From 0d87dc5d6af056bb6b70631f852ec3f9f9f78be1 Mon Sep 17 00:00:00 2001
From: Andy Ford <andyford993@gmail.com>
Date: Sat, 1 Jul 2023 10:56:05 +0100
Subject: [PATCH] perf: predetermine history trail draw function

On every render, we were checking the fields to determine the type of dot
we are rendering. However, we don't need to do this, as the dot type can only change
as part of an ASR load or configuration menu change.

This change saves the draw function as a lambda when something changes, allowing us to
reduce the render time by approximately 25% - went from 12ms to 8ms in testing.
---
 .../historytrail/HistoryTrailRenderer.cpp     | 115 +++++++++++-------
 .../historytrail/HistoryTrailRenderer.h       |  13 +-
 2 files changed, 77 insertions(+), 51 deletions(-)

diff --git a/src/plugin/historytrail/HistoryTrailRenderer.cpp b/src/plugin/historytrail/HistoryTrailRenderer.cpp
index 8ab341ca3..f6be8f641 100644
--- a/src/plugin/historytrail/HistoryTrailRenderer.cpp
+++ b/src/plugin/historytrail/HistoryTrailRenderer.cpp
@@ -57,6 +57,9 @@ namespace UKControllerPlugin {
                 userSetting.GetIntegerEntry(this->maxAltitudeFilterUserSettingKey, this->defaultMaxAltitude);
             this->filledDots = userSetting.GetBooleanEntry(this->dotFillUserSettingKey, false);
             this->rotatedDots = userSetting.GetBooleanEntry(this->dotRotateUserSettingKey, false);
+
+            // Load the dot drawing function
+            this->drawDot = this->GetDrawDotFunction();
         }
 
         /*
@@ -136,51 +139,6 @@ namespace UKControllerPlugin {
             return this->antialiasedTrails;
         }
 
-        /*
-            Draws a single dot to the screen.
-        */
-        void
-        HistoryTrailRenderer::DrawDot(GdiGraphicsInterface& graphics, Gdiplus::Pen& pen, const Gdiplus::RectF& area)
-        {
-            if (this->historyTrailType == this->trailTypeDiamond) {
-                graphics.DrawDiamond(area, pen);
-            } else if (this->historyTrailType == this->trailTypeCircle) {
-                graphics.DrawCircle(area, pen);
-            } else if (this->historyTrailType == this->trailTypeLine) {
-                graphics.DrawLine(
-                    pen,
-                    Gdiplus::PointF{area.GetLeft(), area.GetBottom()},
-                    Gdiplus::PointF{area.GetRight(), area.GetTop()});
-            } else {
-                graphics.DrawRect(area, pen);
-            }
-        }
-
-        /*
-            Fills a single dot to the screen.
-        */
-        void
-        HistoryTrailRenderer::FillDot(GdiGraphicsInterface& graphics, Gdiplus::Brush& brush, const Gdiplus::RectF& area)
-        {
-            if (this->historyTrailType == this->trailTypeDiamond) {
-                graphics.FillDiamond(area, brush);
-            } else if (this->historyTrailType == this->trailTypeCircle) {
-                graphics.FillCircle(area, brush);
-            } else {
-                graphics.FillRect(area, brush);
-            }
-        }
-
-        void HistoryTrailRenderer::DoDot(GdiGraphicsInterface& graphics, const Gdiplus::RectF& area)
-        {
-            // Draw the dot
-            if (this->filledDots && this->historyTrailType != this->trailTypeLine) {
-                this->FillDot(graphics, *this->brush, area);
-            } else {
-                this->DrawDot(graphics, *this->pen, area);
-            }
-        }
-
         /*
             Returns the configuration menu item.
         */
@@ -372,9 +330,9 @@ namespace UKControllerPlugin {
                             if (this->rotatedDots) {
                                 graphics.Rotated(
                                     static_cast<Gdiplus::REAL>(position->heading),
-                                    [&graphics, &dot, this]() { this->DoDot(graphics, dot); });
+                                    [&graphics, &dot, this]() { this->drawDot(graphics, dot); });
                             } else {
-                                this->DoDot(graphics, dot);
+                                this->drawDot(graphics, dot);
                             }
                         });
 
@@ -405,5 +363,68 @@ namespace UKControllerPlugin {
         void HistoryTrailRenderer::ResetPosition(void)
         {
         }
+
+        auto HistoryTrailRenderer::GetDoDotFunction() const
+            -> std::function<void(GdiGraphicsInterface&, const Gdiplus::RectF&)>
+        {
+            return this->filledDots && this->historyTrailType != this->trailTypeLine ? this->GetFillDotFunction()
+                                                                                     : this->GetDrawDotFunction();
+        }
+
+        auto HistoryTrailRenderer::GetDrawDotFunction() const
+            -> std::function<void(Windows::GdiGraphicsInterface&, const Gdiplus::RectF&)>
+        {
+            // Diamonds
+            if (this->historyTrailType == this->trailTypeDiamond) {
+                return [this](Windows::GdiGraphicsInterface& graphics, const Gdiplus::RectF& area) {
+                    graphics.DrawDiamond(area, *this->pen);
+                };
+            }
+
+            // Circles
+            if (this->historyTrailType == this->trailTypeCircle) {
+                return [this](Windows::GdiGraphicsInterface& graphics, const Gdiplus::RectF& area) {
+                    graphics.DrawCircle(area, *this->pen);
+                };
+            }
+
+            // Lines
+            if (this->historyTrailType == this->trailTypeLine) {
+                return [this](Windows::GdiGraphicsInterface& graphics, const Gdiplus::RectF& area) {
+                    graphics.DrawLine(
+                        *this->pen,
+                        Gdiplus::PointF{area.GetLeft(), area.GetBottom()},
+                        Gdiplus::PointF{area.GetRight(), area.GetTop()});
+                };
+            }
+
+            // Rectangles
+            return [this](Windows::GdiGraphicsInterface& graphics, const Gdiplus::RectF& area) {
+                graphics.DrawRect(area, *this->pen);
+            };
+        }
+
+        auto HistoryTrailRenderer::GetFillDotFunction() const
+            -> std::function<void(Windows::GdiGraphicsInterface&, const Gdiplus::RectF&)>
+        {
+            // Diamonds
+            if (this->historyTrailType == this->trailTypeDiamond) {
+                return [this](Windows::GdiGraphicsInterface& graphics, const Gdiplus::RectF& area) {
+                    graphics.FillDiamond(area, *this->brush);
+                };
+            }
+
+            // Circles
+            if (this->historyTrailType == this->trailTypeCircle) {
+                return [this](Windows::GdiGraphicsInterface& graphics, const Gdiplus::RectF& area) {
+                    graphics.FillCircle(area, *this->brush);
+                };
+            }
+
+            // Rects
+            return [this](Windows::GdiGraphicsInterface& graphics, const Gdiplus::RectF& area) {
+                graphics.FillRect(area, *this->brush);
+            };
+        }
     } // namespace HistoryTrail
 } // namespace UKControllerPlugin
diff --git a/src/plugin/historytrail/HistoryTrailRenderer.h b/src/plugin/historytrail/HistoryTrailRenderer.h
index 39152b083..ec7ce2142 100644
--- a/src/plugin/historytrail/HistoryTrailRenderer.h
+++ b/src/plugin/historytrail/HistoryTrailRenderer.h
@@ -158,10 +158,12 @@ namespace UKControllerPlugin {
             const int defaultMaxAltitude = 99999;
 
             private:
-            void DrawDot(Windows::GdiGraphicsInterface& graphics, Gdiplus::Pen& pen, const Gdiplus::RectF& area);
-
-            void FillDot(Windows::GdiGraphicsInterface& graphics, Gdiplus::Brush& brush, const Gdiplus::RectF& area);
-            void DoDot(Windows::GdiGraphicsInterface& graphics, const Gdiplus::RectF& area);
+            [[nodiscard]] auto GetDoDotFunction() const
+                -> std::function<void(Windows::GdiGraphicsInterface&, const Gdiplus::RectF&)>;
+            [[nodiscard]] auto GetFillDotFunction() const
+                -> std::function<void(Windows::GdiGraphicsInterface&, const Gdiplus::RectF&)>;
+            [[nodiscard]] auto GetDrawDotFunction() const
+                -> std::function<void(Windows::GdiGraphicsInterface&, const Gdiplus::RectF&)>;
 
             // Handles dialogs
             const Dialog::DialogManager& dialogManager;
@@ -222,6 +224,9 @@ namespace UKControllerPlugin {
 
             // The dot command for opening the configuration modal.
             const std::string dotCommand = ".ukcp h";
+
+            // Function for drawing the dot - saved as a lambda so we dont have to keep checking the trail type
+            std::function<void(Windows::GdiGraphicsInterface&, const Gdiplus::RectF&)> drawDot;
         };
     } // namespace HistoryTrail
 } // namespace UKControllerPlugin