From fdd6de0d12ea17f713ec3e73e7968198339b7b6d Mon Sep 17 00:00:00 2001
From: David Robillard <d@drobilla.net>
Date: Sat, 21 May 2022 21:28:08 -0400
Subject: Add puglGetScaleFactor()

---
 src/win.c | 43 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

(limited to 'src/win.c')

diff --git a/src/win.c b/src/win.c
index 8f2a26b..5e70b6f 100644
--- a/src/win.c
+++ b/src/win.c
@@ -35,6 +35,8 @@
 #define PUGL_USER_TIMER_MIN 9470
 
 typedef BOOL(WINAPI* PFN_SetProcessDPIAware)(void);
+typedef HRESULT(WINAPI* PFN_GetProcessDpiAwareness)(HANDLE, DWORD*);
+typedef HRESULT(WINAPI* PFN_GetScaleFactorForMonitor)(HMONITOR, DWORD*);
 
 LRESULT CALLBACK
 wndProc(HWND hwnd, UINT message, WPARAM wParam, LPARAM lParam);
@@ -112,6 +114,35 @@ puglWinGetWindowExFlags(const PuglView* const view)
   return WS_EX_NOINHERITLAYOUT | (view->parent ? 0u : WS_EX_APPWINDOW);
 }
 
+static double
+puglWinGetViewScaleFactor(const PuglView* const view)
+{
+  const HMODULE shcore = LoadLibrary("Shcore.dll");
+  if (!shcore) {
+    return 1.0;
+  }
+
+  const PFN_GetProcessDpiAwareness GetProcessDpiAwareness =
+    (PFN_GetProcessDpiAwareness)GetProcAddress(shcore,
+                                               "GetProcessDpiAwareness");
+
+  const PFN_GetScaleFactorForMonitor GetScaleFactorForMonitor =
+    (PFN_GetScaleFactorForMonitor)GetProcAddress(shcore,
+                                                 "GetScaleFactorForMonitor");
+
+  DWORD dpiAware    = 0;
+  DWORD scaleFactor = 100;
+  if (GetProcessDpiAwareness && GetScaleFactorForMonitor &&
+      !GetProcessDpiAwareness(NULL, &dpiAware) && dpiAware) {
+    GetScaleFactorForMonitor(
+      MonitorFromWindow(view->impl->hwnd, MONITOR_DEFAULTTOPRIMARY),
+      &scaleFactor);
+  }
+
+  FreeLibrary(shcore);
+  return (double)scaleFactor / 100.0;
+}
+
 PuglWorldInternals*
 puglInitWorldInternals(PuglWorldType type, PuglWorldFlags PUGL_UNUSED(flags))
 {
@@ -214,7 +245,8 @@ puglRealize(PuglView* view)
     puglSetWindowTitle(view, view->title);
   }
 
-  view->impl->cursor = LoadCursor(NULL, IDC_ARROW);
+  view->impl->scaleFactor = puglWinGetViewScaleFactor(view);
+  view->impl->cursor      = LoadCursor(NULL, IDC_ARROW);
 
   puglSetFrame(view, view->frame);
   SetWindowLongPtr(impl->hwnd, GWLP_USERDATA, (LONG_PTR)view);
@@ -604,6 +636,9 @@ handleMessage(PuglView* view, UINT message, WPARAM wParam, LPARAM lParam)
       InvalidateRect(view->impl->hwnd, NULL, false);
     }
     break;
+  case WM_DISPLAYCHANGE:
+    view->impl->scaleFactor = puglWinGetViewScaleFactor(view);
+    break;
   case WM_WINDOWPOSCHANGED:
     handleConfigure(view, &event);
     break;
@@ -1002,6 +1037,12 @@ adjustedWindowRect(PuglView* const view,
   return rect;
 }
 
+double
+puglGetScaleFactor(const PuglView* const view)
+{
+  return view->impl->scaleFactor;
+}
+
 PuglStatus
 puglSetFrame(PuglView* view, const PuglRect frame)
 {
-- 
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