Question

I’m sending mouseclicks to an ActiveX control in C++ one after the other (I’m using AutoDesk Design Review (a CAD system) and sending the clicks to draw an arc).

The only problem I’m having is that if two of the clicks are near each other it registers as a double click.
Is there a value in Windows which determines if the clicks’ coordinates make it a double click?

e.g. If the coordinates are less than 10 pixels apart it’s a double click, otherwise it’s two single clicks.

I cannot intercept the click or cancel the click event in the ActiveX control so I need to stop it firing before.

Many thanks

Alex

Answer 1

The Windows API does provide a way to determine the double-click time and the double-click rectangle:

• GetDoubleClickTime() to get the double-click time.
• GetSystemMetrics() with the SM_CXDOUBLECLK index to get the rectangle width.
• GetSystemMetrics() with the SM_CYDOUBLECLK index to get the rectangle height.

According to the MSDN documentation for mouse input:

Double-Click Messages

The system generates a double-click message when the user clicks a
mouse button twice in quick succession. When the user clicks a button,
the system establishes a rectangle centered around the cursor hot
spot. It also marks the time at which the click occurred. When the
user clicks the same button a second time, the system determines
whether the hot spot is still within the rectangle and calculates the
time elapsed since the first click. If the hot spot is still within
the rectangle and the elapsed time does not exceed the double-click
time-out value, the system generates a double-click message.

This should be sufficient information for detecting double-mouse clicks.