RFR: 8372415: Stage size should match visual window bounds

[Michael Strauß]

On Tue, 2 Dec 2025 19:01:11 GMT, Martin Fox <mfox at openjdk.org> wrote:

> I haven't uncovered any problems so far but it took me a while to get my bearings. You're working with two coordinate systems, the one used by JavaFX which doesn't include the invisible border and the one used by Windows which does. The naming convention is confusing since the "extended" rectangle is actually the smaller of the two. It would also be good to see some comments clarifying that `m_insets`, `m_maxSize`, and `m_minSize` are all specified in the JavaFX system.

I don’t think it’s quite "two coordinate systems" (JavaFX vs Windows). `Stage.width/height` are intended to include the normal system decorations (title bar + borders), which historically also matches what people mean by "window size": it includes the non-client area, but not purely visual effects like drop shadows. The weirdness on Windows 10+ is that GetWindowRect started including an extra invisible resize border that’s not part of the visible frame, so the window ends up being reported a few pixels larger than it looks. Using `DwmGetWindowAttribute(DWMA_EXTENDED_FRAME_BOUNDS)` is basically a way to get the visually perceived bounds back.

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PR Comment: https://git.openjdk.org/jfx/pull/1982#issuecomment-3603720855