implement animation panel interaction

src/canvas.cpp

@@ -1252,6 +1252,16 @@ void Canvas::layer_add(std::string name, std::shared_ptr<Layer> layer /*= nullpt
     }
     m_current_layer_idx = index;
 }
+
+std::shared_ptr<Layer> Canvas::layer_with_id(uint32_t id)
+{
+    auto layer = std::find_if(m_layers.begin(), m_layers.end(), 
+        [id](const auto& l) { return l->id == id; });
+    if (layer != m_layers.end())
+        return *layer;
+    return nullptr;
+}
+
 void Canvas::layer_remove(int idx) // m_order index
 {
     LOG("canvas layer_remove %d", idx);
@@ -1324,6 +1334,21 @@ void Canvas::layer_merge(int source_idx, int dest_idx) // m_layer index
     });
 }
 
+int Canvas::anim_duration() const noexcept
+{
+    int frames = 1;
+    for (auto& l : m_layers)
+        frames = glm::max(frames, l->total_duration());
+    return frames;
+}
+
+void Canvas::anim_goto_frame(int frame) noexcept
+{
+    m_anim_frame = frame;
+    for (auto& l : m_layers)
+        l->goto_frame(frame);
+}
+
 void Canvas::flood_fill(int layer, int plane, std::vector<glm::ivec2> pos, FloodData& plane_data,
     float threshold, glm::vec4 dest_color, std::unique_ptr<glm::vec4>& source_color)
 {