Addressing code review.

NEWS

@@ -5,6 +5,7 @@ here.
 vx.xx.x (2026-xx-xx)
 --------------------
 
+- Ability to pin/anchor threads and plots to the viewport.
 - Added the monitor utility. This Linux-specific tool can launch or attach
   to a program that has no Tracy instrumentation and perform a profiling run
   based on sampling call stacks.

manual/tracy.tex

@@ -4130,6 +4130,7 @@ Labels accompanied by the \faCaretDown{}~symbol can be collapsed out of the view
 
 \begin{itemize}
 \item \emph{\faEyeSlash{}~Hide} -- Hides the label along with the content associated to it. To make the label visible again, you must find it in the options menu (section~\ref{options}).
+\item \emph{\faThumbtack{}~Pin} -- Pins the track so that it remains visible while scrolling the timeline view vertically. Pinned threads and GPU queues are anchored to the top of the view, while pinned plots are anchored to the bottom. Selecting \emph{Unpin} on a pinned track releases it.
 \end{itemize}
 
 Under the \faCaretDown{}~symbol are a series of points that allow to limit the depth of the zones displayed. Hover the~\faArrowPointer{}~mouse pointer over a circle to display a line visualizing the cutting point, then click the \MMB{}~middle mouse button to apply or remove a zone depth limit.

profiler/src/profiler/TracyTimelineController.cpp

@@ -16,7 +16,6 @@ TimelineController::TimelineController( View& view, Worker& worker, bool threadi
     , m_scroll( 0 )
     , m_centerItemkey( nullptr )
     , m_centerItemOffsetY( 0 )
-    , m_pinnedTop( 0 )
     , m_firstFrame( true )
     , m_view( view )
     , m_worker( worker )
@@ -42,7 +41,7 @@ void TimelineController::Begin()
     m_items.clear();
 }
 
-void TimelineController::UpdateCenterItem()
+void TimelineController::UpdateCenterItem( int pinnedTop )
 {
     ImVec2 mousePos = ImGui::GetMousePos();
 
@@ -66,7 +65,7 @@ void TimelineController::UpdateCenterItem()
     }
 
     int yBegin = 0;
-    int yEnd = m_pinnedTop;
+    int yEnd = pinnedTop;
     for( auto& item : m_items )
     {
         if( item->IsPinned() ) continue;
@@ -85,7 +84,7 @@ void TimelineController::UpdateCenterItem()
     }
 }
 
-std::optional<int> TimelineController::CalculateScrollPosition() const
+std::optional<int> TimelineController::CalculateScrollPosition( int pinnedTop ) const
 {
     if( !m_centerItemkey ) return std::nullopt;
 
@@ -96,7 +95,7 @@ std::optional<int> TimelineController::CalculateScrollPosition() const
     const auto timelineMousePosY = mousePos.y - ImGui::GetWindowPos().y;
 
     int yBegin = 0;
-    int yEnd = m_pinnedTop;
+    int yEnd = pinnedTop;
     for( auto& item : m_items )
     {
         if( item->IsPinned() ) continue;
@@ -110,14 +109,16 @@ std::optional<int> TimelineController::CalculateScrollPosition() const
         return scrollY;
     }
 
+    // A "just-pinned" center item is gone from the normal run but will be
+    // "re-picked" on next mouse move.
     return std::nullopt;
 }
 
 void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, bool vcenter, float yMin, float yMax )
 {
-    // Pinned tracks are lifted out of the scrolling flow and drawn fixed to the
-    // top (queues/threads) or bottom (plots) of the viewport. Heights are the
-    // previous frame's values (zero on the first frame); items still animate.
+    // GetHeight() is 0 on the first frame, so the scroll extent would be shorter
+    // if a track was pinned at load, but would "self-correct" in the next frame.
+    // (Also, nothing is pinned at load anyway.)
     int pinnedTop = 0;
     int pinnedBottom = 0;
     for( auto& item : m_items )
@@ -126,7 +127,6 @@ void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, bool
         if( item->PinToBottom() ) pinnedBottom += item->GetHeight();
         else pinnedTop += item->GetHeight();
     }
-    m_pinnedTop = pinnedTop;
 
     auto shouldUpdateCenterItem = [&] () {
         const auto imguiChangedScroll = m_scroll != ImGui::GetScrollY();
@@ -144,7 +144,7 @@ void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, bool
     }
     else if( shouldUpdateCenterItem() )
     {
-        UpdateCenterItem();
+        UpdateCenterItem( pinnedTop );
     }
 
     const auto& viewData = m_view.GetViewData();
@@ -167,11 +167,11 @@ void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, bool
 
     const int curScrollY = (int)ImGui::GetScrollY();
     const int windowHeight = (int)ImGui::GetWindowHeight();
-    const int bottomStart = curScrollY + windowHeight - pinnedBottom;
+    // Keep the pinned bands from overlapping (top wins), otherwise bottom items
+    // would cover top ones while leaving them clickable underneath.
+    const int bottomStart = std::max( curScrollY + pinnedTop, curScrollY + windowHeight - pinnedBottom );
 
-    // Content-space Y offset an item is drawn at. Pinned items compensate for the
-    // scroll position so they stay fixed in the viewport; normal items flow in the
-    // middle band, below the pinned-top band.
+    // Pinned items add the scroll offset so they stay fixed as content scrolls.
     auto itemYOffset = [&] ( TimelineItem* item, int topRun, int normalRun, int bottomRun ) -> int {
         if( !item->IsPinned() ) return pinnedTop + normalRun;
         return item->PinToBottom() ? bottomStart + bottomRun : curScrollY + topRun;
@@ -197,9 +197,8 @@ void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, bool
     auto draw = ImGui::GetWindowDrawList();
     const auto bgColor = ImGui::GetColorU32( ImGuiCol_WindowBg );
 
-    // Normal (middle) items. Cull headers to the band between the pinned regions,
-    // and suppress interaction whenever the mouse is over a pinned band, so tracks
-    // scrolling underneath a pinned band stay inert.
+    // Keep tracks scrolling under a pinned band inert (cull their headers to the
+    // middle region and drop hover while the mouse is over a band).
     TimelineContext ctxNormal = ctx;
     if( pinnedTop > 0 ) ctxNormal.yMin = std::max<float>( ctx.yMin, wpos.y + curScrollY + pinnedTop );
     if( pinnedBottom > 0 ) ctxNormal.yMax = std::min<float>( ctx.yMax, wpos.y + bottomStart );
@@ -217,7 +216,6 @@ void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, bool
         normalRunning += h;
     }
 
-    // Pinned-top band (queues/threads), fixed at the viewport top.
     if( pinnedTop > 0 ) draw->AddRectFilled( ImVec2( wpos.x, wpos.y + curScrollY ), ImVec2( wpos.x + ctx.w, wpos.y + curScrollY + pinnedTop ), bgColor );
     int topRunning = 0;
     for( auto& item : m_items )
@@ -229,7 +227,6 @@ void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, bool
         topRunning += h;
     }
 
-    // Pinned-bottom band (plots), fixed at the viewport bottom.
     if( pinnedBottom > 0 ) draw->AddRectFilled( ImVec2( wpos.x, wpos.y + bottomStart ), ImVec2( wpos.x + ctx.w, wpos.y + curScrollY + windowHeight ), bgColor );
     int bottomRunning = 0;
     for( auto& item : m_items )
@@ -243,7 +240,7 @@ void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, bool
 
     int yOffset = pinnedTop + normalRunning + pinnedBottom;
 
-    if( const auto scrollY = CalculateScrollPosition() )
+    if( const auto scrollY = CalculateScrollPosition( pinnedTop ) )
     {
         int clampedScrollY = std::min<int>( *scrollY, std::max<int>( yOffset - ImGui::GetWindowHeight(), 0 ) );
         ImGui::SetScrollY( clampedScrollY );

profiler/src/profiler/TracyTimelineController.hpp

@@ -46,8 +46,8 @@ public:
     }
 
 private:
-    void UpdateCenterItem();
-    std::optional<int> CalculateScrollPosition() const;
+    void UpdateCenterItem( int pinnedTop );
+    std::optional<int> CalculateScrollPosition( int pinnedTop ) const;
 
     std::vector<TimelineItem*> m_items;
     unordered_flat_map<const void*, std::unique_ptr<TimelineItem>> m_itemMap;
@@ -58,8 +58,6 @@ private:
     const void* m_centerItemkey;
     int m_centerItemOffsetY;
 
-    int m_pinnedTop;
-
     bool m_firstFrame;
 
     View& m_view;

profiler/src/profiler/TracyTimelineItem.cpp

@@ -122,9 +122,9 @@ void TimelineItem::Draw( bool firstFrame, const TimelineContext& ctx, int yOffse
             SetVisible( false );
             ImGui::CloseCurrentPopup();
         }
-        if( ImGui::MenuItem( m_pinned ? ICON_FA_THUMBTACK_SLASH " Unpin" : ICON_FA_THUMBTACK " Pin" ) )
+        if( ImGui::MenuItem( IsPinned() ? ICON_FA_THUMBTACK_SLASH " Unpin" : ICON_FA_THUMBTACK " Pin" ) )
         {
-            m_pinned = !m_pinned;
+            SetPinned( !IsPinned() );
             ImGui::CloseCurrentPopup();
         }
         DrawExtraPopupItems();