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

[Alexander Scherbatiy]

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