// dear imgui: Renderer Backend for SDL_Renderer for SDL2

// (Requires: SDL 2.0.17+)

// Note how SDL_Renderer is an _optional_ component of SDL2.

// For a multi-platform app consider using e.g. SDL+DirectX on Windows and SDL+OpenGL on Linux/OSX.

// If your application will want to render any non trivial amount of graphics other than UI,

// please be aware that SDL_Renderer currently offers a limited graphic API to the end-user and

// it might be difficult to step out of those boundaries.

// Implemented features:

//  [X] Renderer: User texture binding. Use 'SDL_Texture*' as ImTextureID. Read the FAQ about ImTextureID!

//  [X] Renderer: Large meshes support (64k+ vertices) with 16-bit indices.

//  [X] Renderer: Expose selected render state for draw callbacks to use. Access in '(ImGui_ImplXXXX_RenderState*)GetPlatformIO().Renderer_RenderState'.

// Missing features:

//  [ ] Renderer: Multi-viewport support (multiple windows).

// You can copy and use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.

// Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.

// Learn about Dear ImGui:

// - FAQ                  https://dearimgui.com/faq

// - Getting Started      https://dearimgui.com/getting-started

// - Documentation        https://dearimgui.com/docs (same as your local docs/ folder).

// - Introduction, links and more at the top of imgui.cpp

// CHANGELOG

//  2024-10-09: Expose selected render state in ImGui_ImplSDLRenderer2_RenderState, which you can access in 'void* platform_io.Renderer_RenderState' during draw callbacks.

//  2024-05-14: *BREAKING CHANGE* ImGui_ImplSDLRenderer3_RenderDrawData() requires SDL_Renderer* passed as parameter.

//  2023-05-30: Renamed imgui_impl_sdlrenderer.h/.cpp to imgui_impl_sdlrenderer2.h/.cpp to accommodate for upcoming SDL3.

//  2022-10-11: Using 'nullptr' instead of 'NULL' as per our switch to C++11.

//  2021-12-21: Update SDL_RenderGeometryRaw() format to work with SDL 2.0.19.

//  2021-12-03: Added support for large mesh (64K+ vertices), enable ImGuiBackendFlags_RendererHasVtxOffset flag.

//  2021-10-06: Backup and restore modified ClipRect/Viewport.

//  2021-09-21: Initial version.

#include "imgui.h"

#ifndef IMGUI_DISABLE

#include "imgui_impl_sdlrenderer2.h"

#include <stdint.h>     // intptr_t

// Clang warnings with -Weverything

#if defined(__clang__)

#pragma clang diagnostic push

#pragma clang diagnostic ignored "-Wsign-conversion"    // warning: implicit conversion changes signedness

#endif

// SDL

#include <SDL.h>

#if !SDL_VERSION_ATLEAST(2,0,17)

#error This backend requires SDL 2.0.17+ because of SDL_RenderGeometry() function

#endif

// SDL_Renderer data

struct ImGui_ImplSDLRenderer2_Data

{

    SDL_Renderer*   Renderer;       // Main viewport's renderer

    SDL_Texture*    FontTexture;

    ImGui_ImplSDLRenderer2_Data()   { memset((void*)this, 0, sizeof(*this)); }

};

// Backend data stored in io.BackendRendererUserData to allow support for multiple Dear ImGui contexts

// It is STRONGLY preferred that you use docking branch with multi-viewports (== single Dear ImGui context + multiple windows) instead of multiple Dear ImGui contexts.

static ImGui_ImplSDLRenderer2_Data* ImGui_ImplSDLRenderer2_GetBackendData()

{

    return ImGui::GetCurrentContext() ? (ImGui_ImplSDLRenderer2_Data*)ImGui::GetIO().BackendRendererUserData : nullptr;

}

// Functions

bool ImGui_ImplSDLRenderer2_Init(SDL_Renderer* renderer)

{

    ImGuiIO& io = ImGui::GetIO();

    IMGUI_CHECKVERSION();

    IM_ASSERT(io.BackendRendererUserData == nullptr && "Already initialized a renderer backend!");

    IM_ASSERT(renderer != nullptr && "SDL_Renderer not initialized!");

    // Setup backend capabilities flags

    ImGui_ImplSDLRenderer2_Data* bd = IM_NEW(ImGui_ImplSDLRenderer2_Data)();

    io.BackendRendererUserData = (void*)bd;

    io.BackendRendererName = "imgui_impl_sdlrenderer2";

    io.BackendFlags |= ImGuiBackendFlags_RendererHasVtxOffset;  // We can honor the ImDrawCmd::VtxOffset field, allowing for large meshes.

    bd->Renderer = renderer;

    return true;

}

void ImGui_ImplSDLRenderer2_Shutdown()

{

    ImGui_ImplSDLRenderer2_Data* bd = ImGui_ImplSDLRenderer2_GetBackendData();

    IM_ASSERT(bd != nullptr && "No renderer backend to shutdown, or already shutdown?");

    ImGuiIO& io = ImGui::GetIO();

    ImGui_ImplSDLRenderer2_DestroyDeviceObjects();

    io.BackendRendererName = nullptr;

    io.BackendRendererUserData = nullptr;

    io.BackendFlags &= ~ImGuiBackendFlags_RendererHasVtxOffset;

    IM_DELETE(bd);

}

static void ImGui_ImplSDLRenderer2_SetupRenderState(SDL_Renderer* renderer)

{

	// Clear out any viewports and cliprect set by the user

    // FIXME: Technically speaking there are lots of other things we could backup/setup/restore during our render process.

	SDL_RenderSetViewport(renderer, nullptr);

	SDL_RenderSetClipRect(renderer, nullptr);

}

void ImGui_ImplSDLRenderer2_NewFrame()

{

    ImGui_ImplSDLRenderer2_Data* bd = ImGui_ImplSDLRenderer2_GetBackendData();

    IM_ASSERT(bd != nullptr && "Context or backend not initialized! Did you call ImGui_ImplSDLRenderer2_Init()?");

    if (!bd->FontTexture)

        ImGui_ImplSDLRenderer2_CreateDeviceObjects();

}

void ImGui_ImplSDLRenderer2_RenderDrawData(ImDrawData* draw_data, SDL_Renderer* renderer)

{

	// If there's a scale factor set by the user, use that instead

    // If the user has specified a scale factor to SDL_Renderer already via SDL_RenderSetScale(), SDL will scale whatever we pass

    // to SDL_RenderGeometryRaw() by that scale factor. In that case we don't want to be also scaling it ourselves here.

    float rsx = 1.0f;

	float rsy = 1.0f;

	SDL_RenderGetScale(renderer, &rsx, &rsy);

    ImVec2 render_scale;

	render_scale.x = (rsx == 1.0f) ? draw_data->FramebufferScale.x : 1.0f;

	render_scale.y = (rsy == 1.0f) ? draw_data->FramebufferScale.y : 1.0f;

	// Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)

	int fb_width = (int)(draw_data->DisplaySize.x * render_scale.x);

	int fb_height = (int)(draw_data->DisplaySize.y * render_scale.y);

	if (fb_width == 0 || fb_height == 0)

		return;

    // Backup SDL_Renderer state that will be modified to restore it afterwards

    struct BackupSDLRendererState

    {

        SDL_Rect    Viewport;

        bool        ClipEnabled;

        SDL_Rect    ClipRect;

    };

    BackupSDLRendererState old = {};

    old.ClipEnabled = SDL_RenderIsClipEnabled(renderer) == SDL_TRUE;

    SDL_RenderGetViewport(renderer, &old.Viewport);

    SDL_RenderGetClipRect(renderer, &old.ClipRect);

    // Setup desired state

    ImGui_ImplSDLRenderer2_SetupRenderState(renderer);

    // Setup render state structure (for callbacks and custom texture bindings)

    ImGuiPlatformIO& platform_io = ImGui::GetPlatformIO();

    ImGui_ImplSDLRenderer2_RenderState render_state;

    render_state.Renderer = renderer;

    platform_io.Renderer_RenderState = &render_state;

	// Will project scissor/clipping rectangles into framebuffer space

	ImVec2 clip_off = draw_data->DisplayPos;         // (0,0) unless using multi-viewports

	ImVec2 clip_scale = render_scale;

    // Render command lists

    for (int n = 0; n < draw_data->CmdListsCount; n++)

    {

        const ImDrawList* draw_list = draw_data->CmdLists[n];

        const ImDrawVert* vtx_buffer = draw_list->VtxBuffer.Data;

        const ImDrawIdx* idx_buffer = draw_list->IdxBuffer.Data;

        for (int cmd_i = 0; cmd_i < draw_list->CmdBuffer.Size; cmd_i++)

        {

            const ImDrawCmd* pcmd = &draw_list->CmdBuffer[cmd_i];

            if (pcmd->UserCallback)

            {

                // User callback, registered via ImDrawList::AddCallback()

                // (ImDrawCallback_ResetRenderState is a special callback value used by the user to request the renderer to reset render state.)

                if (pcmd->UserCallback == ImDrawCallback_ResetRenderState)

                    ImGui_ImplSDLRenderer2_SetupRenderState(renderer);

                else

                    pcmd->UserCallback(draw_list, pcmd);

            }

            else

            {

                // Project scissor/clipping rectangles into framebuffer space

                ImVec2 clip_min((pcmd->ClipRect.x - clip_off.x) * clip_scale.x, (pcmd->ClipRect.y - clip_off.y) * clip_scale.y);

                ImVec2 clip_max((pcmd->ClipRect.z - clip_off.x) * clip_scale.x, (pcmd->ClipRect.w - clip_off.y) * clip_scale.y);

                if (clip_min.x < 0.0f) { clip_min.x = 0.0f; }

                if (clip_min.y < 0.0f) { clip_min.y = 0.0f; }

                if (clip_max.x > (float)fb_width) { clip_max.x = (float)fb_width; }

                if (clip_max.y > (float)fb_height) { clip_max.y = (float)fb_height; }

                if (clip_max.x <= clip_min.x || clip_max.y <= clip_min.y)

                    continue;

                SDL_Rect r = { (int)(clip_min.x), (int)(clip_min.y), (int)(clip_max.x - clip_min.x), (int)(clip_max.y - clip_min.y) };

                SDL_RenderSetClipRect(renderer, &r);

                const float* xy = (const float*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, pos));

                const float* uv = (const float*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, uv));

#if SDL_VERSION_ATLEAST(2,0,19)

                const SDL_Color* color = (const SDL_Color*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, col)); // SDL 2.0.19+

#else

                const int* color = (const int*)(const void*)((const char*)(vtx_buffer + pcmd->VtxOffset) + offsetof(ImDrawVert, col)); // SDL 2.0.17 and 2.0.18

#endif

                // Bind texture, Draw

				SDL_Texture* tex = (SDL_Texture*)pcmd->GetTexID();

                SDL_RenderGeometryRaw(renderer, tex,

                    xy, (int)sizeof(ImDrawVert),

                    color, (int)sizeof(ImDrawVert),

                    uv, (int)sizeof(ImDrawVert),

                    draw_list->VtxBuffer.Size - pcmd->VtxOffset,

                    idx_buffer + pcmd->IdxOffset, pcmd->ElemCount, sizeof(ImDrawIdx));

            }

        }

    }

    platform_io.Renderer_RenderState = NULL;

    // Restore modified SDL_Renderer state

    SDL_RenderSetViewport(renderer, &old.Viewport);

    SDL_RenderSetClipRect(renderer, old.ClipEnabled ? &old.ClipRect : nullptr);

}

// Called by Init/NewFrame/Shutdown

bool ImGui_ImplSDLRenderer2_CreateFontsTexture()

{

    ImGuiIO& io = ImGui::GetIO();

    ImGui_ImplSDLRenderer2_Data* bd = ImGui_ImplSDLRenderer2_GetBackendData();

    // Build texture atlas

    unsigned char* pixels;

    int width, height;

    io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);   // Load as RGBA 32-bit (75% of the memory is wasted, but default font is so small) because it is more likely to be compatible with user's existing shaders. If your ImTextureId represent a higher-level concept than just a GL texture id, consider calling GetTexDataAsAlpha8() instead to save on GPU memory.

    // Upload texture to graphics system

    // (Bilinear sampling is required by default. Set 'io.Fonts->Flags |= ImFontAtlasFlags_NoBakedLines' or 'style.AntiAliasedLinesUseTex = false' to allow point/nearest sampling)

    bd->FontTexture = SDL_CreateTexture(bd->Renderer, SDL_PIXELFORMAT_ABGR8888, SDL_TEXTUREACCESS_STATIC, width, height);

    if (bd->FontTexture == nullptr)

    {

        SDL_Log("error creating texture");

        return false;

    }

    SDL_UpdateTexture(bd->FontTexture, nullptr, pixels, 4 * width);

    SDL_SetTextureBlendMode(bd->FontTexture, SDL_BLENDMODE_BLEND);

    SDL_SetTextureScaleMode(bd->FontTexture, SDL_ScaleModeLinear);

    // Store our identifier

    io.Fonts->SetTexID((ImTextureID)(intptr_t)bd->FontTexture);

    return true;

}

void ImGui_ImplSDLRenderer2_DestroyFontsTexture()

{

    ImGuiIO& io = ImGui::GetIO();

    ImGui_ImplSDLRenderer2_Data* bd = ImGui_ImplSDLRenderer2_GetBackendData();

    if (bd->FontTexture)

    {

        io.Fonts->SetTexID(0);

        SDL_DestroyTexture(bd->FontTexture);

        bd->FontTexture = nullptr;

    }

}

bool ImGui_ImplSDLRenderer2_CreateDeviceObjects()

{

    return ImGui_ImplSDLRenderer2_CreateFontsTexture();

}

void ImGui_ImplSDLRenderer2_DestroyDeviceObjects()

{

    ImGui_ImplSDLRenderer2_DestroyFontsTexture();

}

//-----------------------------------------------------------------------------

#if defined(__clang__)

#pragma clang diagnostic pop

#endif

#endif // #ifndef IMGUI_DISABLE