CODEWITHSUNDEEP
c++winapi
user2462027
user2462027

Reputation: 353

Calling SendInput() results in unexpected behaviour

Calling SendInput to simulate pressing down left click appears to be executed after code written below said call to SendInput is executed.

I made a listbox and I want right click to select items from the list box so I decided to make the message WM_CONTEXTMENU call SendInput to simulate a left click immediately before opening a context menu, but I believe the context menu is popping up before the left click occurs, resulting in the left click clicking the edge of the context menu (which does nothing).

Adding MessageBox(0,0,0,0); right in between the call to SendInput and the creation of the popup menu results in the left click successfully occurring and selecting an item, this is the behaviour I expected and desire. Strangely calling Sleep(1000) after the call to SendInput delays the program but doesn't cause the SendInput to behave as expected.

EDIT: Yes I know one solution to my problem is to select it using LB_SETSEL, but I'm partially doing this for learning purposes and if I run into a similar problem using SendInput I want to know how to solve it, so please help me resolve this specific bug.

Upvotes: 0

Views: 244

Answers (1)

Remy Lebeau
Remy Lebeau

Reputation: 596332

SendInput() merely injects keystrokes into the keyboard's input buffer and then exits immediately, letting your app do other things while Windows handles the keystrokes in the background as if the user had typed them manually. That is not the solution to your problem.

In your WM_CONTEXTMENU handler, simply send a LB_SETCURSEL message (for a single-select ListBox) or a LB_SETSEL message (for a multi-select ListBox) directly to the ListBox's HWND to select the desired list item(s) before then displaying your popup menu.

Upvotes: 2

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