algo/scroll: fix std::clamp assertion crash on resume from suspend (#13737)

2 files changed, 22 insertions, 1 deletions

diff --git a/src/layout/algorithm/tiled/scrolling/ScrollTapeController.cpp b/src/layout/algorithm/tiled/scrolling/ScrollTapeController.cpp
index 93a7dac1..6cd7da9c 100644
--- a/src/layout/algorithm/tiled/scrolling/ScrollTapeController.cpp
+++ b/src/layout/algorithm/tiled/scrolling/ScrollTapeController.cpp
@@ -240,7 +240,17 @@ void CScrollTapeController::fitStrip(size_t stripIndex, const CBox& usableArea,
     const double stripStart    = calculateStripStart(stripIndex, usableArea, fullscreenOnOne);
     const double stripSize     = calculateStripSize(stripIndex, usableArea, fullscreenOnOne);
 
-    m_offset = std::clamp(m_offset, stripStart - usablePrimary + stripSize, stripStart);
+    const double lo = stripStart - usablePrimary + stripSize;
+    const double hi = stripStart;
+
+    if (lo > hi) {
+        // strip is wider than viewport (e.g. during monitor reconnection after suspend),
+        // center the strip instead of hitting the std::clamp assertion
+        m_offset = stripStart - (usablePrimary - stripSize) / 2.0;
+        return;
+    }
+
+    m_offset = std::clamp(m_offset, lo, hi);
 }
 
 bool CScrollTapeController::isStripVisible(size_t stripIndex, const CBox& usableArea, bool fullscreenOnOne, bool full) const {
diff --git a/src/layout/algorithm/tiled/scrolling/ScrollingAlgorithm.cpp b/src/layout/algorithm/tiled/scrolling/ScrollingAlgorithm.cpp
index a64edb3a..5de27b97 100644
--- a/src/layout/algorithm/tiled/scrolling/ScrollingAlgorithm.cpp
+++ b/src/layout/algorithm/tiled/scrolling/ScrollingAlgorithm.cpp
@@ -795,6 +795,11 @@ void CScrollingAlgorithm::resizeTarget(const Vector2D& delta, SP<ITarget> target
 }
 
 void CScrollingAlgorithm::recalculate() {
+    // guard against recalculation during transitional monitor states
+    // (e.g. monitor reconnecting after suspend where workspace/monitor may not be ready)
+    if (!m_parent || !m_parent->space() || !m_parent->space()->workspace() || !m_parent->space()->workspace()->m_monitor)
+        return;
+
     if (Desktop::focusState()->window()) {
         const auto TARGET = Desktop::focusState()->window()->layoutTarget();
 
@@ -1516,6 +1521,12 @@ CBox CScrollingAlgorithm::usableArea() {
         return box;
 
     box.translate(-m_parent->space()->workspace()->m_monitor->m_position);
+
+    // ensure dimensions are never zero or negative, which can happen during
+    // monitor transitions (e.g. reconnection after suspend with stale reserved areas)
+    box.w = std::max(box.w, 1.0);
+    box.h = std::max(box.h, 1.0);
+
     return box;
 }