KarmaGuiOpenGLHandler.h

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// Dear ImGui (1.89.2) is Copyright (c) 2014-2023 Omar Cornut.
 
// Major and heavy modifications of the original Dear ImGUI's take on OpenGL3 implementation
// https://github.com/ravimohan1991/imgui/blob/07334fa9c67e6c7c827cc76c2ac4de419a1658c1/backends/imgui_impl_opengl3.h
// Disclaimer:
// Most of the member variables and function naming in the herein is credited to the author(s) of Dear ImGUI. I take no responsibility
// of damage caused by short names herein.
 
#pragma once
#include "KarmaGui.h"
#include "Karma/Renderer/Scene.h"
 
#define KGGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
 
#ifdef _WIN64
typedef signed   long long int khronos_ssize_t;
#else
typedef signed   long  int     khronos_ssize_t;
#endif
 
typedef unsigned int GLuint;
typedef int GLint;
 
typedef khronos_ssize_t GLsizeiptr;
 
namespace Karma
{
    struct MesaDecalData
    {
        GLuint DecalRef;

        KGTextureID DecalID;

        int width;

        int height;
    };

    struct KarmaGui_ImplOpenGL3_Data
    {
        GLuint          GlVersion;

        char            GlslVersionString[32];

        GLuint          FontTexture;

        std::vector<MesaDecalData>  openglMesaDecalDataList;

        GLuint          ShaderHandle;

        GLint           AttribLocationTex;

        GLint           AttribLocationProjMtx;

        GLuint          AttribLocationVtxPos;

        GLuint          AttribLocationVtxUV;

        GLuint          AttribLocationVtxColor;

        unsigned int    VboHandle;

        unsigned int ElementsHandle;

        GLsizeiptr      VertexBufferSize;

        GLsizeiptr      IndexBufferSize;
 
        // Detect extensions we support
        bool            HasClipOrigin;

        bool            UseBufferSubData;

        KarmaGui_ImplOpenGL3_Data()
        {
            //memset((void*)this, 0, sizeof(*this));
            VertexBufferSize = IndexBufferSize = 0;
        }
    };
 
    // OpenGL vertex attribute state (for ES 1.0 and ES 2.0 only)
#ifndef KGGUI_IMPL_OPENGL_USE_VERTEX_ARRAY
    struct ImGui_ImplOpenGL3_VtxAttribState
    {
        GLint   Enabled, Size, Type, Normalized, Stride;
        GLvoid* Ptr;
 
        void GetState(GLint index)
        {
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_ENABLED, &Enabled);
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_SIZE, &Size);
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_TYPE, &Type);
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_NORMALIZED, &Normalized);
            glGetVertexAttribiv(index, GL_VERTEX_ATTRIB_ARRAY_STRIDE, &Stride);
            glGetVertexAttribPointerv(index, GL_VERTEX_ATTRIB_ARRAY_POINTER, &Ptr);
        }
        void SetState(GLint index)
        {
            glVertexAttribPointer(index, Size, Type, (GLboolean)Normalized, Stride, Ptr);
            if (Enabled) glEnableVertexAttribArray(index); else glDisableVertexAttribArray(index);
        }
    };
#endif

    class KARMA_API KarmaGuiOpenGLHandler
    {
    public:
        // Backend API

        static bool KarmaGui_ImplOpenGL3_Init(const char* glsl_version = NULL);

        static void KarmaGui_ImplOpenGL3_InitPlatformInterface();

        static void KarmaGui_ImplOpenGL3_ShutdownPlatformInterface();

        static void KarmaGui_ImplOpenGL3_Shutdown();

        static void KarmaGui_ImplOpenGL3_NewFrame();

        static void KarmaGui_ImplOpenGL3_RenderDrawData(KGDrawData* draw_data);
        /*
        inline static KarmaGui_ImplOpenGL3_Data* KarmaGui_ImplOpenGL3_GetBackendData()
        {
            return KarmaGui::GetCurrentContext() ? (KarmaGui_ImplOpenGL3_Data*)KarmaGui::GetIO().BackendRendererUserData : NULL;
        }*/

        static void KarmaGui_ImplOpenGL3_SetupRenderState(KGDrawData* draw_data, int fb_width, int fb_height, GLuint vertex_array_object);

        static bool CheckShader(GLuint handle, const char* desc);

        static bool CheckProgram(GLuint handle, const char* desc);

        static void KarmaGui_ImplOpenGL3_RenderWindow(KarmaGuiViewport* viewport, void* render_arg);

        static void KarmaGui_ImplOpenGL3_CreateTexture(char const* fileName, const std::string& label = "");
 
        // (Optional) Called by Init/NewFrame/Shutdown
        static bool KarmaGui_ImplOpenGL3_CreateFontsTexture();

        static void KarmaGui_ImplOpenGL3_DestroyFontsTexture();

        static bool KarmaGui_ImplOpenGL3_CreateDeviceObjects();

        static void KarmaGui_ImplOpenGL3_DestroyDeviceObjects();
    };
}