#include "../../libslic3r/libslic3r.h"
#include "ImGuiWrapper.hpp"

#include "Utils.hpp"

#include <wx/event.h>

#include <GL/glew.h>

namespace Slic3r {
namespace GUI {
    

ImGuiWrapper::ImGuiWrapper()
    : m_glsl_version_string("")
    , m_shader_handle(0)
    , m_vert_handle(0)
    , m_frag_handle(0)
    , m_font_texture(0)
    , m_vbo_handle(0)
    , m_elements_handle(0)
    , m_attrib_location_tex(0)
    , m_attrib_location_proj_mtx(0)
    , m_attrib_location_position(0)
    , m_attrib_location_uv(0)
    , m_attrib_location_color(0)
{
}

bool ImGuiWrapper::init()
{
    // Store GLSL version string so we can refer to it later in case we recreate shaders. Note: GLSL version is NOT the same as GL version. Leave this to NULL if unsure.
    std::string glsl_version;

#ifdef USE_GL_ES3
    glsl_version = "#version 300 es";
#else
    glsl_version = "#version 130";
#endif

    m_glsl_version_string = glsl_version + "\n";

    ImGui::CreateContext();

    ImGuiIO& io = ImGui::GetIO();
    ImFont* font = io.Fonts->AddFontFromFileTTF((Slic3r::resources_dir() + "\\fonts\\NotoSans-Regular.ttf").c_str(), 18.0f);
    if (font == nullptr)
    {
        font = io.Fonts->AddFontDefault();
        if (font == nullptr)
            return false;
    }
    else
        m_fonts.insert(FontsMap::value_type("Noto Sans Regular 18", font));

    io.IniFilename = nullptr;

    return true;
}

void ImGuiWrapper::shutdown()
{
    destroy_device_objects();
    ImGui::DestroyContext();
}

void ImGuiWrapper::set_display_size(float w, float h)
{
    ImGuiIO& io = ImGui::GetIO();
    io.DisplaySize = ImVec2(w, h);
    io.DisplayFramebufferScale = ImVec2(1.0f, 1.0f);
}

void ImGuiWrapper::update_mouse_data(wxMouseEvent& evt)
{
    ImGuiIO& io = ImGui::GetIO();
    io.MousePos = ImVec2((float)evt.GetX(), (float)evt.GetY());
    io.MouseDown[0] = evt.LeftDown();
    io.MouseDown[1] = evt.RightDown();
    io.MouseDown[2] = evt.MiddleDown();

    if (io.MouseDown[0])
    {
        int a = 0;
    }
}

void ImGuiWrapper::new_frame()
{
    if (m_font_texture == 0)
        create_device_objects();

    ImGui::NewFrame();
}

void ImGuiWrapper::render()
{
    ImGuiIO& io = ImGui::GetIO();


    ImGui::Render();
    render_draw_data(ImGui::GetDrawData());
}

void ImGuiWrapper::set_next_window_pos(float x, float y, int flag)
{
    ImGui::SetNextWindowPos(ImVec2(x, y), (ImGuiCond)flag);
}

void ImGuiWrapper::set_next_window_bg_alpha(float alpha)
{
    ImGui::SetNextWindowBgAlpha(alpha);
}

bool ImGuiWrapper::begin(const std::string& name, int flags)
{
    return ImGui::Begin(name.c_str(), nullptr, (ImGuiWindowFlags)flags);
}

void ImGuiWrapper::end()
{
    ImGui::End();
}

bool ImGuiWrapper::input_double(const std::string& label, double& value, const std::string& format)
{
    return ImGui::InputDouble(label.c_str(), &value, 0.0f, 0.0f, format.c_str());
}

bool ImGuiWrapper::input_vec3(const std::string& label, Vec3d& value, float width, const std::string& format)
{
    bool value_changed = false;

    ImGui::BeginGroup();

    for (int i = 0; i < 3; ++i)
    {
        std::string item_label = (i == 0) ? "X" : ((i == 1) ? "Y" : "Z");
        ImGui::PushID(i);
        ImGui::PushItemWidth(width);
        value_changed |= ImGui::InputDouble(item_label.c_str(), &value(i), 0.0f, 0.0f, format.c_str());
        ImGui::PopID();
    }
    ImGui::EndGroup();

    return value_changed;
}

void ImGuiWrapper::create_device_objects()
{
    // Backup GL state
    GLint last_texture, last_array_buffer, last_vertex_array;
    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
    glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
    glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);

    // Parse GLSL version string
    int glsl_version = 130;
    ::sscanf(m_glsl_version_string.c_str(), "#version %d", &glsl_version);

    const GLchar* vertex_shader_glsl_120 =
        "uniform mat4 ProjMtx;\n"
        "attribute vec2 Position;\n"
        "attribute vec2 UV;\n"
        "attribute vec4 Color;\n"
        "varying vec2 Frag_UV;\n"
        "varying vec4 Frag_Color;\n"
        "void main()\n"
        "{\n"
        "    Frag_UV = UV;\n"
        "    Frag_Color = Color;\n"
        "    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
        "}\n";

    const GLchar* vertex_shader_glsl_130 =
        "uniform mat4 ProjMtx;\n"
        "in vec2 Position;\n"
        "in vec2 UV;\n"
        "in vec4 Color;\n"
        "out vec2 Frag_UV;\n"
        "out vec4 Frag_Color;\n"
        "void main()\n"
        "{\n"
        "    Frag_UV = UV;\n"
        "    Frag_Color = Color;\n"
        "    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
        "}\n";

    const GLchar* vertex_shader_glsl_300_es =
        "precision mediump float;\n"
        "layout (location = 0) in vec2 Position;\n"
        "layout (location = 1) in vec2 UV;\n"
        "layout (location = 2) in vec4 Color;\n"
        "uniform mat4 ProjMtx;\n"
        "out vec2 Frag_UV;\n"
        "out vec4 Frag_Color;\n"
        "void main()\n"
        "{\n"
        "    Frag_UV = UV;\n"
        "    Frag_Color = Color;\n"
        "    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
        "}\n";

    const GLchar* vertex_shader_glsl_410_core =
        "layout (location = 0) in vec2 Position;\n"
        "layout (location = 1) in vec2 UV;\n"
        "layout (location = 2) in vec4 Color;\n"
        "uniform mat4 ProjMtx;\n"
        "out vec2 Frag_UV;\n"
        "out vec4 Frag_Color;\n"
        "void main()\n"
        "{\n"
        "    Frag_UV = UV;\n"
        "    Frag_Color = Color;\n"
        "    gl_Position = ProjMtx * vec4(Position.xy,0,1);\n"
        "}\n";

    const GLchar* fragment_shader_glsl_120 =
        "#ifdef GL_ES\n"
        "    precision mediump float;\n"
        "#endif\n"
        "uniform sampler2D Texture;\n"
        "varying vec2 Frag_UV;\n"
        "varying vec4 Frag_Color;\n"
        "void main()\n"
        "{\n"
        "    gl_FragColor = Frag_Color * texture2D(Texture, Frag_UV.st);\n"
        "}\n";

    const GLchar* fragment_shader_glsl_130 =
        "uniform sampler2D Texture;\n"
        "in vec2 Frag_UV;\n"
        "in vec4 Frag_Color;\n"
        "out vec4 Out_Color;\n"
        "void main()\n"
        "{\n"
        "    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
        "}\n";

    const GLchar* fragment_shader_glsl_300_es =
        "precision mediump float;\n"
        "uniform sampler2D Texture;\n"
        "in vec2 Frag_UV;\n"
        "in vec4 Frag_Color;\n"
        "layout (location = 0) out vec4 Out_Color;\n"
        "void main()\n"
        "{\n"
        "    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
        "}\n";

    const GLchar* fragment_shader_glsl_410_core =
        "in vec2 Frag_UV;\n"
        "in vec4 Frag_Color;\n"
        "uniform sampler2D Texture;\n"
        "layout (location = 0) out vec4 Out_Color;\n"
        "void main()\n"
        "{\n"
        "    Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
        "}\n";

    // Select shaders matching our GLSL versions
    const GLchar* vertex_shader = nullptr;
    const GLchar* fragment_shader = nullptr;
    if (glsl_version < 130)
    {
        vertex_shader = vertex_shader_glsl_120;
        fragment_shader = fragment_shader_glsl_120;
    }
    else if (glsl_version == 410)
    {
        vertex_shader = vertex_shader_glsl_410_core;
        fragment_shader = fragment_shader_glsl_410_core;
    }
    else if (glsl_version == 300)
    {
        vertex_shader = vertex_shader_glsl_300_es;
        fragment_shader = fragment_shader_glsl_300_es;
    }
    else
    {
        vertex_shader = vertex_shader_glsl_130;
        fragment_shader = fragment_shader_glsl_130;
    }

    // Create shaders
    const GLchar* vertex_shader_with_version[2] = { m_glsl_version_string.c_str(), vertex_shader };
    m_vert_handle = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(m_vert_handle, 2, vertex_shader_with_version, nullptr);
    glCompileShader(m_vert_handle);
    check_shader(m_vert_handle, "vertex shader");

    const GLchar* fragment_shader_with_version[2] = { m_glsl_version_string.c_str(), fragment_shader };
    m_frag_handle = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(m_frag_handle, 2, fragment_shader_with_version, nullptr);
    glCompileShader(m_frag_handle);
    check_shader(m_frag_handle, "fragment shader");

    m_shader_handle = glCreateProgram();
    glAttachShader(m_shader_handle, m_vert_handle);
    glAttachShader(m_shader_handle, m_frag_handle);
    glLinkProgram(m_shader_handle);
    check_program(m_shader_handle, "shader program");

    m_attrib_location_tex = glGetUniformLocation(m_shader_handle, "Texture");
    m_attrib_location_proj_mtx = glGetUniformLocation(m_shader_handle, "ProjMtx");
    m_attrib_location_position = glGetAttribLocation(m_shader_handle, "Position");
    m_attrib_location_uv = glGetAttribLocation(m_shader_handle, "UV");
    m_attrib_location_color = glGetAttribLocation(m_shader_handle, "Color");

    // Create buffers
    glGenBuffers(1, &m_vbo_handle);
    glGenBuffers(1, &m_elements_handle);

    create_fonts_texture();

    // Restore modified GL state
    glBindTexture(GL_TEXTURE_2D, last_texture);
    glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
    glBindVertexArray(last_vertex_array);
}

void ImGuiWrapper::create_fonts_texture()
{
    // Build texture atlas
    ImGuiIO& io = ImGui::GetIO();
    unsigned char* pixels;
    int width, height;
    io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height);   // Load as RGBA 32-bits (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
    GLint last_texture;
    glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
    glGenTextures(1, &m_font_texture);
    glBindTexture(GL_TEXTURE_2D, m_font_texture);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glPixelStorei(GL_UNPACK_ROW_LENGTH, 0);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, pixels);

    // Store our identifier
    io.Fonts->TexID = (ImTextureID)(intptr_t)m_font_texture;

    // Restore state
    glBindTexture(GL_TEXTURE_2D, last_texture);
}

bool ImGuiWrapper::check_program(unsigned int handle, const char* desc)
{
    GLint status = 0, log_length = 0;
    glGetProgramiv(handle, GL_LINK_STATUS, &status);
    glGetProgramiv(handle, GL_INFO_LOG_LENGTH, &log_length);
    if ((GLboolean)status == GL_FALSE)
        fprintf(stderr, "ERROR: ImGuiWrapper::check_program(): failed to link %s! (with GLSL '%s')\n", desc, m_glsl_version_string);
    if (log_length > 0)
    {
        ImVector<char> buf;
        buf.resize((int)(log_length + 1));
        glGetProgramInfoLog(handle, log_length, NULL, (GLchar*)buf.begin());
        fprintf(stderr, "%s\n", buf.begin());
    }
    return (GLboolean)status == GL_TRUE;
}

bool ImGuiWrapper::check_shader(unsigned int handle, const char* desc)
{
    GLint status = 0, log_length = 0;
    glGetShaderiv(handle, GL_COMPILE_STATUS, &status);
    glGetShaderiv(handle, GL_INFO_LOG_LENGTH, &log_length);
    if ((GLboolean)status == GL_FALSE)
        fprintf(stderr, "ERROR: ImGui_ImplOpenGL3_CreateDeviceObjects: failed to compile %s!\n", desc);
    if (log_length > 0)
    {
        ImVector<char> buf;
        buf.resize((int)(log_length + 1));
        glGetShaderInfoLog(handle, log_length, NULL, (GLchar*)buf.begin());
        fprintf(stderr, "%s\n", buf.begin());
    }
    return (GLboolean)status == GL_TRUE;
}

void ImGuiWrapper::render_draw_data(ImDrawData* draw_data)
{
    // Avoid rendering when minimized, scale coordinates for retina displays (screen coordinates != framebuffer coordinates)
    ImGuiIO& io = ImGui::GetIO();
    int fb_width = (int)(draw_data->DisplaySize.x * io.DisplayFramebufferScale.x);
    int fb_height = (int)(draw_data->DisplaySize.y * io.DisplayFramebufferScale.y);
    if (fb_width <= 0 || fb_height <= 0)
        return;
    draw_data->ScaleClipRects(io.DisplayFramebufferScale);

    // Backup GL state
    GLenum last_active_texture; glGetIntegerv(GL_ACTIVE_TEXTURE, (GLint*)&last_active_texture);
    glActiveTexture(GL_TEXTURE0);
    GLint last_program; glGetIntegerv(GL_CURRENT_PROGRAM, &last_program);
    GLint last_texture; glGetIntegerv(GL_TEXTURE_BINDING_2D, &last_texture);
#ifdef GL_SAMPLER_BINDING
    GLint last_sampler; glGetIntegerv(GL_SAMPLER_BINDING, &last_sampler);
#endif
    GLint last_array_buffer; glGetIntegerv(GL_ARRAY_BUFFER_BINDING, &last_array_buffer);
    GLint last_vertex_array; glGetIntegerv(GL_VERTEX_ARRAY_BINDING, &last_vertex_array);
#ifdef GL_POLYGON_MODE
    GLint last_polygon_mode[2]; glGetIntegerv(GL_POLYGON_MODE, last_polygon_mode);
#endif
    GLint last_viewport[4]; glGetIntegerv(GL_VIEWPORT, last_viewport);
    GLint last_scissor_box[4]; glGetIntegerv(GL_SCISSOR_BOX, last_scissor_box);
    GLenum last_blend_src_rgb; glGetIntegerv(GL_BLEND_SRC_RGB, (GLint*)&last_blend_src_rgb);
    GLenum last_blend_dst_rgb; glGetIntegerv(GL_BLEND_DST_RGB, (GLint*)&last_blend_dst_rgb);
    GLenum last_blend_src_alpha; glGetIntegerv(GL_BLEND_SRC_ALPHA, (GLint*)&last_blend_src_alpha);
    GLenum last_blend_dst_alpha; glGetIntegerv(GL_BLEND_DST_ALPHA, (GLint*)&last_blend_dst_alpha);
    GLenum last_blend_equation_rgb; glGetIntegerv(GL_BLEND_EQUATION_RGB, (GLint*)&last_blend_equation_rgb);
    GLenum last_blend_equation_alpha; glGetIntegerv(GL_BLEND_EQUATION_ALPHA, (GLint*)&last_blend_equation_alpha);
    GLboolean last_enable_blend = glIsEnabled(GL_BLEND);
    GLboolean last_enable_cull_face = glIsEnabled(GL_CULL_FACE);
    GLboolean last_enable_depth_test = glIsEnabled(GL_DEPTH_TEST);
    GLboolean last_enable_scissor_test = glIsEnabled(GL_SCISSOR_TEST);

    // Setup render state: alpha-blending enabled, no face culling, no depth testing, scissor enabled, polygon fill
    glEnable(GL_BLEND);
    glBlendEquation(GL_FUNC_ADD);
    glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    glDisable(GL_CULL_FACE);
    glDisable(GL_DEPTH_TEST);
    glEnable(GL_SCISSOR_TEST);
#ifdef GL_POLYGON_MODE
    glPolygonMode(GL_FRONT_AND_BACK, GL_FILL);
#endif

    // Setup viewport, orthographic projection matrix
    // Our visible imgui space lies from draw_data->DisplayPos (top left) to draw_data->DisplayPos+data_data->DisplaySize (bottom right). DisplayMin is typically (0,0) for single viewport apps.
    glViewport(0, 0, (GLsizei)fb_width, (GLsizei)fb_height);
    float L = draw_data->DisplayPos.x;
    float R = draw_data->DisplayPos.x + draw_data->DisplaySize.x;
    float T = draw_data->DisplayPos.y;
    float B = draw_data->DisplayPos.y + draw_data->DisplaySize.y;
    const float ortho_projection[4][4] =
    {
        { 2.0f / (R - L), 0.0f, 0.0f, 0.0f },
        { 0.0f, 2.0f / (T - B), 0.0f, 0.0f },
        { 0.0f, 0.0f, -1.0f, 0.0f },
        { (R + L) / (L - R), (T + B) / (B - T), 0.0f, 1.0f },
    };
    glUseProgram(m_shader_handle);
    glUniform1i(m_attrib_location_tex, 0);
    glUniformMatrix4fv(m_attrib_location_proj_mtx, 1, GL_FALSE, &ortho_projection[0][0]);
#ifdef GL_SAMPLER_BINDING
    glBindSampler(0, 0); // We use combined texture/sampler state. Applications using GL 3.3 may set that otherwise.
#endif
    // Recreate the VAO every time
    // (This is to easily allow multiple GL contexts. VAO are not shared among GL contexts, and we don't track creation/deletion of windows so we don't have an obvious key to use to cache them.)
    GLuint vao_handle = 0;
    glGenVertexArrays(1, &vao_handle);
    glBindVertexArray(vao_handle);
    glBindBuffer(GL_ARRAY_BUFFER, m_vbo_handle);
    glEnableVertexAttribArray(m_attrib_location_position);
    glEnableVertexAttribArray(m_attrib_location_uv);
    glEnableVertexAttribArray(m_attrib_location_color);
    glVertexAttribPointer(m_attrib_location_position, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, pos));
    glVertexAttribPointer(m_attrib_location_uv, 2, GL_FLOAT, GL_FALSE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, uv));
    glVertexAttribPointer(m_attrib_location_color, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(ImDrawVert), (GLvoid*)IM_OFFSETOF(ImDrawVert, col));

    // Draw
    ImVec2 pos = draw_data->DisplayPos;
    for (int n = 0; n < draw_data->CmdListsCount; n++)
    {
        const ImDrawList* cmd_list = draw_data->CmdLists[n];
        const ImDrawIdx* idx_buffer_offset = 0;

        glBindBuffer(GL_ARRAY_BUFFER, m_vbo_handle);
        glBufferData(GL_ARRAY_BUFFER, (GLsizeiptr)cmd_list->VtxBuffer.Size * sizeof(ImDrawVert), (const GLvoid*)cmd_list->VtxBuffer.Data, GL_STREAM_DRAW);

        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, m_elements_handle);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, (GLsizeiptr)cmd_list->IdxBuffer.Size * sizeof(ImDrawIdx), (const GLvoid*)cmd_list->IdxBuffer.Data, GL_STREAM_DRAW);

        for (int cmd_i = 0; cmd_i < cmd_list->CmdBuffer.Size; cmd_i++)
        {
            const ImDrawCmd* pcmd = &cmd_list->CmdBuffer[cmd_i];
            if (pcmd->UserCallback)
            {
                // User callback (registered via ImDrawList::AddCallback)
                pcmd->UserCallback(cmd_list, pcmd);
            }
            else
            {
                ImVec4 clip_rect = ImVec4(pcmd->ClipRect.x - pos.x, pcmd->ClipRect.y - pos.y, pcmd->ClipRect.z - pos.x, pcmd->ClipRect.w - pos.y);
                if (clip_rect.x < fb_width && clip_rect.y < fb_height && clip_rect.z >= 0.0f && clip_rect.w >= 0.0f)
                {
                    // Apply scissor/clipping rectangle
                    glScissor((int)clip_rect.x, (int)(fb_height - clip_rect.w), (int)(clip_rect.z - clip_rect.x), (int)(clip_rect.w - clip_rect.y));

                    // Bind texture, Draw
                    glBindTexture(GL_TEXTURE_2D, (GLuint)(intptr_t)pcmd->TextureId);
                    glDrawElements(GL_TRIANGLES, (GLsizei)pcmd->ElemCount, sizeof(ImDrawIdx) == 2 ? GL_UNSIGNED_SHORT : GL_UNSIGNED_INT, idx_buffer_offset);
                }
            }
            idx_buffer_offset += pcmd->ElemCount;
        }
    }
    glDeleteVertexArrays(1, &vao_handle);

    // Restore modified GL state
    glUseProgram(last_program);
    glBindTexture(GL_TEXTURE_2D, last_texture);
#ifdef GL_SAMPLER_BINDING
    glBindSampler(0, last_sampler);
#endif
    glActiveTexture(last_active_texture);
    glBindVertexArray(last_vertex_array);
    glBindBuffer(GL_ARRAY_BUFFER, last_array_buffer);
    glBlendEquationSeparate(last_blend_equation_rgb, last_blend_equation_alpha);
    glBlendFuncSeparate(last_blend_src_rgb, last_blend_dst_rgb, last_blend_src_alpha, last_blend_dst_alpha);
    if (last_enable_blend) glEnable(GL_BLEND); else glDisable(GL_BLEND);
    if (last_enable_cull_face) glEnable(GL_CULL_FACE); else glDisable(GL_CULL_FACE);
    if (last_enable_depth_test) glEnable(GL_DEPTH_TEST); else glDisable(GL_DEPTH_TEST);
    if (last_enable_scissor_test) glEnable(GL_SCISSOR_TEST); else glDisable(GL_SCISSOR_TEST);
#ifdef GL_POLYGON_MODE
    glPolygonMode(GL_FRONT_AND_BACK, (GLenum)last_polygon_mode[0]);
#endif
    glViewport(last_viewport[0], last_viewport[1], (GLsizei)last_viewport[2], (GLsizei)last_viewport[3]);
    glScissor(last_scissor_box[0], last_scissor_box[1], (GLsizei)last_scissor_box[2], (GLsizei)last_scissor_box[3]);
}

void ImGuiWrapper::destroy_device_objects()
{
    if (m_vbo_handle != 0)
    {
        glDeleteBuffers(1, &m_vbo_handle);
        m_vbo_handle = 0;
    }
    if (m_elements_handle != 0)
    {
        glDeleteBuffers(1, &m_elements_handle);
        m_elements_handle = 0;
    }

    if ((m_shader_handle != 0) && (m_vert_handle != 0))
        glDetachShader(m_shader_handle, m_vert_handle);

    if (m_vert_handle != 0)
    {
        glDeleteShader(m_vert_handle);
        m_vert_handle = 0;
    }
    if ((m_shader_handle != 0) && (m_frag_handle != 0))
        glDetachShader(m_shader_handle, m_frag_handle);

    if (m_frag_handle != 0)
    {
        glDeleteShader(m_frag_handle);
        m_frag_handle = 0;
    }

    if (m_shader_handle != 0)
    {
        glDeleteProgram(m_shader_handle);
        m_shader_handle = 0;
    }

    destroy_fonts_texture();
}

void ImGuiWrapper::destroy_fonts_texture()
{
    if (m_font_texture)
    {
        ImGuiIO& io = ImGui::GetIO();
        io.Fonts->TexID = 0;
        glDeleteTextures(1, &m_font_texture);
        m_font_texture = 0;
    }
}

} // namespace GUI
} // namespace Slic3r