Add tool interface skeleton

modules/core/inc/tactile/core/tool/mouse_event.hpp

@@ -0,0 +1,28 @@
+// Copyright (C) 2023 Albin Johansson (GNU General Public License v3.0)
+
+#pragma once
+
+#include "tactile/core/api.hpp"
+#include "tactile/core/math/vector.hpp"
+#include "tactile/core/prelude.hpp"
+
+namespace tactile {
+
+/**
+ * \brief Simply represents different mouse buttons.
+ */
+enum class MouseButton : int8 {
+  kLeft,
+  kMiddle,
+  kRight
+};
+
+/**
+ * \brief Provides information about a mouse event, used by tool implementations.
+ */
+struct TACTILE_CORE_API MouseEvent final {
+  MouseButton button;  ///< The active mouse button.
+  Float2 position;     ///< The current mouse position.
+};
+
+}  // namespace tactile

modules/core/inc/tactile/core/tool/tool.hpp

@@ -0,0 +1,64 @@
+// Copyright (C) 2023 Albin Johansson (GNU General Public License v3.0)
+
+#pragma once
+
+#include "tactile/core/api.hpp"
+#include "tactile/core/prelude.hpp"
+#include "tactile/core/tool/mouse_event.hpp"
+
+namespace tactile {
+
+/**
+ * \interface ITool
+ * \brief Interface for editor tool implementations.
+ */
+class TACTILE_CORE_API ITool {
+ public:
+  TACTILE_INTERFACE_CLASS(ITool);
+
+  /**
+   * \brief Called whenever the tool is enabled (activated).
+   */
+  virtual void on_enable() = 0;
+
+  /**
+   * \brief Called whenever the tool is disabled (deactivated).
+   *
+   * \details This function is always called before a tool switch happens. The same is
+   *          not guaranteed for other functions. For example, `on_mouse_pressed` is not
+   *          necessarily followed by a `on_mouse_released` call. Therefore, tool
+   *          implementations should reset any in-flight state in this function.
+   */
+  virtual void on_disable() = 0;
+
+  /**
+   * \brief Called whenever the mouse is pressed in the document.
+   *
+   * \param event the mouse event information.
+   */
+  virtual void on_mouse_pressed(const MouseEvent& event) = 0;
+
+  /**
+   * \brief Called whenever the mouse is dragged (while being pressed) in the document.
+   *
+   * \param event the mouse event information.
+   */
+  virtual void on_mouse_dragged(const MouseEvent& event) = 0;
+
+  /**
+   * \brief Called whenever the mouse is released in the document.
+   *
+   * \param event the mouse event information.
+   */
+  virtual void on_mouse_released(const MouseEvent& event) = 0;
+
+  /**
+   * \brief Indicates whether the tool is currently usable.
+   *
+   * \return true if the tool can be used; false otherwise.
+   */
+  [[nodiscard]]
+  virtual auto is_usable() const -> bool = 0;
+};
+
+}  // namespace tactile