X11: Write WM_NORMAL_HINTS in a single call

[emezeske]

On Linux a window does not open where JUCE puts it. A DialogWindow launched with componentToCentreAround set, which should appear centred on its owner, instead opens at the centre of the screen under mutter or in a bottom corner under openbox, wherever the window manager's own placement policy decides to put it. The same property is also responsible for windows being resizable below their constrainer minimum.

To reproduce, run any JUCE app on Xorg under a window manager that has a placement policy (mutter and openbox both do), move its main window well off the centre of the display, and open a dialog through DialogWindow::LaunchOptions with componentToCentreAround pointing at a component in that window. The dialog lands somewhere unrelated to its owner. Nothing in JUCE reports anything wrong, because the peer's own idea of its bounds stays correct right up until the window manager's ConfigureNotify arrives and overwrites it. Reading WM_NORMAL_HINTS off the dialog (xprop -id) shows the size limits and no user position at all.

The cause is that XSetWMNormalHints replaces the whole property, and the X11 peer writes that property from two places: setBounds writes USSize and USPosition, and updateConstraints writes PMinSize and PMaxSize. Whichever runs second wipes the other one's fields, so a window never carries both. Without the constraints the window manager may resize the window below its minimum; without USPosition it may ignore the requested geometry entirely. Reordering the two writes only trades one symptom for the other.

This fills both halves into a single XSizeHints and writes it once, in updateSizeHints. updateWindowBounds now calls that after refreshing the bounds and the scale factor rather than before, since the hints restate the geometry it has just read back. The commit also clamps the constrainer limits before scaling them, since constrainers commonly use the maximum int value to mean unbounded and for scale factors above 1.0 the conversion back to int is undefined behaviour that advertises garbage maximum sizes.

Tested on Xorg under both mutter and openbox, with a dialog centred on its owner window: before the change the manager placed it by its own policy in both, after it the window lands where it was asked to.