improve scrollbar detection and scroll behavior

src/app_layout.cpp

@@ -822,8 +822,6 @@ void App::initLayout()
 
         brush_update();
         
-        TextureManager::load("data/paper.jpg");
-        
         // hacky thing to make the toolbar buttons not steal events when moving cursor fast
         if (auto* toolbar = layout[main_id]->find<Node>("toolbar"))
             toolbar->m_flood_events = true;

src/node.cpp

@@ -241,6 +241,7 @@ void Node::add_child(Node* n)
     n->m_manager = m_manager;
     YGNodeInsertChild(y_node, n->y_node, YGNodeGetChildCount(y_node));
     n->added(this);
+    on_child_added(n);
 }
 
 void Node::add_child(Node* n, int index)
@@ -250,6 +251,7 @@ void Node::add_child(Node* n, int index)
     n->m_manager = m_manager;
     YGNodeInsertChild(y_node, n->y_node, index);
     n->added(this);
+    on_child_added(n);
 }
 
 void Node::add_child(std::shared_ptr<Node> n)
@@ -259,6 +261,7 @@ void Node::add_child(std::shared_ptr<Node> n)
     n->m_manager = m_manager;
     YGNodeInsertChild(y_node, n->y_node, YGNodeGetChildCount(y_node));
     n->added(this);
+    on_child_added(n.get());
 }
 
 void Node::add_child(std::shared_ptr<Node> n, int index)
@@ -268,6 +271,7 @@ void Node::add_child(std::shared_ptr<Node> n, int index)
     n->m_manager = m_manager;
     YGNodeInsertChild(y_node, n->y_node, index);
     n->added(this);
+    on_child_added(n.get());
 }
 
 void Node::remove_child(Node* n)
@@ -277,6 +281,7 @@ void Node::remove_child(Node* n)
     {
         n->removed(this);
         YGNodeRemoveChild(y_node, n->y_node);
+        on_child_removed(n);
         m_children.erase(i);
     }
 }
@@ -287,6 +292,7 @@ void Node::remove_all_children()
     {
         n->removed(this);
         YGNodeRemoveChild(y_node, n->y_node);
+        on_child_removed(n.get());
     }
     m_children.clear();
 }

src/node.h

@@ -224,6 +224,8 @@ public:
     virtual void loaded();
     virtual void added(Node* parent);
     virtual void removed(Node* parent);
+    virtual void on_child_added(Node* child) { };
+    virtual void on_child_removed(Node* child) { };
     const Node* init_template(const char* id);
     void tick(float dt);
     void app_redraw();

src/node_scroll.cpp

@@ -24,6 +24,35 @@ void NodeScroll::fix_scroll()
     auto rect = get_children_rect();
     m_offset = glm::clamp(m_offset, - zw(rect) + zw(m_clip_uncut) - padoff, { 0, 0 });
     m_pos_offset_childred = m_offset;
+
+    // fix scrollbar
+    float sz = m_size.y - (pad[0] + pad[2]);
+    if (rect.w == 0 || rect.w <= sz)
+    {
+        YGNodeStyleSetPadding(y_node, YGEdgeRight, 5);
+        return;
+    }
+    YGNodeStyleSetPadding(y_node, YGEdgeRight, 35);
+}
+
+void NodeScroll::loaded()
+{
+    fix_scroll();
+}
+
+void NodeScroll::added(Node* parent)
+{
+    fix_scroll();
+}
+
+void NodeScroll::on_child_added(Node* child)
+{
+    fix_scroll();
+}
+
+void NodeScroll::on_child_removed(Node* child)
+{
+    fix_scroll();
 }
 
 void NodeScroll::handle_resize(glm::vec2 old_size, glm::vec2 new_size)
@@ -35,15 +64,10 @@ void NodeScroll::handle_resize(glm::vec2 old_size, glm::vec2 new_size)
 void NodeScroll::draw()
 {
     NodeBorder::draw();
+    fix_scroll();
     glm::vec4 rect = get_children_rect();
     glm::vec4 pad = GetPadding();
     float sz = m_size.y - (pad[0] + pad[2]);
-    if (rect.w == 0 || rect.w <= sz)
-    {
-        YGNodeStyleSetPadding(y_node, YGEdgeRight, 5);
-        return;
-    }
-    YGNodeStyleSetPadding(y_node, YGEdgeRight, 35);
     float h = sz / rect.w * sz;
     float offset_percent = m_offset.y / (rect.w - sz);
     float pr = YGNodeLayoutGetPadding(y_node, YGEdgeRight) - 5;
@@ -71,7 +95,7 @@ kEventResult NodeScroll::handle_event(Event* e)
         m_drag_start = me->m_pos;
         m_offset_start = m_offset;
         // if click on the scroll area use scrolling direction, otherwise natural
-        m_scroll_dir = me->m_pos.x > (m_size.x - YGNodeLayoutGetPadding(y_node, YGEdgeRight) + 5) ? -1 : 1;
+        m_scroll_dir = (me->m_pos.x - m_pos.x) > (m_size.x - YGNodeLayoutGetPadding(y_node, YGEdgeRight)) ? -1 : 1;
         mouse_capture();
         break;
     case kEventType::MouseMove:
@@ -79,7 +103,7 @@ kEventResult NodeScroll::handle_event(Event* e)
         {
             glm::vec4 rect = get_children_rect();
             glm::vec4 pad = GetPadding();
-            float speed = rect.w / (m_size.y - (pad[0] + pad[2]));
+            float speed = m_scroll_dir < 0 ? rect.w / (m_size.y - (pad[0] + pad[2])) : 1;
             m_offset = m_offset_start + (me->m_pos - m_drag_start) * m_mask * m_scroll_dir * speed;
             fix_scroll();
         }

src/node_scroll.h

@@ -15,5 +15,9 @@ public:
     virtual kEventResult handle_event(Event* e) override;
     virtual void draw() override;
     virtual void handle_resize(glm::vec2 old_size, glm::vec2 new_size) override;
+    virtual void on_child_added(Node* child) override;
+    virtual void on_child_removed(Node* child) override;
+    virtual void added(Node* parent) override;
+    virtual void loaded() override;
     void fix_scroll();
 };