Re: [platform-swt-dev] Making Controls out of existing native components

[Steve Northover <Steve_Northover@xxxxxxxxxx>]

See http://www.eclipse.org/articles/Article-Writing%20Your%20Own%20Widget/Writing%20Your%20Own%20Widget.htm

NOTE: The article talks about creating
controls in C, but doesn't address mouse or keyboard events.  The
safest way to create a native control is to write your own native library
instead of accessing the private classes in org.eclipse.swt.internal.*
and subpackages (yes, they aren't real subpackages because Java doesn't
have that).  Adding yourself to the package exposes you to the implementation
details of the toolkit and makes your code fragile.  Having said all
that, we haven't redesigned the platform interface (PI) for a while now.

It's a problem.  On Windows, OLE
uses a HHOOK to see keys meant for OLE controls and deliver them to SWT
composites.  Recently, the browser was rewritten to use DOM events
for mouse and keyboard because we couldn't get the low level equivalents
to Windows HHOOK's to work on all the platforms.  Specifically, Safari
(written in cocoa) didn't play nice.

Rather than add API to wrap every single
native handle that might be inside a C control that you wrap, I'd investigate
operating system hooks and try to get mouse and keyboard that way.  We
failed, but you might succeed.

Scott Kovatch <skovatch@xxxxxxx>
Sent by: platform-swt-dev-bounces@xxxxxxxxxxx

03/28/2008 07:49 PM

Please respond to
"Eclipse Platform SWT component developers list."        <platform-swt-dev@xxxxxxxxxxx>

To	"Eclipse Platform SWT component developers list." <platform-swt-dev@xxxxxxxxxxx>
cc
Subject	[platform-swt-dev] Making Controls out of existing native components

Hello,

A coworker came up with an interesting problem. We are
embedding a natively-created HIView into an SWT Canvas. Our HIView displays
but doesn't receive mouse or key events because the SWT doesn't deliver
events to HIViewRefs that it doesn't know about (i.e., that it created.)

The solution should be this: Create a subclass of Control
that takes an int as a parameter, where the int is the handle to the pre-created
native object. Instances of this subclass own the native control passed
in at creation time, and will dispose of it when disposed. createHandle()
is overridden to just stuff the int passed in at creation time into the
'handle', and then it gets registered with Display, and hookEvents() hangs
the OS event handlers on the control.

Is it okay to subclass Control in this way? createHandle()
is package private, so I don't see a good way to do this cleanly without
putting the class in the SWT package. I'd like to avoid that if possible.

Scott

------------------
Scott Kovatch
Cupertino, CA
skovatch@xxxxxxx


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