On Windows, make AdjustRect calls DPI-aware when possible (#1015)

* Use AdjustWidowRectExForDPI when available

* Prioritize presevering logical size when handling WM_DPICHANGED

* Format

* Add changelog entry

src/platform_impl/windows/util.rs

@@ -6,51 +6,22 @@ use std::{
     sync::atomic::{AtomicBool, Ordering},
 };
 
-use crate::window::CursorIcon;
+use crate::{dpi::PhysicalSize, window::CursorIcon};
 use winapi::{
     ctypes::wchar_t,
     shared::{
-        minwindef::{BOOL, DWORD},
-        windef::{HWND, RECT},
+        minwindef::{BOOL, DWORD, UINT},
+        windef::{DPI_AWARENESS_CONTEXT, HMONITOR, HWND, LPRECT, RECT},
     },
     um::{
         libloaderapi::{GetProcAddress, LoadLibraryA},
+        shellscalingapi::{MONITOR_DPI_TYPE, PROCESS_DPI_AWARENESS},
         winbase::lstrlenW,
-        winnt::LPCSTR,
+        winnt::{HRESULT, LONG, LPCSTR},
         winuser,
     },
 };
 
-// Helper function to dynamically load function pointer.
-// `library` and `function` must be zero-terminated.
-pub(super) fn get_function_impl(library: &str, function: &str) -> Option<*const c_void> {
-    assert_eq!(library.chars().last(), Some('\0'));
-    assert_eq!(function.chars().last(), Some('\0'));
-
-    // Library names we will use are ASCII so we can use the A version to avoid string conversion.
-    let module = unsafe { LoadLibraryA(library.as_ptr() as LPCSTR) };
-    if module.is_null() {
-        return None;
-    }
-
-    let function_ptr = unsafe { GetProcAddress(module, function.as_ptr() as LPCSTR) };
-    if function_ptr.is_null() {
-        return None;
-    }
-
-    Some(function_ptr as _)
-}
-
-macro_rules! get_function {
-    ($lib:expr, $func:ident) => {
-        crate::platform_impl::platform::util::get_function_impl(
-            concat!($lib, '\0'),
-            concat!(stringify!($func), '\0'),
-        )
-        .map(|f| unsafe { std::mem::transmute::<*const _, $func>(f) })
-    };
-}
-
 pub fn has_flag<T>(bitset: T, flag: T) -> bool
 where
     T: Copy + PartialEq + BitAnd<T, Output = T>,
@@ -105,6 +76,18 @@ pub fn get_client_rect(hwnd: HWND) -> Result<RECT, io::Error> {
     }
 }
 
+pub fn adjust_size(hwnd: HWND, size: PhysicalSize) -> PhysicalSize {
+    let (width, height): (u32, u32) = size.into();
+    let rect = RECT {
+        left: 0,
+        right: width as LONG,
+        top: 0,
+        bottom: height as LONG,
+    };
+    let rect = adjust_window_rect(hwnd, rect).unwrap_or(rect);
+    PhysicalSize::new((rect.right - rect.left) as _, (rect.bottom - rect.top) as _)
+}
+
 pub fn adjust_window_rect(hwnd: HWND, rect: RECT) -> Option<RECT> {
     unsafe {
         let style = winuser::GetWindowLongW(hwnd, winuser::GWL_STYLE);
@@ -124,7 +107,14 @@ pub fn adjust_window_rect_with_styles(
             *r = rect;
 
             let b_menu = !winuser::GetMenu(hwnd).is_null() as BOOL;
-            winuser::AdjustWindowRectEx(r, style as _, b_menu, style_ex as _)
+            if let (Some(get_dpi_for_window), Some(adjust_window_rect_ex_for_dpi)) =
+                (*GET_DPI_FOR_WINDOW, *ADJUST_WINDOW_RECT_EX_FOR_DPI)
+            {
+                let dpi = get_dpi_for_window(hwnd);
+                adjust_window_rect_ex_for_dpi(r, style as _, b_menu, style_ex as _, dpi)
+            } else {
+                winuser::AdjustWindowRectEx(r, style as _, b_menu, style_ex as _)
+            }
         })
     }
 }
@@ -206,3 +196,71 @@ impl CursorIcon {
         }
     }
 }
+
+// Helper function to dynamically load function pointer.
+// `library` and `function` must be zero-terminated.
+pub(super) fn get_function_impl(library: &str, function: &str) -> Option<*const c_void> {
+    assert_eq!(library.chars().last(), Some('\0'));
+    assert_eq!(function.chars().last(), Some('\0'));
+
+    // Library names we will use are ASCII so we can use the A version to avoid string conversion.
+    let module = unsafe { LoadLibraryA(library.as_ptr() as LPCSTR) };
+    if module.is_null() {
+        return None;
+    }
+
+    let function_ptr = unsafe { GetProcAddress(module, function.as_ptr() as LPCSTR) };
+    if function_ptr.is_null() {
+        return None;
+    }
+
+    Some(function_ptr as _)
+}
+
+macro_rules! get_function {
+    ($lib:expr, $func:ident) => {
+        crate::platform_impl::platform::util::get_function_impl(
+            concat!($lib, '\0'),
+            concat!(stringify!($func), '\0'),
+        )
+        .map(|f| unsafe { std::mem::transmute::<*const _, $func>(f) })
+    };
+}
+
+pub type SetProcessDPIAware = unsafe extern "system" fn() -> BOOL;
+pub type SetProcessDpiAwareness =
+    unsafe extern "system" fn(value: PROCESS_DPI_AWARENESS) -> HRESULT;
+pub type SetProcessDpiAwarenessContext =
+    unsafe extern "system" fn(value: DPI_AWARENESS_CONTEXT) -> BOOL;
+pub type GetDpiForWindow = unsafe extern "system" fn(hwnd: HWND) -> UINT;
+pub type GetDpiForMonitor = unsafe extern "system" fn(
+    hmonitor: HMONITOR,
+    dpi_type: MONITOR_DPI_TYPE,
+    dpi_x: *mut UINT,
+    dpi_y: *mut UINT,
+) -> HRESULT;
+pub type EnableNonClientDpiScaling = unsafe extern "system" fn(hwnd: HWND) -> BOOL;
+pub type AdjustWindowRectExForDpi = unsafe extern "system" fn(
+    rect: LPRECT,
+    dwStyle: DWORD,
+    bMenu: BOOL,
+    dwExStyle: DWORD,
+    dpi: UINT,
+) -> BOOL;
+
+lazy_static! {
+    pub static ref GET_DPI_FOR_WINDOW: Option<GetDpiForWindow> =
+        get_function!("user32.dll", GetDpiForWindow);
+    pub static ref ADJUST_WINDOW_RECT_EX_FOR_DPI: Option<AdjustWindowRectExForDpi> =
+        get_function!("user32.dll", AdjustWindowRectExForDpi);
+    pub static ref GET_DPI_FOR_MONITOR: Option<GetDpiForMonitor> =
+        get_function!("shcore.dll", GetDpiForMonitor);
+    pub static ref ENABLE_NON_CLIENT_DPI_SCALING: Option<EnableNonClientDpiScaling> =
+        get_function!("user32.dll", EnableNonClientDpiScaling);
+    pub static ref SET_PROCESS_DPI_AWARENESS_CONTEXT: Option<SetProcessDpiAwarenessContext> =
+        get_function!("user32.dll", SetProcessDpiAwarenessContext);
+    pub static ref SET_PROCESS_DPI_AWARENESS: Option<SetProcessDpiAwareness> =
+        get_function!("shcore.dll", SetProcessDpiAwareness);
+    pub static ref SET_PROCESS_DPI_AWARE: Option<SetProcessDPIAware> =
+        get_function!("user32.dll", SetProcessDPIAware);
+}