[Windows] Set the cursor icon when the cursor first enters a window

[maroider]

• Tested on all platforms changed
• Compilation warnings were addressed
• cargo fmt has been run on this branch
• cargo doc builds successfully
• Added an entry to CHANGELOG.md if knowledge of this change could be valuable to users
• Updated documentation to reflect any user-facing changes, including notes of platform-specific behavior
• Created or updated an example program if it would help users understand this functionality
• Updated feature matrix, if new features were added or implemented

I'm not sure if this is the best way to address #1682 since I'm not familiar with how Windows handles cursors WRT windows, and I plan on looking further into this before converting from a draft PR to a normal PR.

Fixes #1682

[maroider]

It turns out that the first attempt at a fix made it so the "resize" cursor icons never appeared when hovering the cursor over the window borders.

[maroider]

It turns out that WM_SETCURSOR arrives with hit-test results in the low-order "word" of lParam, so we can use that instead of relying on other messages.

I'm mildly concerned about ordering guarantees here (if any such thing exists for this case), since users may want to set a cursor and have it applied immediately when the cursor enters the window. It may actually be fine in practice, but I don't know for sure.

[msiglreith]

Thanks!

[msiglreith]

(lparam & 0xFFFF) -> LOWORD(lparam)
Also, wrapping the condition into a separate let statement and/or short command regarding hit-testing here would be great

[maroider]

command

I assume you meant to write "comment" here.

[maroider]

Never mind that push. I trusted rust-analyzer a bit too much while I simultaneously did something rust-analyzer didn't support.