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

[Jim Graham]

Hi Mike,

One more question about @2x handling on MacOS.

Clearly, in the simple case of someone loading an ordinary "foo.png" and 
painting it on a retina display without doing anything special with the 
transform, it will be scaled up by 2x to retain proper size.

Also, clearly, if a "foo at 2x.png" file exists, it will be loaded 
automatically and found to be twice as large and displayed with no 
scaling so that it is the same "size".

But, what if in the first step they manually specified the image file 
name as "foo at 2x.png" (and assuming there is no "foo at 2x@2x.png")?  Will 
it display with its pixels scaled up to double sized because it was the 
direct image that they specified?  Or, does the system recognize that it 
came from a file named @2x and assume that it is a 
double-screen-resolution image and paint it the same way it would have 
done if it was implicitly loaded as the higher resolution variant of 
"foo.png"?

Let me spell out the scenarios:

Scenario 1:
- app is retina-enabled
- app has WxH foo.png media (and no @2x versions)
- app loads image from "foo.png"
- app displays image with standard default scaling on a retina screen
=> result is image takes up 2W x 2H pixels on the retina screen

Scenario 2:
- app is retina-enabled
- app has WxH foo.png media
- app also has 2W x 2H foo at 2x.png media
- app loads image from "foo.png"
- app displays image with standard default scaling on a retina screen
=> result is system also loads foo at 2x.png and displays it with 2W x 2H 
retina pixels on the retina screen - the same physical size as in the 
previous example

Scenario 3:
- app is retina-enabled
- app has WxH foo.png media
- app also has 2W x 2H foo at 2x.png media
- app loads image from "foo at 2x.png" rather than "foo.png"
- app displays image with standard default scaling on a retina screen
=> result is ???
=> I'm guessing that it gets drawn twice the size as Scenario's 1 and 2 
because it is no longer relative to the WxH base image?

Scenario 4:
same as Scenario 3, but foo.png doesn't exist, foo at 2x.png is the only 
version found in the media for the app
=> result is ???
=> I'm guessing the result is the same as Scenario 3

Also, the convention is for the @2x image to be twice the pixel size of 
the regular image, but what if it isn't?  Is it always drawn at a 0.5x 
relative scale because of the implication of the @2x file name, or will 
it be dynamically sized for "basew/@2xw, baseh/@2xh" which just usually 
works out to 0.5x if the author followed conventions?

			...jim