This message occurs when the user presses the middle mouse button.
| wParam |
Contains a value that indicates whether various virtual keys are down. It can be any combination of the following values: |
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| |
Value |
Meaning |
| |
MK_CONTROL |
Set if CONTROL key is down. |
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MK_LBUTTON |
Set if left button is down. |
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MK_RBUTTON |
Set if right button is down. |
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MK_SHIFT |
Set if SHIFT key is down. |
| lParam |
Contains the x- and y-coordinates of the cursor. The x-coordinate is in the low-order word; the y-coordinate is in the high-order word. These coordinates are always relative to the upper-left corner of the window. |
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