From f887979ec03f0f2be8fe7d13b0a9cb8b33068d6d Mon Sep 17 00:00:00 2001
From: reuk <reuk@users.noreply.github.com>
Date: Wed, 11 Dec 2024 21:42:35 +0000
Subject: [PATCH] Direct2D: Fix performance issue when drawing transformed
 unclipped regions

This issue could be observed in the GraphicsDemo's SVG pane, when the
"rotation" option was enabled.

Drawables internally enable the unclipped painting flag, which normally
prevents slow clipping when drawing subcomponents of the drawable.

The Direct2D graphics context was using the frame area as the default
area, used to signal that no clipping should be applied. However, when
non-axis-aligned transform was active, this area was incorrectly applied
as a geometric clipping region. D2D geometric clips are relatively slow,
so this caused large slowdowns.

This solution adds a flag that is set whenever a clip is explicitly
requested. If no clip is explicitly requested, then clipping will be
entirely bypassed. This can make rendering of Drawables significantly
faster.
---
 .../juce_Direct2DGraphicsContext_windows.cpp  |  9 +++++---
 .../juce_Direct2DGraphicsContext_windows.h    | 21 +++++++++++++++++--
 2 files changed, 25 insertions(+), 5 deletions(-)

diff --git a/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.cpp b/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.cpp
index 654996c40e..206f2473d0 100644
--- a/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.cpp
+++ b/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.cpp
@@ -1070,21 +1070,24 @@ void Direct2DGraphicsContext::resetPendingClipList()
 
 void Direct2DGraphicsContext::applyPendingClipList()
 {
+    if (! pendingClipList.isClipApplied())
+        return;
+
     auto& transform = currentState->currentTransform;
-    bool const axisAligned = currentState->isCurrentTransformAxisAligned();
+    const auto axisAligned = currentState->isCurrentTransformAxisAligned();
     const auto list = pendingClipList.getList();
 
     // Clip if the pending clip list is not empty and smaller than the frame size
     if (! list.containsRectangle (getPimpl()->getFrameSize().toFloat()) && ! list.isEmpty())
     {
-        if (list.getNumRectangles() == 1 && (transform.isOnlyTranslated || axisAligned))
+        if (list.getNumRectangles() == 1 && axisAligned)
         {
             auto r = list.getRectangle (0);
             currentState->pushAliasedAxisAlignedClipLayer (r);
         }
         else
         {
-            auto clipTransform = transform.isOnlyTranslated || axisAligned ? AffineTransform{} : transform.getTransform();
+            auto clipTransform = axisAligned ? AffineTransform{} : transform.getTransform();
             if (auto clipGeometry = D2DHelpers::rectListToPathGeometry (getPimpl()->getDirect2DFactory(),
                                                                         list,
                                                                         clipTransform,
diff --git a/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.h b/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.h
index ba906a00cf..bc71df5908 100644
--- a/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.h
+++ b/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.h
@@ -122,29 +122,46 @@ protected:
     public:
         void clipTo (Rectangle<float> i)
         {
-            list.clipTo (i);
+            if (std::exchange (clipApplied, true))
+                list.clipTo (i);
+            else
+                list = i;
         }
 
         template <typename Numeric>
         void clipTo (const RectangleList<Numeric>& other)
         {
-            list.clipTo (other);
+            if (std::exchange (clipApplied, true))
+            {
+                list.clipTo (other);
+            }
+            else
+            {
+                list.clear();
+
+                for (const auto& r : other)
+                    list.add (r.toFloat());
+            }
         }
 
         void subtract (Rectangle<float> i)
         {
             list.subtract (i);
+            clipApplied = true;
         }
 
         RectangleList<float> getList() const { return list; }
+        bool isClipApplied() const { return clipApplied; }
 
         void reset (Rectangle<float> maxBounds)
         {
             list = maxBounds;
+            clipApplied = false;
         }
 
     private:
         RectangleList<float> list;
+        bool clipApplied = false;
     };
 
     PendingClipList pendingClipList;