Preferred monitor: chosen in Optionen > Allgemein, used at the next start

The Internet-Optionen frame becomes Bildschirm with a Monitor dropdown
(Hauptmonitor or a connected monitor, kept by device path in
[display] Monitor=). The borderless window and the render size use that
monitor, falling back to the main monitor when it is not connected.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/mods/borderless.cpp

@@ -3,7 +3,7 @@
 // The game renders at a fixed resolution (1024x768). Unmodified, windowed mode
 // shows that as a 1024x768 popup centred on the desktop; fullscreen mode
 // switches the display mode. With this mod the game always runs windowed, the
-// popup covers the whole monitor, and each frame is scaled up into the largest
+// popup covers the whole monitor (mods/monitor.h: the preferred one), and each frame is scaled up into the largest
 // centred rectangle with the game's aspect ratio (black bars elsewhere).
 //
 // Mouse positions are mapped back from that rectangle to game pixels, both in
@@ -35,6 +35,7 @@
 #include "game/render/dx_driver7.h"
 #include "mods/hud.h"
 #include "mods/input.h"
+#include "mods/monitor.h"
 #include "mods/widescreen.h"
 #include "re/config.h"
 #include "game/addresses.h"
@@ -90,9 +91,7 @@ RECT FitRect(int areaWidth, int areaHeight, int width, int height, bool integerS
 
 void ApplyBorderless(game::DxDriver7* driver) {
     HWND window = driver->window;
-    MONITORINFO monitor = {sizeof(monitor)};
-    GetMonitorInfoW(MonitorFromWindow(window, MONITOR_DEFAULTTONEAREST), &monitor);
-    const RECT& area = monitor.rcMonitor;
+    const RECT area = mods::monitor::GameMonitorRect();
     const int areaWidth = area.right - area.left;
     const int areaHeight = area.bottom - area.top;
 
@@ -171,7 +170,7 @@ int __fastcall DxDriver7_SetDisplayMode(DxDriver7* self, void* edx, void* device
     }
     DxDisplayMode windowed = *mode;
     windowed.fullscreen = 0;
-    mods::widescreen::ApplyRenderSize(windowed, self->window);
+    mods::widescreen::ApplyRenderSize(windowed);
     g_viewport.active = false;
     const int result = DxDriver7_SetDisplayMode_original(self, edx, deviceCaps, &windowed, unknown);
     if (result) {