<Swing Dev> [9] Review request for 8132119 Provide public API for text related methods in SwingUtilities2

[Phil Race]

Hi,

Is that a response to my suggestion we not over-specify, or something else ?
Can you point to an example of how this changed in the latest webrev ?

-phil.

On 03/31/2016 01:09 PM, Sergey Bylokhov wrote:
> Just a small clarification. In general implementations of these 
> methods can make some "magic", but the purpose of the change is to 
> provide to the user this "magic", I mean the user's components will be 
> able to apply this "magic" to the custom components(or change behavior 
> of standard l&f). So in the latest webrev some of implementations 
> details of these methods were hidden.
> I am not sure we express this goal successfully or not.
>
> On 31.03.16 22:23, Phil Race wrote:
>> Maybe the test to pass in that case is whether the default 
>> implementation
>> is going to be satisfactory for 90% of uses. If they are frequently
>> over-ridden
>> it would not be an appropriate use.
>>
>> Based on that criterion I think it is OK to use here.
>>
>> Another thought:
>> When you add default implementations you should also be on the hook
>> for explaining what that does. It is a deeper contract than you would
>> otherwise have as an interface and maybe needs to be an @implNote
>> or you need to call out the default implementation.
>> ie there is what someone must code to satisfy the contract of the
>> interface and what is a behaviour in the default method ?
>>
>>
>> Also here is a link to some comments by Brian Goetz on default methods :
>>
>> http://stackoverflow.com/questions/28681737/java-8-default-methods-as-traits-safe/28684917#28684917 
>>
>>
>>
>>    75      * No character is underlined if the index is negative or 
>> greater
>>    76      * than the string length {@code (index < 0 || index >=
>> string.length())}
>>    77      * or if the char value specified at the given index
>>    78      * is in the low-surrogate range.
>>
>>
>> I suppose if you point at the last char and it is a hi-surrogate nothing
>> is underlined in that case either.
>>
>> But I find the whole writing of this a bit inadequate as if you are
>> going to
>> this kind of detail you perhaps also need to say what happens in a 
>> complex
>> script where what happens is two unicode characters end up as a 
>> ligature,
>> and/or perhaps you aren't even pointing to a base character.
>> Maybe it is in fact over-specified. I see that the implementation draws
>> the underline itself rather than delegate to TextLayout. This might
>> make sense for performance reasons where it is simple text but some day
>> this maybe should be re-examined and so I would not over-specify it.
>>
>> How about :
>> "The underline will be positioned at the base glyph which
>> represents the valid char indicated by the index.
>> If the char index is not valid or is not the index of a
>> valid unicode code point then no underline is drawn"
>>
>> -phil.
>>
>>
>>
>> On 03/24/2016 07:22 AM, Sergey Bylokhov wrote:
>>> On 24.03.16 16:52, Alexander Scherbatiy wrote:
>>>> On 24/03/16 10:36, Semyon Sadetsky wrote:
>>>>> Hi Alexander,
>>>>>
>>>>> Could you answer one question:
>>>>> Why did you choose default interface methods to implement
>>>>> TextUIDrawing and not implement them in DefaultTextUIDrawing having
>>>>> declarations only in the interface?
>>>>> AFAIK the common point of view is default methods should be used
>>>>> rarely because they may lead to unreadable code.
>>>>>
>>>>    The only problem which I know about default methods is multiple
>>>> inheritance which has its own solution.
>>>
>>> What kind of problems? The benefit is obvious: it will not be
>>> necessary to implement all methods if only one of them should be 
>>> tweaked.
>>>
>>>>
>>>>    Could you give links to discussion or provide use cases where 
>>>> default
>>>> methods leads to the unreadable code and show how does it relate to 
>>>> the
>>>> TextUIDrawing  implementation?
>>>>
>>>>    Thanks,
>>>>    Alexandr.
>>>>> --Semyon
>>>>>
>>>>> On 3/18/2016 6:49 PM, Alexander Scherbatiy wrote:
>>>>>>
>>>>>> Could you review the updated fix:
>>>>>>   http://cr.openjdk.java.net/~alexsch/8132119/webrev.08/
>>>>>>
>>>>>>   - Public TextUIDrawing interface is added to the javax.swing.plaf
>>>>>> package
>>>>>>   - TextUIDrawing methods description does not mention component
>>>>>> properties to be more general
>>>>>>   - TextUIDrawing methods are made default
>>>>>>   - L&F sets an instance of the TextUIDrawing to look and feel
>>>>>> defaults using "uiDrawing.text" property
>>>>>>   - ComponentUI class is not changed
>>>>>>   - Each ComponentUI reads TextUIDrawing from UI defaults
>>>>>>   - There is an interesting issue described in
>>>>>> http://mail.openjdk.java.net/pipermail/swing-dev/2016-March/005509.html 
>>>>>>
>>>>>>
>>>>>>     which is related to the fact that MetalLabelUI returns a static
>>>>>> field from createUI() method.
>>>>>>     TitleBorder creates a JLabel but does not put it to any 
>>>>>> component
>>>>>> hierarchy. In this case SwingUtilities.updateComponentTreeUI() 
>>>>>> method
>>>>>> calls MetalLabelUI.uninstallDefaults() on the static metalLabelUI
>>>>>> field and sets a new LabelUI for ordinary labels. The TitleBorder
>>>>>> label UI is not changed in this case and it still uses the
>>>>>> metalLabelUI field which is not initialized.
>>>>>>     It seems that other applications can also use components just 
>>>>>> for
>>>>>> drawing and have the same issue.
>>>>>>     For this case the textUIDrawing field is not cleared in the
>>>>>> uninstallDefaults but just set to a static default value which 
>>>>>> should
>>>>>> not lead to memory leaks.
>>>>>>
>>>>>>   Thanks,
>>>>>>   Alexandr.
>>>>>>
>>>>>> On 29/01/16 19:51, Alexander Scherbatiy wrote:
>>>>>>> On 25/01/16 13:44, Andrej Golovnin wrote:
>>>>>>>> Hi Alexandr,
>>>>>>>>
>>>>>>>>> Could you review the updated fix:
>>>>>>>>> http://cr.openjdk.java.net/~alexsch/8132119/webrev.07/
>>>>>>>> ....
>>>>>>>>> - public TextUIDrawing interface is added to the javax.swing.plaf
>>>>>>>>> package
>>>>>>>>> - public "TextUIDrawing getTextUIDrawing()" method is added to 
>>>>>>>>> the
>>>>>>>>> ComponentUI class
>>>>>>>>> - L&F sets an instance of the TextUIDrawing to look and feel
>>>>>>>>> defaults using
>>>>>>>>> "uiDrawing.text" property
>>>>>>>>> - Look and Feel delegates use the instance of the TextUIDrawing
>>>>>>>>> for text
>>>>>>>>> drawing and measuring
>>>>>>>> Some thoughts on the current design/implementation:
>>>>>>>>
>>>>>>>> By adding a field to the ComponentUI class the current
>>>>>>>> implementation increases
>>>>>>>> memory consumption for all Swing applications. And you get the
>>>>>>>> feeling that
>>>>>>>> there are different implementations of TextUIDrawing per
>>>>>>>> ComponentUI instances.
>>>>>>>> Personally I can't imagine to have different implementations of
>>>>>>>> TextUIDrawing for
>>>>>>>> a given LookAndFeel. If I would design/implement it, then I would
>>>>>>>> implement it as
>>>>>>>> a property of the LookAndFeel class (similar to LayoutStyle) 
>>>>>>>> and not
>>>>>>>> the ComponentUI.
>>>>>>>> Developers can use then the following code to obtain the 
>>>>>>>> instance of
>>>>>>>> TextUIDrawing:
>>>>>>>>
>>>>>>>> UIManager.getLookAndFeel().getUIDrawing() // or
>>>>>>>> UIManager.getLookAndFeelUIDrawing() // use this static method as a
>>>>>>>> short cut for the line above.
>>>>>>>   LayoutStyle keeps its instance per App context. The same is for
>>>>>>> the LookAndFeel
>>>>>>>   when it is got through UIManager.getLookAndFeel() call.
>>>>>>>   It means that accessing an instance of a TextUIDrawing will leads
>>>>>>> to a time consumption.
>>>>>>>
>>>>>>>   There are 3 main ways of the SwingUtilities2.drawString(...) 
>>>>>>> usage:
>>>>>>>   1. ComponentUI classes
>>>>>>>   2. Components created in UI (like BasicInternalFrameTitlePane)
>>>>>>>   3. Public utilities methods (like 
>>>>>>> WindowsGraphicsUtils.paintText())
>>>>>>>
>>>>>>>   For the cases 1 and 2 it is possible to load and store the
>>>>>>> UIDrawing instance during installUI()/updateUI() calls to 
>>>>>>> decrease a
>>>>>>> time access to it.
>>>>>>>
>>>>>>>   For the case 3 it is necessary to get LookAndFeel instance each
>>>>>>> time (which is taken from an App context)
>>>>>>>   or use the passed JComponent object. It requires to have a public
>>>>>>> method and the associated variable for each instance of
>>>>>>> JComponent/ComponentUI/... class.
>>>>>>>> You can use this methods then in JDK too.
>>>>>>>>
>>>>>>>> And maybe rename the TextUIDrawing class to just UIDrawing and add
>>>>>>>> more useful methods,
>>>>>>>> e.g. a method to create a composite font, a method to convert DLUs
>>>>>>>> to pixels.
>>>>>>>   UIDrawing name may look like it should be used for any UI 
>>>>>>> drawing,
>>>>>>> not only for text ones. I am afraid that it can be misleading.
>>>>>>>
>>>>>>>   Thanks,
>>>>>>>   Alexandr.
>>>>>>>
>>>>>>>>
>>>>>>>> Best regards,
>>>>>>>> Andrej Golovnin
>>>>>>>
>>>>>>
>>>>>
>>>>
>>>
>>>
>>
>
>