From 2ae3598b51829b4fbed16605739bae272c90e1b2 Mon Sep 17 00:00:00 2001
From: Trey Moen <50057480+greatgitsby@users.noreply.github.com>
Date: Sun, 13 Sep 2026 15:56:21 -0700
Subject: [PATCH] cabana: prevent signal panel collapse (#38903)

* cabana: keep signal scrolling inside the list

* cabana: reserve space for the signal panel
---
 openpilot/tools/cabana/ui/widgets/detailwidget.cc |  7 ++++---
 openpilot/tools/cabana/ui/widgets/signalview.cc   | 13 ++++++++++---
 openpilot/tools/cabana/ui/widgets/signalview.h    |  1 +
 3 files changed, 15 insertions(+), 6 deletions(-)

diff --git a/openpilot/tools/cabana/ui/widgets/detailwidget.cc b/openpilot/tools/cabana/ui/widgets/detailwidget.cc
index 988cf4b3cb..8f42b63d80 100644
--- a/openpilot/tools/cabana/ui/widgets/detailwidget.cc
+++ b/openpilot/tools/cabana/ui/widgets/detailwidget.cc
@@ -218,16 +218,17 @@ void DetailWidget::drawTabWidget() {
   ImGui::BeginChild("page", ImVec2(0, std::max(page_rect.GetHeight() - pill_height - gap, 1.0f)),
                     ImGuiChildFlags_None, ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse);
   if (tab_widget_index_ == 0) {
-    // binary_view_ keeps its size hint, signal_view_ takes the rest
+    // Reserve the signal toolbar and rows before giving the byte grid its preferred height.
     const float min_height = binary_view_->minimumSizeHint().y;
     const float avail = ImGui::GetContentRegionAvail().y;
-    const float max_height = std::max(avail - style.ItemSpacing.y - 1.0f, 1.0f);
+    const float max_height = std::max(avail - style.ItemSpacing.y - SignalView::minimumHeight(), 1.0f);
     const float height = std::clamp(min_height, 1.0f, max_height);
     ImGui::BeginChild("binary_view", ImVec2(0, height), ImGuiChildFlags_None, ImGuiWindowFlags_HorizontalScrollbar);
     binary_view_rect_ = ImGui::GetCurrentWindow()->Rect();
     binary_view_->draw();
     ImGui::EndChild();
-    ImGui::BeginChild("signal_view", ImVec2(0, 0));
+    ImGui::BeginChild("signal_view", ImVec2(0, 0), ImGuiChildFlags_None,
+                      ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse);
     signal_view_rect_ = ImGui::GetCurrentWindow()->Rect();
     signal_view_->draw();
     ImGui::EndChild();
diff --git a/openpilot/tools/cabana/ui/widgets/signalview.cc b/openpilot/tools/cabana/ui/widgets/signalview.cc
index 269df6158c..48a74fd111 100644
--- a/openpilot/tools/cabana/ui/widgets/signalview.cc
+++ b/openpilot/tools/cabana/ui/widgets/signalview.cc
@@ -690,9 +690,16 @@ float SignalView::minimumWidth() {
   return left_width + style.ItemSpacing.x + toolBarRightWidth("00:00") + (style.WindowPadding.x + style.ChildBorderSize) * 2;
 }
 
+float SignalView::minimumHeight() {
+  const ImGuiStyle &style = ImGui::GetStyle();
+  return ImGui::GetFrameHeight() + style.ItemSpacing.y + signalRowHeight() * 3 +
+         (style.WindowPadding.y + style.ChildBorderSize + CONTROL_OUTLINE_PADDING) * 2;
+}
+
 void SignalView::draw() {
   ImGui::PushStyleColor(ImGuiCol_ChildBg, palette().surface);
-  if (!ImGui::BeginChild("SignalView", ImVec2(0, 0), ImGuiChildFlags_Borders)) {
+  if (!ImGui::BeginChild("SignalView", ImVec2(0, 0), ImGuiChildFlags_Borders,
+                         ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse)) {
     ImGui::EndChild();
     ImGui::PopStyleColor();
     return;
@@ -740,8 +747,8 @@ void SignalView::collapseAll() {
 
 void SignalView::drawTree() {
   ImGui::PushStyleVar(ImGuiStyleVar_ItemSpacing, ImVec2(ImGui::GetStyle().ItemSpacing.x, 0.0f));
-  const float min_height = std::max(ImGui::GetContentRegionAvail().y, 300.0f);
-  const bool visible = beginControlChild("tree", ImVec2(0, min_height));
+  // Keep the toolbar fixed; only the signal rows scroll within the remaining space.
+  const bool visible = beginControlChild("tree", ImVec2(0, 0));
   if (visible) {
     DrawContext ctx{ImGui::GetWindowDrawList(), ImGui::GetCursorScreenPos().x, ImGui::GetContentRegionAvail().x, rowHeight()};
     // the press that closes an open editor is consumed by the focus change, the index widgets never see it
diff --git a/openpilot/tools/cabana/ui/widgets/signalview.h b/openpilot/tools/cabana/ui/widgets/signalview.h
index dc77ad7b37..d6ba246097 100644
--- a/openpilot/tools/cabana/ui/widgets/signalview.h
+++ b/openpilot/tools/cabana/ui/widgets/signalview.h
@@ -110,6 +110,7 @@ public:
   void setMessage(const MessageId &id);
   void draw();
   static float minimumWidth();
+  static float minimumHeight();
   void signalHovered(const cabana::Signal *sig);  // handler for BinaryView::signalHovered
   void updateChartState();
   void selectSignal(const cabana::Signal *sig, bool expand = false);