RFR: JDK-8294427 - Check boxes and radio buttons have rendering issues on Windows in High DPI env [v12]

[Rajat Mahajan]

On Thu, 8 Jun 2023 00:16:27 GMT, Sergey Bylokhov <serb at openjdk.org> wrote:

>> So, basically for w,h =19 we calculate a DPI of 140 and Dimension d = getPartSize(getTheme(widget, dpi), part, state); at line 172 of ThemeReader.java call returns a part size of 13 x 13 provided by windows as it is closer to DPI=120 (for 125% scaling).
>> While for  w,h =20 we calculate a DPI of 147 and Dimension d = getPartSize(getTheme(widget, dpi), part, state); at line 172 of ThemeReader.java call returns a part size of 20 x 20 provided by windows as it is closer to DPI=144 (for 150% scaling).
>> Thus part size calculated by us and provided by Windows matches and hence we see bigger properly rendered buttons while for the w,h=19 case we have 19x19 , while windows gives 13x13 
>> and hence you see scaled down buttons with bad rendering.
>
> Probably I missed something but I would like to clarify. As you mention above we ask Windows to return the image for the component for some specific size, the Windows may return image of exactly requested size if available or any other size. What we will do if the size is different? In the image above it seems we use it as is, but should we? probably we should rescale it?

So, we ask Windows for the component image based on a particular DPI , not some specific size.
The basic premise here is that we expect Windows returning image that would match the DPI , and then we perform our calculations accordingly. In the case above (if Region.clipRound is used) that basic premise is not met (if w, h=19) due to us calculating a DPI value of 140 which is closer to 120 or 125% scaling while our scaling is acytually 150% and Windows returns us a smaller size of the component than expected.
So we don't need to add extra code to rescale , I believe.
If we provide windows with correctly calculated DPI value which my code change does it should work fine as Windows will give us image of the correct size.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13701#discussion_r1222316115