split app.cpp into multiple files, add NodeScroll and use it to scroll the side panels, some fixes to the events system

engine/node.h

@@ -67,6 +67,7 @@ enum class kWidget : uint16_t
     ColorQuad = const_hash("color-quad"),
     StrokePreview = const_hash("stroke-preview"),
     Canvas = const_hash("canvas"),
+    Scroll = const_hash("scroll"),
 };
 
 class Node
@@ -88,12 +89,16 @@ public:
     glm::mat4 m_mvp;
     bool m_mouse_inside = false;
     bool m_flood_events = false;
+    bool m_capture_children = true; // wether to capture children events when xx_capture() is used
     bool m_destroyed = false;
 
     bool m_mouse_ignore = true;
     float m_zoom = 1.f;
     glm::vec2 m_scale{ 1.f };
     glm::vec2 m_pos;
+    glm::vec2 m_pos_origin; // original layout position without offset
+    glm::vec2 m_pos_offset; // artificial position offset for scrolling
+    glm::vec2 m_pos_offset_childred; // artificial position offset for scrolling
     glm::vec2 m_size;
     glm::vec4 m_clip;
     glm::vec4 m_clip_uncut;
@@ -114,6 +119,7 @@ public:
     void SetSize(float w, float h);
 
     void SetPadding(float t, float r, float b, float l);
+    glm::vec4 GetPadding() const;
     void SetPosition(float l, float t, float r, float b);
     void SetPosition(float l, float t);
     void SetPosition(const glm::vec2 pos);
@@ -132,7 +138,8 @@ public:
     float GetHeight();
     glm::vec2 GetSize();
 
-    glm::vec4 rect_intersection(glm::vec4 a, glm::vec4 b);
+    glm::vec4 rect_intersection(glm::vec4 a, glm::vec4 b) const;
+    glm::vec4 rect_union(glm::vec4 a, glm::vec4 b) const;
 
     virtual void restore_context();;
     virtual void clear_context();
@@ -177,6 +184,7 @@ public:
     void move_child(Node* n, int index);
     void move_child_offset(Node* n, int offset);
     int get_child_index(Node* n);
+    glm::vec4 get_children_rect() const;
     void mouse_capture();
     void mouse_release();
     void key_capture();