compositor: check for monitor layout issues post rule apply

fixes #12108

3 files changed, 37 insertions, 3 deletions

diff --git a/src/Compositor.cpp b/src/Compositor.cpp
index 5ea88b11..78b19c71 100644
--- a/src/Compositor.cpp
+++ b/src/Compositor.cpp
@@ -2842,6 +2842,38 @@ PHLWINDOW CCompositor::getForceFocus() {
     return nullptr;
 }
 
+void CCompositor::scheduleMonitorStateRecheck() {
+    static bool scheduled = false;
+
+    if (!scheduled) {
+        scheduled = true;
+        g_pEventLoopManager->doLater([this] {
+            arrangeMonitors();
+            checkMonitorOverlaps();
+
+            scheduled = false;
+        });
+    }
+}
+
+void CCompositor::checkMonitorOverlaps() {
+    CRegion monitorRegion;
+
+    for (const auto& m : m_monitors) {
+        if (!monitorRegion.copy().intersect(m->logicalBox()).empty()) {
+            Debug::log(ERR, "Monitor {}: detected overlap with layout", m->m_name);
+            g_pHyprNotificationOverlay->addNotification(std::format("Your monitor layout is set up incorrectly. Monitor {} overlaps with other monitor(s) in the "
+                                                                    "layout.\nPlease see the wiki (Monitors page) for more. This will cause issues.",
+                                                                    m->m_name),
+                                                        CHyprColor{}, 15000, ICON_WARNING);
+
+            break;
+        }
+
+        monitorRegion.add(m->logicalBox());
+    }
+}
+
 void CCompositor::arrangeMonitors() {
     static auto* const      PXWLFORCESCALEZERO = rc<Hyprlang::INT* const*>(g_pConfigManager->getConfigValuePtr("xwayland:force_zero_scaling"));
 
diff --git a/src/Compositor.hpp b/src/Compositor.hpp
index b3e048b2..49222d05 100644
--- a/src/Compositor.hpp
+++ b/src/Compositor.hpp
@@ -156,7 +156,9 @@ class CCompositor {
     void                                performUserChecks();
     void                                moveWindowToWorkspaceSafe(PHLWINDOW pWindow, PHLWORKSPACE pWorkspace);
     PHLWINDOW                           getForceFocus();
+    void                                scheduleMonitorStateRecheck();
     void                                arrangeMonitors();
+    void                                checkMonitorOverlaps();
     void                                enterUnsafeState();
     void                                leaveUnsafeState();
     void                                setPreferredScaleForSurface(SP<CWLSurfaceResource> pSurface, double scale);
diff --git a/src/helpers/Monitor.cpp b/src/helpers/Monitor.cpp
index 1ec035fd..ac9c065f 100644
--- a/src/helpers/Monitor.cpp
+++ b/src/helpers/Monitor.cpp
@@ -344,7 +344,7 @@ void CMonitor::onDisconnect(bool destroy) {
         g_pEventManager->postEvent(SHyprIPCEvent{"monitorremoved", m_name});
         g_pEventManager->postEvent(SHyprIPCEvent{"monitorremovedv2", std::format("{},{},{}", m_id, m_name, m_shortDescription)});
         EMIT_HOOK_EVENT("monitorRemoved", m_self.lock());
-        g_pCompositor->arrangeMonitors();
+        g_pCompositor->scheduleMonitorStateRecheck();
     }};
 
     m_frameScheduler.reset();
@@ -955,7 +955,7 @@ bool CMonitor::applyMonitorRule(SMonitorRule* pMonitorRule, bool force) {
     if (WAS10B != m_enabled10bit || OLDRES != m_pixelSize)
         g_pHyprOpenGL->destroyMonitorResources(m_self);
 
-    g_pCompositor->arrangeMonitors();
+    g_pCompositor->scheduleMonitorStateRecheck();
 
     m_damage.setSize(m_transformedSize);
 
@@ -1181,7 +1181,7 @@ void CMonitor::setMirror(const std::string& mirrorOf) {
         // remove from mvmonitors
         std::erase_if(g_pCompositor->m_monitors, [&](const auto& other) { return other == m_self; });
 
-        g_pCompositor->arrangeMonitors();
+        g_pCompositor->scheduleMonitorStateRecheck();
 
         g_pCompositor->setActiveMonitor(g_pCompositor->m_monitors.front());