RFR: 8211294: ScrollPane content is blurry with 125% scaling

[Frederic Thevenet]

On Thu, 17 Dec 2020 23:43:39 GMT, Kevin Rushforth <kcr at openjdk.org> wrote:

>> Your latest patch looks exactly like what I would expect. I need to do some multi-screen testing on Windows with different scale factors.
>> 
>>> ... the repaint for the affected Region does not seem to occur right away on moving the window to another screen, but only once the Region is interacted with (e.g. hovering the mouse over it).
>> 
>> This seems like a different (and preexisting) bug then. I think we're up to three follow-on issues if I haven't lost track:
>> 
>> 1. Rendering a cached node doesn't match rendering it directly even when the transform is unchanged.
>> 2. TextFlow: methods copied from Region have not picked up subsequent changes in those methods
>> 3. Need to Render and layout scene out when scale changes (either when moving to a screen with a different scale or when the scale changes as the result of changing the setting of the current screen)
>
> I did some testing with your latest patch, and I don't see any problem when dragging a window between screens with different scales. It seems to be recalculating the cached insets and using them in layout as I would expect. Do you have a test case that shows the problem?

Unfortunately I've only seen it within an application with a fairly complex scene graph, which make isolating the issue  tricky. 

I'm still trying to reproduce it a minimal sample, but in the mean time, please have a look at the a screen capture below, which should at least help clarify the issue I'm observing:

![8211294](https://user-images.githubusercontent.com/7450507/102610169-064d6000-412d-11eb-8ebd-b1999a6c6009.gif)

This snippet is captured after the window had been moved from a screen scaled to 100% to a second one scaled to 150%; notice how the controls in the "Chart Properties" pane only snap to pixel when the mouse pointer enters the pane.

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PR: https://git.openjdk.java.net/jfx/pull/308