canvas.c

/* nuklear - v1.05 - public domain */
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdarg.h>
#include <string.h>
#include <math.h>
#include <assert.h>
#include <time.h>
#include <limits.h>

#include <GL/glew.h>
#include <GLFW/glfw3.h>

#define NK_PRIVATE
#define NK_INCLUDE_FIXED_TYPES
#define NK_INCLUDE_STANDARD_IO
#define NK_INCLUDE_DEFAULT_ALLOCATOR
#define NK_INCLUDE_VERTEX_BUFFER_OUTPUT
#define NK_INCLUDE_FONT_BAKING
#define NK_INCLUDE_DEFAULT_FONT
#define NK_IMPLEMENTATION
#include "../nuklear.h"

#define STB_IMAGE_IMPLEMENTATION
#include "stb_image.h"

/* macros */
#define WINDOW_WIDTH 1200
#define WINDOW_HEIGHT 800

#define MAX_VERTEX_MEMORY 512 * 1024
#define MAX_ELEMENT_MEMORY 128 * 1024

#define UNUSED(a) (void)a
#define MIN(a,b) ((a) < (b) ? (a) : (b))
#define MAX(a,b) ((a) < (b) ? (b) : (a))
#define LEN(a) (sizeof(a)/sizeof(a)[0])

#define NK_SHADER_VERSION "#version 150\n"

/* ===============================================================
 *
 *                          DEVICE
 *
 * ===============================================================*/
struct nk_glfw_vertex {
    float position[2];
    float uv[2];
    nk_byte col[4];
};

struct device {
    struct nk_buffer cmds;
    struct nk_draw_null_texture tex_null;
    GLuint vbo, vao, ebo;
    GLuint prog;
    GLuint vert_shdr;
    GLuint frag_shdr;
    GLint attrib_pos;
    GLint attrib_uv;
    GLint attrib_col;
    GLint uniform_tex;
    GLint uniform_proj;
    GLuint font_tex;
};

/* function icon_load () is not used to build this file but might still be useful :) */
/*
static void
die(const char *fmt, ...)
{
    va_list ap;
    va_start(ap, fmt);
    vfprintf(stderr, fmt, ap);
    va_end(ap);
    fputs("\n", stderr);
    exit(EXIT_FAILURE);
}

static struct nk_image
icon_load(const char *filename)
{
    int x,y,n;
    GLuint tex;
    unsigned char *data = stbi_load(filename, &x, &y, &n, 0);
    if (!data) die("[SDL]: failed to load image: %s", filename);

     glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR_MIPMAP_NEAREST);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, x, y, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
    glGenerateMipmap(GL_TEXTURE_2D);
    stbi_image_free(data);
    return nk_image_id((int)tex);
}
*/

static void
device_init(struct device *dev)
{
    GLint status;
    static const GLchar *vertex_shader =
        NK_SHADER_VERSION
        "uniform mat4 ProjMtx;\n"
        "in vec2 Position;\n"
        "in vec2 TexCoord;\n"
        "in vec4 Color;\n"
        "out vec2 Frag_UV;\n"
        "out vec4 Frag_Color;\n"
        "void main() {\n"
        "   Frag_UV = TexCoord;\n"
        "   Frag_Color = Color;\n"
        "   gl_Position = ProjMtx * vec4(Position.xy, 0, 1);\n"
        "}\n";
    static const GLchar *fragment_shader =
        NK_SHADER_VERSION
        "precision mediump float;\n"
        "uniform sampler2D Texture;\n"
        "in vec2 Frag_UV;\n"
        "in vec4 Frag_Color;\n"
        "out vec4 Out_Color;\n"
        "void main(){\n"
        "   Out_Color = Frag_Color * texture(Texture, Frag_UV.st);\n"
        "}\n";

    nk_buffer_init_default(&dev->cmds);
    dev->prog = glCreateProgram();
    dev->vert_shdr = glCreateShader(GL_VERTEX_SHADER);
    dev->frag_shdr = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(dev->vert_shdr, 1, &vertex_shader, 0);
    glShaderSource(dev->frag_shdr, 1, &fragment_shader, 0);
    glCompileShader(dev->vert_shdr);
    glCompileShader(dev->frag_shdr);
    glGetShaderiv(dev->vert_shdr, GL_COMPILE_STATUS, &status);
    assert(status == GL_TRUE);
    glGetShaderiv(dev->frag_shdr, GL_COMPILE_STATUS, &status);
    assert(status == GL_TRUE);
    glAttachShader(dev->prog, dev->vert_shdr);
    glAttachShader(dev->prog, dev->frag_shdr);
    glLinkProgram(dev->prog);
    glGetProgramiv(dev->prog, GL_LINK_STATUS, &status);
    assert(status == GL_TRUE);

    dev->uniform_tex = glGetUniformLocation(dev->prog, "Texture");
    dev->uniform_proj = glGetUniformLocation(dev->prog, "ProjMtx");
    dev->attrib_pos = glGetAttribLocation(dev->prog, "Position");
    dev->attrib_uv = glGetAttribLocation(dev->prog, "TexCoord");
    dev->attrib_col = glGetAttribLocation(dev->prog, "Color");

    {
        /* buffer setup */
        GLsizei vs = sizeof(struct nk_glfw_vertex);
        size_t vp = offsetof(struct nk_glfw_vertex, position);
        size_t vt = offsetof(struct nk_glfw_vertex, uv);
        size_t vc = offsetof(struct nk_glfw_vertex, col);

        glGenBuffers(1, &dev->vbo);
        glGenBuffers(1, &dev->ebo);
        glGenVertexArrays(1, &dev->vao);

        glBindVertexArray(dev->vao);
        glBindBuffer(GL_ARRAY_BUFFER, dev->vbo);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, dev->ebo);

        glEnableVertexAttribArray((GLuint)dev->attrib_pos);
        glEnableVertexAttribArray((GLuint)dev->attrib_uv);
        glEnableVertexAttribArray((GLuint)dev->attrib_col);

        glVertexAttribPointer((GLuint)dev->attrib_pos, 2, GL_FLOAT, GL_FALSE, vs, (void*)vp);
        glVertexAttribPointer((GLuint)dev->attrib_uv, 2, GL_FLOAT, GL_FALSE, vs, (void*)vt);
        glVertexAttribPointer((GLuint)dev->attrib_col, 4, GL_UNSIGNED_BYTE, GL_TRUE, vs, (void*)vc);
    }

    glBindTexture(GL_TEXTURE_2D, 0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
}

static void
device_upload_atlas(struct device *dev, const void *image, int width, int height)
{
    glGenTextures(1, &dev->font_tex);
    glBindTexture(GL_TEXTURE_2D, dev->font_tex);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, (GLsizei)width, (GLsizei)height, 0,
                GL_RGBA, GL_UNSIGNED_BYTE, image);
}

static void
device_shutdown(struct device *dev)
{
    glDetachShader(dev->prog, dev->vert_shdr);
    glDetachShader(dev->prog, dev->frag_shdr);
    glDeleteShader(dev->vert_shdr);
    glDeleteShader(dev->frag_shdr);
    glDeleteProgram(dev->prog);
    glDeleteTextures(1, &dev->font_tex);
    glDeleteBuffers(1, &dev->vbo);
    glDeleteBuffers(1, &dev->ebo);
    nk_buffer_free(&dev->cmds);
}

static void
device_draw(struct device *dev, struct nk_context *ctx, int width, int height,
    enum nk_anti_aliasing AA)
{
    GLfloat ortho[4][4] = {
        {2.0f, 0.0f, 0.0f, 0.0f},
        {0.0f,-2.0f, 0.0f, 0.0f},
        {0.0f, 0.0f,-1.0f, 0.0f},
        {-1.0f,1.0f, 0.0f, 1.0f},
    };
    ortho[0][0] /= (GLfloat)width;
    ortho[1][1] /= (GLfloat)height;

    /* setup global state */
    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);
    glActiveTexture(GL_TEXTURE0);

    /* setup program */
    glUseProgram(dev->prog);
    glUniform1i(dev->uniform_tex, 0);
    glUniformMatrix4fv(dev->uniform_proj, 1, GL_FALSE, &ortho[0][0]);
    {
        /* convert from command queue into draw list and draw to screen */
        const struct nk_draw_command *cmd;
        void *vertices, *elements;
        const nk_draw_index *offset = NULL;

        /* allocate vertex and element buffer */
        glBindVertexArray(dev->vao);
        glBindBuffer(GL_ARRAY_BUFFER, dev->vbo);
        glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, dev->ebo);

        glBufferData(GL_ARRAY_BUFFER, MAX_VERTEX_MEMORY, NULL, GL_STREAM_DRAW);
        glBufferData(GL_ELEMENT_ARRAY_BUFFER, MAX_ELEMENT_MEMORY, NULL, GL_STREAM_DRAW);

        /* load draw vertices & elements directly into vertex + element buffer */
        vertices = glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);
        elements = glMapBuffer(GL_ELEMENT_ARRAY_BUFFER, GL_WRITE_ONLY);
        {
            /* fill convert configuration */
            struct nk_convert_config config;
            static const struct nk_draw_vertex_layout_element vertex_layout[] = {
                {NK_VERTEX_POSITION, NK_FORMAT_FLOAT, NK_OFFSETOF(struct nk_glfw_vertex, position)},
                {NK_VERTEX_TEXCOORD, NK_FORMAT_FLOAT, NK_OFFSETOF(struct nk_glfw_vertex, uv)},
                {NK_VERTEX_COLOR, NK_FORMAT_R8G8B8A8, NK_OFFSETOF(struct nk_glfw_vertex, col)},
                {NK_VERTEX_LAYOUT_END}
            };
            NK_MEMSET(&config, 0, sizeof(config));
            config.vertex_layout = vertex_layout;
            config.vertex_size = sizeof(struct nk_glfw_vertex);
            config.vertex_alignment = NK_ALIGNOF(struct nk_glfw_vertex);
            config.tex_null = dev->tex_null;
            config.circle_segment_count = 22;
            config.curve_segment_count = 22;
            config.arc_segment_count = 22;
            config.global_alpha = 1.0f;
            config.shape_AA = AA;
            config.line_AA = AA;

            /* setup buffers to load vertices and elements */
            {struct nk_buffer vbuf, ebuf;
            nk_buffer_init_fixed(&vbuf, vertices, MAX_VERTEX_MEMORY);
            nk_buffer_init_fixed(&ebuf, elements, MAX_ELEMENT_MEMORY);
            nk_convert(ctx, &dev->cmds, &vbuf, &ebuf, &config);}
        }
        glUnmapBuffer(GL_ARRAY_BUFFER);
        glUnmapBuffer(GL_ELEMENT_ARRAY_BUFFER);

      /* iterate over and execute each draw command */
        nk_draw_foreach(cmd, ctx, &dev->cmds)
        {
            if (!cmd->elem_count) continue;
            glBindTexture(GL_TEXTURE_2D, (GLuint)cmd->texture.id);
            glScissor(
                (GLint)(cmd->clip_rect.x),
                (GLint)((height - (GLint)(cmd->clip_rect.y + cmd->clip_rect.h))),
                (GLint)(cmd->clip_rect.w),
                (GLint)(cmd->clip_rect.h));
            glDrawElements(GL_TRIANGLES, (GLsizei)cmd->elem_count, GL_UNSIGNED_SHORT, offset);
            offset += cmd->elem_count;
        }
        nk_clear(ctx);
        nk_buffer_clear(&dev->cmds);
    }

    /* default OpenGL state */
    glUseProgram(0);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    glBindVertexArray(0);
    glDisable(GL_BLEND);
    glDisable(GL_SCISSOR_TEST);
}

/* glfw callbacks (I don't know if there is a easier way to access text and scroll )*/
static void error_callback(int e, const char *d){printf("Error %d: %s\n", e, d);}
static void text_input(GLFWwindow *win, unsigned int codepoint)
{nk_input_unicode((struct nk_context*)glfwGetWindowUserPointer(win), codepoint);}
static void scroll_input(GLFWwindow *win, double _, double yoff)
{UNUSED(_);nk_input_scroll((struct nk_context*)glfwGetWindowUserPointer(win), nk_vec2(0, (float)yoff));}

static void
pump_input(struct nk_context *ctx, GLFWwindow *win)
{
    double x, y;
    nk_input_begin(ctx);
    glfwPollEvents();

    nk_input_key(ctx, NK_KEY_DEL, glfwGetKey(win, GLFW_KEY_DELETE) == GLFW_PRESS);
    nk_input_key(ctx, NK_KEY_ENTER, glfwGetKey(win, GLFW_KEY_ENTER) == GLFW_PRESS);
    nk_input_key(ctx, NK_KEY_TAB, glfwGetKey(win, GLFW_KEY_TAB) == GLFW_PRESS);
    nk_input_key(ctx, NK_KEY_BACKSPACE, glfwGetKey(win, GLFW_KEY_BACKSPACE) == GLFW_PRESS);
    nk_input_key(ctx, NK_KEY_LEFT, glfwGetKey(win, GLFW_KEY_LEFT) == GLFW_PRESS);
    nk_input_key(ctx, NK_KEY_RIGHT, glfwGetKey(win, GLFW_KEY_RIGHT) == GLFW_PRESS);
    nk_input_key(ctx, NK_KEY_UP, glfwGetKey(win, GLFW_KEY_UP) == GLFW_PRESS);
    nk_input_key(ctx, NK_KEY_DOWN, glfwGetKey(win, GLFW_KEY_DOWN) == GLFW_PRESS);

    if (glfwGetKey(win, GLFW_KEY_LEFT_CONTROL) == GLFW_PRESS ||
        glfwGetKey(win, GLFW_KEY_RIGHT_CONTROL) == GLFW_PRESS) {
        nk_input_key(ctx, NK_KEY_COPY, glfwGetKey(win, GLFW_KEY_C) == GLFW_PRESS);
        nk_input_key(ctx, NK_KEY_PASTE, glfwGetKey(win, GLFW_KEY_P) == GLFW_PRESS);
        nk_input_key(ctx, NK_KEY_CUT, glfwGetKey(win, GLFW_KEY_X) == GLFW_PRESS);
        nk_input_key(ctx, NK_KEY_CUT, glfwGetKey(win, GLFW_KEY_E) == GLFW_PRESS);
        nk_input_key(ctx, NK_KEY_SHIFT, 1);
    } else {
        nk_input_key(ctx, NK_KEY_COPY, 0);
        nk_input_key(ctx, NK_KEY_PASTE, 0);
        nk_input_key(ctx, NK_KEY_CUT, 0);
        nk_input_key(ctx, NK_KEY_SHIFT, 0);
    }

    glfwGetCursorPos(win, &x, &y);
    nk_input_motion(ctx, (int)x, (int)y);
    nk_input_button(ctx, NK_BUTTON_LEFT, (int)x, (int)y, glfwGetMouseButton(win, GLFW_MOUSE_BUTTON_LEFT) == GLFW_PRESS);
    nk_input_button(ctx, NK_BUTTON_MIDDLE, (int)x, (int)y, glfwGetMouseButton(win, GLFW_MOUSE_BUTTON_MIDDLE) == GLFW_PRESS);
    nk_input_button(ctx, NK_BUTTON_RIGHT, (int)x, (int)y, glfwGetMouseButton(win, GLFW_MOUSE_BUTTON_RIGHT) == GLFW_PRESS);
    nk_input_end(ctx);
}

struct nk_canvas {
    struct nk_command_buffer *painter;
    struct nk_vec2 item_spacing;
    struct nk_vec2 panel_padding;
    struct nk_style_item window_background;
};

static void
canvas_begin(struct nk_context *ctx, struct nk_canvas *canvas, nk_flags flags,
    int x, int y, int width, int height, struct nk_color background_color)
{
    /* save style properties which will be overwritten */
    canvas->panel_padding = ctx->style.window.padding;
    canvas->item_spacing = ctx->style.window.spacing;
    canvas->window_background = ctx->style.window.fixed_background;

    /* use the complete window space and set background */
    ctx->style.window.spacing = nk_vec2(0,0);
    ctx->style.window.padding = nk_vec2(0,0);
    ctx->style.window.fixed_background = nk_style_item_color(background_color);

    /* create/update window and set position + size */
    flags = flags & ~NK_WINDOW_DYNAMIC;
    nk_window_set_bounds(ctx, "Window", nk_rect(x, y, width, height));
    nk_begin(ctx, "Window", nk_rect(x, y, width, height), NK_WINDOW_NO_SCROLLBAR|flags);

    /* allocate the complete window space for drawing */
    {struct nk_rect total_space;
    total_space = nk_window_get_content_region(ctx);
    nk_layout_row_dynamic(ctx, total_space.h, 1);
    nk_widget(&total_space, ctx);
    canvas->painter = nk_window_get_canvas(ctx);}
}

static void
canvas_end(struct nk_context *ctx, struct nk_canvas *canvas)
{
    nk_end(ctx);
    ctx->style.window.spacing = canvas->panel_padding;
    ctx->style.window.padding = canvas->item_spacing;
    ctx->style.window.fixed_background = canvas->window_background;
}

int main(int argc, char *argv[])
{
    /* Platform */
    static GLFWwindow *win;
    int width = 0, height = 0;

    /* GUI */
    struct device device;
    struct nk_font_atlas atlas;
    struct nk_context ctx;

    NK_UNUSED(argc);
    NK_UNUSED(argv);

    /* GLFW */
    glfwSetErrorCallback(error_callback);
    if (!glfwInit()) {
        fprintf(stdout, "[GFLW] failed to init!\n");
        exit(1);
    }
    glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
    glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
    glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
    glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
    win = glfwCreateWindow(WINDOW_WIDTH, WINDOW_HEIGHT, "Demo", NULL, NULL);
    glfwMakeContextCurrent(win);
    glfwSetWindowUserPointer(win, &ctx);
    glfwSetCharCallback(win, text_input);
    glfwSetScrollCallback(win, scroll_input);
    glfwGetWindowSize(win, &width, &height);

    /* OpenGL */
    glViewport(0, 0, WINDOW_WIDTH, WINDOW_HEIGHT);
    glewExperimental = 1;
    if (glewInit() != GLEW_OK) {
        fprintf(stderr, "Failed to setup GLEW\n");
        exit(1);
    }

    /* GUI */
    {device_init(&device);
    {const void *image; int w, h;
    struct nk_font *font;
    nk_font_atlas_init_default(&atlas);
    nk_font_atlas_begin(&atlas);
    font = nk_font_atlas_add_default(&atlas, 13, 0);
    image = nk_font_atlas_bake(&atlas, &w, &h, NK_FONT_ATLAS_RGBA32);
    device_upload_atlas(&device, image, w, h);
    nk_font_atlas_end(&atlas, nk_handle_id((int)device.font_tex), &device.tex_null);
    nk_init_default(&ctx, &font->handle);

    glEnable(GL_TEXTURE_2D);
    while (!glfwWindowShouldClose(win))
    {
        /* input */
        pump_input(&ctx, win);

        /* draw */
        {struct nk_canvas canvas;
        canvas_begin(&ctx, &canvas, 0, 0, 0, width, height, nk_rgb(250,250,250));
        {
            nk_fill_rect(canvas.painter, nk_rect(15,15,210,210), 5, nk_rgb(247, 230, 154));
            nk_fill_rect(canvas.painter, nk_rect(20,20,200,200), 5, nk_rgb(188, 174, 118));
            nk_draw_text(canvas.painter, nk_rect(30, 30, 150, 20), "Text to draw", 12, &font->handle, nk_rgb(188,174,118), nk_rgb(0,0,0));
            nk_fill_rect(canvas.painter, nk_rect(250,20,100,100), 0, nk_rgb(0,0,255));
            nk_fill_circle(canvas.painter, nk_rect(20,250,100,100), nk_rgb(255,0,0));
            nk_fill_triangle(canvas.painter, 250, 250, 350, 250, 300, 350, nk_rgb(0,255,0));
            nk_fill_arc(canvas.painter, 300, 180, 50, 0, 3.141592654f * 3.0f / 4.0f, nk_rgb(255,255,0));

            {float points[12];
            points[0] = 200; points[1] = 250;
            points[2] = 250; points[3] = 350;
            points[4] = 225; points[5] = 350;
            points[6] = 200; points[7] = 300;
            points[8] = 175; points[9] = 350;
            points[10] = 150; points[11] = 350;
            nk_fill_polygon(canvas.painter, points, 6, nk_rgb(0,0,0));}

            nk_stroke_line(canvas.painter, 15, 10, 200, 10, 2.0f, nk_rgb(189,45,75));
            nk_stroke_rect(canvas.painter, nk_rect(370, 20, 100, 100), 10, 3, nk_rgb(0,0,255));
            nk_stroke_curve(canvas.painter, 380, 200, 405, 270, 455, 120, 480, 200, 2, nk_rgb(0,150,220));
            nk_stroke_circle(canvas.painter, nk_rect(20, 370, 100, 100), 5, nk_rgb(0,255,120));
            nk_stroke_triangle(canvas.painter, 370, 250, 470, 250, 420, 350, 6, nk_rgb(255,0,143));
        }
        canvas_end(&ctx, &canvas);}

        /* Draw */
        /* Framebuffer size is used instead of window size because the window size is in screen coordinates instead of pixels.
         * See https://www.glfw.org/docs/latest/window_guide.html#window_size for more info
         */
        glfwGetFramebufferSize(win, &width, &height);
        glViewport(0, 0, width, height);
        glClear(GL_COLOR_BUFFER_BIT);
        glClearColor(0.2f, 0.2f, 0.2f, 1.0f);
        device_draw(&device, &ctx, width, height, NK_ANTI_ALIASING_ON);
        glfwSwapBuffers(win);
    }}}
    nk_font_atlas_clear(&atlas);
    nk_free(&ctx);
    device_shutdown(&device);
    glfwTerminate();
    return 0;
}