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fix(startmenu): correct Start menu positioning on mixed-resolution multi-monitor setups #5138

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fix(startmenu): correct Start menu positioning on mixed-resolution multi-monitor setups #5138

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1dcc626
fix(startmenu): correct Start menu positioning on mixed-resolution mu…
SnowAmberX Aug 11, 2026
ab91382
fix(startmenu): fix Explorer heap corruption in Start menu monitor ha…
SnowAmberX Aug 22, 2026
dcd6e61
fix(startmenu): keep target monitor stable across start lifecycle
SnowAmberX Sep 11, 2026
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4 changes: 4 additions & 0 deletions ExplorerPatcher/ExplorerPatcher.vcxproj
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Original file line number Diff line number Diff line change
Expand Up @@ -245,6 +245,9 @@
<ClCompile Include="StartMenu.c">
<ExcludedFromBuild Condition="'$(WithMainPatcher)'!='true'">true</ExcludedFromBuild>
</ClCompile>
<ClCompile Include="StartMenuMonitorState.c">
<ExcludedFromBuild Condition="'$(WithMainPatcher)'!='true'">true</ExcludedFromBuild>
</ClCompile>
<ClCompile Include="StartMenuSettings.cpp">
<ExcludedFromBuild Condition="'$(WithMainPatcher)'!='true'">true</ExcludedFromBuild>
</ClCompile>
Expand Down Expand Up @@ -302,6 +305,7 @@
<ClInclude Include="SettingsMonitor.h" />
<ClInclude Include="StartExperience.h" />
<ClInclude Include="StartMenu.h" />
<ClInclude Include="StartMenuMonitorState.h" />
<ClInclude Include="StartupSound.h" />
<ClInclude Include="symbols.h" />
<ClInclude Include="TaskbarCenter.h" />
Expand Down
22 changes: 18 additions & 4 deletions ExplorerPatcher/StartMenu.c
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Original file line number Diff line number Diff line change
@@ -1,7 +1,10 @@
#include "StartMenu.h"
#include "StartMenuMonitorState.h"

void OpenStartOnMonitor(HMONITOR monitor)
{
START_MENU_MONITOR_REQUEST_ID monitorRequestId = BeginStartMenuTargetMonitorRequest();

HRESULT hr = S_OK;
IUnknown* pImmersiveShell = NULL;
hr = CoCreateInstance(
Expand Down Expand Up @@ -38,16 +41,27 @@ void OpenStartOnMonitor(HMONITOR monitor)
if (pLauncher)
{
BOOL bIsVisible = FALSE;
pLauncher->lpVtbl->IsVisible(pLauncher, &bIsVisible);
hr = pLauncher->lpVtbl->IsVisible(pLauncher, &bIsVisible);
if (SUCCEEDED(hr))
{
if (!bIsVisible)
{
if (pMonitor)
if (PublishStartMenuTargetMonitorRequest(monitorRequestId, monitor))
{
pLauncher->lpVtbl->ConnectToMonitor(pLauncher, pMonitor);
if (pMonitor)
{
pLauncher->lpVtbl->ConnectToMonitor(pLauncher, pMonitor);
}
hr = pLauncher->lpVtbl->ShowStartView(pLauncher, 11, 0);
if (FAILED(hr))
{
CancelStartMenuTargetMonitorRequest(monitorRequestId);
}
else
{
ConfirmStartMenuTargetMonitorRequest(monitorRequestId);
}
}
pLauncher->lpVtbl->ShowStartView(pLauncher, 11, 0);
}
else
{
Expand Down
167 changes: 167 additions & 0 deletions ExplorerPatcher/StartMenuMonitorState.c
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Original file line number Diff line number Diff line change
@@ -0,0 +1,167 @@
#include "StartMenuMonitorState.h"

static SRWLOCK g_startMenuTargetMonitorLock = SRWLOCK_INIT;
static START_MENU_MONITOR_REQUEST_ID g_nextStartMenuTargetMonitorRequestId = 0;
static START_MENU_MONITOR_REQUEST_ID g_latestStartedStartMenuTargetMonitorRequestId = 0;
static START_MENU_MONITOR_REQUEST_ID g_pendingStartMenuTargetMonitorRequestId = 0;
static HMONITOR g_pendingStartMenuTargetMonitor = NULL;
static BOOL g_pendingStartMenuTargetMonitorConfirmed = FALSE;
static START_MENU_MONITOR_REQUEST_ID g_activeStartMenuTargetMonitorLifecycleId = 0;
static HMONITOR g_activeStartMenuTargetMonitor = NULL;

static START_MENU_MONITOR_REQUEST_ID AllocateStartMenuTargetMonitorRequestId(void)
{
do
{
++g_nextStartMenuTargetMonitorRequestId;
} while (!g_nextStartMenuTargetMonitorRequestId);
return g_nextStartMenuTargetMonitorRequestId;
}

START_MENU_MONITOR_REQUEST_ID BeginStartMenuTargetMonitorRequest(void)
{
AcquireSRWLockExclusive(&g_startMenuTargetMonitorLock);
START_MENU_MONITOR_REQUEST_ID requestId = AllocateStartMenuTargetMonitorRequestId();
g_latestStartedStartMenuTargetMonitorRequestId = requestId;
ReleaseSRWLockExclusive(&g_startMenuTargetMonitorLock);
return requestId;
}

BOOL PublishStartMenuTargetMonitorRequest(START_MENU_MONITOR_REQUEST_ID requestId, HMONITOR monitor)
{
BOOL published = FALSE;
AcquireSRWLockExclusive(&g_startMenuTargetMonitorLock);
if (requestId && requestId == g_latestStartedStartMenuTargetMonitorRequestId)
{
g_pendingStartMenuTargetMonitorRequestId = requestId;
g_pendingStartMenuTargetMonitor = monitor;
g_pendingStartMenuTargetMonitorConfirmed = FALSE;
published = TRUE;
}
ReleaseSRWLockExclusive(&g_startMenuTargetMonitorLock);
return published;
}

BOOL ConfirmStartMenuTargetMonitorRequest(START_MENU_MONITOR_REQUEST_ID requestId)
{
BOOL confirmed = FALSE;
AcquireSRWLockExclusive(&g_startMenuTargetMonitorLock);
if (requestId && requestId == g_activeStartMenuTargetMonitorLifecycleId)
{
confirmed = TRUE;
}
else if (requestId && requestId == g_pendingStartMenuTargetMonitorRequestId)
{
g_pendingStartMenuTargetMonitorConfirmed = TRUE;
if (!g_activeStartMenuTargetMonitorLifecycleId)
{
g_activeStartMenuTargetMonitorLifecycleId = g_pendingStartMenuTargetMonitorRequestId;
g_activeStartMenuTargetMonitor = g_pendingStartMenuTargetMonitor;
g_pendingStartMenuTargetMonitorRequestId = 0;
g_pendingStartMenuTargetMonitor = NULL;
g_pendingStartMenuTargetMonitorConfirmed = FALSE;
}
confirmed = TRUE;
}
ReleaseSRWLockExclusive(&g_startMenuTargetMonitorLock);
return confirmed;
}

BOOL CancelStartMenuTargetMonitorRequest(START_MENU_MONITOR_REQUEST_ID requestId)
{
BOOL cancelled = FALSE;
AcquireSRWLockExclusive(&g_startMenuTargetMonitorLock);
if (requestId && requestId == g_pendingStartMenuTargetMonitorRequestId)
{
g_pendingStartMenuTargetMonitorRequestId = 0;
g_pendingStartMenuTargetMonitor = NULL;
g_pendingStartMenuTargetMonitorConfirmed = FALSE;
cancelled = TRUE;
}
if (requestId && requestId == g_activeStartMenuTargetMonitorLifecycleId)
{
g_activeStartMenuTargetMonitorLifecycleId = 0;
g_activeStartMenuTargetMonitor = NULL;
cancelled = TRUE;
}
ReleaseSRWLockExclusive(&g_startMenuTargetMonitorLock);
return cancelled;
}

START_MENU_MONITOR_REQUEST_ID AcquireStartMenuTargetMonitor(HMONITOR defaultMonitor, HMONITOR* monitor)
{
AcquireSRWLockExclusive(&g_startMenuTargetMonitorLock);
if (!g_activeStartMenuTargetMonitorLifecycleId)
{
if (g_pendingStartMenuTargetMonitorRequestId)
{
g_activeStartMenuTargetMonitorLifecycleId = g_pendingStartMenuTargetMonitorRequestId;
g_activeStartMenuTargetMonitor = g_pendingStartMenuTargetMonitor
? g_pendingStartMenuTargetMonitor
: defaultMonitor;
g_pendingStartMenuTargetMonitorRequestId = 0;
g_pendingStartMenuTargetMonitor = NULL;
g_pendingStartMenuTargetMonitorConfirmed = FALSE;
}
else
{
g_activeStartMenuTargetMonitorLifecycleId = AllocateStartMenuTargetMonitorRequestId();
g_activeStartMenuTargetMonitor = defaultMonitor;
}
}
START_MENU_MONITOR_REQUEST_ID lifecycleId = g_activeStartMenuTargetMonitorLifecycleId;
if (!g_activeStartMenuTargetMonitor)
{
g_activeStartMenuTargetMonitor = defaultMonitor;
}
*monitor = g_activeStartMenuTargetMonitor;
ReleaseSRWLockExclusive(&g_startMenuTargetMonitorLock);
return lifecycleId;
}

BOOL UpdateStartMenuTargetMonitor(START_MENU_MONITOR_REQUEST_ID lifecycleId, HMONITOR monitor)
{
BOOL updated = FALSE;
AcquireSRWLockExclusive(&g_startMenuTargetMonitorLock);
if (lifecycleId && lifecycleId == g_activeStartMenuTargetMonitorLifecycleId)
{
g_activeStartMenuTargetMonitor = monitor;
updated = TRUE;
}
ReleaseSRWLockExclusive(&g_startMenuTargetMonitorLock);
return updated;
}

START_MENU_MONITOR_REQUEST_ID GetStartMenuTargetMonitorLifecycleId(void)
{
AcquireSRWLockShared(&g_startMenuTargetMonitorLock);
START_MENU_MONITOR_REQUEST_ID lifecycleId = g_activeStartMenuTargetMonitorLifecycleId;
if (!lifecycleId && g_pendingStartMenuTargetMonitorConfirmed)
{
lifecycleId = g_pendingStartMenuTargetMonitorRequestId;
}
ReleaseSRWLockShared(&g_startMenuTargetMonitorLock);
return lifecycleId;
}

void CompleteStartMenuTargetMonitorLifecycle(START_MENU_MONITOR_REQUEST_ID lifecycleId)
{
if (!lifecycleId)
{
return;
}

AcquireSRWLockExclusive(&g_startMenuTargetMonitorLock);
if (lifecycleId == g_activeStartMenuTargetMonitorLifecycleId)
{
g_activeStartMenuTargetMonitorLifecycleId = 0;
g_activeStartMenuTargetMonitor = NULL;
}
if (lifecycleId == g_pendingStartMenuTargetMonitorRequestId)
{
g_pendingStartMenuTargetMonitorRequestId = 0;
g_pendingStartMenuTargetMonitor = NULL;
g_pendingStartMenuTargetMonitorConfirmed = FALSE;
}
ReleaseSRWLockExclusive(&g_startMenuTargetMonitorLock);
}
25 changes: 25 additions & 0 deletions ExplorerPatcher/StartMenuMonitorState.h
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Original file line number Diff line number Diff line change
@@ -0,0 +1,25 @@
#ifndef _H_STARTMENUMONITORSTATE_H_
#define _H_STARTMENUMONITORSTATE_H_

#include <Windows.h>

#ifdef __cplusplus
extern "C" {
#endif

typedef ULONGLONG START_MENU_MONITOR_REQUEST_ID;

START_MENU_MONITOR_REQUEST_ID BeginStartMenuTargetMonitorRequest(void);
BOOL PublishStartMenuTargetMonitorRequest(START_MENU_MONITOR_REQUEST_ID requestId, HMONITOR monitor);
BOOL ConfirmStartMenuTargetMonitorRequest(START_MENU_MONITOR_REQUEST_ID requestId);
BOOL CancelStartMenuTargetMonitorRequest(START_MENU_MONITOR_REQUEST_ID requestId);
START_MENU_MONITOR_REQUEST_ID AcquireStartMenuTargetMonitor(HMONITOR defaultMonitor, HMONITOR* monitor);
BOOL UpdateStartMenuTargetMonitor(START_MENU_MONITOR_REQUEST_ID lifecycleId, HMONITOR monitor);
START_MENU_MONITOR_REQUEST_ID GetStartMenuTargetMonitorLifecycleId(void);
void CompleteStartMenuTargetMonitorLifecycle(START_MENU_MONITOR_REQUEST_ID lifecycleId);

#ifdef __cplusplus
}
#endif

#endif
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