Question

I have two 100% overlapping panels with different contents on a form.
The first (static display of information) should be visible by default, but the other (user interaction) should replace it if the user moves the mouse near the two – and if the mouse moves away, it should switch back.
Something like this:

if (*the mouse is near*) then
begin
  Panel1.Hide;
  Panel2.Show;
end
else
begin
  Panel2.Hide;
  Panel1.Show;
end;

My problem is: where to capture mouse movement?
Each component has its own OnMouseMove handler – of course I could forward each of them to the forms handler, but I’d rather have something a bit more elegant (and easier to maintain).
The perfect solution would be something like Form1.MousePreview := true;.

Another solution would be assigning a generic handler that translates coordinates and calls the forms handler; The assigning could be done in FormCreate.
But that’s not as easy as it seems, because one TImage already has its own mouse event handlers.

I have tried OnMouseEnter and OnMouseLeave of the two panels but it didn’t work; #1 disappeared, but #2 did not appear. I guess that’s because if the mouse leaves Panel2, it should disappear – but it also leaves it if it enters a button on it.
That’s why I’d like to use a coordinate based approach to make the check more reliable.

Maybe the two panel method is completely wrong?

Update: Yes, it is, as Remy said.
I am now using a TJVPageList because a TPageControl has visual tabs.
The OnMouseEnter handler of the PageList sets one page, the OnMouseLeave sets the other; But once the mouse moves over the PageList, both pages start flickering.
I have tried adding the event handlers to each page, too, but that made no difference.
Should I check all OnMouseEnter / Leave events to filter out the PageList, the two pages and all components sitting on the pages?

Another update: I am using a TPageControl now, but the behaviour is similar.
It doesn’t flicker, but if I move the mouse ontop the TPageControl, no TTabSheet is displayed at all.
Only if I press down the left mousebutton, the UI sheet is displayed. The other sheet is displayed normally if I move away the mouse. (The TJVPageList displays the UI page if I press the left mousebutton, too.)
I have used the mouse event handlers (enter/leave) of the TPageControl and both TTabSheets.

Update 3:
Done it.
The static Panel / TabSheet / JvStandardPage (#1) must not trigger the OnMouseLeave handler.

Answer 1

What you describe might be better served using a single TPageControl instead of two TPanel controls. Use the TPageControl‘s own OnMouseEnter/Leave events (or intercept the CM_MOUSEENTER/LEAVE messages) to switch the TPageControl.ActivePage as needed.