sacred2_k/docs/borderless.md

Borderless fullscreen

Request (2026-10-31): make the game start without crashing, then borderless fullscreen as the first feature.

The start-up crash

Measured 2026-10-31 (3440x1440, options video.fullscreen = 1):

• Started through the launcher from a background process, Windows doesn't hand the game window the foreground. In exclusive fullscreen Direct3D then minimises it (style gains WS_MINIMIZE after ~8 s, during "SETUP AI..." on the loading screen), and the game quits ~20 s later. On the way out s2logicai.dll's static destructors call a pure virtual function (a global allocator object at 0x101BF774 is already destroyed), the game's s2_purecall() handler (sacred2.exe 0x489ada) breaks into the debugger: exception 0x80000003 in KERNELBASE.
• Started with focus (or directly, unmodified), it reaches the main menu.
• cDX9Base::flip minimises the window and sets device flag 4 when Present returns D3DERR_DEVICELOST.

So the crash was exclusive fullscreen losing the focus; it is gone with borderless.

How the mod works (src/mods/borderless.cpp)

cDX9Base::_initDX(const sInitParams&) (s2render 0x1029a736, exported, the only device set-up, reached through initDX / cDX9Advance::initAdvance) has a windowed path: style 0x12c00000, size clamped to GetSystemMetrics(SM_CXSCREEN/SM_CYSCREEN) minus the frame, window centred, back buffer of that size, presentation interval default. See src/game/render/dx9base.h for sInitParams and the addresses.

• The hook passes fullscreen = 0 and the primary monitor's size.
• At startup the four uses of the style constant (0x1029ab49, ab56, ab5b, ab62) become WS_POPUP | WS_VISIBLE, so the game's own code makes a frameless window covering the monitor at (0,0).
• The launcher passes its foreground right to the game (AllowSetForegroundWindow).

Verified 2026-10-31 by automated runs: started without focus the game keeps loading in the background; with focus it reaches the main menu, survives switching to another window for 6 s and back, and quits cleanly on a close request (no crash report, MemLeaks_sacred2.xml written).

Consequences

• The resolution and fullscreen settings in Optionen no longer apply; the game always renders at the monitor's resolution.
• Always the primary monitor.
• In windowed mode the game presents with vsync (interval default); the options' vsync flag only applies to exclusive fullscreen.