[Lazarus] LCLMessageGlue Status

Andrew Haines andrewd207 at aol.com
Mon Mar 16 18:06:38 CET 2015

On 10/31/2014 04:14 PM, Fabio Luis Girardi wrote:
> Hello!!
> I'm doing a virtual keyboard for lazarus using the LCLMessageGlue 
> unit, but methods
> LCLSendKeyUpEvent and LCLSendKeyDownEvent are not working.
> So, what's the current status of LCLMessageGlue unit?
> -- 
> The best regards,
> Fabio Luis Girardi
> PascalSCADA Project
> http://sourceforge.net/projects/pascalscada
> http://www.pascalscada.com
Sorry for the late reply. I stumbled on this question in a google search.

Methods in LCLMessageGlue are not intended for nor should they be used 
directly in user programs or the results could be unexpected.

The LCLMessageGlue unit is only meant to simplify sending messages to 
the lcl as the result of an actual change in the underlying 
widgetset(gtk, qt win32, etc). Using the methods directly in your 
program won't actually cause a change but will probably trigger the 
event for the message you send.

For instance if you used LCLSendClickedMsg(MyButton) the OnClick event 
would be triggered but the button would not visibly react.

Using LCLSendKey[Up/Down]Event won't work the way you want because the 
widgetset (gtk, qt, win32, etc) is actually managing the text content of 
the component. i.e. the LCL isn't doing Text:=Text+NewChar for every 
keypress event, the widgeset is responsible for that. Exceptions to this 
could be custom controls implemented fully in the LCL like TTreeView and 


Andrew Haines

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