<AWT Dev> [13] JDK-8218917: KeyEvent.getModifiers() returns inconsistent values for ALT keys

Sat Mar 16 10:58:09 UTC 2019

Hi Sergey,

Your example is synthetic and shows a problem in the one specific
case. I think if you introduce new mask, you have to use it in your
example too. If you add ALT_GRAPH_DOWN_MASK to 'offmask' your example
will not work (that's how processed all shortcuts in Swing and IDEA).
If you add it to 'onmask' the KeyEvent(new Button(), 0, 0,
ALT_GRAPH_DOWN_MASK, 0) will not work.

Am I right that to support your specific case you have to find and fix
all Alt-based shortcuts in Swing, we should fix all Alt-based
shortcuts in all keymaps in our IDEs and we should notify all our
users that they have to fix all Alt-based shortcuts in their custom
keymaps? The brilliant example of backward compatibility!

> So if the client will follow the spec below it should work as before, isn't it?:
> https://docs.oracle.com/en/java/javase/11/docs/api/java.desktop/java/awt/event/InputEvent.html#getModifiersEx()

If a developer use this method as described his code will be broken
too, because good and attentive developer definitely added
ALT_GRAPH_DOWN_MASK to 'offmask'.

On Sat, Mar 16, 2019 at 1:27 AM Sergey Bylokhov
<Sergey.Bylokhov at oracle.com> wrote:
>
> On 15/03/2019 05:54, Sergey Malenkov wrote:
> > We have a major issue about unexpected AltGr in the keyboard layout
> > that should not have AltGr at all:
> > http://youtrack.jetbrains.com/issue/IDEA-206348
> > Why you decided to support AltGr for every keyboard layout? It really
> > breaks backward compatibility!
>
> Even in your bug report the people complain that altGr key does not work, and
> the only problem here is that it does not assigned by default.
> But on the other side it is possible to set separate shortcuts
> to the "Alt + Alt Graph + Enter"and "Alt + Enter":
>
> > I think the main client is Swing and pressed AltGr that looks like
> > 'Alt+AltGr+' breaks all Alt-based shortcuts defined in
> > javax.swing.plaf.basic.BasicLookAndFeel#initComponentDefaults and
> > other places. Now, if you press "alt LEFT", the "moveColumnLeft"
> > action is performed only for the left Alt. And this also breaks a
> > backward compatibility.
>
> The term "all" is not so critical, there are only few such shortcuts, and it is
> a good thing that potentially we can set different shortcuts for each.
> This is a bug that these places were not updated, it is easy to fix since this
> is not exposed via public API.
> But we will get the same result if we will use the AltGr mask only.
>
> > It is not backward compatible to use AltGr instead of right Alt in
> > both cases. Instead of 'Alt+key' you will get 'AltGr+key' or
> > 'Alt+AltGr+key', which are not bound to any action.
>
> It is compatible to the specification of InputEvent.getModifiersEx():
> KeyEvent event = new KeyEvent(new Button(), 0, 0,
>                                ALT_DOWN_MASK | ALT_GRAPH_DOWN_MASK, 0);
>    int onmask =  ALT_DOWN_MASK;
>    int offmask = CTRL_DOWN_MASK|SHIFT_DOWN_MASK;
>    if ((event.getModifiersEx() & (onmask | offmask)) == onmask) {
>      ...
>    }
>
> The code above works before and after the change for altGr.
> But it will stop working if we will use altGr only, and it will be hard to argue
> why the ALT flag is not set while alt key is pressed(since on some keyboards this key is
> marked as alt and on some other altGr).
>
> And as specially noted in the method above the code should not assume which
> flags(and how many) were set by the actions, if such assumptions exists in
> Swing itself they should be fixed as well.
>
> >
> > On Fri, Mar 15, 2019 at 9:27 AM Krishna Addepalli
> > <krishna.addepalli at oracle.com> wrote:
> >>
> >> Hi Sergey Malenkov,
> >>
> >>> 'Alt+AltGr+Right' does nothing, because we do not assign this shortcut yet
> >> In my personal experience, I did not find any instance, wherein a shortcut had left and right alt in it.
> >> Although it is not impossible, it seems weird to define such shortcuts.
> >> It would be helpful if you could point to some resources, wherein defining such shortcuts is acceptable.
> >>
> >> Thanks,
> >> Krishna
> >>
> >>> On 14-Mar-2019, at 4:03 PM, Sergey Malenkov <malenkov at gmail.com> wrote:
> >>>
> >>> I strongly don't like two masks for one key. If you press VK_ALT,
> >>> ALT_DOWN_MASK should be set. If you press VK_SHIFT then,
> >>> SHIFT_DOWN_MASK should be added to indicate that both keys are
> >>> pressed. And if you press VK_ALT_GRAPH, only ALT_GRAPH_DOWN_MASK
> >>> should be added. Otherwise, you can't distinguish the following key
> >>> strokes: 'AltGr+Right' and 'Alt+AltGr+Right'. But these keystrokes are
> >>> different and should invoke different actions. For example,
> >>> 'Alt+Right' moves cursor to the next word
> >>> 'Alt+Shift+Right' moves cursor to the next word AND adds all skipped
> >>> characters to selection
> >>> 'Alt+AltGr+Right' does nothing, because we do not assign this shortcut yet
> >>>
> >>> On Thu, Mar 14, 2019 at 12:09 AM Sergey Bylokhov
> >>> <Sergey.Bylokhov at oracle.com> wrote:
> >>>>
> >>>> On 13/03/2019 03:59, Sergey Malenkov wrote:
> >>>>> I missed the "for ALT keys" in the bug title and thought that
> >>>>> "KeyEvent.getModifiers() returns inconsistent values" was about
> >>>>> incompatible behaviour on different platforms. In fact, JDK-8218917
> >>>>> should be renamed to something like “The right Alt key on Mac should
> >>>>> behave as Alt and must not break the left Alt key processing”.
> >>>>
> >>>> But the "right Alt" should behave like a "left alt" already, it should use both flags:
> >>>> the common alt(ALT_DOWN_MASK) and the altGr(ALT_GRAPH_DOWN_MASK).
> >>>>
> >>>> So if the client will follow the spec below it should work as before, isn't it?:
> >>>> https://docs.oracle.com/en/java/javase/11/docs/api/java.desktop/java/awt/event/InputEvent.html#getModifiersEx()
> >>>>
> >>>>> On Wed, Mar 13, 2019 at 6:57 AM Sergey Bylokhov
> >>>>> <Sergey.Bylokhov at oracle.com> wrote:
> >>>>>>
> >>>>>> On 12/03/2019 12:28, Sergey Malenkov wrote:
> >>>>>>> Hi Sergey,
> >>>>>>>
> >>>>>>> 1. macOS uses a regular Alt key as "Alternate Character Key". This is
> >>>>>>> the reason why JDK Toolkit defines Ctrl+Alt to select a mnemonic,
> >>>>>>> instead of simple Alt. See
> >>>>>>> https://sites.google.com/site/malenkov/java/141229
> >>>>>>
> >>>>>> Right, but introducing this flag for the "left alt" could cause even more
> >>>>>> issues, so this flag is set only for the right.
> >>>>>>
> >>>>>>> 3. Regression was caused by adding AltGr to key processing on Mac. But
> >>>>>>> I found more issues with inconsistent key processing on different
> >>>>>>> platforms. See http://sites.google.com/site/malenkov/java/190312
> >>>>>>
> >>>>>> Not sure that CAPS_LOCK is related.
> >>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>> On Tue, Mar 12, 2019 at 4:17 AM Sergey Bylokhov
> >>>>>>> <Sergey.Bylokhov at oracle.com> wrote:
> >>>>>>>>
> >>>>>>>> On 11/03/2019 17:37, Philip Race wrote:
> >>>>>>>>> The debate is about AltGraph which an ancient MS-DOSism for
> >>>>>>>>> asking for an ALTernate GRAPHics bitmap font - all pre-dates windows
> >>>>>>>>> and I am sure has never been applicable to any MacOS.
> >>>>>>>>
> >>>>>>>> It also about the "right alt" which is also know as "AltGraph". I guess currently
> >>>>>>>> it is implemented as "right alt" on Linux/macOS/windows.
> >>>>>>>>
> >>>>>>>> BTW on linux it is also named as "Alternative Characters Key":
> >>>>>>>> https://help.ubuntu.com/community/ComposeKey
> >>>>>>>>
> >>>>>>>>> So someone needs to properly explain why we would claim a Mac keyboard
> >>>>>>>>> is OK to generate a keycode it doesn't have and cause a slew of regressions
> >>>>>>>>> in the process ...>
> >>>>>>>>> If Mac doesn't distinguish these two, we should generate the same keycode for both.
> >>>>>>>>
> >>>>>>>> The macOS supports "right alt", otherwise it would not be possible to implement it in java:
> >>>>>>>> https://developer.apple.com/library/archive/technotes/tn2450/_index.html
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>> One could suppose there is a difference else why two keys, but what is the right
> >>>>>>>>> thing to do here  that fixes all the problems. What exactly WAS the problem
> >>>>>>>>> with what was there in the first place ? And if changing it is correct why is it
> >>>>>>>>> causing regressions ?
> >>>>>>>>
> >>>>>>>> Regressions were caused by the bugs in the fix implementation, or am I missed something?
> >>>>>>>>
> >>>>>>>>
> >>>>>>>>>
> >>>>>>>>> -phil.
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>>
> >>>>>>>>> On 3/12/19, 5:34 AM, Sergey Bylokhov wrote:
> >>>>>>>>>> Hi, Phil.
> >>>>>>>>>> On 11/03/2019 07:43, Philip Race wrote:
> >>>>>>>>>>> The reasoning that AltGraph might be useful to someone is a bit weak
> >>>>>>>>>>> and I don't think I'd want to support it via system property or build options.
> >>>>>>>>>>>
> >>>>>>>>>>> If its not a platform keyboard key, why do we need it ?
> >>>>>>>>>>
> >>>>>>>>>> The "AltGraph" key is also commonly referred to as "Right Alt", and
> >>>>>>>>>> it has been implemented on all platforms as a "Right Alt", it is convenient to
> >>>>>>>>>> distinguish the left/right alts.
> >>>>>>>>>>
> >>>>>>>>
> >>>>>>>>
> >>>>>>>> --
> >>>>>>>> Best regards, Sergey.
> >>>>>>>
> >>>>>>>
> >>>>>>>
> >>>>>>
> >>>>>>
> >>>>>> --
> >>>>>> Best regards, Sergey.
> >>>>>
> >>>>>
> >>>>>
> >>>>
> >>>>
> >>>> --
> >>>> Best regards, Sergey.
> >>>
> >>>
> >>>
> >>> --
> >>> Best regards,
> >>> Sergey A. Malenkov
> >>
> >
> >
>
>
> --
> Best regards, Sergey.

-- 
Best regards,
Sergey A. Malenkov