TitleBar buttons are scaled very small at a resolution of 4K (288 DPI)

Description

WPF Gallery Preview close button doesn’t have corners, the close button will be displayed as shown in the screenshot at a resolution of 3840 * 2160 (Set display scaling to 300% which results in 288 DPI).

Another issue is that the minimize, maximize, and close buttons are scaled very small (It also exists in Win32 and WinForms applications) at a resolution of 3840 * 2160 (300% scaling -> 288 DPI).

Actual behavior

Expected behavior

Reproduction Steps

Launch WPF Gallery Preview, change display resolution to 3840 * 2160, and set display scaling to 300% which results in 288 DPI.

Without using WPF Fluent theme

By the way, even without using WPF Fluent theme (.net 9), the TitleBar buttons are still scaled very small (It also exists in Win32 and WinForms applications) at a resolution of 3840 * 2160 (300% scaling -> 288 DPI). Can this problem be solved?

From the left: WPF, WinForms, Win32 (All small buttons) & WinUI 3 (Normal buttons):

Below are the test screenshots for 336 DPI (Small buttons) and 216 DPI (Normal buttons) configurations.

350% scaling -> 336 DPI: Windows Explorer (Left) & Microsoft Store (Right)

225% scaling -> 216 DPI: Windows Explorer (Left) & Microsoft Store (Right)

Start by reproducing the WPF Gallery Preview at 3840×2160 with 300% scaling (288 DPI), then compare the title-bar and close-button rendering with the expected screenshots. Done means the buttons are no longer unusually small and the close button has the expected corners; the issue does not name a file or test to inspect.