Starting an app with WindowState::Maximized doesn't work quite right on macOS

[JarrettBillingsley]

I'm on macOS 10.15.5 and using the git version of Druid (post-0.7.0).

After posting a topic and repro on Zulip, we discovered that this code properly creates a maximized window on Windows, but not on macOS. The issue is that the window is maximized, but the widget layout is not. It still thinks the window is like 400x300 pixels or something. If I then resize the window, the layout corrects itself.

use druid::*;
use druid::widget::*;

#[derive(Clone, Data, Lens)]
struct AppState {}

impl Default for AppState {
    fn default() -> Self {
        Self {}
    }
}

fn build_ui() -> impl Widget<AppState> {
    Split::columns(Label::new("Split A"), Label::new("Split B"))
    .split_point(0.5)
    .draggable(true)
    .solid_bar(true)
    .min_size(250.0, 600.0)
}

fn main() -> Result<(), PlatformError> {
    AppLauncher::with_window(
        WindowDesc::new(build_ui())
        .set_window_state(WindowState::Maximized)
    )
    .launch(AppState::default())
}

Screenshot of what it looks like:

[JarrettBillingsley]

The problem is here:

druid/druid-shell/src/platform/mac/window.rs

Lines 289 to 301 in e60b2ab

	if let Some(window_state) = self.window_state {
	handle.set_window_state(window_state);
	}
	if let Some(level) = self.level {
	handle.set_level(level)
	}
	(*view_state).handler.connect(&handle.clone().into());
	(*view_state).handler.scale(Scale::default());
	(*view_state)
	.handler
	.size(Size::new(frame.size.width, frame.size.height));

On line 290, it correctly calls set_window_state which maximizes the window. But then on line 299, it calls size using frame.size which is now out of sync with the real window size.

I added the first two lines - and sorry if this is absolutely the wrong way to do it, I'm not at all familiar with how mac OS windowing works - and it worked. The first layout call now sees the correct maximized window size.

            // set_window_state above could have invalidated the frame size
            let frame = NSView::frame(content_view);

            (*view_state).handler.connect(&handle.clone().into());
            (*view_state).handler.scale(Scale::default());
            (*view_state)
                .handler
                .size(Size::new(frame.size.width, frame.size.height));

[cmyr]

yep this looks good to me, feel free to PR if you want!