Bug ID: JDK-8166954 Drawing artifacts with floating point UI scale

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JDK 10
10Resolved

The issue is created to track the discussed problems with floating point UI scale. See http://mail.openjdk.java.net/pipermail/2d-dev/2016-September/007718.html
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Hello,

JDK9 comes with HiDPI support on Windows/Linux which is really great. As
we gave it a try, we found it looking pretty good with an integer scale
(2x) but revealed some rendering flaws with float scales.

Let me please demonstrate it with SwingSet2 + JDK9-ea-b137 + Windows 8.1
in 150% scale (1.5f)

demo1 <http://cr.openjdk.java.net/%7Eant/hidpi_pics/demo1.png>

Dragging Frame-0 behind the pallet makes the pallet wavy.
Also, as Frame-0 moves it may leave traces.

demo2 <http://cr.openjdk.java.net/%7Eant/hidpi_pics/demo2.png>

Unstable look of a control. For instance, these two combos are decorated
differently (and not perfectly).

demo3 <http://cr.openjdk.java.net/%7Eant/hidpi_pics/demo3.png>

Scrolling traces.

demo4 <http://cr.openjdk.java.net/%7Eant/hidpi_pics/demo4.png>

Menu traces.
Colored rendering artifacts.

Additionally, I'm attaching a test source & pics kindly provided by
Renaud (cc'd) from AndroidStudio. The demo finely shows problems on the
example of primitive rendering.

Scaling 100%
<http://cr.openjdk.java.net/%7Eant/hidpi_pics/Scaling-100-percent.png>

Scaling 125%
<http://cr.openjdk.java.net/%7Eant/hidpi_pics/Scaling-125-percent.png>

Scaling 150%
<http://cr.openjdk.java.net/%7Eant/hidpi_pics/Scaling-150-percent.png>

It seems like most of the mentioned issues are caused by inaccurate
rounding performed during the rendering cycle.
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Not able to reproduce with windows 7. Need to verify with 8.1
08-08-2017
Targeted to 10 as an issue introduced in 8u or 9
17-02-2017
Approved by component triage team to defer
15-12-2016
SQE: OK to defer
15-12-2016
This is a request to defer the issue. The main part as drawing artifacts with the internal frames moving and list scrolling are fixed by JDK-8162350 There are still small artifacts with the JComboBox drawing http://cr.openjdk.java.net/%7Eant/hidpi_pics/demo2.png Squares in MinimalSwingApplication from the mentioned email could look rectangular when floating point scale is used just because they are painted using user space coordinates and their shape depends on the point from each it is drawn. If The first and last points are even then it is drawn as square. If one of the points is odd then it is drawn as a rectangle.
14-12-2016
One more case: Run the SwingSet2 demo with uiScale=1.5, go to the JSlider demo and move the vertical slider bar. There are some artifacts left.
03-11-2016

Relates :	JDK-8167305 - RepaintManager.copyArea() method should be updated for floating point UI scale
Relates :	JDK-8162350 - RepaintManager shifts repainted region when the floating point UI scale is used
Relates :	JDK-8167303 - Draw JInternalFrame borders by rectangles for floating point UI scale