From 6ca54e8c97a550798a10c615b5be18160b025dc3 Mon Sep 17 00:00:00 2001
From: Matt Gonzalez <matt@echoaudio.com>
Date: Fri, 10 May 2024 20:31:30 -0700
Subject: [PATCH] Direct2D: Add debug check for axis-aligned clip layers

This is similar to the check performed by the D2D debug layer that will still work with the debug layer disabled.
---
 .../juce_Direct2DGraphicsContext_windows.cpp  | 67 ++++++++++++++++++-
 1 file changed, 64 insertions(+), 3 deletions(-)

diff --git a/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.cpp b/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.cpp
index 0fce545030..96adea4cc9 100644
--- a/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.cpp
+++ b/modules/juce_graphics/native/juce_Direct2DGraphicsContext_windows.cpp
@@ -54,9 +54,70 @@ public:
 
     void push (ComSmartPtr<ID2D1DeviceContext1> context, const D2D1_LAYER_PARAMETERS& layerParameters)
     {
-        // Clipping and transparency are all handled by pushing Direct2D layers. The SavedState creates an internal stack
-        // of Layer objects to keep track of how many layers need to be popped.
-        // Pass nullptr for the PushLayer layer parameter to allow Direct2D to manage the layers (Windows 8 or later)
+        // Clipping and transparency are all handled by pushing Direct2D
+        // layers.The SavedState creates an internal stack of Layer objects to
+        // keep track of how many layers need to be popped. Pass nullptr for
+        // the PushLayer layer parameter to allow Direct2D to manage the layers
+        // (Windows 8 or later)
+
+       #if JUCE_DEBUG
+
+        // Check if this should be an axis-aligned clip layer (per the D2D
+        // debug layer)
+        const auto isGeometryAxisAlignedRectangle = [&]
+        {
+            auto* geometry = layerParameters.geometricMask;
+
+            if (geometry == nullptr)
+                return false;
+
+            struct Sink : public ComBaseClassHelper<ID2D1SimplifiedGeometrySink>
+            {
+                D2D1_POINT_2F lastPoint{};
+                bool axisAlignedLines = true;
+                UINT32 lineCount = 0;
+
+                STDMETHOD (Close)() override { return S_OK; }
+                STDMETHOD_ (void, SetFillMode) (D2D1_FILL_MODE) override {}
+                STDMETHOD_ (void, SetSegmentFlags) (D2D1_PATH_SEGMENT) override {}
+                STDMETHOD_ (void, EndFigure) (D2D1_FIGURE_END) override {}
+
+                STDMETHOD_ (void, BeginFigure) (D2D1_POINT_2F p, D2D1_FIGURE_BEGIN) override { lastPoint = p; }
+
+                STDMETHOD_ (void, AddLines) (const D2D1_POINT_2F* points, UINT32 count) override
+                {
+                    for (UINT32 i = 0; i < count; ++i)
+                    {
+                        auto p = points[i];
+
+                        axisAlignedLines &= (approximatelyEqual (p.x, lastPoint.x) || approximatelyEqual (p.y, lastPoint.y));
+                        lastPoint = p;
+                    }
+
+                    lineCount += count;
+                }
+
+                STDMETHOD_ (void, AddBeziers) (const D2D1_BEZIER_SEGMENT*, UINT32) override
+                {
+                    axisAlignedLines = false;
+                }
+            };
+
+            Sink sink;
+            geometry->Simplify (D2D1_GEOMETRY_SIMPLIFICATION_OPTION_CUBICS_AND_LINES,
+                                D2D1::Matrix3x2F::Identity(),
+                                1.0f,
+                                &sink);
+
+            // Check for 3 lines; the BeginFigure counts as 1 line
+            return sink.axisAlignedLines && sink.lineCount == 3;
+        }();
+
+        jassert (layerParameters.opacity != 1.0f
+                 || layerParameters.opacityBrush
+                 || ! isGeometryAxisAlignedRectangle);
+       #endif
+
         context->PushLayer (layerParameters, nullptr);
         pushedLayers.emplace_back (popLayerFlag);
     }