<AWT Dev> [OpenJDK 2D-Dev] [8] Review request for 8011059 [macosx] Make JDK demos look perfect on retina displays

Sergey Bylokhov Sergey.Bylokhov at oracle.com
Wed Nov 6 15:09:54 PST 2013

Hi , Jim.
On 07.11.2013 1:40, Jim Graham wrote:
> On 11/6/13 5:19 AM, Alexander Scherbatiy wrote:
>> On 11/6/2013 5:39 AM, Jim Graham wrote:
>>> Why is getScaledInstance() being consulted here?  It seems a misuse of
>>> that method.
>>      We need to introduce a new API that allows developers to return
>> scaled images for HiDPI displays.
> Then we should introduce new API.
Well during draw of the image we should request appropriate scale image 
from the user, who possible know better how its image can be scaled.
What can be better, than a method which "Creates a scaled version of 
this image."?
>>      The good way is to allow a user to override a method like
>> getScaledImage() which has either scaledFactor or width and height
>> parameters and returns necessary scaled images.
> If that is a new API with new semantics, then I agree.
>>      But the  getScaledImage(width, height) method looks similar to the
>> getScaledInstance(width, height, hints). It also can confuse a user
>> which method should be overridden to return
>>      the scaled version of an image.
> A better name would help.  I don't think width/height are really the 
> best parameters for such a method since you want an image that can be 
> substituted and the original image has already established an aspect 
> ratio.  A single resolution would have been preferable.
But it can be used independently, if the graphics is scaled in one 
direction. And to allow the user to decide how to scale the picture 
depending on how it will be expanded. And there is no direct 
relationship with retina and its scale factor.

We can move deeper and request here the actual size of the image 
including transform of the graphics (<=TRANSFORM_TRANSLATESCALE). So the 
user can apply IMAGE_SCALING hint to the transformed sg2d and all images 
will have a chance to use custom scale instead of  some scaling from the 
> And there are 10 years of potential overrides that developers could 
> have created that could be even worse than the default implementation 
> from a performance perspective.  "Whether or not the method is 
> overridden" is a bad heuristic from the get go and it is much, much 
> more inappropriate to apply to a legacy method that has been in the 
> wild for over a decade. 
If user overrides this method and provides some specific scale algorithm 
is not what we want from the beginning?
"Whether or not the method is overridden" come in to play because 
default scale operation in SG2D and the results of default 
implementation of getScaledInstance is quite similar, but performance is 
extremely different.
So it can be rephrased as "Whether or not the default scale algorithm is 
use", so in the fix we use default from the S2G2 not Image.
> The suggestion to add a new hint to a decade old API is unwise. 
> Additionally, the hint requested "SCALE_CUSTOM" could mean anything 
> and is documented so loosely that resolution swapping is only one of 
> an infinite number of responses an application could make.  The spec 
> of that hint also violates the contract of the getScaledInstance() 
> method which states that the returned instance will be of the 
> requested size, but you are planning on returning an image that can 
> have a different size.
It return the image which is rendered to appropriate width and height by 
default. It is not necessary to be always the same sized image. Moreover 
it can be a different size image in case of negative width/height.
This hint will be enabled on the retina device by default, but can be 
enabled by the user as well for any graphics

In general an idea of the fix is: The image know better how it could be 
  - It could use some pixel replicate scale filters
  - it could use different files images
  - it could redraw itself from scratch if it use vectors graphics.
The only parameters it needed is width and height.

The CUSTOM hint is used for two reasons
  - to use default scale from graphics and to skip default in image
  - to explicitly document new usage of getScaledInstance().

And additionally about compatibility you can compare this version of the 
fix and version of jdk7(where demos was rewritten). If I understand it 
correctly nothing should be changed in demos in the current version of 
the fix(except new x2 images.)

>             ...jim
>>> The @2x mechanism should be based on different API.  I guess it would
>>> have to be internal-only for 8.0 and could be exposed to allow
>>> developers to call it and possibly to be a provider for it in JDK9...
>>>             ...jim
>>> On 10/31/13 9:19 AM, Alexander Scherbatiy wrote:
>>>>   Could you review the updated fix:
>>>> http://cr.openjdk.java.net/~alexsch/8011059/webrev.04/
>>>>     The reflection is used to skip the Image.getScaledInstance() 
>>>> method
>>>> call if it is not overridden by a user.
>>>> On 10/29/2013 11:08 PM, Sergey Bylokhov wrote:
>>>>> Hi, Alexander.
>>>>> The fix looks fine to me in general. But there is at least one issue.
>>>>> I build you fix and test it:
>>>>>  - Consuming of cpu increased by 500 times Java2Demo on images tab.
>>>>>  - FPS is dropped from 220(jdk8)/35(jdk7u40) to 15 in guimark2. Note
>>>>> that jdk6 has the same FPS(15) on my system.
>>>>     The main problem is that the Image.SCALE_DEFAULT hint is used to
>>>> retrieve a scaled image from Image.getScaledInstance() method.
>>>>     It always uses the ReplicateScaleFilter for images which
>>>> getScaledInstance() method has not been overridden.
>>>>     The ReplicateScaleFilter creates a lot of arrays and consumes the
>>>> CPU during the image parsing.
>>>>     The better fix would be to introduce the new Image.SCALE_CUSTOM 
>>>> hint
>>>> which could be used to get a scaled image and does not use filters by
>>>> default.
>>>>     But it should be a separated bug with a new CCC request.
>>>>    Thanks,
>>>>    Alexandr.
>>>>> On 29.10.2013 20:45, Alexander Scherbatiy wrote:
>>>>>>   Could you review the updated fix:
>>>>>> http://cr.openjdk.java.net/~alexsch/8011059/webrev.03
>>>>>> On 10/28/2013 2:33 PM, Artem Ananiev wrote:
>>>>>>> Hi, Alexander,
>>>>>>> a few comments:
>>>>>>> 1. SunGraphics2D.java:3076 - should isHiDPIImage() be used here?
>>>>>>      The isHiDPIImage() method is used to check that the
>>>>>> drawHiDPIImage should be called like:
>>>>>>         if (isHiDPIImage(img)) {
>>>>>>             return drawHiDPIImage(...);
>>>>>>         }
>>>>>>> 2. I'm not sure that the proposed getScaledImageName()
>>>>>>> implementation in ScalableToolkitImage works perfectly for URLs 
>>>>>>> like
>>>>>>> this:
>>>>>>> http://www.exampmle.com/dir/image
>>>>>>> In this case it will try to find 2x image here:
>>>>>>> http://www.example@2x.com/dir/image
>>>>>>> which doesn't look correct.
>>>>>>        Fixed. Only path part of a URL is converted to path2x.
>>>>>>> 3. RenderingHints spec references Retina or non-Retina displays,
>>>>>>> which should be removed.
>>>>>>        Fixed.
>>>>>>     - devScale is used instead of transform parsing in the
>>>>>> drawHiDPIImage() method just to not have performance regression more
>>>>>> than 2 times on HiDPI displays
>>>>>>     - LWCToolkit.ScalableToolkitImage is made public for the fix
>>>>>> 8024926 [macosx] AquaIcon HiDPI support.
>>>>>>     Thanks,
>>>>>>     Alexandr.
>>>>>>> Thanks,
>>>>>>> Artem
>>>>>>> On 10/25/2013 5:18 PM, Alexander Scherbatiy wrote:
>>>>>>>>    Could you review the updated fix:
>>>>>>>> http://cr.openjdk.java.net/~alexsch/8011059/webrev.02/
>>>>>>>>    - Scaled image width and height are transformed according to 
>>>>>>>> the
>>>>>>>> AffineTransform type.
>>>>>>>>    - ToolkitImage subclass is used to hold @2x image instance.
>>>>>>>>   Thanks,
>>>>>>>>   Alexandr.
>>>>>>>> On 10/23/2013 7:24 PM, Alexander Scherbatiy wrote:
>>>>>>>>>   Could you review the updated fix:
>>>>>>>>> http://cr.openjdk.java.net/~alexsch/8011059/webrev.01/
>>>>>>>>>   The JCK failures has been resolved:
>>>>>>>>>     - Some tests tries to draw an image with Integer.MAX_VALUE
>>>>>>>>> width
>>>>>>>>> or height. Passing large values to image.getScaledImage(width,
>>>>>>>>> height,
>>>>>>>>> hints).
>>>>>>>>>        leads that an Image filter is not able to create necessary
>>>>>>>>> arrays.  The fix uses the original image if width or height are
>>>>>>>>> equal
>>>>>>>>> to Integer.MAX_VALUE.
>>>>>>>>>     - Using Image.SCALE_DEFAULT hint for the 
>>>>>>>>> getScaledImage(width,
>>>>>>>>> height, hints) method to get the high resolution image interferes
>>>>>>>>> with
>>>>>>>>>        JCK tests that expect that the scaled image by certain
>>>>>>>>> algorithm is returned. This is fixed by invoking the
>>>>>>>>> super.getScaledImage(width, height, hints)
>>>>>>>>>        method in ToolkitImage in case if a high resolution 
>>>>>>>>> image is
>>>>>>>>> not set.
>>>>>>>>>     Thanks,
>>>>>>>>>     Alexandr.
>>>>>>>>> On 10/22/2013 1:31 PM, Alexander Scherbatiy wrote:
>>>>>>>>>> Hello,
>>>>>>>>>> Could you review the fix:
>>>>>>>>>>   bug: https://bugs.openjdk.java.net/browse/JDK-8011059
>>>>>>>>>>   webrev: http://cr.openjdk.java.net/~alexsch/8011059/webrev.00
>>>>>>>>>>   The IMAGE_SCALING rendering hint is added to the 
>>>>>>>>>> RenderingHints
>>>>>>>>>> class.
>>>>>>>>>>   Enabling the image scaling rendering hint forces the
>>>>>>>>>> SunGraphics2D
>>>>>>>>>> to use getScaledInstance(width, height, hints) method
>>>>>>>>>>   from Image class with SCALE_DEFAULT hint.
>>>>>>>>>>   By default the image scaling rendering hint is enabled on 
>>>>>>>>>> HiDPI
>>>>>>>>>> display and disabled for standard displays.
>>>>>>>>>>   User can override the getScaledInstance(width, height, hints)
>>>>>>>>>> method and return necessary high resolution image
>>>>>>>>>>   according to the given image width and height.
>>>>>>>>>>   For example:
>>>>>>>>>>   ---------------------
>>>>>>>>>>         final Image highResolutionImage =
>>>>>>>>>>                 new BufferedImage(2 * WIDTH, 2 * HEIGHT,
>>>>>>>>>> BufferedImage.TYPE_INT_RGB);
>>>>>>>>>>         Image image = new BufferedImage(WIDTH, HEIGHT,
>>>>>>>>>> BufferedImage.TYPE_INT_RGB) {
>>>>>>>>>>             @Override
>>>>>>>>>>             public Image getScaledInstance(int width, int 
>>>>>>>>>> height,
>>>>>>>>>> int
>>>>>>>>>> hints) {
>>>>>>>>>>                 if ((hints & Image.SCALE_DEFAULT) != 0) {
>>>>>>>>>>                     return (width <= WIDTH && height <= HEIGHT)
>>>>>>>>>>                             ? this : highResolutionImage;
>>>>>>>>>>                 }
>>>>>>>>>>                 return super.getScaledInstance(width, height,
>>>>>>>>>> hints);
>>>>>>>>>>             }
>>>>>>>>>>         };
>>>>>>>>>>   ---------------------
>>>>>>>>>>   The LWCToolkit and ToolkitImage classes are patched to
>>>>>>>>>> automatically get provided image at 2x.ext images on MacOSX.
>>>>>>>>>>   There are no significant changes in the Java2D demo to make it
>>>>>>>>>> look
>>>>>>>>>> perfect on Retina displays.
>>>>>>>>>>   It needs only to put necessary images with the @2x postfix and
>>>>>>>>>> they
>>>>>>>>>> will be automatically drawn.
>>>>>>>>>> Thanks,
>>>>>>>>>> Alexandr.

Best regards, Sergey.

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