get display DPI info to scale mouse movement

common/src/platform/windows/CMakeLists.txt

@@ -7,6 +7,7 @@ include_directories(
 
 add_library(lg_common_platform_code STATIC
     crash.c
+    dpi.c
     sysinfo.c
     thread.c
     event.c

common/src/platform/windows/dpi.c

@@ -0,0 +1,37 @@
+#include "common/dpi.h"
+#include "common/windebug.h"
+
+typedef enum MONITOR_DPI_TYPE {
+  MDT_EFFECTIVE_DPI,
+  MDT_ANGULAR_DPI,
+  MDT_RAW_DPI,
+  MDT_DEFAULT
+} MONITOR_DPI_TYPE;
+typedef HRESULT (WINAPI *GetDpiForMonitor_t)(HMONITOR hmonitor, MONITOR_DPI_TYPE dpiType, UINT * dpiX, UINT * dpiY);
+
+UINT monitor_dpi(HMONITOR hMonitor)
+{
+  HMODULE shcore = LoadLibraryA("shcore.dll");
+  if (!shcore)
+  {
+    DEBUG_ERROR("Could not load shcore.dll");
+    return DPI_100_PERCENT;
+  }
+
+  GetDpiForMonitor_t GetDpiForMonitor = (GetDpiForMonitor_t) GetProcAddress(shcore, "GetDpiForMonitor");
+  if (!GetDpiForMonitor)
+  {
+    DEBUG_ERROR("Could not find GetDpiForMonitor");
+    return DPI_100_PERCENT;
+  }
+
+  UINT dpiX, dpiY;
+  HRESULT status = GetDpiForMonitor(hMonitor, MDT_EFFECTIVE_DPI, &dpiX, &dpiY);
+  if (FAILED(status))
+  {
+    DEBUG_WINERROR("GetDpiForMonitor failed", status);
+    return DPI_100_PERCENT;
+  }
+
+  return dpiX;
+}