ImGuiBackend.h

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#pragma once
 
#include "ui/UIBackend.h"
 
#include <imgui.h>
 
#include <cstdint>
#include <deque>
#include <map>
#include <vector>
 
namespace eve::ui {
 
class ImGuiBackend final : public UIBackend {
public:
    ImGuiBackend() = default;
    ~ImGuiBackend() override;
 
    ImGuiBackend(const ImGuiBackend &) = delete;
    ImGuiBackend &operator=(const ImGuiBackend &) = delete;
 
    bool init(SDL_Window *window, eve::graphics::Graphics *gfx) override;
    void shutdown() override;
    bool isInitialized() const override { return initialized_; }
 
    void processEvent(const SDL_Event *event) override;
    void newFrame() override;
 
    bool wantCaptureMouse() const override;
    bool wantCaptureKeyboard() const override;
 
    void setScale(float scale) override;
    float getScale() const override { return uiScale_; }
 
private:
    void renderDrawData(void *vkCommandBuffer);
    static bool presentOverlayThunk(void *userdata, void *commandBuffer);
    static void textureDrawThunk(const ImDrawList* list, const ImDrawCmd* command);
    static void windowDestroyedThunk(void *userdata);
    void applyScale(float scale);
    float computeInitialScale() const;
    float computeDpiScale() const;
    void loadFonts();
    void rebuildFonts();
    void checkFontCoverage() const;
 
    [[nodiscard("retain the UI texture registration id or explicitly handle failure")]]
    uint64_t registerTexture(graphics::Texture *tex) override;
    void unregisterTexture(uint64_t id) override;
    bool textureSize(uint64_t id, int *w, int *h) const override;
    void *textureHandle(uint64_t id) const override;
    bool usesQueuedTextureDraws() const override;
    void queueTextureDraw(uint64_t id, float x, float y, float w, float h, float u0, float v0,
                          float u1, float v1, float r, float g, float b, float a,
                          bool opaque) override;
 
    struct RegisteredTexture {
        ImTextureID imId = nullptr;
        graphics::Texture *texture = nullptr;
        int width = 0;
        int height = 0;
    };
    struct QueuedTextureDraw {
        uint64_t id = 0;
        float x = 0.f;
        float y = 0.f;
        float w = 0.f;
        float h = 0.f;
        float u0 = 0.f;
        float v0 = 0.f;
        float u1 = 1.f;
        float v1 = 1.f;
        float r = 1.f;
        float g = 1.f;
        float b = 1.f;
        float a = 1.f;
        float clipX = 0.f;
        float clipY = 0.f;
        float clipW = 0.f;
        float clipH = 0.f;
        bool opaque = false;
        ImGuiBackend* owner       = nullptr;  // ImGui callback ABI; owned by this backend until frame end.
        std::size_t   bufferIndex = 0;
    };
    std::map<uint64_t, RegisteredTexture> textures_;
    std::deque<QueuedTextureDraw>         queuedTextureDraws_;  // Stable callback addresses while appending.
    void*             activeCommandBuffer_ = nullptr;  // Borrowed only during renderDrawData's synchronous callbacks.
    uint64_t nextTextureKey_ = 1;
    ImVector<ImWchar> fontRanges_;  // kept alive for cfg.GlyphRanges across font builds
    ImVector<ImWchar> cjkRanges_;   // kept alive for the merged CJK font config
 
    bool initialized_ = false;
    bool fontsUploaded_ = false;
    bool frameOpen_ = false;
    float uiScale_ = 1.f;
    float dpiScale_ = 1.f;
    eve::graphics::Graphics *gfx_ = nullptr;
    SDL_Window *window_ = nullptr;
    void *imguiDescriptorPool_ = nullptr;   // VkDescriptorPool
    void *imguiTexturePool_ = nullptr;      // VkDescriptorPool (texture sets)
    void *imguiTextureLayout_ = nullptr;    // VkDescriptorSetLayout (texture sets)
    ImGuiContext *ctx_ = nullptr;           // ImGui context owned by this backend
};
 
}  // namespace eve::ui