Added canvas example

Added another example to show how to use Nuklear to only draw stuff
to the screen instead of using it for UI (or both).

example/canvas.c

@@ -0,0 +1,455 @@
+/* nuklear - v1.00 - public domain */
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdarg.h>
+#include <string.h>
+#include <math.h>
+#include <assert.h>
+#include <math.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 device {
+    struct nk_buffer cmds;
+    struct nk_draw_null_texture 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;
+};
+
+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_draw_vertex);
+        size_t vp = offsetof(struct nk_draw_vertex, position);
+        size_t vt = offsetof(struct nk_draw_vertex, uv);
+        size_t vc = offsetof(struct nk_draw_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 converting configuration */
+            struct nk_convert_config config;
+            memset(&config, 0, sizeof(config));
+            config.global_alpha = 1.0f;
+            config.shape_AA = AA;
+            config.line_AA = AA;
+            config.circle_segment_count = 22;
+            config.curve_segment_count = 22;
+            config.arc_segment_count = 22;
+            config.null = dev->null;
+
+            /* 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);
+    }
+
+    /* 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), (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)) {
+        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);
+}
+
+static void
+canvas_begin(struct nk_context *ctx, int x, int y, int width, int height, struct nk_command_buffer **out)
+{
+    static struct nk_panel layout;
+    struct nk_rect total_space;
+    ctx->style.window.spacing = nk_vec2(0,0);
+    ctx->style.window.padding = nk_vec2(0,0);
+    nk_begin(ctx, &layout, "Window", nk_rect(x, y, width, height), NK_WINDOW_NO_SCROLLBAR);
+    nk_window_set_bounds(ctx, nk_rect(x, y, width, height));
+    total_space = nk_window_get_content_region(ctx);
+    nk_layout_row_dynamic(ctx, total_space.h, 1);
+    nk_widget(&total_space, ctx);
+    *out = nk_window_get_canvas(ctx);
+}
+
+static void
+canvas_end(struct nk_context *ctx)
+{
+    nk_end(ctx);
+    ctx->style.window.spacing = nk_vec2(4,4);
+    ctx->style.window.padding = nk_vec2(8,8);
+}
+
+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;
+
+    /* 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);
+    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.null);
+    nk_init_default(&ctx, &font->handle);
+
+    glEnable(GL_TEXTURE_2D);
+    while (!glfwWindowShouldClose(win))
+    {
+        /* input */
+        pump_input(&ctx, win);
+
+        /* draw */
+        {struct nk_command_buffer *canvas;
+        canvas_begin(&ctx, 0, 0, width, height, &canvas);
+        {
+            nk_fill_rect(canvas, nk_rect(0,0,width,height), 0, nk_rgb(150,150,150));
+            nk_fill_rect(canvas, nk_rect(15,15,210,210), 5, nk_rgb(247, 230, 154));
+            nk_fill_rect(canvas, nk_rect(20,20,200,200), 5, nk_rgb(188, 174, 118));
+            nk_draw_text(canvas, 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, nk_rect(250,20,100,100), 0, nk_rgb(0,0,255));
+            nk_fill_circle(canvas, nk_rect(20,250,100,100), nk_rgb(255,0,0));
+            nk_fill_triangle(canvas, 250, 250, 350, 250, 300, 350, nk_rgb(0,255,0));
+            nk_fill_arc(canvas, 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, points, 6, nk_rgb(255,255,255));}
+
+            nk_stroke_line(canvas, 15, 10, 200, 10, 2.0f, nk_rgb(189,45,75));
+            nk_stroke_rect(canvas, nk_rect(370, 20, 100, 100), 10, 3, nk_rgb(0,0,255));
+            nk_stroke_curve(canvas, 380, 200, 405, 270, 455, 120, 480, 200, 2, nk_rgb(0,150,220));
+            nk_stroke_circle(canvas, nk_rect(20, 370, 100, 100), 5, nk_rgb(0,255,120));
+            nk_stroke_triangle(canvas, 370, 250, 470, 250, 420, 350, 6, nk_rgb(255,0,143));
+        }
+        canvas_end(&ctx);}
+
+        /* Draw */
+        glfwGetWindowSize(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;
+}
+