common: support static scene mode (internal)

This adds support for a static scene mode,
allowing a scene to be treated as a static image.

In this mode, partial rendering for the inner
drawable components is skipped. This is especially
useful for scenes designed to be fully updated as a whole,
such as those used in fully dynamic Lottie contents.

issue: https://github.com/thorvg/thorvg/issues/1747

src/loaders/lottie/tvgLottieBuilder.cpp

@@ -23,6 +23,7 @@
 #include <algorithm>
 #include "tvgCommon.h"
 #include "tvgMath.h"
+#include "tvgScene.h"
 #include "tvgLottieModel.h"
 #include "tvgLottieBuilder.h"
 #include "tvgLottieExpressions.h"
@@ -1560,4 +1561,7 @@ void LottieBuilder::build(LottieComposition* comp)
     auto clip = Shape::gen();
     clip->appendRect(0, 0, comp->w, comp->h);
     comp->root->scene->clip(clip);
-}
+
+    //turn off partial rendering for children
+    SCENE(comp->root->scene)->size({comp->w, comp->h});
+}

src/renderer/tvgPaint.h

@@ -149,6 +149,11 @@ namespace tvg
             if (renderer) renderer->damage(bounds(renderer));
         }
 
+        void damage(const RenderRegion& vport)
+        {
+            if (renderer) renderer->damage(vport);
+        }
+
         void mark(RenderUpdateFlag flag)
         {
             renderFlag |= flag;

src/renderer/tvgScene.h

@@ -66,8 +66,10 @@ struct SceneImpl : Scene
     list<Paint*> paints;     //children list
     RenderRegion vport = {};
     Array<RenderEffect*>* effects = nullptr;
-    uint8_t opacity;         //for composition
+    Point fsize;          //fixed scene size
+    bool fixed = false;   //true: fixed scene size, false: dynamic size
     bool vdirty = false;
+    uint8_t opacity;      //for composition
 
     SceneImpl() : impl(Paint::Impl(this))
     {
@@ -75,8 +77,14 @@ struct SceneImpl : Scene
 
     ~SceneImpl()
     {
-        resetEffects();
         clearPaints();
+        resetEffects();
+    }
+
+    void size(const Point& size)
+    {
+        this->fsize = size;
+        fixed = (size.x > 0 && size.y > 0) ? true : false;
     }
 
     uint8_t needComposition(uint8_t opacity)
@@ -117,22 +125,36 @@ struct SceneImpl : Scene
             this->opacity = opacity;
             opacity = 255;
         }
+
+        //allow partial rendering?
+        auto recover = fixed ? renderer->partial(true) : false;
+
         for (auto paint : paints) {
             PAINT(paint)->update(renderer, transform, clips, opacity, flag, false);
         }
 
+        //recover the condition
+        renderer->partial(recover);
+
         if (effects) {
             ARRAY_FOREACH(p, *effects) {
                 renderer->prepare(*p, transform);
             }
         }
 
-        //this viewport update is more performant than in bounds()?
+        //this viewport update is more performant than in bounds(). No idea.
         vport = renderer->viewport();
-        vdirty = true;
 
-        //bounds(renderer) here hinders parallelization.
-        if (effects) renderer->damage(vport);
+        if (fixed) {
+            auto pt = fsize * transform;
+            vport.intersect({int32_t(round(transform.e13)), int32_t(round(transform.e23))}, {int32_t(round(pt.x)), int32_t(round(pt.y))});
+        } else {
+            vdirty = true;
+        }
+
+        //bounds(renderer) here hinders parallelization
+        //TODO: we can bring the precise effects region here
+        if (fixed || effects) impl.damage(vport);
 
         return true;
     }
@@ -262,10 +284,13 @@ struct SceneImpl : Scene
         while (itr != paints.end()) {
             auto paint = PAINT((*itr));
             //when the paint is destroyed damage will be triggered
-            if (paint->refCnt > 1) paint->damage();
+            if (paint->refCnt > 1 && !fixed) paint->damage();
             paint->unref();
             paints.erase(itr++);
         }
+
+        if (!effects && fixed) impl.damage(vport);
+
         return Result::Success;
     }
 
@@ -318,7 +343,7 @@ struct SceneImpl : Scene
             }
             delete(effects);
             effects = nullptr;
-            impl.renderer->damage(vport);
+            impl.damage(vport);
         }
         return Result::Success;
     }