ui_system.h

#pragma once
 
#include <string_view>
#include <vector>
 
#include <glm/glm.hpp>
 
#include "core/system.h"
#include "ecs/entity.h"
#include "ecs/component/ui/ui_element.h"
#include "ecs/component/ui/ui_shape.h"
#include "system/ui/ui_draw_data.h"
 
namespace Vkm::Engine {

class UISystem : public System {
    public:
        UISystem() = default;
        ~UISystem() override = default;
 
        UISystem(const UISystem& other) = delete;
        UISystem& operator=(const UISystem& other) = delete;
 
        UISystem(UISystem && other) = delete;
        UISystem& operator=(UISystem && other) = delete;
 
    public:
        void update(FrameContext& ctx) override;
 
    private:
        struct CanvasRef {
            int32_t  sortOrder;
            EntityId entity;
        };

        struct ButtonHit {
            EntityId entity;
            uint32_t firstVertex;  
        };

        struct ScrollTarget {
            EntityId entity;
            size_t   blockersBefore;  
        };
 
    private:
        glm::vec2 resolveElement(
            FrameContext& ctx,
            EntityId entity,
            const UIRect& parentRect,
            const UIRect& clip,
            float scale,
            uint32_t depth
        );

        void appendCommand(
            uint32_t first,
            uint32_t count,
            FontHandle font,
            TextureHandle image,
            const UIRect& clip
        );

        bool emitImage(
            FrameContext& ctx,
            EntityId entity,
            const UIElement& element,
            const UIRect& clip,
            float canvasScale
        );

        bool emitButton(
            FrameContext& ctx,
            EntityId entity,
            const UIElement& element,
            const UIRect& clip,
            float canvasScale
        );

        glm::vec2 emitText(
            FrameContext& ctx,
            EntityId entity,
            const UIElement& element,
            const UIRect& clip,
            float canvasScale
        );

        void breakLines(std::string_view text, const FontAsset& font, float scale, float maxWidth, bool wrap);

        void resolveInteraction(FrameContext& ctx);

        void appendQuad(
            const glm::vec2& p0,
            const glm::vec2& p1,
            const glm::vec2& uv0,
            const glm::vec2& uv1,
            const glm::vec4& color,
            const glm::vec4& bottom,
            const glm::vec2& shape,
            const glm::vec4& border,
            bool image
        );

        void recolourQuad(uint32_t first, const glm::vec4& top, const glm::vec4& bottom);

        void appendShaped(
            const UIRect& rect,
            const glm::vec4& color,
            const UIShape& shape,
            float scale,
            bool image
        );
 
    private:
        UIDrawData m_drawData;            
 
        std::vector<CanvasRef> m_canvases;    
        std::vector<ButtonHit> m_buttonHits;

        std::vector<ScrollTarget> m_scrollTargets;

        std::vector<std::string_view> m_lines;

        std::vector<EntityId> m_pointerBlockers;
 
        EntityId  m_pressedButton{};        
        glm::vec2 m_pointer{0.0f};          
        float     m_wheel         = 0.0f;   
        bool      m_mouseDown     = false;  
        bool      m_mouseDownEdge = false;  
        bool      m_mouseUpEdge   = false;  
        bool      m_cursorFree    = false;  
        bool      m_pointerIsOurs = false;  
};
 
} // namespace Vkm::Engine