<Swing Dev> [9] Review request for 8162350 RepaintManager shifts repainted region when the floating point UI scale is used
Jim Graham
james.graham at oracle.com
Tue Nov 1 20:23:46 UTC 2016
Is SunGraphics2D accessible from Swing? If so, then I'd recommend
putting the isFPScale() method right on that class so we don't have to
clone the transform by calling g.getTransform(). Also note that
g.getTransform() does more than clone the transform as it has to factor
out the constrainXY translation - which are always integers so it won't
have any effect on the results of "isFPScale()" and is additional wasted
work. Eventually we could tie this into the transformState variable in
SG2D to differentiate integer and fp scale, but that would take a little
more work as those flags are used in a lot of places - for now we can at
least get rid of the transform clone and the constraint translation
processing.
In the implementation of isFPScale(tx), do you really want to return
false for non-scale transforms? It seems to me that if the transform
has rotations or shears in it then we might need to punt and just
repaint the whole viewport. Also, you could simplify it a little to
avoid an extra "getter" and extra bit math:
isFPScale(AffineTransform tx) {
int type = tx.getType() & ~(FLIP | TRANSLATE);
if (type == 0) {
return false;
} else if (type == SCALE) {
// check for integers
} else {
return true or false?;
}
}
The changes to SG2D.drawHiDPIImage point out that we should probably
allow fp subimage paramters in the image pipeline for better accuracy,
but that's a much bigger change. Until then sub-image blits are not
going to be accurate on scaled images. Won't this inaccuracy affect our
back buffer blits in Swing?
The changes to RepaintManager took me a couple of tries to figure out.
It looks like you are now rendering the dirty region at the appropriate
X,Y location in the back buffer (rather than at 0,0) in all cases to
adjust for the fact that rendering the same primitive at different
locations doesn't always match. First, you expand the back buffer even
for the unscaled case which wasn't affected by HiDPI. Second, as long
as the translate is in device pixels, it shouldn't matter where in the
buffer you render it, so it should be enough to just ensure integer
translations - did you try using an integer origin for the rendering
instead?
...jim
On 10/24/2016 9:11 AM, Alexandr Scherbatiy wrote:
>
> Hello,
>
> Could you review the updated fix:
> http://cr.openjdk.java.net/~alexsch/8162350/webrev.01
> - JScrollPane copy area functionality is disabled for floating point scale
> - VolatileImage buffer size is recalculates using transform translate
>
> Using floating point scale leads that drawing the same thing from
> different coordinates gives different results. For example filling a
> rectangle with size (1, 1) from location (0, 0) and UI scale 1.5 gives
> scaled region (0, 0, 1.5, 1.5) which is rounded to (0, 0, 2, 2). The
> same rectangle filled from the location (1, 1) gives the scaled region
> (1.5, 1.5, 3, 3) which is rounded to (2, 2, 3, 3). The first rectangle
> has size 2 in the device space and the second one has 1.
> As a result drawing a component from some coordinates and using
> Graphics.copyArea() to translate an image to a new location could have a
> differ results than just drawing the same component from the new location.
> The fix suggests to disable the JScrollPane area copying for floating
> point scales.
>
> Thanks,
> Alexandr.
>
> On 10/7/2016 4:30 PM, Alexandr Scherbatiy wrote:
>> On 10/6/2016 11:42 PM, Sergey Bylokhov wrote:
>>> Hi, Alexandr.
>>> Can you please provide some standalone small example, which emulates
>>> this artifacts via java2d API. (The pattern which we use in
>>> RepainManager). It will help to understand the problem.
>>
>> The code sample [1] draws two the same shapes (with different colors)
>> one after another into areas (x, y, w, h) and (x+w, y, w, h)
>> accordingly in different ways.
>>
>> The shape is constructed from the following parts:
>> 1. Fill clip area
>> - set clip (x, y, w, h)
>> - fill the whole image
>> As a result only clipped area is filled.
>>
>> 2. Fill rect
>> - fill rect(x, y, w, h) // big rect
>> - fill rect(x+1, y+1, w-2, h-2) // small rect
>>
>> 3. Draw center lines
>> - draw line (x, cy, x + w, cy)
>> - draw line (cx, y, cx, y + h)
>>
>> The program has the following options:
>> RECT - draw two shapes one after another from point (0, 0)
>> SHIFTED_RECT - draw two shapes one after another from point (x, y)
>> BACKBUFFER - draw the shape into a backbuffer with size (w, h) and
>> draw the backbuffer from the point (x, y)
>> SCALED_BACKBUFFER - draw the shape into a scaled backbuffer with
>> size (ceil(w*scale), ceil(h*scale)) with scaled graphics from point
>> (0, 0) and draw it into the rectangle (x, y, w, h)
>> ENLARGED_SCALED_BACKBUFFER - draw the shape into a scaled backbuffer
>> with size (ceil((x+w)*scale), ceil((y+h)*scale)) with scaled graphics
>> from point (x, y) and draw it into the rectangle (0, 0, x+w, y+h)
>>
>> The resulted images are placed in the directory [2].
>> Directory name "rect-[7,5,10,8]" means that the rectangles (7,5,10,8)
>> was used for the shape drawing.
>> Each screenshot name follows the template "
>> screenshot-N-[x,y,w,h]-TYPE.png" where the type is a program option
>> used for the image generation.
>> Screenshots with suffix "-compare" compares the golden image (shape
>> drawn in to the rectangle (x, y, w, h)) with the generated image. The
>> golden image is on the top left side. The generated image is shown on
>> the right and bottom side.
>>
>> The RepaintManager has an assumption that drawing something in some
>> area (x, y, w, h) or just drawing the same thing into an image with
>> translated graphics g.translate(-x1, -y1) and drawing the image into
>> the area(x, y, w, h) has the the same result.
>>
>> As it is shown on screenshots this statement is not true for floating
>> point scales.
>> For example the same shape drawn from the point (0,0) and (x,y) look
>> differently (see [3] and [4]).
>>
>> The solution could be just to use an enlarged backbuffer with size
>> (x+w, y+h) with scaled graphics, draw the component into the rectangle
>> (x, y, w, h) and draw the backbuffer into the area (0,0, x+w, y+h).
>> Even the scaled enlarged backbuffer is used the results can be differ
>> (see [5] where the rectangle [7, 5, 11, 9] is used. The backbuffer is
>> drawn into bigger size).
>>
>>
>> [1] code samples:
>> http://cr.openjdk.java.net/~alexsch/8162350/code/00/Java2DFPSamples.java
>> [2] dir with screenshots results:
>> http://cr.openjdk.java.net/~alexsch/8162350/results
>> [3] RECT:
>> http://cr.openjdk.java.net/~alexsch/8162350/results/rect-%5b7%2c5%2c10%2c8%5d/screenshot-01-%5b7%2c5%2c10%2c8%5d-rects.png
>> [4] SHIFTED_RECT:
>> http://cr.openjdk.java.net/~alexsch/8162350/results/rect-%5b7%2c5%2c10%2c8%5d/screenshot-02-%5b7%2c5%2c10%2c8%5d-shifted-rects.png
>> [5] ENLARGED_SCALED_BACKBUFFER compare:
>> http://cr.openjdk.java.net/~alexsch/8162350/results/rect-%5b7%2c5%2c11%2c9%5d/screenshot-05-%5b7%2c5%2c11%2c9%5d-enlarged-scaled-backbuffers-compare.png
>>
>> Thanks,
>> Alexandr.
>>
>>>
>>> On 06.10.16 20:07, Alexandr Scherbatiy wrote:
>>>> Hello,
>>>>
>>>> Could you review the fix:
>>>> bug: https://bugs.openjdk.java.net/browse/JDK-8162350
>>>> webrev: http://cr.openjdk.java.net/~alexsch/8162350/webrev.00
>>>>
>>>> The fix uses the solution suggest by Jim in the email:
>>>> http://mail.openjdk.java.net/pipermail/2d-dev/2016-October/007737.html
>>>>
>>>> To draw to a VolatileImage backbuffer its graphics transform is
>>>> set to
>>>> identity and device coordinates are used to set the buffer clip.
>>>> Copying the backbuffer image to the graphics has some problems.
>>>> -------------
>>>> // Since there is no drawImage(img, float x, float y)...
>>>> destination.translate(pixelx1 / scaleX, pixely1 / scaleY)
>>>> destination.drawImage(img, 0, 0)
>>>> -------------
>>>> This code solves the problem for the top left corner of the region.
>>>> All Graphics.drawImage(...) methods scales the image size and it looks
>>>> like ceil(img.getWidth() * scaleX) can be differ from the
>>>> ceil(pixelx1 +
>>>> img.getWidth() * scaleX) - pixelx1 so the right bottom corner of the
>>>> image does not fit the required point.
>>>> There is also a question could a line drawn from one point and then
>>>> from another has a different width in pixels because the graphics scale
>>>> is not integer.
>>>>
>>>> The proposed fix prepares a backbuffer with size [x + w, y + h] in a
>>>> user space and a component is drawn in to the region [pixelx1, pixely1,
>>>> pixely2, pixely2] in the device space.
>>>> After that the necessary clip is set to the graphics and whole image
>>>> is just drawn into it.
>>>>
>>>> The new logic is used only the component graphics configuration is
>>>> scaled the graphics configuration has the same scales. So it possible
>>>> just to copy the backbuffer surface data to the graphics surface data.
>>>> For other cases like for rotated graphics transform it seems it is
>>>> necessary to have more complicated algorithm.
>>>>
>>>> This solves problems with repainted region but there are still
>>>> artifacts with JInternalFrame moving or a component scrolling, This can
>>>> be related to the RepaintManager.copyArea() method which needs to be
>>>> updated in the similar way. I have created an issue on it:
>>>> JDK-8167305 RepaintManager.copyArea() method should be updated for
>>>> floating point UI scale
>>>> https://bugs.openjdk.java.net/browse/JDK-8167305
>>>>
>>>> Thanks,
>>>> Alexandr.
>>>>
>>>
>>>
>>
>
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