MouseAndKeyInput (Linux: XTestFakeKeyEvent), no key up event with certain keys

• Lazarus/FPC Version: Lazarus 2.3.0 (rev main-2_3-1602-gdb285860) FPC 3.3.1 x86_64-linux-gtk2
• Operating System: Linux Mint 20.1 Mate
• CPU / Bitness: x86_64

What happens

KeyInput.Press(VK_INSERT) and KeyInput.Up(VK_INSERT) both generate a continuing sequence of VK_INSERT down events.

Same is true for other values such as VK_DELETE and VK_NEXT but not with letters such as VK_A.

This is bug is not often encountered. Only 1 of 13 other distros displayed the same problem in a test performed by dbannon.

What did you expect

Press(VK_INSERT) should generate a single key down event followed by a single key up event.

Steps to reproduce

Try showkeys program showkeys2.zip, corrected version.

Solution

Change is_press type from Boolean to Boolean32 in XTestFakeKeyEvent declaration in XKeyInput:

function XTestFakeKeyEvent(dpy: PDisplay; keycode: dword; is_press: Boolean32;
 delay: dword): longint; cdecl; external;

Rationale

The current declaration of XTestFakeKeyEvent in Xtest.c is

int XTestFakeKeyEvent(Display *dpy, unsigned int keycode, Bool is_press, unsigned long delay) {...

Bool is a macro for int defined in XLib.h. Since int and unsigned int are usually the same size and since the keycode type in the Pascal declaration is dword (32 bits), would it not make sense to declare is_press as a 32 bit boolean also?

Credit

bytesbites in an August 16, 2016 Lazarus forum post and issue #27819 by delfion. Many thanks to dbannon for all the work on this issue.