This replaces my 4.x Proposal, which was titled "I have a way to support
*ALL* MOUSE BUTTONS in Qt, while staying compatible with the 4.x
series!" http://developer.qt.nokia.com/forums/viewthread/6547/ This
message duplicates a new forum topic at:
http://developer.qt.nokia.com/forums/viewthread/10970/
Here are the main changes:
(1) Qt 5.0 eliminates a very large number of plugins :)) making the job
much smaller. On Linux (my platform), I propose to implement only XCB
and Wayland.
(2) Since Qt 5.0 will require re-compilation of Applications written
against earlier versions of Qt, BIINARY compatibility is a non-issue
(right?). SOURCE Compatibility remains critical- and so, I will not try
to add the (int) button number into the event signatures. Instead, I
will expand the range of values which Qt::MouseButton (and the
corresponding flags) can take, using 31 bits. Should I go ahead and use
the high-order bit as well?
(3) XCB does not automatically provide a 32-bit mask field (the kernel
evdev driver, which we use for Wayland input, does include the full
mask). It is TBD whether our code should:
(A) obtain the full mask automatically, and setting
Qt::MouseButtons accordingly; or
(B) leave high-order bits unset in events, returning the full
mask as the value of a SEPARATE function call.
I feel that alternative (A) is far less confusing, and have been advised
by some X11 experts (Peter H., Daniel S.,) that the overhead and
reliability of mixing a query-state function call (i.e., to get the
mask) into the code path of this Event processing is a non-issue -- as
long as we avoid doing it with every single XCB event which occurs on on
Wheel "Buttons". (Wait until we're done compressing these lower-level
events, and acquire the current mask field when we're preparing to
create the QWheelEvent.)
The need for this 'enhancement' seems to be even more severe than it
appeared to be a year ago -- our current 5.0 Wayland/evdev plugin code
actually REDUCES the number of Qt-supported buttons, from 5 to 3. We're
losing the "Back" and "Forward" buttons, AKA "XButton1" and "XButton2".
(IMO, That's not a healthy direction; Qt becomes less attractive for
writing web Browsers, FIle Managers, and etc.)
This would be my first submission of code into Qt. If it's no-go, please
advise: What are the problems with this approach, and are there ways to
avoid the problems which I don't yet see?
In any case, you all have my greatest thanks for any advice and replies. ;)
_______________________________________________
Development mailing list
Development@qt-project.org
http://lists.qt-project.org/mailman/listinfo/development
