<Swing Dev> [9] Review request for 8132119 Provide public API for text related methods in SwingUtilities2
Phil Race
philip.race at oracle.com
Thu Mar 31 19:23:10 UTC 2016
Another webrev where you have to slip past 40_ files to get to the two
that really matter :-)
I would have put SwingUtilities2.java and TextUIDrawing.java as the
first files.
Some of what I have to say here is more along the lines of things to think
about rather than things that are wrong .. but there are also maybe some
things
that need to be fixed.
Is javax.swing.plaf really the right package for the new class ?
I suppose it is for the use by the UI classes so maybe its right.
Should the methods be taking "double" instead of "int" for location ?
This means the measurement APIs too.
None of the JDK 1.2 text APIs use ints. That is all 1.0 legacy.
So if Swing internally wants to use ints that is OK but maybe the API
should be floating point (double).
Would that help hi-dpi at all ?
I suppose it would add over-head since all the existing code uses int
and we are no worse off and can add double methods later if we want to.
Regarding FontMetrics we need to add a caution that is must be a FontMetrics
*obtained from the correct font and graphics*.
i.e what about attributes on the font such as "tracking" ?
or on the graphics such as FRACTIONALMETRICS
It looks like Swing might already fail if that were used.
Look at this code :-
public static int stringWidth(JComponent c, FontMetrics fm, String
string){
if (string == null || string.equals("")) {
return 0;
}
boolean needsTextLayout = ((c != null) &&
(c.getClientProperty(TextAttribute.NUMERIC_SHAPING) != null));
if (needsTextLayout) {
synchronized(charsBufferLock) {
int length = syncCharsBuffer(string);
needsTextLayout = isComplexLayout(charsBuffer, 0, length);
}
}
if (needsTextLayout) {
TextLayout layout = createTextLayout(c, string,
fm.getFont(),
fm.getFontRenderContext());
return (int) layout.getAdvance();
} else {
return fm.stringWidth(string);
}
}
The only thing Swing is looking at is one TextAttribute and whether we
have complex text.
That is not enough. This is an existing implementation issue but one we
should fix here.
You need to examine all the methods for similar issues.
The usage of default methods is worth thinking about.
There is a significant subjective element to this and I've really
thought only myself about
using them for the case where default methods are useful when you need
to extend an
existing interface.
But I can imagine they may also be handy when someone would typically
want to implement
only one or two out of a larger number in an interface and the default
and you for some
reason don't want to do that with an abstract class (notably you want an
other class to
be able to implement the interface).
So what do I think about the case where the interface is brand new and
what you've done is more or less implement a concrete class, but it's
one that
can be mixed in to another class ? Is that an appropriate use ?
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
>>>>>
>>>>
>>>
>>
>
>
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