to an application function, such as forward and backward navigation in a Web browser.
Use the following code to get the information in the wParam parameter.
nHittest = GET_NCHITTEST_WPARAM(wParam);
fwButton = GET_XBUTTON_WPARAM(wParam);
You can also use the following code to get the x- and y-coordinates from lParam:
xPos = GET_X_LPARAM(lParam);
yPos = GET_Y_LPARAM(lParam);
Important
Do not use the LOWORD or HIWORD macros to extract the x- and y- coordinates of the cursor position because these macros return incorrect results on systems with multiple monitors. Systems with multiple monitors can have negative x- and y- coordinates, and LOWORD and HIWORD treat the coordinates as unsigned quantities.
By default, the DefWindowProc function tests the specified point to get the position of the cursor and performs the appropriate action. If appropriate, it sends the WM_SYSCOMMAND message to the window.
Unlike the WM_NCLBUTTONUP, WM_NCMBUTTONUP, and WM_NCRBUTTONUP messages, an application should return TRUE from this message if it processes it. Doing so will allow software that simulates this message on Windows systems earlier than Windows 2000 to determine whether the window procedure processed the message or called DefWindowProc to process it.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client |
Windows 2000 Professional [desktop apps only] |
| Minimum supported server |
Windows 2000 Server [desktop apps only] |
| Header |
|
See also
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Reference
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Conceptual
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Other Resources