glterm.c

#include "glterm.h"

#include <stdio.h>
#include <stdlib.h>
#include <math.h>

#include <GL/glew.h>
#include <SDL2/SDL.h>
#include <png.h>


#define PANEL_SIZE 256

typedef struct quad_vertex_t {
    float x, y, u, v;
    GLubyte fg[4];
    GLubyte bg[4];
} quad_vertex;


struct window_t {
    int width, height;
    SDL_Window *sdlwindow;
    SDL_GLContext glcontext;
    GLuint shader_program;
    GLuint shader_program2;
    GLuint vbo;
    GLuint fgtex, bgtex;
    
    int quad_vbo_size;
    GLuint quad_vbo;
    quad_vertex *quad_buffer;
    
    float transform[16];
    
    char fg[4*256*256];
    char bg[4*256*256];
    int mousex, mousey;
}* window = NULL;

struct tileset_t {
    int imgwidth, imgheight, components;
    int width, height;
    char *data;
    GLuint tex;
    int refcount;
};

static char* image_load(const char *file_name, int *width, int *height, int *components) {
    char *data = NULL;
    
    png_byte header[8];

    FILE *fp = fopen(file_name, "rb");
    png_structp png_ptr = NULL;
    
    if(!fp) goto error;
    if(fread(header, 1, 8, fp) != 8 || png_sig_cmp(header, 0, 8)) goto error;

    png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);

    if(!png_ptr) goto error;

    png_infop info_ptr = png_create_info_struct(png_ptr);
    if(!info_ptr) goto error;
    if(setjmp(png_jmpbuf(png_ptr))) goto error;
    png_init_io(png_ptr, fp);
    png_set_sig_bytes(png_ptr, 8);

    png_read_png(png_ptr, info_ptr, PNG_TRANSFORM_STRIP_16 | PNG_TRANSFORM_PACKING, NULL);

    *width = png_get_image_width(png_ptr, info_ptr);
    *height = png_get_image_height(png_ptr, info_ptr);
    *components = png_get_channels(png_ptr,info_ptr);

    png_bytep *rows = png_get_rows(png_ptr, info_ptr);
    data = malloc(*width * *height * *components);

    int i = 0;
    for(int h = 0;h<*height;++h) {
        for(int w = 0;w<*width * *components;++w) {
            data[i++] = rows[h][w];
        }
    }
error:
    png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
    if(fp) fclose(fp);
    return data;
}

static GLuint texture_create(char *data, int width, int height, int components) {
    GLuint tex;
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    switch(components) {
        case 1:
            glTexImage2D(GL_TEXTURE_2D, 0, GL_R8, width, height, 0, GL_RED, GL_UNSIGNED_BYTE, data);
            break;
        case 3:
            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);
            break;
        case 4:
            glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, data);
            break;
    }

    return tex;
}

static int check_shader_compile_status(GLuint obj) {
    GLint status;
    glGetShaderiv(obj, GL_COMPILE_STATUS, &status);
    if(status == GL_FALSE) {
        GLint length;
        glGetShaderiv(obj, GL_INFO_LOG_LENGTH, &length);
        char *log = malloc(length);
        glGetShaderInfoLog(obj, length, &length, &log[0]);
        fprintf(stderr, "%s", log);
        free(log);
        return 0;
    }
    return 1;
}

static int check_program_link_status(GLuint obj) {
    GLint status;
    glGetProgramiv(obj, GL_LINK_STATUS, &status);
    if(status == GL_FALSE) {
        GLint length;
        glGetProgramiv(obj, GL_INFO_LOG_LENGTH, &length);
        char *log = malloc(length);
        glGetProgramInfoLog(obj, length, &length, &log[0]);
        fprintf(stderr, "%s", log);
        free(log);
        return 0;
    }
    return 1;
}

typedef struct attribbind_t {
    const char *name;
    int location;
} attribbind;

static GLuint shader_build(const char *tile_vertex_source, const char *tile_fragment_source, const attribbind *attribs) {
    GLuint shader_program, vertex_shader, fragment_shader;

    vertex_shader = glCreateShader(GL_VERTEX_SHADER);
    glShaderSource(vertex_shader, 1, &tile_vertex_source, 0);
    glCompileShader(vertex_shader);
    if(!check_shader_compile_status(vertex_shader)) {
        return 0;
    }

    fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(fragment_shader, 1, &tile_fragment_source, 0);
    glCompileShader(fragment_shader);
    if(!check_shader_compile_status(fragment_shader)) {
        return 0;
    }

    shader_program = glCreateProgram();
    glAttachShader(shader_program, vertex_shader);
    glAttachShader(shader_program, fragment_shader);
    glDeleteShader(vertex_shader);
    glDeleteShader(fragment_shader);
    
    while(attribs->name != NULL) {
        glBindAttribLocation(shader_program, attribs->location, attribs->name);
        ++attribs;
    }
    
    glLinkProgram(shader_program);
    if(!check_program_link_status(shader_program)) {
        return 0;
    }
    return shader_program;
}

const char *tile_vertex_source =
    "#version 120\n"
    "uniform mat4 transform;\n"
    "void main() {\n"
    "   gl_TexCoord[0] = gl_MultiTexCoord0;\n"
    "   gl_Position = transform*gl_Vertex;\n"
    "}\n";

const char *tile_fragment_source =
    "#version 120\n"
    "uniform sampler2D font;\n"
    "uniform sampler2D foreground;\n"
    "uniform sampler2D background;\n"
    "uniform vec2 panelsize;\n"
    "uniform vec2 tilesize;\n"
    "uniform vec2 texsize;\n"
    "const float eps = 0.001;\n"
    "void main() {\n"
    "   vec2 tilecoord = eps + (1.0-2.0*eps)*fract(gl_TexCoord[0].xy*panelsize);\n"
    "   vec4 fg = texture2D(foreground, gl_TexCoord[0].xy*texsize);\n"
    "   vec4 bg = texture2D(background, gl_TexCoord[0].xy*texsize);\n"
    "   vec2 tile = vec2(fg.w, bg.w)*255.;\n"
    "   vec4 glyph = texture2D(font, (tile.xy+tilecoord)*tilesize);\n"
    "   gl_FragColor.xyz = mix(bg.xyz, fg.xyz, glyph.xyz);\n"
    "   gl_FragColor.w = glyph.w;\n"
    "}\n";

const char *quad_vertex_source =
    "#version 120\n"
    "uniform mat4 transform;\n"
    "attribute vec4 foreground;\n"
    "attribute vec4 background;\n"
    "varying vec4 fg;\n"
    "varying vec4 bg;\n"
    "void main() {\n"
    "   fg = foreground;\n"
    "   bg = background;\n"
    "   gl_TexCoord[0] = gl_MultiTexCoord0;\n"
    "   gl_Position = transform*gl_Vertex;\n"
    "}\n";

const char *quad_fragment_source =
    "#version 120\n"
    "uniform sampler2D font;\n"
    "varying vec4 fg;\n"
    "varying vec4 bg;\n"
    "void main() {\n"
    "   vec4 glyph = texture2D(font, gl_TexCoord[0].xy);\n"
    "   gl_FragColor.xyz = mix(bg.xyz, fg.xyz, glyph.xyz);\n"
    "   gl_FragColor.w = glyph.w;\n"
    "}\n";

const GLfloat quad_data[] = {
    1.0f,  1.0f,       1.0f, 0.0f,
   -1.0f,  1.0f,       0.0f, 0.0f,
    1.0f, -1.0f,       1.0f, 1.0f,
    1.0f, -1.0f,       1.0f, 1.0f,
   -1.0f,  1.0f,       0.0f, 0.0f,
   -1.0f, -1.0f,       0.0f, 1.0f,
};

tileset tileset_load(int width, int height, const char *filename) {
    tileset ts = malloc(sizeof(struct tileset_t));
    ts->refcount = 1;
    ts->width = width;
    ts->height = height;
    ts->data = image_load(filename, &ts->imgwidth, &ts->imgheight, &ts->components);
    if(ts->data == NULL) {
        fprintf(stderr, "failed to load tileset");
        free(ts);
        return NULL;
    }
    ts->tex = texture_create(ts->data, ts->imgwidth, ts->imgheight, ts->components);
    return ts;
}

void tileset_retain(tileset ts) {
    ++(ts->refcount);
}

void tileset_destroy(tileset ts) {
    if(--(ts->refcount) <= 0) {
        glDeleteTextures(1, &ts->tex);
        free(ts);
    }
}

int window_create(const char *title, int width, int height) {
    window = malloc(sizeof(struct window_t));
    window->width = width;
    window->height = height;
    window_transform_identity();
    
    if(SDL_Init(SDL_INIT_VIDEO | SDL_INIT_EVENTS) < 0) {
        fprintf(stderr, "failed to init SDL");
        return 1;
    }
        
    if((window->sdlwindow = SDL_CreateWindow(title, SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, width, height, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN)) == 0) {
        fprintf(stderr, "failed to open window");
        SDL_Quit();
        free(window);
        window = NULL;
        return 1;
    }

    SDL_GetMouseState(&window->mousex, &window->mousey);

    window->glcontext = SDL_GL_CreateContext(window->sdlwindow);

    if(glewInit()) {
        fprintf(stderr, "failed to init GLEW");
        SDL_GL_DeleteContext(window->glcontext);
        SDL_DestroyWindow(window->sdlwindow);
        SDL_Quit();
        free(window);
        window = NULL;
        return 1;
    }

    attribbind attribs[] = {
        {NULL, 0}
    };
    window->shader_program = shader_build(tile_vertex_source, tile_fragment_source, attribs);
    glUseProgram(window->shader_program);
    glUniform1i(glGetUniformLocation(window->shader_program, "font"), 0);
    glUniform1i(glGetUniformLocation(window->shader_program, "foreground"), 1);
    glUniform1i(glGetUniformLocation(window->shader_program, "background"), 2);

    attribbind attribs2[] = {
        {"foreground", 1},
        {"background", 2},
        {NULL, 0}
    };
    window->shader_program2 = shader_build(quad_vertex_source, quad_fragment_source, attribs2);
    glUseProgram(window->shader_program2);
    glUniform1i(glGetUniformLocation(window->shader_program2, "font"), 0);

    glGenBuffers(1, &window->vbo);
    glBindBuffer(GL_ARRAY_BUFFER, window->vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(GLfloat)*6*4, quad_data, GL_STATIC_DRAW);

    window->quad_vbo_size = 1024;
    glGenBuffers(1, &window->quad_vbo);
    glBindBuffer(GL_ARRAY_BUFFER, window->quad_vbo);
    glBufferData(GL_ARRAY_BUFFER, sizeof(quad_vertex)*6*window->quad_vbo_size, 0, GL_STREAM_DRAW);
    window->quad_buffer = malloc(sizeof(quad_vertex)*6*window->quad_vbo_size);

    glActiveTexture(GL_TEXTURE1);
    glGenTextures(1, &window->fgtex);
    glBindTexture(GL_TEXTURE_2D, window->fgtex);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, PANEL_SIZE, PANEL_SIZE, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);

    glActiveTexture(GL_TEXTURE2);
    glGenTextures(1, &window->bgtex);
    glBindTexture(GL_TEXTURE_2D, window->bgtex);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, PANEL_SIZE, PANEL_SIZE, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);

    return 0;
}

void window_destroy() {
    if(window != NULL) {
        glDeleteTextures(1, &window->fgtex);
        glDeleteTextures(1, &window->bgtex);
        glDeleteBuffers(1, &window->vbo);
        glDeleteBuffers(1, &window->quad_vbo);
        free(window->quad_buffer);
        glDeleteProgram(window->shader_program);
        glDeleteProgram(window->shader_program2);
        SDL_GL_DeleteContext(window->glcontext);
        SDL_DestroyWindow(window->sdlwindow);
        SDL_Quit();
        free(window);
        window = NULL;
    }
}

#define RED_FLOAT(c) (((c>>16u) & 0xFFu)/255.0f)
#define GREEN_FLOAT(c) (((c>>8u) & 0xFFu)/255.0f)
#define BLUE_FLOAT(c) (((c>>0u) & 0xFFu)/255.0f)

void window_clear(uint32_t color) {
    glClearColor(RED_FLOAT(color), GREEN_FLOAT(color), BLUE_FLOAT(color), 1.0f);
    glClear(GL_COLOR_BUFFER_BIT);
}

void window_blit_tiles(tileset ts, tile *tiles, int width, int height, mode md) {
    if(md == OPAQUE) {
        glDisable(GL_BLEND);
    } else if(md == ALPHA_BLEND) {
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    } else if(ADD){
        glEnable(GL_BLEND);
        glBlendFunc(GL_ONE, GL_ONE);
    }

    for(int i = 0;i<width*height;++i) {
        uint32_t fg = tiles[i].foreground;
        uint32_t bg = tiles[i].background;
        uint32_t idx = tiles[i].index;
        window->fg[4*i + 0] = (fg>>16) & 0xFF;
        window->fg[4*i + 1] = (fg>> 8) & 0xFF;
        window->fg[4*i + 2] = (fg>> 0) & 0xFF;
        window->fg[4*i + 3] = idx % ts->width;

        window->bg[4*i + 0] = (bg>>16) & 0xFF;
        window->bg[4*i + 1] = (bg>> 8) & 0xFF;
        window->bg[4*i + 2] = (bg>> 0) & 0xFF;
        window->bg[4*i + 3] = idx / ts->width;
    }

    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_2D, window->fgtex);
    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, window->fg);

    glActiveTexture(GL_TEXTURE2);
    glBindTexture(GL_TEXTURE_2D, window->bgtex);
    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, window->bg);

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, ts->tex);

    glUseProgram(window->shader_program);

    glUniformMatrix4fv(glGetUniformLocation(window->shader_program, "transform"), 1, GL_FALSE, window->transform);
    glUniform2f(glGetUniformLocation(window->shader_program, "panelsize"), width, height);
    glUniform2f(glGetUniformLocation(window->shader_program, "tilesize"), 1./ts->width, 1./ts->height);
    glUniform2f(glGetUniformLocation(window->shader_program, "texsize"), width/256., height/256.);
    
    glBindBuffer(GL_ARRAY_BUFFER, window->vbo);

    glEnableClientState(GL_VERTEX_ARRAY);
    glVertexPointer(2, GL_FLOAT, 4*sizeof(GLfloat), (char*)0 + 0*sizeof(GLfloat));

    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glTexCoordPointer(2, GL_FLOAT, 4*sizeof(GLfloat), (char*)0 + 2*sizeof(GLfloat));

    glDrawArrays(GL_TRIANGLES, 0, 6);
}

void window_draw_quads(tileset ts, quad *quads, int amount, mode md) {
    if(md == OPAQUE) {
        glDisable(GL_BLEND);
    } else if(md == ALPHA_BLEND) {
        glEnable(GL_BLEND);
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
    } else if(ADD){
        glEnable(GL_BLEND);
        glBlendFunc(GL_ONE, GL_ONE);
    }

    glUseProgram(window->shader_program2);

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, ts->tex);

    glUseProgram(window->shader_program2);

    glUniformMatrix4fv(glGetUniformLocation(window->shader_program2, "transform"), 1, GL_FALSE, window->transform);

    float x[] = {-1.0f, 1.0f, 1.0f,-1.0f, 1.0f,-1.0f};
    float y[] = {-1.0f,-1.0f, 1.0f,-1.0f, 1.0f, 1.0f};
    const float eps = 0.001; 
    float u[] = { 0.0f+eps, 1.0f-eps, 1.0f-eps, 0.0f+eps, 1.0f-eps, 0.0f+eps};
    float v[] = { 1.0f-eps, 1.0f-eps, 0.0f+eps, 1.0f-eps, 0.0f+eps, 0.0f+eps};
    float w = 1.0f/ts->width;
    float h = 1.0f/ts->height;
        
    quad_vertex *data = window->quad_buffer;
    for(int i = 0;i<amount;++i) {
        uint32_t idx = quads[i].index;
        uint32_t fg = quads[i].foreground;
        uint32_t bg = quads[i].background;
        float c = cos(quads[i].angle) * quads[i].scale;
        float s = sin(quads[i].angle) * quads[i].scale;
        float u0 = (idx % ts->width)*w;
        float v0 = (idx / ts->width)*h;
        for(int j = 0;j<6;++j) {
            data[6*i + j].x = quads[i].x + c*x[j] + s*y[j];
            data[6*i + j].y = quads[i].y - s*x[j] + c*y[j];
            data[6*i + j].u = u0+w*u[j];
            data[6*i + j].v = v0+h*v[j];
            data[6*i + j].fg[0] = (fg>>16) & 0xFF;
            data[6*i + j].fg[1] = (fg>> 8) & 0xFF;
            data[6*i + j].fg[2] = (fg>> 0) & 0xFF;
            data[6*i + j].fg[3] = 0;
            data[6*i + j].bg[0] = (bg>>16) & 0xFF;
            data[6*i + j].bg[1] = (bg>> 8) & 0xFF;
            data[6*i + j].bg[2] = (bg>> 0) & 0xFF;
            data[6*i + j].bg[3] = 0;
         }
    }
    glBindBuffer(GL_ARRAY_BUFFER, window->quad_vbo);

    glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(quad_vertex)*6*amount, data);

    glEnableClientState(GL_VERTEX_ARRAY);
    glVertexPointer(2, GL_FLOAT, sizeof(quad_vertex), (char*)0 + 0*sizeof(GLfloat));

    glEnableClientState(GL_TEXTURE_COORD_ARRAY);
    glTexCoordPointer(2, GL_FLOAT, sizeof(quad_vertex), (char*)0 + 2*sizeof(GLfloat));

    int fgattr = 1;
    int bgattr = 2;

    glEnableVertexAttribArray(fgattr);
    glVertexAttribPointer(fgattr, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(quad_vertex), (char*)0 + 4*sizeof(GLfloat));

    glEnableVertexAttribArray(bgattr);
    glVertexAttribPointer(bgattr, 4, GL_UNSIGNED_BYTE, GL_TRUE, sizeof(quad_vertex), (char*)0 + 5*sizeof(GLfloat));
 
    glDrawArrays(GL_TRIANGLES, 0, 6*amount);
 
    glEnableVertexAttribArray(bgattr);
    glDisableVertexAttribArray(fgattr);
}

static void mul3(float *A, float *B, float *C) {
    for(int i = 0;i<4;++i) {
        for(int j = 0;j<4;++j) {
            float dot = 0;
            for(int k = 0;k<4;++k) {
                dot += B[i+4*k]*C[k+4*j];
            }
            A[i+4*j] = dot;
        }
    }
}

static void mul2(float *A, float *C) {
    float B[16];
    for(int i = 0;i<16;++i) {
        B[i] = A[i];
    }
    mul3(A,B,C);
}

void window_transform_set(float *transform) {
    for(int i = 0;i<16;++i) {
        window->transform[i] = transform[i];
    }
}

void window_transform_get(float *transform) {
    for(int i = 0;i<16;++i) {
        transform[i] = window->transform[i];
    }
}

void window_transform_multiply(float *transform) {
    mul2(window->transform, transform);
}

void window_transform_identity() {
    window->transform[0] = 1.0f; window->transform[4] = 0.0f; window->transform[8]  = 0.0f; window->transform[12] = 0.0f;
    window->transform[1] = 0.0f; window->transform[5] = 1.0f; window->transform[9]  = 0.0f; window->transform[13] = 0.0f;
    window->transform[2] = 0.0f; window->transform[6] = 0.0f; window->transform[10] = 1.0f; window->transform[14] = 0.0f;
    window->transform[3] = 0.0f; window->transform[7] = 0.0f; window->transform[11] = 0.0f; window->transform[15] = 1.0f;
}

void window_transform_rect(double x, double y, double width, double height) {
    double x0 = x, y0 = y, x1 = x+width, y1 = y+height;
    x0 = 2*x0-1; x1 = 2*x1-1; y0 = 1-2*y0; y1 = 1-2*y1;
    window->transform[0] = 0.5*(x1-x0); window->transform[4] = 0.0f;        window->transform[8]  = 0.0f; window->transform[12] = 0.5*(x0+x1);
    window->transform[1] = 0.0f;        window->transform[5] = 0.5*(y0-y1); window->transform[9]  = 0.0f; window->transform[13] = 0.5*(y0+y1);
    window->transform[2] = 0.0f;        window->transform[6] = 0.0f;        window->transform[10] = 1.0f; window->transform[14] = 0.0f;
    window->transform[3] = 0.0f;        window->transform[7] = 0.0f;        window->transform[11] = 0.0f; window->transform[15] = 1.0f;
}

void window_transform_scale(double sx, double sy) {
    float transform[16] = {
        sx,  0,  0,  0,
         0, sy,  0,  0,
         0,  0,  1,  0,
         0,  0,  0,  1,
    };
    window_transform_multiply(transform);
}

void window_transform_translate(double dx, double dy) {
    float transform[16] = {
         1,  0,  0,  0,
         0,  1,  0,  0,
         0,  0,  1,  0,
        dx, dy,  0,  1,
    };
    window_transform_multiply(transform);
}

void window_transform_rotate(double angle) {
    float c = cos(angle);
    float s = sin(angle);
    float transform[16] = {
         c, -s,  0,  0,
         s,  c,  0,  0,
         0,  0,  1,  0,
         0,  0,  0,  1,
    };
    window_transform_multiply(transform);
}

void window_show() {
    SDL_GL_SwapWindow(window->sdlwindow);
}

event window_poll_event(int wait) {
    event e;
    SDL_Event event;
    while(wait?SDL_WaitEvent(&event):SDL_PollEvent(&event)) {
        switch(event.type) {
            case SDL_KEYDOWN:
                e.type = KEYBOARD_KEY_DOWN;
                e.value = event.key.keysym.sym;
                e.x = window->mousex;
                e.y = window->mousey;
                return e;
            case SDL_KEYUP:
                e.type = KEYBOARD_KEY_UP;
                e.value = event.key.keysym.sym;
                e.x = window->mousex;
                e.y = window->mousey;
                return e;
            case SDL_MOUSEBUTTONDOWN:
                e.type = MOUSE_BUTTON_DOWN;
                e.value = event.button.button;
                e.x = window->mousex = event.button.x;
                e.y = window->mousey = event.button.y;
                return e;
            case SDL_MOUSEBUTTONUP:
                e.type = MOUSE_BUTTON_UP;
                e.value = event.button.button;
                e.x = window->mousex = event.button.x;
                e.y = window->mousey = event.button.y;
                return e;
            case SDL_MOUSEMOTION:
                e.type = MOUSE_MOTION;
                e.value = 0;
                e.x = window->mousex = event.motion.x;
                e.y = window->mousey = event.motion.y;
                return e;
            case SDL_WINDOWEVENT:
                if(event.window.event == SDL_WINDOWEVENT_CLOSE) {
                    e.type = WINDOW_CLOSE;
                    e.value = 0;
                    e.x = window->mousex;
                    e.y = window->mousey;
                    return e;
                } else {
                    break;
                }
            default: break;
        }
    }
    e.type = NO_EVENT;
    return e;
}

glterm.h

#ifndef GLTERM_H
#define GLTERM_H

#include <stdint.h>

typedef struct tileset_t* tileset;

typedef enum {
    OPAQUE, ALPHA_BLEND, ADD,
} mode;

typedef struct tile_t {
    uint32_t index;
    uint32_t foreground;
    uint32_t background;
} tile;

typedef struct quad_t {
    uint32_t index;
    uint32_t foreground;
    uint32_t background;
    double angle, scale, x, y;
} quad;

typedef enum {
    NO_EVENT, WINDOW_CLOSE,
    KEYBOARD_KEY_DOWN, KEYBOARD_KEY_UP,
    MOUSE_BUTTON_DOWN, MOUSE_BUTTON_UP,
    MOUSE_MOTION
} event_type;

enum {
    KEY_RETURN = '\r',
    KEY_ESCAPE = '\033',
    KEY_BACKSPACE = '\b',
    KEY_TAB = '\t',
    KEY_SPACE = ' ',
    KEY_MASK = (1<<30),
    KEY_F1 = 58 | KEY_MASK,
    KEY_F2 = 59 | KEY_MASK,
    KEY_F3 = 60 | KEY_MASK,
    KEY_F4 = 61 | KEY_MASK,
    KEY_F5 = 62 | KEY_MASK,
    KEY_F6 = 63 | KEY_MASK,
    KEY_F7 = 64 | KEY_MASK,
    KEY_F8 = 65 | KEY_MASK,
    KEY_F9 = 66 | KEY_MASK,
    KEY_F10 = 67 | KEY_MASK,
    KEY_F11 = 68 | KEY_MASK,
    KEY_F12 = 69 | KEY_MASK,
    KEY_HOME = 74 | KEY_MASK,
    KEY_PAGEUP = 75 | KEY_MASK,
    KEY_DELETE = 76 | KEY_MASK,
    KEY_END = 77 | KEY_MASK,
    KEY_PAGEDOWN = 78 | KEY_MASK,
    KEY_RIGHT = 79 | KEY_MASK,
    KEY_LEFT = 80 | KEY_MASK,
    KEY_DOWN = 81 | KEY_MASK,
    KEY_UP = 82 | KEY_MASK,
    KEY_KP_DIVIDE = 84 | KEY_MASK,
    KEY_KP_MULTIPLY = 85 | KEY_MASK,
    KEY_KP_MINUS = 86 | KEY_MASK,
    KEY_KP_PLUS = 87 | KEY_MASK,
    KEY_KP_ENTER = 88 | KEY_MASK,
    KEY_KP_1 = 89 | KEY_MASK,
    KEY_KP_2 = 90 | KEY_MASK,
    KEY_KP_3 = 91 | KEY_MASK,
    KEY_KP_4 = 92 | KEY_MASK,
    KEY_KP_5 = 93 | KEY_MASK,
    KEY_KP_6 = 94 | KEY_MASK,
    KEY_KP_7 = 95 | KEY_MASK,
    KEY_KP_8 = 96 | KEY_MASK,
    KEY_KP_9 = 97 | KEY_MASK,
    KEY_KP_0 = 98 | KEY_MASK,
    KEY_KP_PERIOD = 99 | KEY_MASK,
    KEY_LCTRL = 224 | KEY_MASK,
    KEY_LSHIFT = 225 | KEY_MASK,
    KEY_LALT = 226 | KEY_MASK,
    KEY_LGUI = 227 | KEY_MASK,
    KEY_RCTRL = 228 | KEY_MASK,
    KEY_RSHIFT = 229 | KEY_MASK,
    KEY_RALT = 230 | KEY_MASK,
    KEY_RGUI = 231 | KEY_MASK,
};

typedef struct event_t {
    event_type type;
    unsigned int value;
    int x, y;
} event;

// loads a tileset of widthxheight tiles from a png image and sets
// the reference count to 1
tileset tileset_load(int width, int height, const char *filename);

// increases the reference count
void tileset_retain(tileset ts);

// decreases the reference count and frees the tileset when the count is zero
void tileset_destroy(tileset ts);

// creates the window with size width x height
int window_create(const char *title, int width, int height);
// destroys the window
void window_destroy();

// clears the window to the specified color
void window_clear(uint32_t color);

// draws a rectangle of xtiles * ytiles tiles as specified by the tiles
// array in row major order
// the mode parameter specifies the blend mode
//    OPAQUE: overwrite previous content
//    ALPHA_BLEND: alpha transparency (alpha from tileset image)
//    ADD: additive blend

void window_blit_tiles(tileset ts, tile *tiles, int xtiles, int ytiles, mode md);

void window_draw_quads(tileset ts, quad *quads, int amount, mode md);

// window transform manipulation functions modify the internal 4x4
// column major transformation matrix.

// set copies 16 elements from the argument to the window transform matrix
void window_transform_set(float *transform);

// get copies 16 elements from the window transform matrix to the argument
void window_transform_get(float *transform);

// multiplies the window transform with transform
void window_transform_multiply(float *transform);

// set the window transform to the identity matrix
void window_transform_identity();

// set the window transform such that the rect [-1,1]x[-1,1] gets
// transformed to the rect specified by x,y,width and height in normalized
// window coordinates
void window_transform_rect(double x, double y, double width, double height);

// multiply the window transform with a scale matrix
void window_transform_scale(double sx, double sy);

// multiply the window transform with a translation matrix
void window_transform_translate(double sx, double sy);

// multiply the window transform with a rotation matrix (angle in radians)
void window_transform_rotate(double angle);


// swap backbuffer
void window_show();

// polls for events. wait = 1 will block until a event is received.
// returns a NO_EVENT event in case there are no events in the queue
event window_poll_event(int wait);

#endif