Hi Alexandr,
I looked at the testcase 8162350 closely and found your explanation
below not quite precise...
When you repaint a letter with an slightly expanded dirty rect, you've
got it as [40-1, 0-1, 80+2, 60+2] = [39, -1, 82, 62]. Let's count only "x".
As Jim noted, the code to draw is:
// repainting x,y,w,h
img = make image (w,h)
g = img.getGraphics()
g.setClip(x,y,w,h)
g.translate(-x,-y)
component.paint(g)
destination.drawImage(img, x,y)
The transformation matrix of "g" is double (AffineTransform.java). So,
g.translate(-39) translates to -39*1.5=-58.5. The top-left pixel of the
letter [40, 0]=[40*1.5, 0]=[60, 0] thus is painted into x=[60-58.5]=1.5
of the intermediate "img". And I suspect it's eventually not rounded up
but is floor'ed to x=1. Then, the "img" is drawn at x=[39]=[39*1.5]=58.5
which I suspect is also eventually floor'ed to x=58. As the result, the
top-left pixel of the letter appears at x=[58+1]=59, not at x=60. That's
the shift. Not sure if my guess is correct though.
The Jim's last suggestion seems to address the problem, as it scales &
rounds first and then passes already computed values down. Does the
solution affect RepaintManager only? Or I suspect there will be a
problem with:
// Not sure if there is a mechanism for this since I think
// all of the interfaces to get a compatible image are
// designed to assume that the caller is not scale-aware.
img = make pixel-sized image (pixelw, pixelh)
because the comments are true.
Thanks,
Anton.
On 9/30/2016 1:22 PM, Alexandr Scherbatiy wrote:
Hello Anton,
Yes, we are working on it.
For example, there is the known issue DK-8162350 RepaintManager shifts
repainted region when the floating point UI scale is used.
https://bugs.openjdk.java.net/browse/JDK-8162350
The problem is that the RepaintManager draws a region to a buffered
image at first and draws the image after that to the window.
Suppose the image has int coordinates and size (x, y, w, h) in the
user space. It should be drawn into the region with coordinates (x, y,
x+width, y+height) = (x1, y1, x2, y2).
If floating point UI scale is used (like 1.5) the region coordinates
are converted to values (1.5 * x1, 1.5 * y1, 1.5 * x2, 1.5 * y2) in
the dev space.
Now these coordinates need to be rounded and the process really
depends on the evenness or oddness of the start and end coordinates.
They both can be rounded to one side or to opposite. Depending on this
some lines near the drawn image region can be not filled or just
wrongly filled.
If I try to not use a buffered image in the RepaintManager it seems
that some problems are just gone away (internal frame moving artifacts
on the SwingSet2 demo or squares in MinimalSwingApplication are drawn
as squares and not rectangles).
But not all of them. The artifacts during the scrolling in the
SwingSet2 demo still exist.
I have filled an issue on it just to keep track of them: JDK-8166954
Drawing artifacts with floating point UI scale
https://bugs.openjdk.java.net/browse/JDK-8166954
The another problem which we are working on is that a selected text is
just shifted: 8156217 Selected text is shifted on HiDPI display
https://bugs.openjdk.java.net/browse/JDK-8156217
To support this we were needed to add some new API which support
floating point coordinates in the View, TextUI and JTextComponent classes.
The issue is on the review:
http://mail.openjdk.java.net/pipermail/swing-dev/2016-September/006705.html
Thanks,
Alexandr.
On 9/28/2016 1:17 PM, Anton Tarasov wrote:
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.
So, I'd like to ask you please share your thoughts on it. How serious
is the problem at all (I guess you're aware of it)? What is solvable
on the JDK side, and what is not (e.g. demo2 and the Renaud's test case)?
Do you have plans to resolve it by jdk9 GA, or earlier/later? Any
technical details behind it are very welcome as well.
Thanks in advance,
Anton.
