Review request for 7124554: [macosx] JWindow does ignore setAlwaysOnTop property

Anthony Petrov anthony.petrov at oracle.com
Tue Jan 17 11:07:25 PST 2012 

Hi Mike,

On 1/17/2012 8:52 PM, Mike Swingler wrote:
> On Jan 17, 2012, at 3:54 AM, Anthony Petrov wrote:
>> On 1/16/2012 8:24 PM, Mike Swingler wrote:
>>> I still don't understand why the list of hardcoded window levels 
>>> needs to be included. Can't you just compare the window levels by 
>>> their NSInteger numeric values?
>>
>> There are two reasons for not using the numeric values directly, or 
>> comparing them directly:
>>
>> 1. Cocoa specification doesn't define the numeric values for the 
>> NS*WindowLevel constants. They may (theoretically) change in the 
>> future. As long as they aren't specified, we don't want to rely on 
>> their current values.
> 
> Why do you have to know the values at all? Couldn't you just reset the 
> child window level if it's different after the parent/child operation? 
> After I re-read what you are trying to accomplish, even numeric 
> comparison seems inappropriate.

I've already answered this question to Leonid on Jan 12, but I'll copy 
my reply here for your convenience:

If the parent window is an always-on-top window, its level is 
NSFloatingWindowLevel. Suppose a child window being added to it hasn't 
been assigned any level explicitly, so its default level is 
NSNormalWindowLevel.

Now, when we call -addChildWindow:, we really want to update the level
of the child window so that both the parent and the child share the same
window level. The if check ensures that we don't reset the level of the
child window back to normal in this case.


>> 2. There's a reference to the Quartz spec that defines the 
>> kCG*WindowLevel constants as a enum. The NS*WindowLevel macros are 
>> defined using these constants. However, if you take a look at the 
>> order of the constants in that enum [1] (and therefore their relative 
>> numerical order), you may notice that they don't exactly reflect the 
>> relative visual z-order between the levels as defined in the Cocoa 
>> spec [2]. E.g. kCGModalPanelWindowLevelKey is greater than 
>> kCGDockWindowLevelKey, while NSDockWindowLevel is defined being 
>> visually above the NSModalPanelWindowLevel. As such, a direct numeric 
>> comparison of window levels produces incorrect results.
> 
> Have you tried setting something at the "dock" level? That level may 
> have been true for the NextStep dock, but not the Mac. And BTW: 
> the NSDockWindowLevel is deprecated. Don't use it.

Yes, this is a good tip. I've removed the NSDockWindowLevel from the 
array. An updated fix is available at:

http://cr.openjdk.java.net/~anthony/x-6-alwaysOnTop.1/


>> The array of hardcoded window levels allows us to convert between 
>> window levels ordered arbitrarily and integer values ordered according 
>> to their visual z-order. This allows us to compare windows level with 
>> respect to their relative z-order as specified by Cocoa documentation.
> 
> These constants are for assignment based on intention, not simple 
> comparison of stacking level. They have behavioral meaning beyond just 
> simple visual level ordering. Windows above the normal window level will 
> disappear in Exposé/Mission Control, and certain levels will float in 
> all Spaces. Other levels exclude the window from Cmd-~ keyboard window 
> cycling, or showing up in the Dock window menu. Please, please, please 
> test the side effects of these changes before just popping windows into 
> different levels.

Could you please clarify what exact "different levels" you're talking 
about here? AWT currently uses only two window levels: 
NSNormalWindowLevel is used for regular windows, and 
NSFloatingWindowLevel for always-on-top windows (see AWTWindow.m). This 
code is already in the repository, and tests for always-on-top windows 
do work OK.

So back to the fix we're discussing, in reality the oldChildLevel in the 
CWrapper.addChildWindow() implementation can be either of these two 
levels, but not anything else. I guess we could simplify the fix and 
only include these two levels in the ORDERED_LEVELS{} array. I suppose 
Lubomir just wanted to provide a more generic and complete 
implementation that won't break if we ever start using any other levels 
in the future (or e.g. if OS temporarily puts our window on some other 
level). This is certainly unlikely, of course, however, I see absolutely 
no problems with an implementation of compareWindowLevels() that can 
work with all window levels officially supported by Cocoa, not just the 
two that we use currently.


> The safest thing to do (if it works) is just to simply re-assign the 
> window level after adding the child to the parent, but you will have to 
> recursively descend into the child windows of the child, because setting 
> the window level sets the level of all the children too (and changes 
> their collection/spaces/cycle behavior). This may not be an issue if you 
> never change a child window's parent.

I've clarified above why simple reassignment won't work well.

--
best regards,
Anthony

> 
> Regards,
> Mike Swingler
> Apple Inc.
> 
>> Does this clarify the need for the array of window levels? Do you have 
>> any other concerns regarding the fix?
>>
>> [1] 
>> http://developer.apple.com/library/mac/documentation/GraphicsImaging/Reference/Quartz_Services_Ref/Reference/reference.html#//apple_ref/c/tdef/CGWindowLevelKey
>>
>> [2] 
>> http://developer.apple.com/library/mac/documentation/Cocoa/Reference/ApplicationKit/Classes/NSWindow_Class/Reference/Reference.html#//apple_ref/doc/constant_group/Window_Levels
>>
>> --
>> best regards,
>> Anthony
>>
>>
>>> Regards,
>>> Mike Swingler
>>> Apple Inc.
>>> On Jan 14, 2012, at 7:40 PM, Mike Swingler wrote:
>>>> In the course of preparing to contribute our current window stacking 
>>>> algorithm, I realized that there was a pair of internal SPI calls it 
>>>> was making. In the next revision we ship of the 
>>>> JavaRuntimeSupport.framework we can provide cover methods of these 
>>>> SPI, however that is of little benefit to the OpenJDK port in the 
>>>> immediate here-and-now.
>>>>
>>>> For now, using -addChildWindow: will be sufficient, however, we can 
>>>> provide an alternate implementation that uses a new pair of category 
>>>> methods on NSWindow if -respondsToSelector: shows that they are 
>>>> available:
>>>> - (void)javaAddToOrderingGroup:(NSWindow *)ownedWindow;
>>>> - (void)javaRemoveFromOrderingGroup:(NSWindow *)ownedWindow;
>>>>
>>>> These functions will allow the window server to move each child 
>>>> window with respect to it's parent's level, but without being added 
>>>> to it's movement group.
>>>>
>>>> Once customers get an updated JavaNativeFoundation.framework by 
>>>> either Java update or OS update, the implementation will switch over 
>>>> dynamically at runtime.
>>>>
>>>> How does this sound for a plan?
>>>>
>>>> Regards,
>>>> Mike Swingler
>>>> Apple Inc.
>>>>
>>>> On Jan 12, 2012, at 2:13 PM, steve.x.northover at oracle.com 
>>>> <mailto:steve.x.northover at oracle.com> wrote:
>>>>
>>>>> We fought this one in SWT and ended up going with the puppy route.
>>>>>
>>>>> Steve
>>>>>
>>>>> On 12/01/2012 2:57 PM, Anthony Petrov wrote:
>>>>>> Hi Mike,
>>>>>>
>>>>>> I recall we've discussed this issue with you back in 2010. 
>>>>>> Unfortunately, I wasn't able to implement anything like this that 
>>>>>> would work reliably back then (and I tried hard, really), that's 
>>>>>> why we ended up with -addChildWindow:. Note that JCK is very happy 
>>>>>> with this implementation, and so are we, I presume. As long as 
>>>>>> child windows receive their respective MOVE events, it seems that 
>>>>>> everything is all right. Besides, such behavior is very 
>>>>>> Mac-friendly, making Java apps behave like native apps.
>>>>>>
>>>>>> I realize that for some developers this behavior may be 
>>>>>> inconvenient. But then again, why not listen to MOVE events on the 
>>>>>> parent frame and compensate for its movement repositioning all its 
>>>>>> children? ( :) yeah, yeah, I know, sounds weird, but... as Steve 
>>>>>> says, you gotta do what you gotta do... I mean, there's a 
>>>>>> workaround at least!)
>>>>>>
>>>>>> So, if you or anyone else wish to contribute an alternative 
>>>>>> implementation for owned windows, that would be greatly 
>>>>>> appreciated. Otherwise I'm afraid we have to stick with using 
>>>>>> -addChildWindow: for now since we simply don't have a better solution.
>>>>>>
>>>>>> -- 
>>>>>> best regards,
>>>>>> Anthony
>>>>>>
>>>>>> On 1/12/2012 11:17 PM, Mike Swingler wrote:
>>>>>>> Also, you should not use -addChildWindow:, because you also get 
>>>>>>> added to the movement group of the parent (moving the parent 
>>>>>>> moves all it's children). This is *highly* undesirable behavior 
>>>>>>> for Java's general use (and you can see it in Eclipse when the 
>>>>>>> find window follows around the IDE window like a puppy).
>>>>>>>
>>>>>>> In the Java SE 6 AWT we manually restack every Java window in 
>>>>>>> native with -orderFront: every time a Java window changes it's 
>>>>>>> level to correctly handle it's children and the relationships 
>>>>>>> between them. This actually works out ok, since all the changes 
>>>>>>> happen at once, and when the next turn of the event loop happens, 
>>>>>>> the new stacking order only has one new window moving to the 
>>>>>>> background and one new window becoming key/main.
>>>>>>>
>>>>>>> Regards,
>>>>>>> Mike Swingler
>>>>>>> Apple Inc.
>>>>>>> On Jan 12, 2012, at 6:34 AM, Leonid Romanov wrote:
>>>>>>>
>>>>>>>> Bah, I was wrong. The value of NS*WindowLevel is really funky, 
>>>>>>>> it was a wrong suggestion to rely on it. Sorry for wasting your 
>>>>>>>> time.
>>>>>>>>
>>>>>>>>
>>>>>>>> On 12.01.2012, at 17:52, Anthony Petrov wrote:
>>>>>>>>
>>>>>>>>> The values of the NS*WindowLevel macros are not a part of the 
>>>>>>>>> contract for Cocoa API. Therefore, we shouldn't rely on their 
>>>>>>>>> current numerical values. The names, however, and their 
>>>>>>>>> relative z-order are clearly specified in the documentation, 
>>>>>>>>> and as such we may use them.
>>>>>>>>>
>>>>>>>>> -- 
>>>>>>>>> best regards,
>>>>>>>>> Anthony
>>>>>>>>>
>>>>>>>>> On 01/12/12 17:44, Leonid Romanov wrote:
>>>>>>>>>> I see… It looks like the higher window level is, the higher is 
>>>>>>>>>> the value of corresponding NS*WindowLevel macro.
>>>>>>>>>> Wouldn't it be better to implement compareWindowLevels() by 
>>>>>>>>>> simply subtracting one value from another?
>>>>>>>>>>
>>>>>>>>>> On 12.01.2012, at 17:06, Anthony Petrov wrote:
>>>>>>>>>>
>>>>>>>>>>> Hi Leonid,
>>>>>>>>>>>
>>>>>>>>>>> Thanks for taking a look at the fix.
>>>>>>>>>>>
>>>>>>>>>>> The if check is needed for the following case. If the parent 
>>>>>>>>>>> window is an always-on-top window, its level is 
>>>>>>>>>>> NSFloatingWindowLevel. Suppose a child window being added to 
>>>>>>>>>>> it hasn't been assigned any level explicitly, so its default 
>>>>>>>>>>> level is NSNormalWindowLevel.
>>>>>>>>>>>
>>>>>>>>>>> Now, when we call -addChildWindow:, we really want to update 
>>>>>>>>>>> the level of the child window so that both the parent and the 
>>>>>>>>>>> child share the same window level. The if check ensures that 
>>>>>>>>>>> we don't reset the level of the child window back to normal 
>>>>>>>>>>> in this case.
>>>>>>>>>>>
>>>>>>>>>>> -- 
>>>>>>>>>>> best regards,
>>>>>>>>>>> Anthony
>>>>>>>>>>>
>>>>>>>>>>> On 01/11/12 21:48, Leonid Romanov wrote:
>>>>>>>>>>>> Just wondering: what would happen if you simply set 
>>>>>>>>>>>> oldChildlevel without that "if" check?
>>>>>>>>>>>>
>>>>>>>>>>>> On 11.01.2012, at 19:22, Anthony Petrov wrote:
>>>>>>>>>>>>
>>>>>>>>>>>>> Hello,
>>>>>>>>>>>>>
>>>>>>>>>>>>> Please review a fix for 
>>>>>>>>>>>>> http://bugs.sun.com/view_bug.do?bug_id=7124554 at:
>>>>>>>>>>>>>
>>>>>>>>>>>>> http://cr.openjdk.java.net/~anthony/x-6-alwaysOnTop.0/
>>>>>>>>>>>>>
>>>>>>>>>>>>> Lubomir Nerad (CC'ed) should be credited for the fix 
>>>>>>>>>>>>> itself. I'm just going to integrate it into the repository.
>>>>>>>>>>>>>
>>>>>>>>>>>>> A JWindow object is always a child window with either an 
>>>>>>>>>>>>> explicit parent, or a shared invisible owner frame. 
>>>>>>>>>>>>> Therefore, we always call NSWindow -addChildWindow: when 
>>>>>>>>>>>>> showing a JWindow object. The root cause of the issue is 
>>>>>>>>>>>>> that the -addChildWindow: resets the level of the child 
>>>>>>>>>>>>> window to match that of the parent window. With this fix we 
>>>>>>>>>>>>> restore the level back to its original value after the 
>>>>>>>>>>>>> -addChildWindow: call, and as such preserve the 
>>>>>>>>>>>>> always-on-top state of the child window.
>>>>>>>>>>>>>
>>>>>>>>>>>>> I've verified the fix with a test app attached to the 
>>>>>>>>>>>>> original issue at 
>>>>>>>>>>>>> http://java.net/jira/browse/MACOSX_PORT-158 , and it works 
>>>>>>>>>>>>> fine.
>>>>>>>>>>>>>
>>>>>>>>>>>>> -- 
>>>>>>>>>>>>> best regards,
>>>>>>>>>>>>> Anthony
>

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