Supporting setting panel layout

engine/include/sophia/ui/dock_layout.hpp

@@ -0,0 +1,23 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+namespace sophia {
+
+struct DockLayout {
+  float leftWidth = 0.2f;
+  float rightWidth = 0.25f;
+  float bottomHeight = 0.25f;
+
+  std::vector<std::string> left;
+  std::vector<std::string> right;
+  std::vector<std::string> bottom;
+  std::vector<std::string> center;
+
+  bool empty() const {
+    return left.empty() && right.empty() && bottom.empty() && center.empty();
+  }
+};
+
+}  // namespace sophia

engine/include/sophia/ui/panel.hpp

@@ -1,5 +1,7 @@
 #pragma once
 
+#include <glm/glm.hpp>
+#include <optional>
 #include <sophia/frame_info.hpp>
 #include <string>
 #include <utility>
@@ -8,28 +10,46 @@ namespace sophia {
 
 class Panel {
  public:
+  struct Config {
+    std::string name;
+
+    // Locked panels can't be moved, resized, docked, collapsed or closed.
+    bool locked = false;
+    bool closable = true;
+
+    // A zero component lets ImGui size the window. Applied on first use, or
+    // every frame when locked.
+    glm::vec2 size{0.0f, 0.0f};
+    std::optional<glm::vec2> position;
+  };
+
   Panel(const Panel&) = delete;
   Panel& operator=(const Panel&) = delete;
 
   Panel(Panel&&) noexcept = default;
   Panel& operator=(Panel&&) noexcept = default;
 
-  explicit Panel(std::string name = {}) : name{std::move(name)} {}
+  explicit Panel(Config config) : config{std::move(config)} {}
   virtual ~Panel() = default;
 
-  virtual void onUpdate(const FrameInfo& frameInfo) = 0;
+  // Owns the ImGui window: Begin, onUpdate, End.
+  void draw(const FrameInfo& frameInfo);
 
-  const std::string& getName() const { return name; }
+  const std::string& getName() const { return config.name; }
+  bool isLocked() const { return config.locked; }
 
   bool isVisible() const { return this->visible; }
   void setVisible(bool visible) { this->visible = visible; }
   void toggleVisible() { this->visible = !this->visible; }
 
  protected:
+  // Draw the panel's contents; the window is already open.
+  virtual void onUpdate(const FrameInfo& frameInfo) = 0;
+
   bool visible = true;
 
  private:
-  std::string name;
+  Config config;
 };
 
 }  // namespace sophia

engine/include/sophia/ui/panel_registry.hpp

@@ -3,6 +3,7 @@
 #include <memory>
 #include <sophia/frame_info.hpp>
 #include <sophia/handles.hpp>
+#include <sophia/ui/dock_layout.hpp>
 #include <sophia/ui/panel.hpp>
 #include <sophia/util/assert.hpp>
 #include <string_view>
@@ -94,6 +95,11 @@ class PanelRegistry {
 
   void update(const FrameInfo& frameInfo);
 
+  void setDefaultLayout(DockLayout layout) {
+    defaultLayout = std::move(layout);
+  }
+  const DockLayout& getDefaultLayout() const { return defaultLayout; }
+
  private:
   struct Slot {
     std::unique_ptr<Panel> panel;
@@ -102,6 +108,7 @@ class PanelRegistry {
 
   std::vector<Slot> slots;
   std::vector<u32> freeList;
+  DockLayout defaultLayout;
 };
 
 }  // namespace sophia