API: Replace the Canvas::clear() API with Canvas::remove() & draw()

Added a `clear` parameter to Canvas::draw(), allowing users to decide
whether to clear the target buffer before drawing.

To remove the paints from a canvas, please use Canvas::remove()

C++ API Removals:
- Result Canvas::clear(bool paints, bool buffer)

C++ API Modifications:
- Result Canvas::draw()
 -> Result Canvas::draw(bool clear)

C API Removals:
- Tvg_Result tvg_canvas_clear(bool paints, bool buffer)

C API Modifications:
- Tvg_Result tvg_canvas_draw(Tvg_Canvas* canvas)
 -> Tvg_Result tvg_canvas_draw(Tvg_Canvas* canvas, bool clear)

issue: https://github.com/thorvg/thorvg/issues/1372

examples/Animation.cpp

@@ -90,5 +90,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 1024, 1024);
+    return tvgexam::main(new UserExample, argc, argv, false, 1024, 1024);
 }

examples/Blending.cpp

@@ -175,5 +175,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 1024, 1024);
+    return tvgexam::main(new UserExample, argc, argv, true, 1024, 1024);
 }

examples/Capi.cpp

@@ -332,9 +332,6 @@ int main(int argc, char **argv)
             }
         }
 
-        //Clear the canvas
-        tvg_canvas_clear(canvas, false, true);
-
         //Update the animation
         if (animation) {
             float duration, totalFrame;
@@ -345,7 +342,7 @@ int main(int argc, char **argv)
 
         //Draw the canvas
         tvg_canvas_update(canvas);
-        tvg_canvas_draw(canvas);
+        tvg_canvas_draw(canvas, true);
         tvg_canvas_sync(canvas);
 
         SDL_UpdateWindowSurface(window);

examples/CustomTransform.cpp

@@ -37,7 +37,7 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        if (!tvgexam::verify(canvas->clear())) return false;
+        if (!tvgexam::verify(canvas->remove())) return false;
 
         auto progress = tvgexam::progress(elapsed, 2.0f, true);  //play time 2 sec.
 
@@ -108,5 +108,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv);
+    return tvgexam::main(new UserExample, argc, argv, true);
 }

examples/DirectUpdate.cpp

@@ -87,9 +87,6 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        //clear buffer and redraw!
-        if (!tvgexam::verify(canvas->clear(false))) return false;
-
         auto progress = tvgexam::progress(elapsed, 2.0f, true);  //play time 2 sec.
 
         //Reset Shape

examples/EffectDropShadow.cpp

@@ -96,8 +96,6 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        canvas->clear(false);
-
         auto progress = tvgexam::progress(elapsed, 2.5f, true);   //2.5 seconds
 
         //Clear the previously applied effects
@@ -125,5 +123,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 800, 800, 4, true);
+    return tvgexam::main(new UserExample, argc, argv, false, 800, 800, 4, true);
 }

examples/EffectGaussianBlur.cpp

@@ -53,8 +53,6 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        canvas->clear(false);
-
         auto progress = tvgexam::progress(elapsed, 2.5f, true);   //2.5 seconds
 
         for (int i = 0; i < 3; ++i) {
@@ -78,5 +76,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 1200, 400, 4, true);
+    return tvgexam::main(new UserExample, argc, argv, true, 1200, 400, 4, true);
 }

examples/Example.h

@@ -137,6 +137,7 @@ struct Window
     bool needResize = false;
     bool needDraw = false;
     bool initialized = false;
+    bool clearBuffer = false;
     bool print = false;
 
     Window(tvg::CanvasEngine engine, Example* example, uint32_t width, uint32_t height, uint32_t threadsCnt)
@@ -170,7 +171,7 @@ struct Window
     bool draw()
     {
         //Draw the contents to the Canvas
-        if (verify(canvas->draw())) {
+        if (verify(canvas->draw(clearBuffer))) {
             verify(canvas->sync());
             return true;
         }
@@ -525,7 +526,7 @@ bool verify(tvg::Result result, string failMsg)
 }
 
 
-int main(Example* example, int argc, char **argv, uint32_t width = 800, uint32_t height = 800, uint32_t threadsCnt = 4, bool print = false)
+int main(Example* example, int argc, char **argv, bool clearBuffer = false, uint32_t width = 800, uint32_t height = 800, uint32_t threadsCnt = 4, bool print = false)
 {
     auto engine = tvg::CanvasEngine::Sw;
 
@@ -544,6 +545,7 @@ int main(Example* example, int argc, char **argv, uint32_t width = 800, uint32_t
         window = unique_ptr<Window>(new WgWindow(example, width, height, threadsCnt));
     }
 
+    window->clearBuffer = clearBuffer;
     window->print = print;
 
     if (window->ready()) {

examples/GradientTransform.cpp

@@ -37,7 +37,7 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        if (!tvgexam::verify(canvas->clear())) return false;
+        tvgexam::verify(canvas->remove());
 
         auto progress = tvgexam::progress(elapsed, 2.0f, true);  //play time 2 sec.
 
@@ -129,5 +129,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv);
+    return tvgexam::main(new UserExample, argc, argv, true);
 }

examples/ImageRotation.cpp

@@ -54,8 +54,6 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        canvas->clear(false);
-
         tvg::Matrix m = {1.0f, 0.0f, 0.0f, 0.0f, 0.1f, 0.0f, 0.0f, 0.0f, 1.0f};
 
         //center pivoting
@@ -95,5 +93,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv);
+    return tvgexam::main(new UserExample, argc, argv, true);
 }

examples/ImageScaleDown.cpp

@@ -48,8 +48,6 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        canvas->clear(false);
-
         auto progress = tvgexam::progress(elapsed, 7.0f, true);  //play time 7 sec.
 
         picture->scale(1.0f - progress);
@@ -67,5 +65,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv);
+    return tvgexam::main(new UserExample, argc, argv, true);
 }

examples/ImageScaleUp.cpp

@@ -49,8 +49,6 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        canvas->clear(false);
-
         auto progress = tvgexam::progress(elapsed, 7.0f, true);  //play time 7 sec.
 
         picture->scale(progress * 4.0f);
@@ -68,5 +66,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv);
+    return tvgexam::main(new UserExample, argc, argv, true);
 }

examples/Interaction.cpp

@@ -145,5 +145,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 1024, 1024, 0);
+    return tvgexam::main(new UserExample, argc, argv, true, 1024, 1024, 0);
 }

examples/Lottie.cpp

@@ -121,5 +121,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 1280, 1280, 4, true);
+    return tvgexam::main(new UserExample, argc, argv, false, 1280, 1280, 4, true);
 }

examples/LottieExpressions.cpp

@@ -122,5 +122,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 800, 800, 0, true);
+    return tvgexam::main(new UserExample, argc, argv, false, 800, 800, 0, true);
 }

examples/MaskingMethods.cpp

@@ -566,5 +566,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 1500, 1024);
+    return tvgexam::main(new UserExample, argc, argv, false, 1500, 1024);
 }

examples/Performance.cpp

@@ -59,8 +59,6 @@ struct UserExample : tvgexam::Example
 
         auto progress = tvgexam::progress(elapsed, 2.0f, true);  //play time 2 sec.
 
-        canvas->clear(false);
-
         picture->translate(w * progress * 0.05f, h * progress * 0.05f);
 
         canvas->update();
@@ -76,5 +74,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 1024, 1024, 4, true);
+    return tvgexam::main(new UserExample, argc, argv, true, 1024, 1024, 4, true);
 }

examples/Retaining.cpp

@@ -106,5 +106,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv);
+    return tvgexam::main(new UserExample, argc, argv, true);
 }

examples/SceneTransform.cpp

@@ -37,7 +37,7 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        if (!tvgexam::verify(canvas->clear())) return false;
+        if (!tvgexam::verify(canvas->remove())) return false;
 
         auto progress = tvgexam::progress(elapsed, 2.0f, true);  //play time 2 sec.
 
@@ -129,5 +129,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv);
+    return tvgexam::main(new UserExample, argc, argv, true);
 }

examples/Svg.cpp

@@ -114,5 +114,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 1280, 1280);
+    return tvgexam::main(new UserExample, argc, argv, false, 1280, 1280);
 }

examples/Transform.cpp

@@ -37,7 +37,7 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        if (!tvgexam::verify(canvas->clear())) return false;
+        if (!tvgexam::verify(canvas->remove())) return false;
 
         auto progress = tvgexam::progress(elapsed, 2.0f, true);  //play time 2 sec.
 
@@ -86,5 +86,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv);
+    return tvgexam::main(new UserExample, argc, argv, true);
 }

examples/Update.cpp

@@ -45,7 +45,7 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        if (!tvgexam::verify(canvas->clear())) return false;
+        if (!tvgexam::verify(canvas->remove())) return false;
 
         auto progress = tvgexam::progress(elapsed, 2.0f, true);  //play time 2 sec.
 
@@ -70,5 +70,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv);
+    return tvgexam::main(new UserExample, argc, argv, true);
 }

examples/Viewport.cpp

@@ -58,8 +58,6 @@ struct UserExample : tvgexam::Example
     {
         if (!canvas) return false;
 
-        canvas->clear(false);
-
         auto progress = tvgexam::progress(elapsed, 2.0f, true);  //play time 2 sec.
 
         if (!tvgexam::verify(canvas->viewport((w - VPORT_SIZE) * progress, (h - VPORT_SIZE) * progress, VPORT_SIZE, VPORT_SIZE))) return false;
@@ -77,5 +75,5 @@ struct UserExample : tvgexam::Example
 
 int main(int argc, char **argv)
 {
-    return tvgexam::main(new UserExample, argc, argv, 1024, 1024, 4, true);
+    return tvgexam::main(new UserExample, argc, argv, true, 1024, 1024, 4, true);
 }

inc/thorvg.h

@@ -642,7 +642,7 @@ public:
      *
      * @warning Please avoid accessing the paints during Canvas update/draw. You can access them after calling sync().
      * @see Canvas::push()
-     * @see Canvas::clear()
+     * @see Canvas::remove()
      *
      * @warning This is read-only. Do not modify the list.
      * @note 1.0
@@ -667,25 +667,10 @@ public:
      * @note The rendering order of the paints is the same as the order as they were pushed. Consider sorting the paints before pushing them if you intend to use layering.
      *
      * @see Canvas::paints()
-     * @see Canvas::clear()
+     * @see Canvas::remove()
      */
     Result push(Paint* target, Paint* at = nullptr) noexcept;
 
-    /**
-     * @brief Clear the internal canvas resources that used for the drawing.
-     *
-     * This API sets the total number of paints pushed into the canvas to zero.
-     * Depending on the value of the @p paints argument, the paints are either freed or retained.
-     * So if you need to update paint properties while maintaining the existing scene structure, you can set @p paints = false.
-     *
-     * @param[in] paints If @c true, the memory occupied by paints is deallocated; otherwise, the paints will be retained on the canvas.
-     * @param[in] buffer If @c true, the canvas target buffer is cleared with a zero value.
-     *
-     * @see Canvas::push()
-     * @see Canvas::paints()
-     */
-    Result clear(bool paints = true, bool buffer = true) noexcept;
-
     /**
      * @brief Removes a paint object or all paint objects from the root scene.
      *
@@ -716,12 +701,18 @@ public:
     Result update(Paint* paint = nullptr) noexcept;
 
     /**
-     * @brief Requests the canvas to draw the Paint objects.
+     * @brief Requests the canvas to render Paint objects.
+     *
+     * @param[in] clear If @c true, clears the target buffer to zero before drawing.
+     *
+     * @note Clearing the buffer is unnecessary if the canvas will be fully covered 
+     *       with opaque content, which can improve performance.
+     * @note Drawing may be asynchronous if the thread count is greater than zero. 
+     *       To ensure drawing is complete, call sync() afterwards.
      *
-     * @note Drawing can be asynchronous if the assigned thread number is greater than zero. To guarantee the drawing is done, call sync() afterwards.
      * @see Canvas::sync()
      */
-    Result draw() noexcept;
+    Result draw(bool clear = false) noexcept;
 
     /**
      * @brief Sets the drawing region in the canvas.

src/bindings/capi/thorvg_capi.h

@@ -589,11 +589,6 @@ TVG_API Tvg_Result tvg_wgcanvas_set_target(Tvg_Canvas* canvas, void* device, voi
 *
 * @return Tvg_Result enumeration.
 * @retval TVG_RESULT_INVALID_ARGUMENT An invalid pointer to the Tvg_Canvas object is passed.
-*
-* @note If the paints from the canvas should not be released, the tvg_canvas_clear() with a @c free argument value set to @c false should be called.
-* Please be aware that in such a case TVG is not responsible for the paints release anymore and it has to be done manually in order to avoid memory leaks.
-*
-* @see tvg_canvas_clear()
 */
 TVG_API Tvg_Result tvg_canvas_destroy(Tvg_Canvas* canvas);
 
@@ -605,7 +600,7 @@ TVG_API Tvg_Result tvg_canvas_destroy(Tvg_Canvas* canvas);
 * @param[in] paint The Tvg_Paint object to be drawn.
 *
 * Only the paints pushed into the canvas will be drawing targets.
-* They are retained by the canvas until you call tvg_canvas_clear() or tvg_canvas_remove()
+* They are retained by the canvas until you call tvg_canvas_remove()
 *
 * @return Tvg_Result return values:
 * @retval TVG_RESULT_INVALID_ARGUMENT In case a @c nullptr is passed as the argument.
@@ -614,7 +609,6 @@ TVG_API Tvg_Result tvg_canvas_destroy(Tvg_Canvas* canvas);
 * @note The rendering order of the paints is the same as the order as they were pushed. Consider sorting the paints before pushing them if you intend to use layering.
 * @see tvg_canvas_push_at()
 * @see tvg_canvas_remove()
-* @see tvg_canvas_clear()
 */
 TVG_API Tvg_Result tvg_canvas_push(Tvg_Canvas* canvas, Tvg_Paint* paint);
 
@@ -639,29 +633,12 @@ TVG_API Tvg_Result tvg_canvas_push(Tvg_Canvas* canvas, Tvg_Paint* paint);
  *
  * @see tvg_canvas_push()
  * @see tvg_canvas_remove()
- * @see tvg_canvas_clear()
+ * @see tvg_canvas_remove()
  * @since 1.0
  */
 TVG_API Tvg_Result tvg_canvas_push_at(Tvg_Canvas* canvas, Tvg_Paint* target, Tvg_Paint* at);
 
 
-/*!
-* @brief Sets the total number of the paints pushed into the canvas to be zero.
-* Tvg_Paint objects stored in the canvas are released if @p paints is set to @c true, otherwise the memory is not deallocated and
-* all paints should be released manually in order to avoid memory leaks.
-*
-* @param[in] canvas The Tvg_Canvas object to be cleared.
-* @param[in] paints If @c true, The memory occupied by paints is deallocated; otherwise, the paints will be retained on the canvas.
-* @param[in] buffer If @c true the canvas target buffer is cleared with a zero value.
-*
-* @return Tvg_Result enumeration.
-* @retval TVG_RESULT_INVALID_ARGUMENT An invalid Tvg_Canvas pointer.
-*
-* @see tvg_canvas_destroy()
-*/
-TVG_API Tvg_Result tvg_canvas_clear(Tvg_Canvas* canvas, bool paints, bool buffer);
-
-
 /**
  * @brief Removes a paint object from the root scene.
  *
@@ -718,14 +695,18 @@ TVG_API Tvg_Result tvg_canvas_update_paint(Tvg_Canvas* canvas, Tvg_Paint* paint)
 * All paints from the given canvas will be rasterized to the buffer.
 *
 * @param[in] canvas The Tvg_Canvas object containing elements to be drawn.
+* @param[in] clear If @c true, clears the target buffer to zero before drawing.
 *
 * @return Tvg_Result enumeration.
 * @retval TVG_RESULT_INVALID_ARGUMENT An invalid Tvg_Canvas pointer.
 *
-* @note Drawing can be asynchronous based on the assigned thread number. To guarantee the drawing is done, call tvg_canvas_sync() afterwards.
+* @note Clearing the buffer is unnecessary if the canvas will be fully covered 
+*       with opaque content, which can improve performance.
+* @note Drawing may be asynchronous if the thread count is greater than zero.
+*       To ensure drawing is complete, call tvg_canvas_sync() afterwards.
 * @see tvg_canvas_sync()
 */
-TVG_API Tvg_Result tvg_canvas_draw(Tvg_Canvas* canvas);
+TVG_API Tvg_Result tvg_canvas_draw(Tvg_Canvas* canvas, bool clear);
 
 
 /*!
@@ -787,10 +768,7 @@ TVG_API Tvg_Result tvg_canvas_set_viewport(Tvg_Canvas* canvas, int32_t x, int32_
 * @return Tvg_Result enumeration.
 * @retval TVG_RESULT_INVALID_ARGUMENT An invalid Tvg_Paint pointer.
 *
-* @warning If this function is used, tvg_canvas_clear() with the @c free argument value set to @c false should be used in order to avoid unexpected behaviours.
-*
 * @see tvg_canvas_remove()
-* @see tvg_canvas_clear()
 */
 TVG_API Tvg_Result tvg_paint_del(Tvg_Paint* paint);
 

src/bindings/capi/tvgCapi.cpp

@@ -130,12 +130,6 @@ TVG_API Tvg_Result tvg_canvas_push_at(Tvg_Canvas* canvas, Tvg_Paint* paint, Tvg_
 }
 
 
-TVG_API Tvg_Result tvg_canvas_clear(Tvg_Canvas* canvas, bool paints, bool buffer)
-{
-    if (!canvas) return TVG_RESULT_INVALID_ARGUMENT;
-    return (Tvg_Result) reinterpret_cast<Canvas*>(canvas)->clear(paints, buffer);
-}
-
 TVG_API Tvg_Result tvg_canvas_remove(Tvg_Canvas* canvas, Tvg_Paint* paint)
 {
     if (!canvas) return TVG_RESULT_INVALID_ARGUMENT;
@@ -157,10 +151,10 @@ TVG_API Tvg_Result tvg_canvas_update_paint(Tvg_Canvas* canvas, Tvg_Paint* paint)
 }
 
 
-TVG_API Tvg_Result tvg_canvas_draw(Tvg_Canvas* canvas)
+TVG_API Tvg_Result tvg_canvas_draw(Tvg_Canvas* canvas, bool clear)
 {
     if (!canvas) return TVG_RESULT_INVALID_ARGUMENT;
-    return (Tvg_Result) reinterpret_cast<Canvas*>(canvas)->draw();
+    return (Tvg_Result) reinterpret_cast<Canvas*>(canvas)->draw(clear);
 }
 
 

src/renderer/gl_engine/tvgGlRenderer.h

@@ -133,7 +133,7 @@ private:
         Key key;
     } mDisposed;
 
-    bool mClearBuffer = true;
+    bool mClearBuffer = true;  //FIXME: clear buffer should be optional (default is false)
 
     BlendMethod mBlendMethod = BlendMethod::Normal;
 };

src/renderer/tvgCanvas.cpp

@@ -49,16 +49,10 @@ Result Canvas::push(Paint* target, Paint* at) noexcept
 }
 
 
-Result Canvas::clear(bool paints, bool buffer) noexcept
+Result Canvas::draw(bool clear) noexcept
-{
-    return pImpl->clear(paints, buffer);
-}
-
-
-Result Canvas::draw() noexcept
 {
     TVGLOG("RENDERER", "Draw S. -------------------------------- Canvas(%p)", this);
-    auto ret = pImpl->draw();
+    auto ret = pImpl->draw(clear);
     TVGLOG("RENDERER", "Draw E. -------------------------------- Canvas(%p)", this);
 
     return ret;
@@ -68,7 +62,6 @@ Result Canvas::draw() noexcept
 Result Canvas::update(Paint* paint) noexcept
 {
     TVGLOG("RENDERER", "Update S. ------------------------------ Canvas(%p)", this);
-
     if (pImpl->scene->paints().empty() || pImpl->status == Status::Drawing) return Result::InsufficientCondition;
     auto ret = pImpl->update(paint, false);
     TVGLOG("RENDERER", "Update E. ------------------------------ Canvas(%p)", this);

src/renderer/tvgCanvas.h

@@ -63,29 +63,12 @@ struct Canvas::Impl
         return update(target, true);
     }
 
-    Result clear(bool paints, bool buffer)
-    {
-        auto ret = Result::Success;
-
-        if (status == Status::Drawing) return Result::InsufficientCondition;
-
-        //Clear render target
-        if (buffer && !renderer->clear()) {
-            ret = Result::InsufficientCondition;
-        }
-
-        if (paints) scene->remove();
-
-        return ret;
-    }
-
     Result remove(Paint* paint)
     {
         if (status == Status::Drawing) return Result::InsufficientCondition;
         return scene->remove(paint);
     }
 
-
     Result update(Paint* paint, bool force)
     {
         Array<RenderData> clips;
@@ -101,9 +84,13 @@ struct Canvas::Impl
         return Result::Success;
     }
 
-    Result draw()
+    Result draw(bool clear)
     {
-        if (status == Status::Drawing || scene->paints().empty()) return Result::InsufficientCondition;
+        if (status == Status::Drawing) return Result::InsufficientCondition;
+
+        if (clear && !renderer->clear()) return Result::InsufficientCondition;
+
+        if (scene->paints().empty()) return Result::InsufficientCondition;
 
         if (status == Status::Damaged) update(nullptr, false);
 
@@ -112,6 +99,7 @@ struct Canvas::Impl
         if (!PP(scene)->render(renderer) || !renderer->postRender()) return Result::InsufficientCondition;
 
         status = Status::Drawing;
+
         return Result::Success;
     }
 

src/renderer/wg_engine/tvgWgRenderer.cpp

@@ -239,6 +239,7 @@ const RenderSurface* WgRenderer::mainSurface()
 
 bool WgRenderer::clear()
 {
+    //TODO: clear the current target buffer only if clear() is called
     return true;
 }
 

src/savers/gif/tvgGifSaver.cpp

@@ -65,11 +65,10 @@ void GifSaver::run(unsigned tid)
     auto duration = animation->duration();
 
     for (auto p = 0.0f; p < duration; p += delay) {
-        canvas->clear(false);
         auto frameNo = animation->totalFrame() * (p / duration);
         animation->frame(frameNo);
         canvas->update();
-        if (canvas->draw() == tvg::Result::Success) {
+        if (canvas->draw(true) == tvg::Result::Success) {
             canvas->sync();
         }
         if (!gifWriteFrame(&writer, reinterpret_cast<uint8_t*>(buffer), w, h, uint32_t(delay * 100.0f), transparent)) {

test/testPaint.cpp

@@ -308,18 +308,15 @@ TEST_CASE("Refernce Count", "[tvgPaint]")
     REQUIRE(shape->ref() == 1);
     canvas->push(shape);
     REQUIRE(shape->refCnt() == 2);
-    canvas->clear();
+    REQUIRE(shape->unref() == 1);
-    REQUIRE(shape->refCnt() == 1);
-    REQUIRE(shape->unref() == 0);
 
     shape = Shape::gen();
     REQUIRE(shape->ref() == 1);
     auto scene = Scene::gen();
     scene->push(shape);
     canvas->push(scene);
-    canvas->clear();
+    REQUIRE(shape->refCnt() == 2);
-    REQUIRE(shape->refCnt() == 1);
+    REQUIRE(shape->unref() == 1);
-    REQUIRE(shape->unref() == 0);
 
     shape = Shape::gen();
     REQUIRE(shape->ref() == 1);
@@ -327,7 +324,6 @@ TEST_CASE("Refernce Count", "[tvgPaint]")
     scene->push(shape);
     scene->remove();
     canvas->push(scene);
-    canvas->clear();
     REQUIRE(shape->unref() == 0);
 
     Initializer::term();

tools/svg2png/svg2png.cpp

@@ -131,8 +131,6 @@ public:
             return 1;
         }
 
-        canvas->clear();
-
         //Background color if needed
         if (bgColor != 0xffffffff) {
             uint8_t r = (uint8_t)((bgColor & 0xff0000) >> 16);
@@ -148,7 +146,7 @@ public:
 
         //Drawing
         canvas->push(picture);
-        canvas->draw();
+        canvas->draw(true);
         canvas->sync();
 
         //Build Png