<Swing Dev> <AWT Dev> [9] Review Request: JDK-8029455 JLightweightFrame: support scaled painting

Wed Dec 11 19:14:01 UTC 2013

Hi Anton,

On 12/11/2013 02:40 PM, Anton V. Tarasov wrote:
>> 2. I'm not sure if adding the scale field to the BI is a good idea. I
>> think that the image shouldn't be aware of any scale. After all, it's
>> just an image, a bitmap. It has its real dimensions corresponding to
>> the actual size of the image stored in RAM. Whether this image is
>> going to be represented as a scaled image is something that a code
>> that uses the image should be concerned with, not the image itself.
>
> There are two options. 1) Follow to your logic, that is to fix every
> place in AWT/Swing where BufferedImage is created. In which case in
> every such place we will have to get a current scale factor from the
> context. 2) Don't touch that code, but solve the task in some generic
> way, the way I tried to implement, when a buffered image is created with
> an extended size right in the factory methods.
>
> The logic of the first approach is simpler. However, it would require
> lots of modifications (in the L&F code, and not only there). And it
> would require to take into account the scale factor every time a new
> buffered image case is added to the code. Still, this is possible.
>
> With the scond approach I don't need to bother about that code, I just
> create scaled images "on the fly".
>
>  > I think that the image shouldn't be aware of any scale.
>
> The "scale" field put into the BufferedImage class means that an image
> instance should (or shouldn't) be treated as a HiDPI image by the
> Graphics.drawImage(). So, this is a kind of a special "scale" case,
> aimed at supporting Retina technology. Probably it deserves a better
> name, "hidpiScale" or something. So, it's not that the image has been
> scaled by the user to be drawn on a lager area, but that the image
> should (or shouldn't) be scaled just to "look smoothly" on a Retina
> display. That's what I was thinking about...

Thanks for the clarification. The idea sounds reasonable indeed.

I've also read your reply to Jim and I'm now concerned about the fact 
that scaled images can report larger dimensions than a Graphics created 
for them would allow one to draw to them. This may be a problem for some 
apps that perform rendering based on the dimensions of a BI object 
passed to them.

Shouldn't the BI.getWidth/Height() methods always report the logical 
size of the image, which is equal to the physical one for scale == 1?

--
best regards,
Anthony

>
>>
>>
>>
>> 3. src/share/classes/java/awt/peer/FramePeer.java
>>>  139     default void notifyScaleFactorChanged() {}
>>
>> I think this deserves to be declared in WindowPeer so that we could
>> use it w/o additional modifications in the future if we add support
>> for public notifications about the scale factor changes.
>
> Ok.
>
>>
>>
>> 4. I'm CC'ing swing-dev@ and Alexander Scherbatiy to review changes in
>> the JViewport class and other Swing classes.
>
> Thanks for the review!
>
> Anton.
>
>>
>> --
>> best regards,
>> Anthony
>>
>> On 12/10/2013 06:22 PM, Anton V. Tarasov wrote:
>>> Hi Jim, Sergey and All,
>>>
>>> Please review the fix that adds support of Retina displays to
>>> JLightweightFrame (which javafx SwingNode is based on).
>>>
>>> webrev: http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1
>>> jira: https://bugs.openjdk.java.net/browse/JDK-8029455
>>>
>>> (After the fix goes into jdk9 it should be ported to 8u20 as well,
>>> because the functionality is essential for SwingNode.)
>>>
>>> The general idea of the fix is as follows.
>>>
>>> A BufferedImage instance, being created in the context in which the
>>> scale factor is determined and is different from one, is automatically
>>> created with appropriately extended size. The image itself becomes a
>>> scaled image (a "scale" private field is set on it). By the "context" I
>>> mean the circumstances where the BufferedImage is related to a
>>> JLightweightFrame, a GraphicsConfiguration, a SurfaceData, or a
>>> GraphicsDevice which determine the scale factor.
>>>
>>> Here are the related changes:
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/java/awt/image/BufferedImage.java.udiff.html
>>>
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/sun/awt/image/OffScreenImage.java.udiff.html
>>>
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/sun/swing/JLightweightFrame.java.udiff.html
>>>
>>> (the resizeBuffer method)
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/macosx/classes/sun/lwawt/LWLightweightFramePeer.java.udiff.html
>>>
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/sun/awt/image/BufferedImageGraphicsConfig.java.udiff.html
>>>
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/macosx/classes/sun/java2d/opengl/CGLGraphicsConfig.java.udiff.html
>>>
>>>
>>>
>>> The "scale" value of a BufferedImage is used when 1)
>>> BufferedImageGraphicsConfig is created 2)
>>> BufImgSurfaceData.getDefaultScale() is called:
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/sun/awt/image/BufferedImageGraphicsConfig.java.udiff.html
>>>
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/sun/awt/image/BufImgSurfaceData.java.udiff.html
>>>
>>>
>>>
>>> The former is used in the GraphicsConfiguration.createCompatibleImage()
>>> calls, and the latter is used in SurfaceManager.getImageScale(Image):
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/sun/awt/image/SurfaceManager.java.udiff.html
>>>
>>>
>>>
>>> A scaled BufferedImage is supported by the SunGraphics2D.drawImage()
>>> primitives. Here's the pattern of how the image may be created and
>>> drawn:
>>>
>>> int scale = <get the scale factor from the context>;
>>> BufferedImage img = new BufferedImage(width * scale, height * scale,
>>> ...);
>>> img.setScale(scale); // an accessor is currently used instead
>>> <...>
>>> g2d.drawImage(img, x, y, ...); // 1) draw the image with auto-scale
>>> g2d.drawImage(img, x, y, dw, dh, ...) // 2) draw the image into a
>>> specified rect
>>>
>>> In the first case, if the BufferedImage is created with an extended
>>> size, the "scale" value of the image matters, it should be drawn as a
>>> HiDPI image.
>>> In the second case, if the BufferedImage is created with an extended
>>> size, the "scale" value of the image doesn't matter (it may not be
>>> evidently set) as the image will anyway be scaled from its physical
>>> bounds into provided logical bounds. This all should (as I suppose)
>>> provide backward compatibility for buffered images that were created in
>>> their logical bounds or without setting the "scale" field. For instance,
>>> the AquaPainter.paintFromSingleCachedImage(...) method creates & draws
>>> an image as follows:
>>>
>>> int scale = ((SunGraphics2D) g).surfaceData.getDefaultScale();
>>> int imgW = bounds.width * scale;
>>> int imgH = bounds.height * scale;
>>> BufferedImage img = new BufferedImage(imgW, imgH, ...);
>>> <paint into the img>
>>> g.drawImage(img, bounds.x, bounds.y, bounds.width, bounds.height, null);
>>>
>>> Here, the img.scale value is not set (I didn't modify this code), and
>>> SunGraphics2D doesn't treat the image as a HiDPI image, however it is
>>> drawn as expected. An alternative way to draw the image would be:
>>>
>>> int scale = ((SunGraphics2D) g).surfaceData.getDefaultScale();
>>> int imgW = bounds.width * scale;
>>> int imgH = bounds.height * scale;
>>> BufferedImage img = new BufferedImage(imgW, imgH, ...);
>>> img.setScale(scale);
>>> <paint into the img>
>>> g.drawImage(img, bounds.x, bounds.y, ...);
>>>
>>> The result would be the same.
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/sun/java2d/SunGraphics2D.java.sdiff.html
>>>
>>>
>>>
>>> The following changes:
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/macosx/classes/sun/lwawt/macosx/CPlatformLWView.java.udiff.html
>>>
>>>
>>>
>>> are defined by this logic. Running Swing via JLightweightFrame (JLF)
>>> makes it "display agnostic". Swing is painted to an off-screen buffer
>>> and it's the host (e.g. SwingNode) that renders the buffer on a
>>> particular device. So, the host should detect the scale of the current
>>> display and set it on JLF.
>>>
>>> However, AWT in order to paint to a volatile image requires
>>> CGraphicsDevice and CGLSurfaceData to be created. By default AWT creates
>>> CGraphicsDevice instances matching all the detected display devices
>>> (CGraphicsEnvironment.initDevices()). But, as JLF doesn't have any
>>> platform window behind it, AWT can't match JLF to the exact device it's
>>> currently displayed on. So, on the one hand, AWT doesn't know which
>>> device is current and what is the current scale (the host passes this
>>> value), but from the other hand, AWT has a list of all the
>>> CGraphicsDevice instances.
>>>
>>> I tried to leverage from that fact. The
>>> CPlatformLWView.getGraphicsDevice() method takes the current scale from
>>> the JLF instance, and then tries to match it to an existent device from
>>> the list. In case it can't find a device with the specified scale (which
>>> should not actually happen, unless the host passes an arbitrary scale
>>> value, which is not the case for SwingNode) it takes a default device
>>> and changes its scale forcedly. I'm not sure if I should create a new
>>> dummy device instance instead. The scale factor of the device (which is
>>> then propagated to CGLSurfaceData on its creation) is the only info that
>>> JLF will take from the device to create a scaled volatile image.
>>>
>>> The following changes:
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/javax/swing/JViewport.java.udiff.html
>>>
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/javax/swing/RepaintManager.java.udiff.html
>>>
>>>
>>>
>>> were made to map a backing store image to a scale factor.
>>>
>>> The JViewPort.paint(...) method calls SunGraphics2D.copyArea(...) on
>>> scrolling. The method was not implemented for a graphics with a scale
>>> transform and a BufImgSurfaceData (it threw exceptions). I took that
>>> code, copied it to the BufImgSurfaceData.copyArea(...) and added a
>>> general translation for the coords:
>>>
>>> -
>>> http://cr.openjdk.java.net/~ant/JDK-8029455/webrev.1/src/share/classes/sun/awt/image/BufImgSurfaceData.java.udiff.html
>>>
>>>
>>>
>>> It works, but I'm not sure the implementation is eligible (I don't know
>>> the details of the Blit class, at least it warns not to use the same
>>> source and dest).
>>>
>>> The rest of the changes (not covered here) should be clear.
>>>
>>> Testing:
>>>
>>> - Using jfc/SwingSet2 and jfc/Java2D demos (in a standalone mode &
>>> embedded into SwingNode [1]).
>>> - Testing both Nimbus and Aqua L&F.
>>> - Setting swing.volatileImageBufferEnabled=false/true for all
>>> combinations.
>>>
>>> Currently, I see no regressions and no visual issues comparing a
>>> standalone mode and a SwingSet mode.
>>>
>>> At the end, I suspect there may be some intersection b/w this fix and
>>> the fix which introduced MultiResolutionToolkitImage. Unfortunately, I
>>> didn't yet read that review saga... Please tell me if I should
>>> incorporate anything from that fix.
>>>
>>> Thanks,
>>> Anton.
>>>
>>> [1] There's a SwingSet part of the fix which I'm going to post to the
>>> jfx alias separately.
>>>
>