<AWT Dev> [15] Review request for 8230926: [macosx] Two apostrophes are entered instead of one with "U.S. International - PC" layout

[Anton Litvinov]

Hi Sergey,

Thank you for review of this fix. I am not sure, that a similar issue 
does not exist for other keyboard layout with same or other modifier 
keys in JDK for macOS, because I do not know all keyboard layouts and do 
not know all their peculiarities. But I am sure that this JDK code 
related to input methods on macOS is very fragile and depends on many 
flags and "if" conditions in Objective-C and Java source code, and that 
is why all bugs related to input methods for last several years were 
fixed in narrow ways to address only those uncovered problematic scenarios.

This particular bug exists in Oracle JDK from the very first release, 
the issue is reproducible with JDK 7u4 b21, this bug always affected 
"U.S. International - PC" layout in JDK. The issue is also reproducible 
with Apple JDK 1.6.0_65-b14-468.

To my mind, a source of these problems with input methods is the fact 
that JDK receives explicit direction from macOS to insert certain 
characters through the method "(void) insertText:(id)aString 
replacementRange:(NSRange)replacementRange" in "AWTView.m" file, and in 
some cases JDK generates "java.awt.event.InputMethodEvent" as a result 
of this call and in some cases does not generate "InputMethodEvent" with 
the intention to generate "java.awt.event.KeyEvent" events instead of it 
as part of invocation of, for example, "(void) keyDown: (NSEvent 
*)event" method in "AWTView.m" file.

In this bug with "U.S. International - PC" layout, after pressing " ' ", 
" p " characters JDK's method "insertText" from "AWTView.m" file is 
invoked by macOS two times: during the first time JDK is asked to insert 
" ' ", and during the second time it is asked to insert " p " character. 
So if JDK followed that direction from macOS, there would not be a bug, 
but JDK has own requirement to generate only key events for Latin 
characters, and "U.S. International - PC" layout relies only on key 
codes corresponding to Latin characters while at the same time provides 
input method functionality for insertion of characters with diacritics 
through pressing these modifier keys " '`"˜ˆ " followed by required 
regular Latin character keys.

I had been debugging this bug and looking at it periodically for three 
years, of course I was trying to fix this bug from different sides. But 
this fix is the only well explained and reliable fix for this bug which 
I managed to create and it excludes a possibility of breaking JDK work 
with any other keyboard layouts on macOS.

Thank you,
Anton

On 20/12/2019 06:36, Sergey Bylokhov wrote:
> Hi, Anton.
>
> How we can be sure that this problem exists only in case of "U.S. 
> International - PC"?
> Did you try to check other layouts and or possible fix variation w/o 
> hardcoded check for the layout?
>
> On 12/16/19 7:01 pm, Anton Litvinov wrote:
>> Hello,
>>
>> Could you please review the following fix for the bug.
>>
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8230926
>> Webrev: http://cr.openjdk.java.net/~alitvinov/8230926/jdk15/webrev.00
>>
>> The bug consists in the fact that if on macOS with currently set 
>> "U.S. International - PC" keyboard layout a user presses any of 5 
>> modifier keys: ' (APOSTROPHE), " (QUOTATION MARK), ` (ACCENT GRAVE), 
>> ˜ (SMALL TILDE), ˆ (CIRCUMFLEX ACCENT) and then presses any consonant 
>> Latin letter key, for example "p" key, then 2 consecutive modifier 
>> keys are entered in AWT or Swing text field and the consonant letter 
>> is not entered.
>>
>> CAUSE OF THE BUG:
>>
>> The second extra modifier key is entered in the text field instead of 
>> the required letter during execution of the function "(void) keyDown: 
>> (NSEvent *)event" in 
>> "src/java.desktop//macosx/native/libawt_lwawt/awt/AWTView.m" for 
>> "NSEvent" instance representing pressing on the consonant letter key, 
>> for example that "p" key, through the next sequence of 
>> function/method calls:
>>
>> "(void) keyDown: (NSEvent *)event" - "AWTView.m" file.
>> |-> "(void) deliverJavaKeyEventHelper: (NSEvent *) event" - 
>> "AWTView.m" file
>>        |-> "sun.lwawt.macosx.CPlatformView.deliverKeyEvent(NSEvent)" 
>> - "CPlatformView.java" file
>>              |-> "sun.lwawt.macosx.CPlatformResponder.handleKeyEvent" 
>> - "CPlatformResponder.java" file
>>
>> The instance of "NSEvent" being handled which corresponds to press on 
>> the consonant letter key, for example "p", has the next values of its 
>> 2 important fields:
>>
>> [event characters] = "'p"
>> [event charactersIgnoringModifiers] = "p"
>>
>> The method "sun.lwawt.macosx.CPlatformResponder.handleKeyEvent" is 
>> designed in such a way that it selects only the first character of 
>> the string variable "chars" whose value in this case equals "'p" and 
>> generates Java AWT key events for " ' " character while ignoring 
>> presence of "p" character both in "chars" and 
>> "charsIgnoringModifiers" string variables.
>>
>> FIX:
>>
>> To change "sun.lwawt.macosx.CPlatformResponder.handleKeyEvent" method 
>> in such a way to let it generate AWT key events for a character from 
>> "charsIgnoringModifiers" string instead of the modifier key from the 
>> "chars" string, when "U.S. International - PC" keyboard layout is used.
>>
>> Thank you,
>> Anton
>
>