RFR: JDK-8294680: Refactor scaled border rendering

[Harshitha Onkar]

On Sat, 10 Dec 2022 23:08:48 GMT, Rajat Mahajan <duke at openjdk.org> wrote:

>> In this fix, the common code required for scaled border rendering is unified and added to SwingUtilities3. This is achieved by adding a functional interface to SwingUtilities3 and calling the the respective paintBorder function passed as parameter to method.  
>> 
>> Following are the usual steps for any border scaling -
>> 
>> - Resetting transform.
>> - Calculating new width, height, x & y-translations.
>> - Perform the required border rendering.
>> - And at the end restore the previous transform.
>> 
>> To test the refactored code, 3 separate border scaling instances were taken (details below) and the SwingUtilities3.paintBorder, (containing the common functionality) was applied. All the tests associated with the respective border changes pass.
>> 
>> 1. EtchedBorder - [PR#7449](https://github.com/openjdk/jdk/pull/7449) - Test: ScaledEtchedBorderTest.java
>> 2. LineBorder - [PR#10681](https://github.com/openjdk/jdk/pull/10681) - Test: ScaledLineBorderTest & ScaledTextFieldBorderTest.java
>> 3. JInternalFrame Border - [PR#10274](https://github.com/openjdk/jdk/pull/10274) - Test: InternalFrameBorderTest.java
>> 
>> The advantage of this solution is - it avoids code repetition and can be reused across all the border classes requiring border scaling fix.
>
> src/java.desktop/share/classes/com/sun/java/swing/SwingUtilities3.java line 174:
> 
>> 172: 
>> 173:             if (resetTransform) {
>> 174:                 g2d.setTransform(new AffineTransform());
> 
> Can we keep the original comment about this:
>                 /* Deactivate the HiDPI scaling transform,
>                  * so we can do paint operations in the device
>                  * pixel coordinate system instead of the logical coordinate system.
>                  */

Sure. I can add it.

> src/java.desktop/share/classes/com/sun/java/swing/SwingUtilities3.java line 190:
> 
>> 188: 
>> 189:         if (resetTransform) {
>> 190:             double xx = at.getScaleX() * x + at.getTranslateX();
> 
> Can we combine this code block with the above if (resetTransform) at line 173 ? or did you keep it separate for a reason?

@rajamah In-order to paint the border even when g is not a Graphics2D object I have added the `resetTransform` check here again and additionally to keep the if & else block close-by, which is easier to understand rather than having the blocks separated.

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PR: https://git.openjdk.org/jdk/pull/11571