[Gambas-user] A Gambas odissey

[Fabien Bodard]

hohoooo there is many thing wrong here !

2008/8/11 Doriano Blengino <doriano.blengino at ...1909...>:
> Hello all...
>
> I am writing a file manager, hybrid between FileRunner and a more
> modern one.
>
> I started with a DirView, and soon discovered that it doesn't raise the
> KeyPress event (but the IDE makes you think that).

dir view is a top level component you can easily rewrite it


> There were other
> things missing in DirView, so I wrote my MyDirView the way I wanted. It
> was easy at first, but then I discovered that it is difficult, or at
> least not clear, how to move the "Current" cursor. I am not sure why,
> but it does work by setting the Selected property of an item. I failed,
> instead, in removing all the children of an item, one by one (there is a
> clear() method, but I need to delete them one by one). The "for each ...
> in item.children" does not work; it is not the first time I see similar
> anomalies, especially while stepping the source.
>
> Writing MyDirView revealed another problem. If in a custom control I
> receive the KeyPress event, I can not re-raise it (stack overflow). So I
> have to raise another event with a different name. This breaks the
> consistency of naming - in a row of four controls, each derived from the
> other, the same event must be called with four different names. I took a
> look at the FileView control to see what has been done in there. It
> receives Click events, and raises Click events. What inside? It does not
> inherit from ListView or similar. Now I understand why it works, but I
> don't like it.
it don't have to inherit it's a composed widget..; not an extention.
>
> Anyway, I went ahead. I put two FileView on the form. They don't raise
> KeyPress event. It's getting tiring. I don't want to rewrite MyFileView
> just now (I will do, because I need more functionalities). I only need
> to catch Backspace and Enter, so I make a menu voice which has the
> Backspace key as its shortcut. Now the backspace works, but... how the
> hell can I tell which control is focused? The only way I found was to
> catch the GotFocus and LostFocus events, and track the focus by hand. I
> have only three controls, but what about if I had dozens of them?
> Grouping them would group all their events, while I am interested in
> grouping only GotFocus/LostFocus events.
>
> To make it short, I succeded in make it work, and passed to the
> Enter key. The Enter key should invoke the selected file in one of the
> two FileView's. A menu voice has only one shortcut, but the Enter keys
> are two (Gambas calls them Enter and Return). Uhm... no way. Then I try
> to use the Form_Keypress event, but it does not fire - the controls are
> stealing the keys. So, there is no way to do this thing. If a FileView
> does not "activate" a file when the user presses Enter, then you can not:
>
>    1: inherit a new control which does, because you must rename all its
> events
what about observer ?
>    2: use a menu voice to do it, because a menu voice has only one
> shortcut; if you want use more keys, no way
???
>    3: use the form KeyPress, which does not fire
>

> The only way left is to create a new control, and then instantiate a
> FileView inside it. This is not inheritance, because you have to
> replicate all the things you need: events, properties, methods.
>
> Coming from Delphi, I must say the following:
>
> Delphi forms have a KeyPreview property. If you set it, then *all* the
> keypresses are first passed to the form. The form then decides wether to
> ignore the key, or make additional things, to let the key pass, or to
> stop it.
>
> Delphi containers have an ActiveControl property which tells which
> control has the focus. Moreover, every control has a Focused property
> which tells if a specific control has the focus or not. The list of
> things Delphi has and Gambas doesn't is long, but I don't want to
> criticize. I am really missing keyboard and focus control. It seems that
> VisualBasic programmers use the mouse a lot, and neglect keyboards, and
> so do many users, so this could be the reason why Gambas seems to do the
> same.
>
> I don't know Gambas very well, and I could have missed a lot of things.
many
> But it is easy to miss things - in the documentation a "See also"
> section in every topic could really help.
there is
>
> Finally, I must say that I think, and *repeat*, I think, the event
> management is wrong or, at least, it is not as flexible as it could be.
> Once a control raises event, you can not make it stop.
not true ... it's STOP EVENT
>If you group
> controls, you group all their events.

yes it's an event handler grouping, not a true group ... to doing a
group you need to store objects in an array
> Once you assign a handler to an
> event, you can no more change it.

wrong : Object.attach(Object, parentclass, "handler name")

> Probably Gambas is too developed to
> change things at this point but, for who cares or is courious, I will
> explain how events work in Delphi. An event in delphi has an associated
> property which contains the address of a routine to launch. For example,
> if a control has a Click event, then it has a OnClick property. That
> property contains the address of the routine to invoke when the control
> wants to "raise" the Click event. The OnClick property is a procedural
> type, a thing that does not exist in Gambas.

true ... gambas is a true oriented object language

> But being a property, the
> main program can disable that event by setting that property to NIL
> (NULL),

PUBLIC SUB MyList_KeyPress()
   STOP EVENT
END

But it's true that we can't turn off an event

> or change the handler by setting the property to another value.
> It is possible to associate many controls to the same handler, but only
> the events we want, not *all* the events of *all* the selected controls.
> In fact, events do not exist in delphi, they are simply procedure calls.
> Instead of writing:
>
>    raise KeyPress   ' Gambas code
>
> which, I suppose, unleashes a textual search for a public subroutine
> named in some correct way, in Delphi one would write:
>
>    if OnKeypress<>NIL then OnKeypress();   // procedural call
>
>
> This paradigm is faster, more sure, more flexible, more easy to
> understand. When deriving controls, the derived one can override the
> methods of the ancestor, and still call the inherited one. Gambas has an
> interesting feature which does the opposite: instead of calling the
> ancestor method on demand, it can stop it on demand. It is quite the
> same, I think.
ok got it in fact




>
>
> Happy holidays to everyone.
>

to you too

Fabien