Component: Improve performance and opaque checks

modules/juce_gui_basics/components/juce_Component.cpp

@@ -209,7 +209,7 @@ public:
         return std::exchange (effect, &i) != &i;
     }
 
-    void paint (Graphics& g, Component& c, bool ignoreAlphaLevel)
+    void paint (Graphics& g, Component& c, bool ignoreAlphaLevel, OpaqueLayer& opaqueLayer)
     {
         auto scale = g.getInternalContext().getPhysicalPixelScaleFactor();
         auto scaledBounds = c.getLocalBounds() * scale;
@@ -238,7 +238,7 @@ public:
             Graphics g2 (effectImage);
             g2.addTransform (AffineTransform::scale ((float) scaledBounds.getWidth()  / (float) c.getWidth(),
                                                      (float) scaledBounds.getHeight() / (float) c.getHeight()));
-            c.paintComponentAndChildren (g2);
+            c.paintComponentAndChildren (g2, opaqueLayer);
         }
 
         Graphics::ScopedSaveState ss (g);
@@ -257,6 +257,183 @@ private:
     ImageEffectFilter* effect;
 };
 
+//==============================================================================
+class Component::OpaqueLayer
+{
+public:
+    explicit OpaqueLayer (const Component* c)
+        : currentComponent (c)
+    {
+        jassert (c != nullptr);
+        appendOpaqueChildren (*c, {}, c->getLocalBounds());
+    }
+
+    [[nodiscard]] auto pushComponent (Component& component)
+    {
+        removeOpaqueComponent (component);
+        currentComponent = &component;
+
+        const auto pos = component.getPosition();
+        offsetFromOrigin += pos;
+
+        return ScopeGuard { [this, pos]
+        {
+            offsetFromOrigin -= pos;
+            currentComponent = nullptr;
+        } };
+    }
+
+    Rectangle<int> getCurrentComponentBounds (const juce::Graphics& g)
+    {
+        // This function must only be called while the object returned by
+        // pushComponent() is still alive!
+        jassert (currentComponent != nullptr);
+        const auto pos = currentComponent->getPosition();
+        const auto bounds = getNonOccludedBoundsForCurrentComponent<ObscuredBy::allButChildren> (g.getClipBounds() - pos);
+
+        if (! bounds.isEmpty())
+            return bounds + pos;
+
+        removeOpaqueChildren (*currentComponent);
+        return {};
+    }
+
+    Rectangle<int> getCurrentComponentPaintBounds (const juce::Graphics& g)
+    {
+        // This function must only be called while the object returned by
+        // pushComponent() is still alive!
+        jassert (currentComponent != nullptr);
+        return getNonOccludedBoundsForCurrentComponent<ObscuredBy::childrenOnly> (g.getClipBounds());
+    }
+
+private:
+    enum class ObscuredBy
+    {
+        childrenOnly,
+        allButChildren
+    };
+
+    template <ObscuredBy obscuredBy>
+    Rectangle<int> getNonOccludedBoundsForCurrentComponent (Rectangle<int> clipBounds) const
+    {
+        auto visibleBounds = currentComponent->getLocalBounds().getIntersection (clipBounds);
+
+        if (visibleBounds.isEmpty())
+            return {};
+
+        RectangleList visibleRegions { visibleBounds };
+
+        const auto occlude = [&] (const OpaqueComponentInfo& opaqueComponentInfo)
+        {
+            const auto opaqueBounds = opaqueComponentInfo.clippedBounds - offsetFromOrigin;
+
+            if (! opaqueBounds.intersects (visibleBounds))
+                return;
+
+            if (opaqueBounds.contains (visibleBounds))
+                visibleRegions.clear();
+            else
+                visibleRegions.subtract (opaqueBounds);
+
+            visibleBounds = visibleRegions.getBounds();
+        };
+
+        if constexpr (obscuredBy == ObscuredBy::childrenOnly)
+        {
+            for (auto i = currentPosition; i < opaqueComponents.size(); ++i)
+            {
+                const auto& opaqueComponentInfo = opaqueComponents.getReference (i);
+
+                if (! currentComponent->isParentOf (opaqueComponentInfo.component))
+                    break;
+
+                occlude (opaqueComponentInfo);
+
+                if (visibleBounds.isEmpty())
+                    return {};
+            }
+        }
+        else
+        {
+            for (int i = opaqueComponents.size(); --i >= currentPosition;)
+            {
+                const auto& opaqueComponentInfo = opaqueComponents.getReference (i);
+
+                if (currentComponent->isParentOf (opaqueComponentInfo.component))
+                    break;
+
+                occlude (opaqueComponentInfo);
+
+                if (visibleBounds.isEmpty())
+                    return {};
+            }
+        }
+
+        return visibleBounds;
+    }
+
+    void removeOpaqueComponent (const Component& component)
+    {
+        if (opaqueComponents[currentPosition].component == &component)
+            ++currentPosition;
+    }
+
+    void removeOpaqueChildren (const Component& component)
+    {
+        for (const auto* child : component.getChildren())
+        {
+            if (currentPosition == opaqueComponents.size())
+                return;
+
+            if (! isVisibleToLayer (*child))
+                continue;
+
+            removeOpaqueComponent (*child);
+            removeOpaqueChildren (*child);
+        }
+    }
+
+    static bool isVisibleToLayer (const Component& c)
+    {
+        return detail::ComponentHelpers::isVisibleWithNonZeroArea (c)
+            && c.componentTransparency == 0
+            && ! c.isTransformed();
+    }
+
+    void appendOpaqueChildren (const Component& parent,
+                               Point<int> parentOrigin,
+                               Rectangle<int> parentClippedBounds)
+    {
+        for (auto* child : parent.getChildren())
+        {
+            if (! isVisibleToLayer (*child))
+                continue;
+
+            const auto childBounds = child->getBounds() + parentOrigin;
+            const auto childClippedBounds = parentClippedBounds.getIntersection (childBounds);
+
+            if (childClippedBounds.isEmpty())
+                continue;
+
+            if (child->isOpaque())
+                opaqueComponents.add ({ child, childClippedBounds });
+
+            appendOpaqueChildren (*child, childBounds.getPosition(), childClippedBounds);
+        }
+    }
+
+    struct OpaqueComponentInfo
+    {
+        const Component* component;
+        Rectangle<int> clippedBounds;
+    };
+
+    int currentPosition{};
+    Point<int> offsetFromOrigin{};
+    const Component* currentComponent;
+    Array<OpaqueComponentInfo> opaqueComponents;
+};
+
 //==============================================================================
 Component::Component() noexcept
   : componentFlags (0)
@@ -1701,17 +1878,17 @@ void Component::paintOverChildren (Graphics&)
 }
 
 //==============================================================================
-void Component::paintWithinParentContext (Graphics& g)
+void Component::paintWithinParentContext (Graphics& g, OpaqueLayer& opaqueLayer)
 {
     g.setOrigin (getPosition());
 
     if (cachedImage != nullptr)
         cachedImage->paint (g);
     else
-        paintEntireComponent (g, false);
+        paintEntireComponent (g, false, opaqueLayer);
 }
 
-void Component::paintComponentAndChildren (Graphics& g)
+void Component::paintComponentAndChildren (Graphics& g, OpaqueLayer& opaqueLayer)
 {
    #if JUCE_ETW_TRACELOGGING
     {
@@ -1727,70 +1904,64 @@ void Component::paintComponentAndChildren (Graphics& g)
     }
    #endif
 
-    auto clipBounds = g.getClipBounds();
+    const auto paintBounds = opaqueLayer.getCurrentComponentPaintBounds (g);
 
-    if (flags.dontClipGraphicsFlag && getNumChildComponents() == 0)
-    {
-        paint (g);
-    }
-    else
+    if (! paintBounds.isEmpty())
     {
         Graphics::ScopedSaveState ss (g);
 
-        if (! (detail::ComponentHelpers::clipObscuredRegions (*this, g, clipBounds, {}) && g.isClipEmpty()))
-            paint (g);
+        if (! isPaintingUnclipped())
+            g.reduceClipRegion (paintBounds);
+
+        paint (g);
     }
 
-    for (int i = 0; i < childComponentList.size(); ++i)
+    for (auto* child : getChildren())
     {
-        auto& child = *childComponentList.getUnchecked (i);
+        if (! detail::ComponentHelpers::isVisibleWithNonZeroArea (*child))
+            continue;
 
-        if (child.isVisible())
+        if (child->isTransformed() || child->componentTransparency != 0)
         {
-            if (child.affineTransform != nullptr)
-            {
-                Graphics::ScopedSaveState ss (g);
+            Graphics::ScopedSaveState ss (g);
 
-                g.addTransform (*child.affineTransform);
+            if (auto& transform = child->affineTransform)
+                g.addTransform (*transform);
 
-                if ((child.flags.dontClipGraphicsFlag && ! g.isClipEmpty()) || g.reduceClipRegion (child.getBounds()))
-                    child.paintWithinParentContext (g);
-            }
-            else if (clipBounds.intersects (child.getBounds()))
-            {
-                Graphics::ScopedSaveState ss (g);
+            child->paintWithinParentContext (g, opaqueLayer);
+        }
+        else
+        {
+            const auto componentPopper = opaqueLayer.pushComponent (*child);
+            const auto componentBounds = opaqueLayer.getCurrentComponentBounds (g);
 
-                if (child.flags.dontClipGraphicsFlag)
-                {
-                    child.paintWithinParentContext (g);
-                }
-                else if (g.reduceClipRegion (child.getBounds()))
-                {
-                    bool nothingClipped = true;
+            if (componentBounds.isEmpty())
+                continue;
 
-                    for (int j = i + 1; j < childComponentList.size(); ++j)
-                    {
-                        auto& sibling = *childComponentList.getUnchecked (j);
+            Graphics::ScopedSaveState ss (g);
 
-                        if (sibling.flags.opaqueFlag && sibling.isVisible() && sibling.affineTransform == nullptr)
-                        {
-                            nothingClipped = false;
-                            g.excludeClipRegion (sibling.getBounds());
-                        }
-                    }
+            if (! child->isPaintingUnclipped())
+                g.reduceClipRegion (componentBounds);
 
-                    if (nothingClipped || ! g.isClipEmpty())
-                        child.paintWithinParentContext (g);
-                }
-            }
+            child->paintWithinParentContext (g, opaqueLayer);
         }
     }
 
     Graphics::ScopedSaveState ss (g);
+
+    if (! isPaintingUnclipped())
+        g.reduceClipRegion (getLocalBounds());
+
     paintOverChildren (g);
 }
 
 void Component::paintEntireComponent (Graphics& g, bool ignoreAlphaLevel)
+{
+    OpaqueLayer opaqueLayer { this };
+    paintEntireComponent (g, ignoreAlphaLevel, opaqueLayer);
+}
+
+void Component::paintEntireComponent (Graphics& g, bool ignoreAlphaLevel, OpaqueLayer& opaqueLayer)
 {
     // If sizing a top-level-window and the OS paint message is delivered synchronously
     // before resized() is called, then we'll invoke the callback here, to make sure
@@ -1806,20 +1977,26 @@ void Component::paintEntireComponent (Graphics& g, bool ignoreAlphaLevel)
 
     if (effectState != nullptr)
     {
-        effectState->paint (g, *this, ignoreAlphaLevel);
+        effectState->paint (g, *this, ignoreAlphaLevel, opaqueLayer);
     }
     else if (componentTransparency > 0 && ! ignoreAlphaLevel)
     {
         if (componentTransparency < 255)
         {
+            OpaqueLayer transparentOpaqueLayer { this };
             g.beginTransparencyLayer (getAlpha());
-            paintComponentAndChildren (g);
+            paintComponentAndChildren (g, transparentOpaqueLayer);
             g.endTransparencyLayer();
         }
     }
+    else if (isTransformed())
+    {
+        OpaqueLayer transformedOpaqueLayer { this };
+        paintComponentAndChildren (g, transformedOpaqueLayer);
+    }
     else
     {
-        paintComponentAndChildren (g);
+        paintComponentAndChildren (g, opaqueLayer);
     }
 
    #if JUCE_DEBUG
@@ -3090,7 +3267,13 @@ struct ComponentTests  : public UnitTest
             ++numPaintCalls;
         }
 
+        void paintOverChildren (Graphics&) final
+        {
+            ++numPaintOverChildrenCalls;
+        }
+
         int numPaintCalls = 0;
+        int numPaintOverChildrenCalls = 0;
         Rectangle<int> lastClipBounds;
     };
 
@@ -3116,12 +3299,16 @@ struct ComponentTests  : public UnitTest
             parent->addAndMakeVisible (*child);
 
             expectEquals (parent->numPaintCalls, 0);
+            expectEquals (parent->numPaintOverChildrenCalls, 0);
             expectEquals (child->numPaintCalls, 0);
+            expectEquals (child->numPaintOverChildrenCalls, 0);
 
             paintComponentBounds (*parent);
 
             expectEquals (parent->numPaintCalls, 1);
+            expectEquals (parent->numPaintOverChildrenCalls, 1);
             expectEquals (child->numPaintCalls, 1);
+            expectEquals (child->numPaintOverChildrenCalls, 1);
         }
 
         beginTest ("Non-opaque children require their parent to repaint");
@@ -3157,6 +3344,7 @@ struct ComponentTests  : public UnitTest
 
             expectEquals (parent->numPaintCalls, 0);
             expectEquals (child->numPaintCalls, 1);
+            expectEquals (parent->numPaintOverChildrenCalls, 1);
         }
 
         beginTest ("Opaque children don't require their parent to repaint (even when the parent uses setPaintingIsUnclipped (true))");
@@ -3176,6 +3364,7 @@ struct ComponentTests  : public UnitTest
 
             expectEquals (parent->numPaintCalls, 0);
             expectEquals (child->numPaintCalls, 1);
+            expectEquals (parent->numPaintOverChildrenCalls, 1);
         }
 
         beginTest ("A partially obscured parent will repaint with reduced clip bounds");
@@ -3218,6 +3407,7 @@ struct ComponentTests  : public UnitTest
             paintComponentBounds (*parent);
 
             expectEquals (parent->numPaintCalls, 0);
+            expectEquals (parent->numPaintOverChildrenCalls, 1);
             expectEquals (child1->numPaintCalls, 1);
             expectEquals (child2->numPaintCalls, 1);
         }
@@ -3245,11 +3435,44 @@ struct ComponentTests  : public UnitTest
             paintComponentBounds (*parent);
 
             expectEquals (parent->numPaintCalls, 0);
+            expectEquals (parent->numPaintOverChildrenCalls, 1);
             expectEquals (child1->numPaintCalls, 0);
+            expectEquals (child1->numPaintOverChildrenCalls, 0);
             expectEquals (child2->numPaintCalls, 1);
             expectEquals (child3->numPaintCalls, 1);
         }
 
+        beginTest ("An opaque component will hide parent-sibling components behind it");
+        {
+            const auto parent = std::make_unique<TestComponent>();
+            const auto child1 = std::make_unique<TestComponent>();
+            const auto child2 = std::make_unique<TestComponent>();
+            const auto child3 = std::make_unique<TestComponent>();
+
+            Rectangle<int> bounds { 0, 0, 100, 100 };
+            parent->setBounds (bounds);
+
+            child1->setBounds (bounds);
+            parent->addAndMakeVisible (*child1);
+
+            child2->setBounds (bounds);
+            parent->addAndMakeVisible (*child2);
+
+            child3->setBounds (bounds);
+            child3->setOpaque (true);
+            child2->addAndMakeVisible (*child3);
+
+            paintComponentBounds (*parent);
+
+            expectEquals (parent->numPaintCalls, 0);
+            expectEquals (parent->numPaintOverChildrenCalls, 1);
+            expectEquals (child1->numPaintCalls, 0);
+            expectEquals (child1->numPaintOverChildrenCalls, 0);
+            expectEquals (child2->numPaintCalls, 0);
+            expectEquals (child2->numPaintOverChildrenCalls, 1);
+            expectEquals (child3->numPaintCalls, 1);
+        }
+
         beginTest ("An opaque component will reduce the clip bounds of sibling components behind it");
         {
             const auto parent = std::make_unique<TestComponent>();
@@ -3427,7 +3650,7 @@ struct ComponentTests  : public UnitTest
             expectEquals (grandchild->numPaintCalls, 0);
         }
 
-        beginTest ("Components with a width of 0 will not have their paint function called");
+        beginTest ("Components with a width of 0 will not have their paint functions called");
         {
             const auto parent = std::make_unique<TestComponent>();
             const auto child = std::make_unique<TestComponent>();
@@ -3442,9 +3665,10 @@ struct ComponentTests  : public UnitTest
 
             expectEquals (parent->numPaintCalls, 1);
             expectEquals (child->numPaintCalls, 0);
+            expectEquals (child->numPaintOverChildrenCalls, 0);
         }
 
-        beginTest ("Components with a height of 0 will not have their paint function called");
+        beginTest ("Components with a height of 0 will not have their paint functions called");
         {
             const auto parent = std::make_unique<TestComponent>();
             const auto child = std::make_unique<TestComponent>();
@@ -3459,6 +3683,7 @@ struct ComponentTests  : public UnitTest
 
             expectEquals (parent->numPaintCalls, 1);
             expectEquals (child->numPaintCalls, 0);
+            expectEquals (child->numPaintOverChildrenCalls, 0);
         }
 
         beginTest ("Transparent components will not be considered opaque");
@@ -3480,6 +3705,30 @@ struct ComponentTests  : public UnitTest
             expectEquals (child->numPaintCalls, 1);
         }
 
+        beginTest ("Opaque components will only be considered opaque up to a transparent parent");
+        {
+            const auto parent = std::make_unique<TestComponent>();
+            const auto child1 = std::make_unique<TestComponent>();
+            const auto child2 = std::make_unique<TestComponent>();
+
+            Rectangle<int> bounds { 0, 0, 100, 100 };
+            parent->setBounds (bounds);
+
+            child1->setBounds (bounds);
+            child1->setAlpha (0.5f);
+            parent->addAndMakeVisible (*child1);
+
+            child2->setBounds (bounds);
+            child2->setOpaque (true);
+            child1->addAndMakeVisible (*child2);
+
+            paintComponentBounds (*parent);
+
+            expectEquals (parent->numPaintCalls, 1);
+            expectEquals (child1->numPaintCalls, 0);
+            expectEquals (child2->numPaintCalls, 1);
+        }
+
         beginTest ("Transformed components will not be considered opaque");
         {
             const auto parent = std::make_unique<TestComponent>();
@@ -3499,6 +3748,30 @@ struct ComponentTests  : public UnitTest
             expectEquals (child->numPaintCalls, 1);
         }
 
+        beginTest ("Opaque components will only be considered opaque up to a transformed parent");
+        {
+            const auto parent = std::make_unique<TestComponent>();
+            const auto child1 = std::make_unique<TestComponent>();
+            const auto child2 = std::make_unique<TestComponent>();
+
+            Rectangle<int> bounds { 0, 0, 100, 100 };
+            parent->setBounds (bounds);
+
+            child1->setBounds (bounds);
+            child1->setTransform (AffineTransform::rotation (degreesToRadians (45.0f)));
+            parent->addAndMakeVisible (*child1);
+
+            child2->setBounds (bounds);
+            child2->setOpaque (true);
+            child1->addAndMakeVisible (*child2);
+
+            paintComponentBounds (*parent);
+
+            expectEquals (parent->numPaintCalls, 1);
+            expectEquals (child1->numPaintCalls, 0);
+            expectEquals (child2->numPaintCalls, 1);
+        }
+
         beginTest ("Nested opaque components prevent parents from being painted");
         {
             const auto parent = std::make_unique<TestComponent>();
@@ -3522,6 +3795,31 @@ struct ComponentTests  : public UnitTest
             expectEquals (child1->numPaintCalls, 0);
             expectEquals (child2->numPaintCalls, 1);
         }
+
+        beginTest ("Areas of an opaque component outside its parent will not be considered opaque");
+        {
+            const auto parent = std::make_unique<TestComponent>();
+            const auto child1 = std::make_unique<TestComponent>();
+            const auto child2 = std::make_unique<TestComponent>();
+            const auto child3 = std::make_unique<TestComponent>();
+
+            parent->setBounds ({ 0, 0, 100, 100 });
+
+            child1->setBounds ({ 50, 0, 50, 100 });
+            parent->addAndMakeVisible (*child1);
+
+            child2->setBounds ({ -50, 0, 100, 100 });
+            child2->setOpaque (true);
+            child1->addAndMakeVisible (*child2);
+
+            paintComponentBounds (*parent);
+
+            expectEquals (parent->numPaintCalls, 1);
+            expect (parent->lastClipBounds == Rectangle { 0, 0, 50, 100 });
+            expectEquals (child1->numPaintCalls, 0);
+            expectEquals (child2->numPaintCalls, 1);
+            expect (child2->lastClipBounds == Rectangle { 50, 0, 50, 100 });
+        }
     }
 };
 

modules/juce_gui_basics/components/juce_Component.h

@@ -1194,7 +1194,7 @@ public:
 
         If you enable this mode, you'll need to make sure your paint method doesn't call anything like
         Graphics::fillAll(), and doesn't draw beyond the component's bounds, because that'll produce
-        artifacts. This option will have no effect on components that contain any child components.
+        artifacts.
     */
     void setPaintingIsUnclipped (bool shouldPaintWithoutClipping) noexcept;
 
@@ -1276,14 +1276,20 @@ public:
     /** Indicates whether any parts of the component might be transparent.
 
         Components that always paint all of their contents with solid colour and
-        thus completely cover any components behind them should use this method
+        thus completely cover any components behind them, can use this method to
         to tell the repaint system that they are opaque.
 
         This information is used to optimise drawing, because it means that
-        objects underneath opaque windows don't need to be painted.
+        objects underneath opaque components or windows don't need to be painted
+        or can have their clip bounds reduced to a smaller size.
 
-        By default, components are considered transparent, unless this is used to
-        make it otherwise.
+        Note however that there is a cost for every other component to check if
+        it is being obscured by opaque components. This cost should be carefully
+        weighed up against the benefits before deciding to enable this.
+
+        The default value of this property is false, which means that a
+        component will be considered transparent unless setOpaque (true) is
+        called on that component.
 
         @see isOpaque
     */
@@ -2712,6 +2718,8 @@ private:
     uint8 componentTransparency = 0;
 
     //==============================================================================
+    class OpaqueLayer;
+
     static void internalMouseEnter (SafePointer<Component>, MouseInputSource, Point<float>, Time);
     static void internalMouseExit  (SafePointer<Component>, MouseInputSource, Point<float>, Time);
     static void internalMouseDown  (SafePointer<Component>, MouseInputSource, const detail::PointerState&, Time);
@@ -2733,8 +2741,9 @@ private:
     void internalRepaintUnchecked (Rectangle<int>, bool);
     Component* removeChildComponent (int index, bool sendParentEvents, bool sendChildEvents);
     void reorderChildInternal (int sourceIndex, int destIndex);
-    void paintComponentAndChildren (Graphics&);
-    void paintWithinParentContext (Graphics&);
+    void paintEntireComponent (Graphics&, bool, OpaqueLayer&);
+    void paintComponentAndChildren (Graphics&, OpaqueLayer&);
+    void paintWithinParentContext (Graphics&, OpaqueLayer&);
     void sendMovedResizedMessages (bool wasMoved, bool wasResized);
     void sendMovedResizedMessagesIfPending();
     void repaintParent();

modules/juce_gui_basics/detail/juce_ComponentHelpers.h

@@ -193,42 +193,6 @@ struct ComponentHelpers
         return convertFromDistantParentSpace (topLevelComp, *target, p);
     }
 
-    static bool clipChildComponent (const Component& child,
-                                    Graphics& g,
-                                    const Rectangle<int> clipRect,
-                                    Point<int> delta)
-    {
-        if (! child.isVisible() || child.isTransformed())
-            return false;
-
-        const auto newClip = clipRect.getIntersection (child.boundsRelativeToParent);
-
-        if (newClip.isEmpty())
-            return false;
-
-        if (child.isOpaque() && child.componentTransparency == 0)
-        {
-            g.excludeClipRegion (newClip + delta);
-            return true;
-        }
-
-        const auto childPos = child.getPosition();
-        return clipObscuredRegions (child, g, newClip - childPos, childPos + delta);
-    }
-
-    static bool clipObscuredRegions (const Component& comp,
-                                     Graphics& g,
-                                     const Rectangle<int> clipRect,
-                                     Point<int> delta)
-    {
-        auto wasClipped = false;
-
-        for (int i = comp.childComponentList.size(); --i >= 0;)
-            wasClipped |= clipChildComponent (*comp.childComponentList.getUnchecked (i), g, clipRect, delta);
-
-        return wasClipped;
-    }
-
     static Rectangle<int> getParentOrMainMonitorBounds (const Component& comp)
     {
         if (auto* p = comp.getParentComponent())
@@ -263,6 +227,13 @@ struct ComponentHelpers
                     function (c, ms, SH::screenPosToLocalPos (*c, ms.getScreenPosition()), Time::getCurrentTime());
     }
 
+    static bool isVisibleWithNonZeroArea (const Component& component)
+    {
+        return component.isVisible()
+            && component.getWidth() > 0
+            && component.getHeight() > 0;
+    }
+
     class ModalComponentManagerChangeNotifier
     {
     public: