diff --git a/docs/hud.md b/docs/hud.md
index be83f9d..690302c 100644
--- a/docs/hud.md
+++ b/docs/hud.md
@@ -115,3 +115,14 @@ game lays them out at creation only).
 
 A window anchored `Screen` still counts as the outermost scope for events, so
 its child buttons (hooked as standalone controls, `Center`) don't shift again.
+
+## Viewports (cursor in the quest book, 2026-10-17)
+
+`SetViewport` inside a moved window is shifted like its vertices. The quest
+book's map tab ("V") draws the zoomed map view (`0x6cc950`), which sets a
+256x256 viewport and, when done, resets it to the full render size
+(`DxDriver7` `0x646510`: 0, 0, width x height). Shifted by the window's
+offset, that reset reached past the render target, `SetViewport` failed and
+the small viewport stayed set: the cursor (drawn after the UI) was only
+visible inside it. A viewport at x 0 across the whole render width is now
+passed unshifted.
diff --git a/src/mods/hud.cpp b/src/mods/hud.cpp
index a5ef398..202efc2 100644
--- a/src/mods/hud.cpp
+++ b/src/mods/hud.cpp
@@ -402,8 +402,13 @@ using ClearFn = HRESULT(__stdcall*)(void* device, DWORD count, Rect7* rects, DWO
 SetViewportFn g_setViewport = nullptr;
 ClearFn g_clear = nullptr;
 
+// A viewport across the whole render width is a reset, not one of the window's
+// own (e.g. the zoomed map view in the quest book restores it with 0x646510
+// when done): shifted, it would reach past the render target, SetViewport
+// fails and the window's small viewport stays set, clipping the cursor.
 HRESULT __stdcall SetViewportShifted(void* device, Viewport7* viewport) {
-    if (g_offsetX == 0 || !viewport) {
+    if (g_offsetX == 0 || !viewport ||
+        (viewport->x == 0 && static_cast<int>(viewport->width) >= mods::widescreen::RenderWidth())) {
         return g_setViewport(device, viewport);
     }
     Viewport7 shifted = *viewport;