From 3b2a75a4e08e13a35b6995d0295a96559beddb85 Mon Sep 17 00:00:00 2001
From: Trey Moen <50057480+greatgitsby@users.noreply.github.com>
Date: Sat, 19 Sep 2026 18:41:58 -0700
Subject: [PATCH] cabana: resize heatmap and prevent signal clipping (#38975)

* cabana: allow heatmap resizing without clipping

* cabana: keep outer grid lines inside the heatmap

* cabana: add a visible heatmap resize handle

* cabana: use the standard pane divider for resizing
---
 .../tools/cabana/ui/widgets/binaryview.cc     |  4 +--
 .../tools/cabana/ui/widgets/detailwidget.cc   | 26 ++++++++++++++-----
 .../tools/cabana/ui/widgets/detailwidget.h    |  1 +
 3 files changed, 22 insertions(+), 9 deletions(-)

diff --git a/openpilot/tools/cabana/ui/widgets/binaryview.cc b/openpilot/tools/cabana/ui/widgets/binaryview.cc
index 56f67075f4..818f8b42a8 100644
--- a/openpilot/tools/cabana/ui/widgets/binaryview.cc
+++ b/openpilot/tools/cabana/ui/widgets/binaryview.cc
@@ -348,8 +348,8 @@ void BinaryView::draw() {
     const float x = std::clamp(grid_pos_.x + IM_ROUND(column * column_width_), grid_pos_.x + 0.5f, right - 0.5f);
     painter->AddLine(ImVec2(x, grid_pos_.y), ImVec2(x, bottom), grid_color);
   }
-  for (int row = 0; row <= rows; ++row) {
-    const float y = grid_pos_.y + row * CELL_HEIGHT;
+  for (int row = 0; rows > 0 && row <= rows; ++row) {
+    const float y = std::clamp(grid_pos_.y + row * CELL_HEIGHT, grid_pos_.y + 0.5f, bottom - 0.5f);
     painter->AddLine(ImVec2(grid_pos_.x, y), ImVec2(right, y), grid_color);
   }
 
diff --git a/openpilot/tools/cabana/ui/widgets/detailwidget.cc b/openpilot/tools/cabana/ui/widgets/detailwidget.cc
index 67169e5561..6378d2f8ca 100644
--- a/openpilot/tools/cabana/ui/widgets/detailwidget.cc
+++ b/openpilot/tools/cabana/ui/widgets/detailwidget.cc
@@ -233,16 +233,29 @@ void DetailWidget::drawTabWidget() {
   page_tabs_.draw();
   if (tab_widget_index_ == 0) {
     if (heatmap_visible_) {
-      // Keep most of a short window available for signal rows.
+      // Allow the heatmap to grow while reserving room for signal rows.
+      const float handle_height = style.DockingSeparatorSize;
       const float avail = ImGui::GetContentRegionAvail().y;
-      const float max_height = std::max(avail - style.ItemSpacing.y - SignalView::minimumHeight(), 1.0f);
-      const float height = std::min(binary_view_->minimumSizeHint().y, max_height);
-      ImGui::BeginChild("binary_view", ImVec2(0, std::max(height, 1.0f)), ImGuiChildFlags_None, ImGuiWindowFlags_HorizontalScrollbar);
+      const float max_height = std::max(avail - handle_height - style.ItemSpacing.y * 2 - SignalView::minimumHeight(), 1.0f);
+      const float min_height = std::min(ImGui::GetFrameHeight(), max_height);
+      float height = std::clamp(heatmap_height_ < 0 ? binary_view_->minimumSizeHint().y : heatmap_height_, min_height, max_height);
+      ImGui::BeginChild("binary_view", ImVec2(0, height), ImGuiChildFlags_None, ImGuiWindowFlags_HorizontalScrollbar);
       binary_view_rect_ = ImGui::GetCurrentWindow()->Rect();
       binary_view_->draw();
       ImGui::EndChild();
+
+      const ImVec2 pos = ImGui::GetCursorScreenPos();
+      const ImVec2 size(std::max(ImGui::GetContentRegionAvail().x, 1.0f), handle_height);
+      const ImRect splitter(pos, ImVec2(pos.x + size.x, pos.y + size.y));
+      float signal_height = std::max(avail - height - handle_height - style.ItemSpacing.y * 2, SignalView::minimumHeight());
+      if (ImGui::SplitterBehavior(splitter, ImGui::GetID("##heatmap_resize"), ImGuiAxis_Y,
+                                  &height, &signal_height, min_height, SignalView::minimumHeight(), 4.0f)) {
+        heatmap_height_ = height;
+      }
+      ImGui::Dummy(size);
     }
-    ImGui::BeginChild("signal_view", ImVec2(0, 0), ImGuiChildFlags_None,
+    const float signal_height = std::max(ImGui::GetContentRegionAvail().y, SignalView::minimumHeight());
+    ImGui::BeginChild("signal_view", ImVec2(0, signal_height), ImGuiChildFlags_None,
                       ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse);
     signal_view_rect_ = ImGui::GetCurrentWindow()->Rect();
     signal_view_->draw();
@@ -254,8 +267,7 @@ void DetailWidget::drawTabWidget() {
 
 void DetailWidget::draw() {
   tabbar_.draw();
-  ImGui::BeginChild("message_content", ImVec2(0, 0), ImGuiChildFlags_AlwaysUseWindowPadding,
-                    ImGuiWindowFlags_NoScrollbar | ImGuiWindowFlags_NoScrollWithMouse);
+  ImGui::BeginChild("message_content", ImVec2(0, 0), ImGuiChildFlags_AlwaysUseWindowPadding);
   drawToolBar();
 
   if (warning_widget_visible_) {
diff --git a/openpilot/tools/cabana/ui/widgets/detailwidget.h b/openpilot/tools/cabana/ui/widgets/detailwidget.h
index 6c64a33bf8..f752488ee1 100644
--- a/openpilot/tools/cabana/ui/widgets/detailwidget.h
+++ b/openpilot/tools/cabana/ui/widgets/detailwidget.h
@@ -88,6 +88,7 @@ private:
   bool action_remove_msg_enabled_ = false;
   bool heatmap_live_ = true;
   bool heatmap_visible_ = true;
+  float heatmap_height_ = -1.0f;
   std::string heatmap_all_text_ = "All";
   ImRect binary_view_rect_, signal_view_rect_;  // child window rects of the last drawTabWidget
   std::unique_ptr<LogsWidget> history_log_;