Add DPI scaling utilities for Windows platform

Introduces dpi_utils_windows.cpp and dpi_utils_windows.h to provide DPI scale factor detection for Windows windows. Updates window_windows.cpp to use logical pixels (DIP) in GetContentBounds by dividing screen coordinates by the DPI scale factor, improving high-DPI support.

Author: lijy91

src/platform/windows/dpi_utils_windows.cpp

@@ -0,0 +1,69 @@
+#include <windows.h>
+
+namespace nativeapi {
+
+// Internal: per-monitor DPI via Shcore when available
+static double GetScaleFactorForMonitor(HMONITOR hmonitor) {
+  if (!hmonitor) return 1.0;
+  typedef HRESULT(WINAPI * GetDpiForMonitorFunc)(HMONITOR, int, UINT*, UINT*);
+  static GetDpiForMonitorFunc pGetDpiForMonitor = nullptr;
+  static bool resolved = false;
+  if (!resolved) {
+    HMODULE hShcore = LoadLibraryW(L"Shcore.dll");
+    if (hShcore) {
+      pGetDpiForMonitor = reinterpret_cast<GetDpiForMonitorFunc>(
+          GetProcAddress(hShcore, "GetDpiForMonitor"));
+    }
+    resolved = true;
+  }
+  if (pGetDpiForMonitor) {
+    UINT dpiX = 96, dpiY = 96;
+    if (SUCCEEDED(pGetDpiForMonitor(hmonitor, 0 /* MDT_EFFECTIVE_DPI */, &dpiX, &dpiY))) {
+      return static_cast<double>(dpiX) / 96.0;
+    }
+  }
+  return 1.0;
+}
+
+double GetScaleFactorForWindow(HWND hwnd) {
+  if (hwnd) {
+    // Prefer GetDpiForWindow if available
+    typedef UINT(WINAPI * GetDpiForWindowFunc)(HWND);
+    static GetDpiForWindowFunc pGetDpiForWindow = nullptr;
+    static bool resolved_win = false;
+    if (!resolved_win) {
+      HMODULE hUser32 = LoadLibraryW(L"user32.dll");
+      if (hUser32) {
+        pGetDpiForWindow = reinterpret_cast<GetDpiForWindowFunc>(
+            GetProcAddress(hUser32, "GetDpiForWindow"));
+      }
+      resolved_win = true;
+    }
+    if (pGetDpiForWindow) {
+      UINT dpi = pGetDpiForWindow(hwnd);
+      if (dpi > 0) {
+        return static_cast<double>(dpi) / 96.0;
+      }
+    }
+
+    // Fallback: per-monitor DPI
+    HMONITOR hmonitor = MonitorFromWindow(hwnd, MONITOR_DEFAULTTONEAREST);
+    double monitor_scale = GetScaleFactorForMonitor(hmonitor);
+    if (monitor_scale > 0.0) return monitor_scale;
+  }
+
+  // Fallback: system DPI
+  HDC hdc = GetDC(nullptr);
+  if (hdc) {
+    int dpiX = GetDeviceCaps(hdc, LOGPIXELSX);
+    ReleaseDC(nullptr, hdc);
+    if (dpiX > 0) {
+      return static_cast<double>(dpiX) / 96.0;
+    }
+  }
+  return 1.0;
+}
+
+}  // namespace nativeapi
+
+

src/platform/windows/dpi_utils_windows.h

@@ -0,0 +1,11 @@
+#pragma once
+#include <windows.h>
+
+namespace nativeapi {
+
+// Returns the DPI scale factor for the given window (1.0 at 96 DPI)
+double GetScaleFactorForWindow(HWND hwnd);
+
+}  // namespace nativeapi
+
+

src/platform/windows/window_windows.cpp

@@ -3,6 +3,7 @@
 #include "../../window.h"
 #include "../../window_manager.h"
 #include "string_utils_windows.h"
+#include "dpi_utils_windows.h"
 
 namespace nativeapi {
 
@@ -258,16 +259,20 @@ Rectangle Window::GetContentBounds() const {
     RECT clientRect;
     GetClientRect(pimpl_->hwnd_, &clientRect);
 
-    // Convert client rect to screen coordinates
+    // Convert client rect to screen coordinates (physical pixels)
     POINT topLeft = {clientRect.left, clientRect.top};
     POINT bottomRight = {clientRect.right, clientRect.bottom};
     ClientToScreen(pimpl_->hwnd_, &topLeft);
     ClientToScreen(pimpl_->hwnd_, &bottomRight);
 
-    bounds.x = topLeft.x;
-    bounds.y = topLeft.y;
-    bounds.width = bottomRight.x - topLeft.x;
-    bounds.height = bottomRight.y - topLeft.y;
+    double scale = GetScaleFactorForWindow(pimpl_->hwnd_);
+    if (scale <= 0.0) scale = 1.0;
+
+    // Return logical pixels (DIP) by dividing by scale
+    bounds.x = static_cast<double>(topLeft.x) / scale;
+    bounds.y = static_cast<double>(topLeft.y) / scale;
+    bounds.width = static_cast<double>(bottomRight.x - topLeft.x) / scale;
+    bounds.height = static_cast<double>(bottomRight.y - topLeft.y) / scale;
   }
   return bounds;
 }