Support per-monitor DPI scaling

main.c

@@ -384,20 +384,6 @@ ResumeConnections()
     }
 }
 
-/*
- * Set scale factor of windows in pixels. Scale = 100% for dpi = 96
- */
-static void
-dpi_setscale(UINT dpix)
-{
-    /* scale factor in percentage compared to the reference dpi of 96 */
-    if (dpix != 0)
-        o.dpi_scale = MulDiv(dpix, 100, 96);
-    else
-        o.dpi_scale = 100;
-    PrintDebug(L"DPI scale set to %u", o.dpi_scale);
-}
-
 /*
  * Get dpi of the system and set the scale factor.
  * The system dpi may be different from the per monitor dpi on
@@ -423,7 +409,7 @@ dpi_initialize(void)
         dpix = 96;
     }
 
-    dpi_setscale(dpix);
+    DpiSetScale(&o, dpix);
 }
 
 static int

misc.c

@@ -340,6 +340,20 @@ ForceForegroundWindow(HWND hWnd)
     return ret;
 }
 
+/*
+ * Set scale factor of windows in pixels. Scale = 100% for dpi = 96
+ */
+void
+DpiSetScale(options_t* options, UINT dpix)
+{
+    /* scale factor in percentage compared to the reference dpi of 96 */
+    if (dpix != 0)
+        options->dpi_scale = MulDiv(dpix, 100, 96);
+    else
+        options->dpi_scale = 100;
+    PrintDebug(L"DPI scale set to %u", options->dpi_scale);
+}
+
 /*
  * Check user has admin rights
  * Taken from https://msdn.microsoft.com/en-us/library/windows/desktop/aa376389(v=vs.85).aspx

misc.h

@@ -32,6 +32,7 @@ BOOL strbegins(const char *str, const char *begin);
 BOOL wcsbegins(LPCWSTR, LPCWSTR);
 
 BOOL ForceForegroundWindow(HWND);
+void DpiSetScale(options_t*, UINT dpix);
 
 BOOL IsUserAdmin(VOID);
 HANDLE InitSemaphore (WCHAR *);

openvpn.c

@@ -35,6 +35,10 @@
 #include <time.h>
 #include <commctrl.h>
 
+#ifndef WM_DPICHANGED
+#define WM_DPICHANGED 0x02E0
+#endif
+
 #include "tray.h"
 #include "main.h"
 #include "openvpn.h"
@@ -1656,6 +1660,13 @@ StatusDialogFunc(HWND hwndDlg, UINT msg, WPARAM wParam, LPARAM lParam)
         SetFocus(hLogWnd);
         return FALSE;
 
+    case WM_DPICHANGED:
+        DpiSetScale(&o, HIWORD(wParam));
+        RECT dlgRect;
+        GetClientRect(hwndDlg, &dlgRect);
+        RenderStatusWindow(hwndDlg, dlgRect.right, dlgRect.bottom);
+        return FALSE;
+
     case WM_SIZE:
         RenderStatusWindow(hwndDlg, LOWORD(lParam), HIWORD(lParam));
         InvalidateRect(hwndDlg, NULL, TRUE);

res/openvpn-gui.manifest

@@ -43,7 +43,14 @@
 <asmv3:application xmlns:asmv3="urn:schemas-microsoft-com:asm.v3">
     <asmv3:windowsSettings
          xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">
-        <dpiAware>true</dpiAware>
+        <!-- Per Monitor V1 [OS >= Windows 8.1] 
+         Values: False, True, Per-monitor, True/PM -->
+        <dpiAware xmlns="http://schemas.microsoft.com/SMI/2005/WindowsSettings">true/PM</dpiAware>
+            <!-- Per Monitor V1 [OS >= Windows 10 Anniversary Update (1607, 10.0.14393, Redstone 1)]
+         Values: Unaware, System, PerMonitor -->
+            <!-- Per Monitor V2 [OS >= Windows 10 Creators Update (1703, 10.0.15063, Redstone 2)]
+         Value: PerMonitorV2 -->
+        <dpiAwareness xmlns="http://schemas.microsoft.com/SMI/2016/WindowsSettings">PerMonitorV2, PerMonitor</dpiAwareness>
     </asmv3:windowsSettings>
 </asmv3:application>
 </assembly>