add BasePanel & add padding property to SplitBox

src/graphics/ui/elements/BasePanel.hpp

@@ -0,0 +1,43 @@
+#pragma once
+
+#include "Container.hpp"
+
+namespace gui {
+    class BasePanel : public Container {
+    public:
+        virtual ~BasePanel() = default;
+
+        virtual void setOrientation(Orientation orientation) {
+            this->orientation = orientation;
+            refresh();
+        }
+
+        Orientation getOrientation() const {
+            return orientation;
+        }
+
+        virtual void setPadding(glm::vec4 padding) {
+            this->padding = padding;
+            refresh();
+        }
+
+        glm::vec4 getPadding() const {
+            return padding;
+        }
+    protected:
+        BasePanel(
+            glm::vec2 size,
+            glm::vec4 padding = glm::vec4(0.0f),
+            float interval = 2.0f,
+            Orientation orientation = Orientation::vertical
+        )
+            : Container(std::move(size)),
+            padding(std::move(padding)),
+            interval(interval) {
+        }
+
+        Orientation orientation = Orientation::vertical;
+        glm::vec4 padding;
+        float interval = 2.0f;
+    };
+}