1 files changed, 115 insertions, 0 deletions
diff --git a/src/ui/render/render_object.cpp b/src/ui/render/render_object.cpp
new file mode 100644
index 00000000..5c6af580
--- /dev/null
+++ b/src/ui/render/render_object.cpp
@@ -0,0 +1,115 @@
+#include "render_object.hpp"
+
+#include <algorithm>
+
+#include "cru_debug.hpp"
+
+namespace cru::ui::render {
+void RenderObject::AddChild(RenderObject* render_object, const int position) {
+  assert(render_object->GetParent() ==
+         nullptr);                       // Render object already has a parent.
+  assert(position >= 0);                 // Position index is less than 0.
+  assert(position <= children_.size());  // Position index is out of bound.
+
+  children_.insert(children_.cbegin() + position, render_object);
+  render_object->SetParent(this);
+  OnAddChild(render_object, position);
+}
+
+void RenderObject::RemoveChild(const int position) {
+  assert(position >= 0);                // Position index is less than 0.
+  assert(position < children_.size());  // Position index is out of bound.
+
+  const auto i = children_.cbegin() + position;
+  const auto removed_child = *i;
+  children_.erase(i);
+  removed_child->SetParent(nullptr);
+  OnRemoveChild(removed_child, position);
+}
+
+void RenderObject::Measure(const Size& available_size) {
+  OnMeasureCore(available_size);
+}
+
+void RenderObject::Layout(const Rect& rect) {
+  SetOffset(rect.GetLeftTop());
+  SetSize(rect.GetSize());
+  OnLayoutCore(Rect{Point::Zero(), rect.GetSize()});
+}
+
+void RenderObject::OnParentChanged(RenderObject* old_parent,
+                                   RenderObject* new_parent) {}
+
+void RenderObject::OnAddChild(RenderObject* new_child, int position) {}
+
+void RenderObject::OnRemoveChild(RenderObject* removed_child, int position) {}
+
+void RenderObject::OnSizeChanged(const Size& old_size, const Size& new_size) {}
+
+void RenderObject::OnMeasureCore(const Size& available_size) {
+  Size margin_padding_size{
+      margin_.GetHorizontalTotal() + padding_.GetHorizontalTotal(),
+      margin_.GetVerticalTotal() + padding_.GetVerticalTotal()};
+
+  auto coerced_margin_padding_size = margin_padding_size;
+  if (coerced_margin_padding_size.width > available_size.width) {
+    debug::DebugMessage(
+        L"Measure: horizontal length of padding and margin is bigger than "
+        L"available length.");
+    coerced_margin_padding_size.width = available_size.width;
+  }
+  if (coerced_margin_padding_size.height > available_size.height) {
+    debug::DebugMessage(
+        L"Measure: vertical length of padding and margin is bigger than "
+        L"available length.");
+    coerced_margin_padding_size.height = available_size.height;
+  }
+
+  const auto coerced_content_available_size =
+      available_size - coerced_margin_padding_size;
+  const auto actual_content_size =
+      OnMeasureContent(coerced_content_available_size);
+
+  SetPreferredSize(coerced_margin_padding_size + actual_content_size);
+}
+
+void RenderObject::OnLayoutCore(const Rect& rect) {
+  Size margin_padding_size{
+      margin_.GetHorizontalTotal() + padding_.GetHorizontalTotal(),
+      margin_.GetVerticalTotal() + padding_.GetVerticalTotal()};
+  const auto content_available_size = rect.GetSize() - margin_padding_size;
+  auto coerced_content_available_size = content_available_size;
+
+  if (coerced_content_available_size.width < 0) {
+    debug::DebugMessage(
+        L"Layout: horizontal length of padding and margin is bigger than "
+        L"available length.");
+    coerced_content_available_size.width = 0;
+  }
+  if (coerced_content_available_size.height < 0) {
+    debug::DebugMessage(
+        L"Layout: vertical length of padding and margin is bigger than "
+        L"available length.");
+    coerced_content_available_size.height = 0;
+  }
+
+  OnLayoutContent(Rect{margin_.left + padding_.left, margin_.top + padding_.top,
+                       coerced_content_available_size.width,
+                       coerced_content_available_size.height});
+}
+
+Rect RenderObject::GetContentRect() const {
+  Rect rect{Point::Zero(), GetSize()};
+  rect = rect.Shrink(GetMargin());
+  rect = rect.Shrink(GetPadding());
+  rect.width = std::max(rect.width, 0.0f);
+  rect.height = std::max(rect.height, 0.0f);
+  return rect;
+}
+
+void RenderObject::SetParent(RenderObject* new_parent) {
+  const auto old_parent = parent_;
+  parent_ = new_parent;
+  OnParentChanged(old_parent, new_parent);
+}
+}  // namespace cru::ui::render