From bca8f28f43c4e0d647fe042ef3002fec91805190 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Toma=C5=BE=20V=C3=B6r=C3=B6=C5=A1?= <tomaz.voros@gmail.com>
Date: Fri, 27 Jan 2023 20:00:05 +0100
Subject: [PATCH] Centering around the mouse pointer.

---
 server/TracyTimelineController.cpp | 89 +++++++++++++++++++++++++++++-
 server/TracyTimelineController.hpp |  9 ++-
 server/TracyView_Timeline.cpp      |  4 +-
 3 files changed, 97 insertions(+), 5 deletions(-)

diff --git a/server/TracyTimelineController.cpp b/server/TracyTimelineController.cpp
index 2badc31c..990a34df 100644
--- a/server/TracyTimelineController.cpp
+++ b/server/TracyTimelineController.cpp
@@ -1,3 +1,5 @@
+#include <algorithm>
+
 #include "imgui.h"
 
 #include "TracyTimelineController.hpp"
@@ -8,6 +10,8 @@ namespace tracy
 TimelineController::TimelineController( View& view, Worker& worker )
     : m_height( 0 )
     , m_scroll( 0 )
+    , m_centerItemkey( nullptr )
+    , m_centerItemOffsetY( 0 )
     , m_firstFrame( true )
     , m_view( view )
     , m_worker( worker )
@@ -24,8 +28,83 @@ void TimelineController::Begin()
     m_items.clear();
 }
 
-void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, float yMin, float yMax )
+void TimelineController::UpdateCenterItem()
 {
+    ImVec2 mousePos = ImGui::GetMousePos();
+
+    m_centerItemkey = nullptr;
+    m_centerItemOffsetY = 0;
+
+    if( m_firstFrame || !ImGui::IsMousePosValid( &mousePos ) ) return;
+
+    const auto timelineMousePosY = mousePos.y - ImGui::GetWindowPos().y;
+    int centerY = timelineMousePosY + ImGui::GetScrollY();
+
+    int yBegin = 0;
+    int yEnd = 0;
+    for( auto& item : m_items )
+    {
+        m_centerItemkey = item->GetKey();
+        yBegin = yEnd;
+        yEnd += item->GetNextFrameHeight();
+
+        const auto inLowerBounds = m_centerItemkey == m_items.front()->GetKey() || yBegin <= centerY;
+        const auto inUpperBounds = m_centerItemkey == m_items.back()->GetKey() || centerY < yEnd;
+
+        if( inLowerBounds && inUpperBounds )
+        {
+            m_centerItemOffsetY = centerY - yBegin;
+            break;
+        }
+    }
+}
+
+std::optional<int> TimelineController::CalculateScrollPosition() const
+{
+    if( !m_centerItemkey ) return std::nullopt;
+
+    ImVec2 mousePos = ImGui::GetMousePos();
+
+    if( !ImGui::IsMousePosValid( &mousePos ) ) return std::nullopt;
+
+    const auto timelineMousePosY = mousePos.y - ImGui::GetWindowPos().y;
+
+    int yBegin = 0;
+    int yEnd = 0;
+    for( auto& item : m_items )
+    {
+        yBegin = yEnd;
+        yEnd += item->GetNextFrameHeight();
+
+        if( item->GetKey() != m_centerItemkey ) continue;
+
+        int scrollY = yBegin + m_centerItemOffsetY - timelineMousePosY;
+
+        return scrollY;
+    }
+
+    return std::nullopt;
+}
+
+void TimelineController::End( double pxns, const ImVec2& wpos, bool hover,  bool vcenter, float yMin, float yMax )
+{
+    auto shouldUpdateCenterItem = [&] () {
+        const auto& mouseDelta = ImGui::GetIO().MouseDelta;
+        const auto mouseMoved = mouseDelta.x != 0.0f || mouseDelta.y != 0.0f;
+        const auto imguiChangedScroll = m_scroll != ImGui::GetScrollY();
+        return ( ( imguiChangedScroll || mouseMoved ) && !ImGui::IsMouseDown( 1 ) ) || !m_centerItemkey;
+    };
+
+    if( !vcenter )
+    {
+        m_centerItemkey = nullptr;
+        m_centerItemOffsetY = 0;
+    }
+    else if( shouldUpdateCenterItem() )
+    {
+        UpdateCenterItem();
+    }
+
     int yOffset = 0;
 
     for( auto& item : m_items )
@@ -36,6 +115,14 @@ void TimelineController::End( double pxns, const ImVec2& wpos, bool hover, float
         yOffset += currentFrameItemHeight;
     }
 
+    if( const auto scrollY = CalculateScrollPosition() )
+    {
+        int clampedScrollY = std::min<int>( *scrollY, yOffset );
+        ImGui::SetScrollY( clampedScrollY );
+        int minHeight = ImGui::GetWindowHeight() + clampedScrollY;
+        yOffset = std::max( yOffset, minHeight );
+    }
+
     const auto scrollPos = ImGui::GetScrollY();
     if( ( scrollPos == 0 && m_scroll != 0 ) || yOffset > m_height )
     {
diff --git a/server/TracyTimelineController.hpp b/server/TracyTimelineController.hpp
index eb9e0af6..b14dca67 100644
--- a/server/TracyTimelineController.hpp
+++ b/server/TracyTimelineController.hpp
@@ -2,6 +2,7 @@
 #define __TRACYTIMELINECONTROLLER_HPP__
 
 #include <assert.h>
+#include <optional>
 #include <vector>
 
 #include "../public/common/TracyForceInline.hpp"
@@ -18,7 +19,7 @@ public:
 
     void FirstFrameExpired();
     void Begin();
-    void End( double pxns, const ImVec2& wpos, bool hover, float yMin, float yMax );
+    void End( double pxns, const ImVec2& wpos, bool hover, bool vcenter, float yMin, float yMax );
 
     template<class T, class U>
     void AddItem( U* data )
@@ -39,12 +40,18 @@ public:
     }
 
 private:
+    void UpdateCenterItem();
+    std::optional<int> CalculateScrollPosition() const;
+
     std::vector<TimelineItem*> m_items;
     unordered_flat_map<const void*, std::unique_ptr<TimelineItem>> m_itemMap;
 
     float m_height;
     float m_scroll;
 
+    const void* m_centerItemkey;
+    int m_centerItemOffsetY;
+
     bool m_firstFrame;
 
     View& m_view;
diff --git a/server/TracyView_Timeline.cpp b/server/TracyView_Timeline.cpp
index eddba3d0..0b88fdd0 100644
--- a/server/TracyView_Timeline.cpp
+++ b/server/TracyView_Timeline.cpp
@@ -327,8 +327,6 @@ void View::DrawTimeline()
     if( m_yDelta != 0 )
     {
         auto& io = ImGui::GetIO();
-        auto y = ImGui::GetScrollY();
-        ImGui::SetScrollY( y - m_yDelta );
         io.MouseClickedPos[1].y = io.MousePos.y;
     }
 
@@ -380,7 +378,7 @@ void View::DrawTimeline()
         }
     }
 
-    m_tc.End( pxns, wpos, hover, yMin, yMax );
+    m_tc.End( pxns, wpos, hover, drawMouseLine && m_viewMode == ViewMode::Paused, yMin, yMax );
     ImGui::EndChild();
 
     m_lockHighlight = m_nextLockHighlight;