Keyboard focus: looking for a general strategy - c++

Question

My application has a big graphics area with some controls (sliders, buttons, text edit controls) in a side panel. The graphics area understands some keyboard commands.
My problem is that when a control in the side panel is in focus, the main graphics area won't receive any keyboard commands, so this confuses the users. However, for some controls, this is intended, e.g. text edit controls.
What I want is the focus to automatically return to the graphics area at the earliest possible occasion (which I call "greedy" focus) -- e.g. when text editing is finished (Enter key), or when the user has selected an item from a combo box.
I am looking for a clean and robust strategy for dealing with the problem, either using Windows API or Borland Vcl.
I'd appreciate if you want to share your ideas.

Answer 1

I haven't fully solved the problem yet, but a very useful message to intercept on form level is CM_DIALOGKEY (Borland Vcl only). It gets sent for every key that is normally used for navigating within the UI. That is, cursor keys, tab and shift-tab, Enter and possibly others.
I've added an event handler for CM_DIALOGKEY that returns the focus to the graphics area and also forwards the key press to that component. This way the user can still control the UI elements via keyboard (important for text entry), but cursor keys are handled by the graphics area.

Answer 2

I know what you mean I had similar problem with some BIG apps lice CAD/CAM ...
My solution is simple, robust and I use it for years.
1.all keystrokes handling for that gfx area
must be done in events of the Form where the area is located
not in panels,paint box whatever...
2.create unfocus function (preferably member of form but it is not required)
this function will loose focus of any VCL item
so the focus goes to form itself which is what you want
I am using this:
//---------------------------------------------------------------------------
void main_unfocus()
{
Main->bt_unfocus->Visible=true;
Main->bt_unfocus->SetFocus();
Main->bt_unfocus->Visible=false;
}
//---------------------------------------------------------------------------
Main is the Form pointer
bt_unfocus is button (can be any focusable VCL component)
I place this button usually on the left upper corner of App and set its size to 2x2 pixels
it is invisible at start
the idea is to set focus to it (but first unhide it so no exception is thrown)
and then hide it so it loses focus
work well in BCB5 and BDS2006 (did not used it with any other IDE)
as you can see most of the time is this component invisible
4.now when to call main_unfocus ?
when you go with mouse from outside to inside of your gfx area (OnMouseMove event)
or when you click on it
also you can combine this with remembering if the focus is or not in gfx area
that can be done with events like OnExit ...
or when you hit Esc while focus is inside edit box ...\
I am sure you grasp the idea and adjust this to your needs
Hope it helps