4coder/platform_linux/linux_4ed.cpp

/*
 * chr  - Andrew Chronister &
 * inso - Alex Baines
 *
 * 12.19.2019
 *
 * Updated linux layer for 4coder
 *
 */

// TOP

#define FPS 60
#define frame_useconds (1000000 / FPS)
#define frame_nseconds (UINT64_C(1000000000) / FPS)
#define SLASH '/'
#define DLL "so"

#include "4coder_base_types.h"
#include "4coder_version.h"
#include "4coder_events.h"

#include "4coder_table.h"
#include "4coder_types.h"
#include "4coder_default_colors.h"
#include "4coder_system_types.h"
#include "4ed_font_interface.h"

#define STATIC_LINK_API
#include "generated/system_api.h"

#define STATIC_LINK_API
#include "generated/graphics_api.h"

#define STATIC_LINK_API
#include "generated/font_api.h"

#include "4ed_font_set.h"
#include "4ed_render_target.h"
#include "4ed_search_list.h"
#include "4ed.h"

#include "generated/system_api.cpp"
#include "generated/graphics_api.cpp"
#include "generated/font_api.cpp"

#include "4coder_base_types.cpp"
#include "4coder_stringf.cpp"
#include "4coder_events.cpp"
#include "4coder_hash_functions.cpp"
#include "4coder_table.cpp"
#include "4coder_log.cpp"

#include "4coder_hash_functions.cpp"
#include "4coder_system_allocator.cpp"
#include "4coder_malloc_allocator.cpp"
#include "4coder_codepoint_map.cpp"

#include "4ed_mem.cpp"
#include "4ed_font_set.cpp"
#include "4ed_search_list.cpp"
#include "4ed_font_provider_freetype.h"
#include "4ed_font_provider_freetype.cpp"

#include <dirent.h>
#include <dlfcn.h>
#include <fcntl.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <locale.h>
#include <errno.h>
#include <pthread.h>

#include <sys/epoll.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/timerfd.h>
#include <sys/eventfd.h>
#include <sys/syscall.h>

#define Cursor XCursor
#undef function
#undef internal
#include <X11/Xlib.h>
#include <X11/Xutil.h>
#include <X11/cursorfont.h>
#include <X11/Xatom.h>
#include <X11/extensions/Xfixes.h>
#include <X11/XKBlib.h>
#include <X11/keysym.h>
#define function static
#undef Cursor

#include <fontconfig/fontconfig.h>
#define internal static

#include <GL/glx.h>
#include <GL/glext.h>

#ifdef INSO_DEBUG
    #define LINUX_FN_DEBUG(fmt, ...) do { \
        fprintf(stderr, "%s: " fmt "\n", __func__, ##__VA_ARGS__);\
    } while (0)

// I want to see a message
    #undef AssertBreak
    #define AssertBreak(m) ({\
        fprintf(stderr, "\n** ASSERTION FAILURE: %s:%d: %s\n\n", __FILE__, __LINE__, #m);\
        *((volatile u64*)0) = 0xba771e70ad5;\
    })
#else
    #define LINUX_FN_DEBUG(...)
#endif

////////////////////////////

struct Linux_Input_Chunk_Transient {
    Input_List event_list;
    b8 mouse_l_press;
    b8 mouse_l_release;
    b8 mouse_r_press;
    b8 mouse_r_release;
    i8 mouse_wheel;
    b8 trying_to_kill;
};

struct Linux_Input_Chunk_Persistent {
    Vec2_i32 mouse;
    Input_Modifier_Set_Fixed modifiers;
    b8 mouse_l;
    b8 mouse_r;
    b8 mouse_out_of_window;
};

struct Linux_Input_Chunk {
    Linux_Input_Chunk_Transient trans;
    Linux_Input_Chunk_Persistent pers;
};

struct Linux_Vars {
    Thread_Context tctx;
    Arena *frame_arena;

    Display* dpy;
    Window win;

    b32 has_xfixes;
    int xfixes_selection_event;
    XIM xim;
    XIC xic;
    FcConfig* fontconfig;
    XkbDescPtr xkb;

    Linux_Input_Chunk input;
    int xkb_event;
    int xkb_group; // active keyboard layout (0-3)

    int epoll;
    int step_timer_fd;
    u64 last_step_time;
    b32 step_pending;

    XCursor xcursors[APP_MOUSE_CURSOR_COUNT];
    Application_Mouse_Cursor cursor;
    XCursor hidden_cursor;
    i32 cursor_show;
    i32 prev_cursor_show;

    Node free_linux_objects;
    Node timer_objects;

    System_Mutex global_frame_mutex;

    Arena* clipboard_arena;
    String_Const_u8 clipboard_contents;
    b32 received_new_clipboard;
    b32 clipboard_catch_all;

    Atom atom_TARGETS;
    Atom atom_CLIPBOARD;
    Atom atom_UTF8_STRING;
    Atom atom__NET_WM_STATE;
    Atom atom__NET_WM_STATE_MAXIMIZED_HORZ;
    Atom atom__NET_WM_STATE_MAXIMIZED_VERT;
    Atom atom__NET_WM_STATE_FULLSCREEN;
    Atom atom__NET_WM_PING;
    Atom atom__NET_WM_WINDOW_TYPE;
    Atom atom__NET_WM_WINDOW_TYPE_NORMAL;
    Atom atom__NET_WM_PID;
    Atom atom_WM_DELETE_WINDOW;
};

global Linux_Vars linuxvars;
global Render_Target render_target;

////////////////////////////

// Defererencing an epoll_event's .data.ptr will always give one of these event types.

typedef i32 Epoll_Kind;
enum {
    EPOLL_STEP_TIMER,
    EPOLL_X11,
    EPOLL_X11_INTERNAL,
    EPOLL_CLI_PIPE,
    EPOLL_USER_TIMER,
};

// Where per-event epoll data is not needed, .data.ptr will point to one of
// these static vars below.
// If per-event data is needed, container_of can be used on data.ptr
// to access the containing struct and all its other members.

internal Epoll_Kind epoll_tag_step_timer = EPOLL_STEP_TIMER;
internal Epoll_Kind epoll_tag_x11 = EPOLL_X11;
internal Epoll_Kind epoll_tag_x11_internal = EPOLL_X11_INTERNAL;
internal Epoll_Kind epoll_tag_cli_pipe = EPOLL_CLI_PIPE;

////////////////////////////

typedef i32 Linux_Object_Kind;
enum {
    LinuxObjectKind_ERROR = 0,
    LinuxObjectKind_Timer = 1,
    LinuxObjectKind_Thread = 2,
    LinuxObjectKind_Mutex = 3,
    LinuxObjectKind_ConditionVariable = 4,
};

struct Linux_Object {
    Linux_Object_Kind kind;
    Node node;
    union {
        struct {
            int fd;
            Epoll_Kind epoll_tag;
        } timer;
        struct {
            pthread_t pthread;
            Thread_Function* proc;
            void* ptr;
        } thread;
        pthread_mutex_t mutex;
        pthread_cond_t condition_variable;
    };
};

Linux_Object*
handle_to_object(Plat_Handle ph){
    return *(Linux_Object**)&ph;
}

internal Linux_Object*
linux_alloc_object(Linux_Object_Kind kind){
    Linux_Object* result = NULL;

    if (linuxvars.free_linux_objects.next != &linuxvars.free_linux_objects) {
        result = CastFromMember(Linux_Object, node, linuxvars.free_linux_objects.next);
    }

    if (result == NULL) {
        i32 count = 512;

        Linux_Object* objects = (Linux_Object*)system_memory_allocate(
            sizeof(Linux_Object) * count,
            file_name_line_number_lit_u8
        );

        objects[0].node.prev = &linuxvars.free_linux_objects;
        linuxvars.free_linux_objects.next = &objects[0].node;
        for (i32 i = 1; i < count; ++i) {
            objects[i - 1].node.next = &objects[i].node;
            objects[i].node.prev = &objects[i - 1].node;
        }
        objects[count - 1].node.next = &linuxvars.free_linux_objects;
        linuxvars.free_linux_objects.prev = &objects[count - 1].node;

        result = CastFromMember(Linux_Object, node, linuxvars.free_linux_objects.next);
    }

    Assert(result != 0);
    dll_remove(&result->node);
    block_zero_struct(result);
    result->kind = kind;
    return result;
}

internal void
linux_free_object(Linux_Object *object){
    if (object->node.next != 0){
        dll_remove(&object->node);
    }
    dll_insert(&linuxvars.free_linux_objects, &object->node);
}

////////////////////////////

internal int
linux_compare_file_infos(File_Info** a, File_Info** b) {
    b32 a_hidden = (*a)->file_name.str[0] == '.';
    b32 b_hidden = (*b)->file_name.str[0] == '.';

    // hidden files lower in list
    if(a_hidden != b_hidden) {
        return a_hidden - b_hidden;
    }

    // push_stringf seems to null terminate
    return strcoll((char*)(*a)->file_name.str, (char*)(*b)->file_name.str);
}

internal int
linux_system_get_file_list_filter(const struct dirent *dirent) {
    String_Const_u8 file_name = SCu8((u8*)dirent->d_name);
    if (string_match(file_name, string_u8_litexpr("."))) {
        return 0;
    }
    else if (string_match(file_name, string_u8_litexpr(".."))) {
        return 0;
    }
    return 1;
}

internal u64
linux_ns_from_timespec(const struct timespec timespec) {
    return timespec.tv_nsec + UINT64_C(1000000000) * timespec.tv_sec;
}

internal File_Attribute_Flag
linux_convert_file_attribute_flags(int mode) {
    File_Attribute_Flag result = {};
    MovFlag(mode, S_IFDIR, result, FileAttribute_IsDirectory);
    return result;
}

internal File_Attributes
linux_file_attributes_from_struct_stat(struct stat* file_stat) {
    File_Attributes result = {};
    result.size = file_stat->st_size;
    result.last_write_time = linux_ns_from_timespec(file_stat->st_mtim);
    result.flags = linux_convert_file_attribute_flags(file_stat->st_mode);
    return result;
}

internal void
linux_schedule_step(){
    if(!__sync_bool_compare_and_swap(&linuxvars.step_pending, 0, 1)) {
        return;
    }

    u64 now  = system_now_time();
    u64 diff = (now - linuxvars.last_step_time);

    struct itimerspec its = {};

    if(diff >= frame_nseconds) {
        its.it_value.tv_nsec = 1;
    } else {
        its.it_value.tv_nsec = frame_nseconds - diff;
    }

    timerfd_settime(linuxvars.step_timer_fd, 0, &its, NULL);
}

enum wm_state_mode {
    WM_STATE_DEL = 0,
    WM_STATE_ADD = 1,
    WM_STATE_TOGGLE = 2,
};

internal void
linux_set_wm_state(Atom one, Atom two, enum wm_state_mode mode){
    //NOTE(inso): this will only work after the window has been mapped

    XEvent e = {};
    e.xany.type = ClientMessage;
    e.xclient.message_type = linuxvars.atom__NET_WM_STATE;
    e.xclient.format = 32;
    e.xclient.window = linuxvars.win;
    e.xclient.data.l[0] = mode;
    e.xclient.data.l[1] = one;
    e.xclient.data.l[2] = two;
    e.xclient.data.l[3] = 1L;

    XSendEvent(linuxvars.dpy,
               RootWindow(linuxvars.dpy, 0),
               0, SubstructureNotifyMask | SubstructureRedirectMask, &e);
}

internal void
linux_window_maximize(enum wm_state_mode mode){
    linux_set_wm_state(linuxvars.atom__NET_WM_STATE_MAXIMIZED_HORZ, linuxvars.atom__NET_WM_STATE_MAXIMIZED_VERT, mode);
}

internal void
linux_window_fullscreen(enum wm_state_mode mode) {
    linux_set_wm_state(linuxvars.atom__NET_WM_STATE_FULLSCREEN, 0, mode);
}

internal int
linux_get_xsettings_dpi(Display* dpy, int screen){
    struct XSettingHeader {
        u8 type;
        u8 pad0;
        u16 name_len;
        char name[0];
    };

    struct XSettings {
        u8 byte_order;
        u8 pad[3];
        u32 serial;
        u32 num_settings;
    };

    enum { XSettingsTypeInt, XSettingsTypeString, XSettingsTypeColor };

    int dpi = -1;
    unsigned char* prop = NULL;
    char sel_buffer[64];
    struct XSettings* xs;
    const char* p;

    snprintf(sel_buffer, sizeof(sel_buffer), "_XSETTINGS_S%d", screen);

    Atom XSET_SEL = XInternAtom(dpy, sel_buffer, True);
    Atom XSET_SET = XInternAtom(dpy, "_XSETTINGS_SETTINGS", True);

    if (XSET_SEL == None || XSET_SET == None){
        //LOG("XSETTINGS unavailable.\n");
        return(dpi);
    }

    Window xset_win = XGetSelectionOwner(dpy, XSET_SEL);
    if (xset_win == None){
        // TODO(inso): listen for the ClientMessage about it becoming available?
        //             there's not much point atm if DPI scaling is only done at startup 
        goto out;
    }

    {
        Atom type;
        int fmt;
        unsigned long pad, num;

        if (XGetWindowProperty(dpy, xset_win, XSET_SET, 0, 1024, False, XSET_SET, &type, &fmt, &num, &pad, &prop) != Success){
            //LOG("XSETTINGS: GetWindowProperty failed.\n");
            goto out;
        }

        if (fmt != 8){
            //LOG("XSETTINGS: Wrong format.\n");
            goto out;
        }
    }

    xs = (struct XSettings*)prop;
    p  = (char*)(xs + 1);

    if (xs->byte_order != 0){
        //LOG("FIXME: XSETTINGS not host byte order?\n");
        goto out;
    }

    for (int i = 0; i < xs->num_settings; ++i){
        struct XSettingHeader* h = (struct XSettingHeader*)p;

        p += sizeof(struct XSettingHeader);
        p += h->name_len;
        p += ((4 - (h->name_len & 3)) & 3);
        p += 4; // serial

        switch (h->type){
            case XSettingsTypeInt: {
                if (strncmp(h->name, "Xft/DPI", h->name_len) == 0){
                    dpi = *(i32*)p;
                    if (dpi != -1) dpi /= 1024;
                }
                p += 4;
            } break;

            case XSettingsTypeString: {
                u32 len = *(u32*)p;
                p += 4;
                p += len;
                p += ((4 - (len & 3)) & 3);
            } break;

            case XSettingsTypeColor: {
                p += 8;
            } break;

            default: {
                //LOG("XSETTINGS: Got invalid type...\n");
                goto out;
            } break;
        }
    }

    out:
        if (prop){
            XFree(prop);
        }

    return dpi;
}

internal void*
linux_thread_proc_start(void* arg) {
    Linux_Object* info = (Linux_Object*)arg;
    Assert(info->kind == LinuxObjectKind_Thread);
    info->thread.proc(info->thread.ptr);
    return NULL;
}

#include "linux_icon.h"
internal void
linux_set_icon(Display* d, Window w){
    Atom WM_ICON = XInternAtom(d, "_NET_WM_ICON", False);
    XChangeProperty(d, w, WM_ICON, XA_CARDINAL, 32, PropModeReplace, (unsigned char*)linux_icon, sizeof(linux_icon) / sizeof(long));
}

#include "linux_error_box.cpp"

////////////////////////////

#include "linux_4ed_functions.cpp"

////////////////////////////

#include <GL/gl.h>
#include "opengl/4ed_opengl_defines.h"
#define GL_FUNC(N,R,P) typedef R (CALL_CONVENTION N##_Function)P; N##_Function *N = 0;
#include "opengl/4ed_opengl_funcs.h"
#include "opengl/4ed_opengl_render.cpp"

internal
graphics_get_texture_sig(){
    return(gl__get_texture(dim, texture_kind));
}

internal
graphics_fill_texture_sig(){
    return(gl__fill_texture(texture_kind, texture, p, dim, data));
}

////////////////////////////

internal Face_Description
linux_find_font(Face_Description* desc) {
    Face_Description result = *desc;

    char* name = strndupa((char*)desc->font.file_name.str, desc->font.file_name.size);

    double size;
    const char* style;
    {
        Face_Load_Parameters* p = &desc->parameters;
        size = p->pt_size;

        if(p->bold && p->italic) {
            style = "Bold Italic";
        } else if(p->bold) {
            style = "Bold";
        } else if(p->italic) {
            style = "Italic";
        } else {
            style = "Regular";
        }
    }

    FcPattern *pattern = FcPatternBuild(
        0,
        FC_POSTSCRIPT_NAME, FcTypeString, name,
        FC_SIZE, FcTypeDouble, size,
        FC_FONTFORMAT, FcTypeString, "TrueType",
        FC_STYLE, FcTypeString, (FcChar8*)style,
        NULL);

    if(!pattern) {
        return result;
    }

    if (FcConfigSubstitute(linuxvars.fontconfig, pattern, FcMatchPattern)){
        FcDefaultSubstitute(pattern);

        FcResult res;
        FcPattern *font = FcFontMatch(linuxvars.fontconfig, pattern, &res);
        if (!font){
            return result;
        }

        FcChar8 *filename = 0;
        FcPatternGetString(font, FC_FILE, 0, &filename);
        if(filename) {
            LINUX_FN_DEBUG("FONTCONFIG FILENAME = %s\n", filename);
            result.font.file_name = push_u8_stringf(linuxvars.frame_arena, "%s", filename);
        }

        FcPatternDestroy(font);
    }

    FcPatternDestroy(pattern);

    return result;
}

internal
font_make_face_sig() {

    Face* result = ft__font_make_face(arena, description, scale_factor);

    // if it failed to load the font directly, try via fontconfig.
    if(!result) {
        Face_Description desc2 = {};
        desc2.parameters = description->parameters;
        desc2.font.file_name = string_front_of_path(description->font.file_name);

        printf("FONT %.*s\n", string_expand(desc2.font.file_name));
        desc2 = linux_find_font(&desc2);
        result = ft__font_make_face(arena, &desc2, scale_factor);
    }

    if(!result) {
        // is this fatal? 4ed.cpp:277 (caller) does not check for null.
        String_Const_u8 s = description->font.file_name;
        char msg[4096];
        snprintf(msg, sizeof(msg), "Unable to load font: %.*s", (int)s.size, s.str);
        system_error_box(msg);
    }

    return(result);
}

////////////////////////////

internal b32
glx_init(void) {
    int glx_maj, glx_min;

    if(!glXQueryVersion(linuxvars.dpy, &glx_maj, &glx_min)) {
        return false;
    }

    return glx_maj > 1 || (glx_maj == 1 && glx_min >= 3);
}

internal b32
glx_get_config(GLXFBConfig* fb_config, XVisualInfo* vi) {

    static const int attrs[] = {
        GLX_X_RENDERABLE , True,
        GLX_DRAWABLE_TYPE, GLX_WINDOW_BIT,
        GLX_RENDER_TYPE  , GLX_RGBA_BIT,
        GLX_X_VISUAL_TYPE, GLX_TRUE_COLOR,
        GLX_RED_SIZE     , 8,
        GLX_GREEN_SIZE   , 8,
        GLX_BLUE_SIZE    , 8,
        GLX_ALPHA_SIZE   , 8,
        GLX_DEPTH_SIZE   , 24,
        GLX_STENCIL_SIZE , 8,
        GLX_DOUBLEBUFFER , True,
        None
    };

    int conf_count = 0;
    GLXFBConfig* conf_list = glXChooseFBConfig(linuxvars.dpy, DefaultScreen(linuxvars.dpy), attrs, &conf_count);
    if(!conf_count || conf_count <= 0) {
        return false;
    }

    *fb_config = *conf_list;
    XFree(conf_list);

    XVisualInfo* xvi = glXGetVisualFromFBConfig(linuxvars.dpy, *fb_config);
    if(!xvi) {
        return false;
    }

    *vi = *xvi;
    XFree(xvi);

    return true;
}

internal b32 glx_ctx_error;

internal int
glx_error_handler(Display* dpy, XErrorEvent* ev){
    glx_ctx_error = true;
    return 0;
}

typedef GLXContext (glXCreateContextAttribsARB_Function)(Display*, GLXFBConfig, GLXContext, Bool, const int*);
typedef void       (glXSwapIntervalEXT_Function)        (Display *dpy, GLXDrawable drawable, int interval);
typedef int        (glXSwapIntervalMESA_Function)       (unsigned int interval);
typedef int        (glXGetSwapIntervalMESA_Function)    (void);
typedef int        (glXSwapIntervalSGI_Function)        (int interval);

internal b32
glx_create_context(GLXFBConfig fb_config){
    const char *glx_exts = glXQueryExtensionsString(linuxvars.dpy, DefaultScreen(linuxvars.dpy));

    glXCreateContextAttribsARB_Function *glXCreateContextAttribsARB = 0;
    glXSwapIntervalEXT_Function         *glXSwapIntervalEXT = 0;
    glXSwapIntervalMESA_Function        *glXSwapIntervalMESA = 0;
    glXGetSwapIntervalMESA_Function     *glXGetSwapIntervalMESA = 0;
    glXSwapIntervalSGI_Function         *glXSwapIntervalSGI = 0;

#define GLXLOAD(f) f = (f##_Function*) glXGetProcAddressARB((const GLubyte*) #f);
    GLXLOAD(glXCreateContextAttribsARB);

    GLXContext ctx = NULL;
    int (*old_handler)(Display*, XErrorEvent*) = XSetErrorHandler(&glx_error_handler);

    if (glXCreateContextAttribsARB == NULL){
        //LOG("glXCreateContextAttribsARB() not found, using old-style GLX context\n" );
        ctx = glXCreateNewContext(linuxvars.dpy, fb_config, GLX_RGBA_TYPE, 0, True);
    } else {
        static const int context_attribs[] = {
            GLX_CONTEXT_MAJOR_VERSION_ARB, 2,
            GLX_CONTEXT_MINOR_VERSION_ARB, 1,
            GLX_CONTEXT_PROFILE_MASK_ARB , GLX_CONTEXT_COMPATIBILITY_PROFILE_BIT_ARB,
#if defined(FRED_INTERNAL)
            GLX_CONTEXT_FLAGS_ARB        , GLX_CONTEXT_DEBUG_BIT_ARB,
#endif
            None
        };

        //LOG("Creating GL 2.1 context... ");
        ctx = glXCreateContextAttribsARB(linuxvars.dpy, fb_config, 0, True, context_attribs);
    }

    XSync(linuxvars.dpy, False);
    if(glx_ctx_error || !ctx) {
        return false;
    }

    XSync(linuxvars.dpy, False);
    XSetErrorHandler(old_handler);

    //b32 direct = glXIsDirect(linuxvars.dpy, ctx);

    //LOG("Making context current\n");
    glXMakeCurrent(linuxvars.dpy, linuxvars.win, ctx);

    //glx_enable_vsync();

    // NOTE(allen): Load gl functions
#define GL_FUNC(f,R,P) GLXLOAD(f)
#include "opengl/4ed_opengl_funcs.h"

#undef GLXLOAD

    return true;
}

////////////////////////////

internal void
linux_x11_init(int argc, char** argv, Plat_Settings* settings) {

    Display* dpy = XOpenDisplay(0);
    if (!dpy){
        fprintf(stderr, "FATAL: Cannot open X11 Display!\n");
        exit(1);
    }

    linuxvars.dpy = dpy;

#define LOAD_ATOM(x) linuxvars.atom_##x = XInternAtom(linuxvars.dpy, #x, False);

    LOAD_ATOM(TARGETS);
    LOAD_ATOM(CLIPBOARD);
    LOAD_ATOM(UTF8_STRING);
    LOAD_ATOM(_NET_WM_STATE);
    LOAD_ATOM(_NET_WM_STATE_MAXIMIZED_HORZ);
    LOAD_ATOM(_NET_WM_STATE_MAXIMIZED_VERT);
    LOAD_ATOM(_NET_WM_STATE_FULLSCREEN);
    LOAD_ATOM(_NET_WM_PING);
    LOAD_ATOM(_NET_WM_WINDOW_TYPE);
    LOAD_ATOM(_NET_WM_WINDOW_TYPE_NORMAL);
    LOAD_ATOM(_NET_WM_PID);
    LOAD_ATOM(WM_DELETE_WINDOW);

#undef LOAD_ATOM

    if (!glx_init()){
        system_error_box("Your XServer's GLX version is too old. GLX 1.3+ is required.");
    }

    GLXFBConfig fb_config;
    XVisualInfo vi;
    if (!glx_get_config(&fb_config, &vi)){
        system_error_box("Could not get a matching GLX FBConfig. Check your OpenGL drivers are installed correctly.");
    }

    // TODO: window size
#define WINDOW_W_DEFAULT 800
#define WINDOW_H_DEFAULT 600
    int w = WINDOW_W_DEFAULT;
    int h = WINDOW_H_DEFAULT;

    // TEMP
    render_target.width = w;
    render_target.height = h;

    XSetWindowAttributes swa = {};
    swa.backing_store = WhenMapped;
    swa.event_mask = StructureNotifyMask;
    swa.bit_gravity = NorthWestGravity;
    swa.colormap = XCreateColormap(dpy, RootWindow(dpy, vi.screen), vi.visual, AllocNone);

    u32 CWflags = CWBackingStore|CWBitGravity|CWBackPixel|CWBorderPixel|CWColormap|CWEventMask;
    linuxvars.win = XCreateWindow(dpy, RootWindow(dpy, vi.screen), 0, 0, w, h, 0, vi.depth, InputOutput, vi.visual, CWflags, &swa);

    if (!linuxvars.win){
        system_error_box("XCreateWindow failed. Make sure your display is set up correctly.");
    }

    //NOTE(inso): Set the window's type to normal
    XChangeProperty(linuxvars.dpy, linuxvars.win, linuxvars.atom__NET_WM_WINDOW_TYPE, XA_ATOM, 32, PropModeReplace, (unsigned char*)&linuxvars.atom__NET_WM_WINDOW_TYPE_NORMAL, 1);

    //NOTE(inso): window managers want the PID as a window property for some reason.
    pid_t pid = getpid();
    XChangeProperty(linuxvars.dpy, linuxvars.win, linuxvars.atom__NET_WM_PID, XA_CARDINAL, 32, PropModeReplace, (unsigned char*)&pid, 1);

    //NOTE(inso): set wm properties
    XStoreName(linuxvars.dpy, linuxvars.win, WINDOW_NAME);

    XSizeHints *sz_hints = XAllocSizeHints();
    XWMHints   *wm_hints = XAllocWMHints();
    XClassHint *cl_hints = XAllocClassHint();

    sz_hints->flags = PMinSize | PMaxSize | PWinGravity;

    sz_hints->min_width = 50;
    sz_hints->min_height = 50;

    sz_hints->max_width = sz_hints->max_height = (1UL << 16UL);
    sz_hints->win_gravity = NorthWestGravity;

    if (settings->set_window_pos){
        sz_hints->flags |= USPosition;
        sz_hints->x = settings->window_x;
        sz_hints->y = settings->window_y;
    }

    wm_hints->flags |= InputHint | StateHint;
    wm_hints->input = True;
    wm_hints->initial_state = NormalState;

    cl_hints->res_name = "4coder";
    cl_hints->res_class = "4coder";

    char* win_name_list[] = { WINDOW_NAME };
    XTextProperty win_name;
    XStringListToTextProperty(win_name_list, 1, &win_name);

    XSetWMProperties(linuxvars.dpy, linuxvars.win, &win_name, NULL, argv, argc, sz_hints, wm_hints, cl_hints);

    XFree(win_name.value);
    XFree(sz_hints);
    XFree(wm_hints);
    XFree(cl_hints);

    linux_set_icon(linuxvars.dpy, linuxvars.win);

    // NOTE(inso): make the window visible
    XMapWindow(linuxvars.dpy, linuxvars.win);

    if(!glx_create_context(fb_config)) {
        system_error_box("Unable to create GLX context.");
    }

    XRaiseWindow(linuxvars.dpy, linuxvars.win);

    if (settings->set_window_pos){
        XMoveWindow(linuxvars.dpy, linuxvars.win, settings->window_x, settings->window_y);
    }

    if (settings->maximize_window){
        linux_set_wm_state(linuxvars.atom__NET_WM_STATE_MAXIMIZED_HORZ, linuxvars.atom__NET_WM_STATE_MAXIMIZED_VERT, WM_STATE_ADD);
    } else if (settings->fullscreen_window){
        linux_set_wm_state(linuxvars.atom__NET_WM_STATE_FULLSCREEN, 0, WM_STATE_ADD);
    }

    XSync(linuxvars.dpy, False);

    Atom wm_protos[] = {
        linuxvars.atom_WM_DELETE_WINDOW,
        linuxvars.atom__NET_WM_PING
    };

    XSetWMProtocols(linuxvars.dpy, linuxvars.win, wm_protos, 2);

    // XFixes extension for clipboard notification.
    {
        int xfixes_version_unused, xfixes_err_unused;
        Bool has_xfixes = XQueryExtension(linuxvars.dpy, "XFIXES", &xfixes_version_unused, &linuxvars.xfixes_selection_event, &xfixes_err_unused);
        linuxvars.has_xfixes = (has_xfixes == True);

        // request notifications for CLIPBOARD updates.
        if(has_xfixes) {
            XFixesSelectSelectionInput(linuxvars.dpy, linuxvars.win, linuxvars.atom_CLIPBOARD, XFixesSetSelectionOwnerNotifyMask);
        }
    }

    // Input handling init

    setlocale(LC_ALL, "");
    XSetLocaleModifiers("");
    b32 locale_supported = XSupportsLocale();

    if (!locale_supported){
        setlocale(LC_ALL, "C");
    }

    linuxvars.xim = XOpenIM(dpy, 0, 0, 0);
    if (!linuxvars.xim){
        // NOTE(inso): Try falling back to the internal XIM implementation that
        // should in theory always exist.
        XSetLocaleModifiers("@im=none");
        linuxvars.xim = XOpenIM(dpy, 0, 0, 0);
    }

    // If it still isn't there we're screwed.
    if (!linuxvars.xim){
        system_error_box("Could not initialize X Input.");
    }

    XIMStyles *styles = NULL;
    const XIMStyle style_want = (XIMPreeditNothing | XIMStatusNothing);
    b32 found_style = false;

    if (!XGetIMValues(linuxvars.xim, XNQueryInputStyle, &styles, NULL) && styles){
        for (i32 i = 0; i < styles->count_styles; ++i){
            XIMStyle style = styles->supported_styles[i];
            if (style == style_want) {
                found_style = true;
                break;
            }
        }
    }

    if(!found_style) {
        system_error_box("Could not find supported X Input style.");
    }

    XFree(styles);

    linuxvars.xic = XCreateIC(linuxvars.xim,
                              XNInputStyle, style_want,
                              XNClientWindow, linuxvars.win,
                              XNFocusWindow, linuxvars.win,
                              NULL);

    if(!linuxvars.xic) {
        system_error_box("Error creating X Input context.");
    }

    int xim_event_mask;
    if (XGetICValues(linuxvars.xic, XNFilterEvents, &xim_event_mask, NULL)){
        xim_event_mask = 0;
    }

    u32 event_mask = ExposureMask
        | KeyPressMask | KeyReleaseMask
        | ButtonPressMask | ButtonReleaseMask
        | EnterWindowMask | LeaveWindowMask
        | PointerMotionMask
        | FocusChangeMask
        | StructureNotifyMask
        | ExposureMask | VisibilityChangeMask
        | xim_event_mask;

    XSelectInput(linuxvars.dpy, linuxvars.win, event_mask);

    // init XKB keyboard extension

    if(!XkbQueryExtension(linuxvars.dpy, 0, &linuxvars.xkb_event, 0, 0, 0)) {
        system_error_box("XKB Extension not available.");
    }

    XkbSelectEvents(linuxvars.dpy, XkbUseCoreKbd, XkbAllEventsMask, XkbAllEventsMask);
    linuxvars.xkb = XkbGetKeyboard(linuxvars.dpy, XkbAllComponentsMask, XkbUseCoreKbd);
    if(!linuxvars.xkb) {
        system_error_box("Error getting XKB keyboard details.");
    }

    // closer to windows behaviour (holding key doesn't generate release events)
    XkbSetDetectableAutoRepeat(linuxvars.dpy, True, NULL);

    XCursor cursors[APP_MOUSE_CURSOR_COUNT] = {
        None,
        None,
        XCreateFontCursor(linuxvars.dpy, XC_xterm),
        XCreateFontCursor(linuxvars.dpy, XC_sb_h_double_arrow),
        XCreateFontCursor(linuxvars.dpy, XC_sb_v_double_arrow)
    };
    block_copy(linuxvars.xcursors, cursors, sizeof(cursors));

    // sneaky invisible cursor
    {
        char data = 0;
        XColor c  = {};
        Pixmap p  = XCreateBitmapFromData(linuxvars.dpy, linuxvars.win, &data, 1, 1);

        linuxvars.hidden_cursor = XCreatePixmapCursor(linuxvars.dpy, p, p, &c, &c, 0, 0);

        XFreePixmap(linuxvars.dpy, p);
    }
}

global Key_Code keycode_lookup_table[255];

internal void
linux_keycode_init(Display* dpy){

    block_zero_array(keycode_lookup_table);

    // Find these keys by physical position, and map to QWERTY KeyCodes
#define K(k) glue(KeyCode_, k)
    static const u8 positional_keys[] = {
        K(1), K(2), K(3), K(4), K(5), K(6), K(7), K(8), K(9), K(0), K(Minus), K(Equal),
        K(Q), K(W), K(E), K(R), K(T), K(Y), K(U), K(I), K(O), K(P), K(LeftBracket), K(RightBracket),
        K(A), K(S), K(D), K(F), K(G), K(H), K(J), K(K), K(L), K(Semicolon), K(Quote), /*uk hash*/0,
        K(Z), K(X), K(C), K(V), K(B), K(N), K(M), K(Comma), K(Period), K(ForwardSlash), 0, 0
    };
#undef K

    // XKB gives the alphanumeric keys names like AE01 -> E is the row (from B-E), 01 is the column (01-12).
    // to get key names in .ps file: setxkbmap -print | xkbcomp - - | xkbprint -label name - out.ps

    static const int ncols = 12;
    static const int nrows = 4;

    for(int i = XkbMinLegalKeyCode; i <= XkbMaxLegalKeyCode; ++i) {
        const char* name = linuxvars.xkb->names->keys[i].name;

        if(name[0] == 'A' && name[1] >= 'B' && name[1] <= 'E') {
            int row = (nrows - 1) - (name[1] - 'B');
            int col = (name[2] - '0') * 10 + (name[3] - '0') - 1;

            if(row >= 0 && row < nrows && col >= 0 && col < ncols) {
                keycode_lookup_table[i] = positional_keys[row * ncols + col];
            }
        }

        // a few special cases:

        else if(memcmp(name, "TLDE", XkbKeyNameLength) == 0) {
            keycode_lookup_table[i] = KeyCode_Tick;
        } else if(memcmp(name, "BKSL", XkbKeyNameLength) == 0) {
            keycode_lookup_table[i] = KeyCode_BackwardSlash;
        } else if(memcmp(name, "LSGT", XkbKeyNameLength) == 0) {
            // UK extra key between left shift and Z, not sure what to do with it...
            // Setting to F13-F16 seems to break text input.
            // it prints \ and | with shift. KeyCode_Backslash will be where UK # is.
            // keycode_lookup_table[i] =
        }
    }

    // Find the rest by their key label
    struct SymCode { KeySym sym; Key_Code code; };
    SymCode sym_table[100];
    SymCode* p = sym_table;

    *p++ = { XK_space, KeyCode_Space };
    *p++ = { XK_Tab, KeyCode_Tab };
    *p++ = { XK_Escape, KeyCode_Escape };
    *p++ = { XK_Pause, KeyCode_Pause };
    *p++ = { XK_Up, KeyCode_Up };
    *p++ = { XK_Down, KeyCode_Down };
    *p++ = { XK_Left, KeyCode_Left };
    *p++ = { XK_Right, KeyCode_Right };
    *p++ = { XK_BackSpace, KeyCode_Backspace };
    *p++ = { XK_Return, KeyCode_Return };
    *p++ = { XK_Delete, KeyCode_Delete };
    *p++ = { XK_Insert, KeyCode_Insert };
    *p++ = { XK_Home, KeyCode_Home };
    *p++ = { XK_End, KeyCode_End };
    *p++ = { XK_Page_Up, KeyCode_PageUp };
    *p++ = { XK_Page_Down, KeyCode_PageDown };
    *p++ = { XK_Caps_Lock, KeyCode_CapsLock };
    *p++ = { XK_Num_Lock, KeyCode_NumLock };
    *p++ = { XK_Scroll_Lock, KeyCode_ScrollLock };
    *p++ = { XK_Menu, KeyCode_Menu };
    *p++ = { XK_Shift_L, KeyCode_Shift };
    *p++ = { XK_Shift_R, KeyCode_Shift };
    *p++ = { XK_Control_L, KeyCode_Control };
    *p++ = { XK_Control_R, KeyCode_Control };
    *p++ = { XK_Alt_L, KeyCode_Alt };
    *p++ = { XK_Alt_R, KeyCode_Alt };
    *p++ = { XK_Super_L, KeyCode_Command };
    *p++ = { XK_Super_R, KeyCode_Command };

    for(Key_Code k = KeyCode_F1; k <= KeyCode_F16; ++k) {
        *p++ = { XK_F1 + (k - KeyCode_F1), k };
    }

    const int table_size = p - sym_table;
    Assert(table_size < ArrayCount(sym_table));

    for(int i = XkbMinLegalKeyCode; i <= XkbMaxLegalKeyCode; ++i) {
        KeySym sym = NoSymbol;

        // lookup key in current layout with no modifiers held (0)
        if(!XkbTranslateKeyCode(linuxvars.xkb, i, XkbBuildCoreState(0, linuxvars.xkb_group), NULL, &sym)) {
            continue;
        }

        for(int j = 0; j < table_size; ++j) {
            if(sym_table[j].sym == sym) {
                keycode_lookup_table[i] = sym_table[j].code;
                break;
            }
        }
    }
}

internal void
linux_epoll_init(void) {
    struct epoll_event e = {};
    e.events = EPOLLIN | EPOLLET;

    linuxvars.step_timer_fd = timerfd_create(CLOCK_MONOTONIC, TFD_NONBLOCK);
    linuxvars.epoll = epoll_create(16);

    e.data.ptr = &epoll_tag_x11;
    epoll_ctl(linuxvars.epoll, EPOLL_CTL_ADD, ConnectionNumber(linuxvars.dpy), &e);

    e.data.ptr = &epoll_tag_step_timer;
    epoll_ctl(linuxvars.epoll, EPOLL_CTL_ADD, linuxvars.step_timer_fd, &e);
}

internal void
linux_clipboard_send(XSelectionRequestEvent* req) {

    XSelectionEvent rsp = {};
    rsp.type = SelectionNotify;
    rsp.requestor = req->requestor;
    rsp.selection = req->selection;
    rsp.target = req->target;
    rsp.time = req->time;
    rsp.property = None;

    Atom formats[] = {
        linuxvars.atom_UTF8_STRING,
        XA_STRING,
    };

    if(linuxvars.clipboard_contents.size == 0) {
        goto done;
    }

    if(req->selection != linuxvars.atom_CLIPBOARD || req->property == None) {
        goto done;
    }

    if (req->target == linuxvars.atom_TARGETS){

        XChangeProperty(
            req->display,
            req->requestor,
            req->property,
            XA_ATOM,
            32,
            PropModeReplace,
            (u8*)formats,
            ArrayCount(formats));

        rsp.property = req->property;

    } else {

        int i;
        for(i = 0; i < ArrayCount(formats); ++i){
            if (req->target == formats[i]){
                break;
            }
        }

        if (i != ArrayCount(formats)){
            XChangeProperty(
                req->display,
                req->requestor,
                req->property,
                req->target,
                8,
                PropModeReplace,
                linuxvars.clipboard_contents.str,
                linuxvars.clipboard_contents.size
            );

            rsp.property = req->property;
        }
    }

done:
    XSendEvent(req->display, req->requestor, True, 0, (XEvent*)&rsp);
}

internal void
linux_clipboard_recv(XSelectionEvent* ev) {

    if(ev->selection != linuxvars.atom_CLIPBOARD ||
        ev->target != linuxvars.atom_UTF8_STRING ||
        ev->property == None) {
        return;
    }

    Atom type;
    int fmt;
    unsigned long nitems;
    unsigned long bytes_left;
    u8 *data;

    int result = XGetWindowProperty(
        linuxvars.dpy,
        linuxvars.win,
        linuxvars.atom_CLIPBOARD,
        0L, 0x20000000L, False,
        linuxvars.atom_UTF8_STRING,
        &type, &fmt, &nitems,
        &bytes_left, &data);

    if(result == Success && fmt == 8){
        linalloc_clear(linuxvars.clipboard_arena);
        linuxvars.clipboard_contents = push_u8_stringf(linuxvars.clipboard_arena, "%.*s", nitems, data);
        linuxvars.received_new_clipboard = true;
        XFree(data);
        XDeleteProperty(linuxvars.dpy, linuxvars.win, linuxvars.atom_CLIPBOARD);
        linux_schedule_step();
    }
}

internal String_Const_u8
linux_filter_text(Arena* arena, u8* buf, int len) {
    u8* const result = push_array(arena, u8, len);
    u8* outp = result;

    for(int i = 0; i < len; ++i) {
        u8 c = buf[i];

        if(c == '\r') {
            *outp++ = '\n';
        } else if(c > 127 || (' ' <= c && c <= '~') || c == '\t') {
            *outp++ = c;
        }
    }

    return SCu8(result, outp - result);
}

internal void
linux_handle_x11_events() {
    static XEvent prev_event = {};
    b32 should_step = false;

    while (XPending(linuxvars.dpy)) {
        XEvent event;
        XNextEvent(linuxvars.dpy, &event);

        if (XFilterEvent(&event, None) == True){
            continue;
        }

        switch(event.type) {
            case KeyPress: {
                should_step = true;

                Input_Modifier_Set_Fixed* mods = &linuxvars.input.pers.modifiers;

                int state = event.xkey.state;
                set_modifier(mods, KeyCode_Shift, state & ShiftMask);
                set_modifier(mods, KeyCode_Control, state & ControlMask);
                set_modifier(mods, KeyCode_CapsLock, state & LockMask);
                set_modifier(mods, KeyCode_Alt, state & Mod1Mask);

                event.xkey.state &= ~(ControlMask);

                Status status;
                KeySym keysym = NoSymbol;
                u8 buf[256] = {};

                int len = Xutf8LookupString(linuxvars.xic, &event.xkey, (char*)buf, sizeof(buf) - 1, &keysym, &status);

                if (status == XBufferOverflow){
                    Xutf8ResetIC(linuxvars.xic);
                    XSetICFocus(linuxvars.xic);
                }

                if (keysym == XK_ISO_Left_Tab){
                    add_modifier(mods, KeyCode_Shift);
                }

                Key_Code key = keycode_lookup_table[(u8)event.xkey.keycode];
                //printf("key %d = %s\n", event.xkey.keycode, key_code_name[key]);

                Input_Event* key_event = NULL;
                if(key) {
                    add_modifier(mods, key);
                    key_event = push_input_event(linuxvars.frame_arena, &linuxvars.input.trans.event_list);
                    key_event->kind = InputEventKind_KeyStroke;
                    key_event->key.code = key;
                    key_event->key.modifiers = copy_modifier_set(linuxvars.frame_arena, mods);
                }

                Input_Event* text_event = NULL;
                if(status == XLookupChars || status == XLookupBoth) {
                    String_Const_u8 str = linux_filter_text(linuxvars.frame_arena, buf, len);
                    if(str.size) {
                        text_event = push_input_event(linuxvars.frame_arena, &linuxvars.input.trans.event_list);
                        text_event->kind = InputEventKind_TextInsert;
                        text_event->text.string = str;
                    }
                }

                if(key_event && text_event) {
                    key_event->key.first_dependent_text = text_event;
                }

            } break;

            case KeyRelease: {
                should_step = true;

                Input_Modifier_Set_Fixed* mods = &linuxvars.input.pers.modifiers;

                int state = event.xkey.state;
                set_modifier(mods, KeyCode_Shift, state & ShiftMask);
                set_modifier(mods, KeyCode_Control, state & ControlMask);
                set_modifier(mods, KeyCode_CapsLock, state & LockMask);
                set_modifier(mods, KeyCode_Alt, state & Mod1Mask);

                Key_Code key = keycode_lookup_table[(u8)event.xkey.keycode];

                Input_Event* key_event = NULL;
                if(key) {
                    remove_modifier(mods, key);
                    key_event = push_input_event(linuxvars.frame_arena, &linuxvars.input.trans.event_list);
                    key_event->kind = InputEventKind_KeyRelease;
                    key_event->key.code = key;
                    key_event->key.modifiers = copy_modifier_set(linuxvars.frame_arena, mods);
                }
            } break;

            case MotionNotify: {
                int x = clamp(0, event.xmotion.x, render_target.width - 1);
                int y = clamp(0, event.xmotion.y, render_target.height - 1);
                linuxvars.input.pers.mouse = { x, y };
                should_step = true;
            } break;

            case ButtonPress: {
                should_step = true;
                switch(event.xbutton.button) {
                    case Button1: {
                        linuxvars.input.trans.mouse_l_press = true;
                        linuxvars.input.pers.mouse_l = true;

                        // NOTE(inso): improves selection dragging (especially in notepad-like mode).
                        // we will still get mouse events when the pointer leaves the window if it's dragging.
                        XGrabPointer(
                            linuxvars.dpy,
                            linuxvars.win,
                            True, PointerMotionMask | ButtonPressMask | ButtonReleaseMask,
                            GrabModeAsync, GrabModeAsync,
                            None, None, CurrentTime);

                    } break;

                    case Button3: {
                        linuxvars.input.trans.mouse_r_press = true;
                        linuxvars.input.pers.mouse_r = true;
                    } break;

                    case Button4: {
                        linuxvars.input.trans.mouse_wheel = -100;
                    } break;

                    case Button5: {
                        linuxvars.input.trans.mouse_wheel = +100;
                    } break;
                }
            } break;

            case ButtonRelease: {
                should_step = true;
                switch(event.xbutton.button) {
                    case Button1: {
                        linuxvars.input.trans.mouse_l_release = true;
                        linuxvars.input.pers.mouse_l = false;

                        XUngrabPointer(linuxvars.dpy, CurrentTime);
                    } break;

                    case Button3: {
                        linuxvars.input.trans.mouse_r_release = true;
                        linuxvars.input.pers.mouse_r = false;
                    } break;
                }
            } break;

            case FocusIn:
            case FocusOut: {
                linuxvars.input.pers.mouse_l = false;
                linuxvars.input.pers.mouse_r = false;
                block_zero_struct(&linuxvars.input.pers.modifiers);
            } break;

            case EnterNotify: {
                linuxvars.input.pers.mouse_out_of_window = 0;
            } break;

            case LeaveNotify: {
                linuxvars.input.pers.mouse_out_of_window = 1;
            } break;

            case ConfigureNotify: {
                i32 w = event.xconfigure.width;
                i32 h = event.xconfigure.height;

                if (w != render_target.width || h != render_target.height){
                    should_step = true;
                    render_target.width = w;
                    render_target.height = h;
                }
            } break;

            case ClientMessage: {
                Atom atom = event.xclient.data.l[0];

                // Window X button clicked
                if(atom == linuxvars.atom_WM_DELETE_WINDOW) {
                    should_step = true;
                    linuxvars.input.trans.trying_to_kill = true;
                }

                // Notify WM that we're still responding (don't grey our window out).
                else if(atom == linuxvars.atom__NET_WM_PING) {
                    event.xclient.window = DefaultRootWindow(linuxvars.dpy);
                    XSendEvent(
                        linuxvars.dpy,
                        event.xclient.window,
                        False,
                        SubstructureRedirectMask | SubstructureNotifyMask,
                        &event);
                }
            } break;

            case SelectionRequest: {
                linux_clipboard_send((XSelectionRequestEvent*)&event);
            } break;

            case SelectionNotify: {
                linux_clipboard_recv((XSelectionEvent*)&event);
            } break;

            case SelectionClear: {
                if(event.xselectionclear.selection == linuxvars.atom_CLIPBOARD) {
                    linalloc_clear(linuxvars.clipboard_arena);
                    block_zero_struct(&linuxvars.clipboard_contents);
                }
            } break;

            case Expose:
            case VisibilityNotify: {
                should_step = true;
            } break;

            default: {
                // clipboard update notification - ask for the new content
                if (linuxvars.clipboard_catch_all && event.type == linuxvars.xfixes_selection_event) {
                    XFixesSelectionNotifyEvent* sne = (XFixesSelectionNotifyEvent*)&event;
                    if (sne->subtype == XFixesSelectionNotify && sne->owner != linuxvars.win){
                        XConvertSelection(
                            linuxvars.dpy,
                            linuxvars.atom_CLIPBOARD,
                            linuxvars.atom_UTF8_STRING,
                            linuxvars.atom_CLIPBOARD,
                            linuxvars.win,
                            CurrentTime);
                    }
                }

                else if(event.type == linuxvars.xkb_event) {
                    XkbEvent* kb = (XkbEvent*)&event;

                    // Keyboard layout changed, refresh lookup table.
                    if(kb->any.xkb_type == XkbStateNotify && kb->state.group != linuxvars.xkb_group) {
                        linuxvars.xkb_group = kb->state.group;
                        XkbRefreshKeyboardMapping((XkbMapNotifyEvent*)kb);
                        linux_keycode_init(linuxvars.dpy);
                    }
                }
            } break;
        }
    }

    if(should_step) {
        linux_schedule_step();
    }
}

internal b32
linux_epoll_process(struct epoll_event* events, int num_events) {
    b32 do_step = false;

    for (int i = 0; i < num_events; ++i){
        struct epoll_event* ev = events + i;
        Epoll_Kind* tag = (Epoll_Kind*)ev->data.ptr;

        switch (*tag){
            case EPOLL_X11: {
                linux_handle_x11_events();
            } break;

            case EPOLL_X11_INTERNAL: {
                //XProcessInternalConnection(linuxvars.dpy, fd);
            } break;

            case EPOLL_STEP_TIMER: {
                u64 count;
                int ret;
                do {
                    ret = read(linuxvars.step_timer_fd, &count, 8);
                } while (ret != -1 || errno != EAGAIN);
                do_step = true;
            } break;

            case EPOLL_CLI_PIPE: {
                linux_schedule_step();
            } break;

            case EPOLL_USER_TIMER: {
                Linux_Object* obj = CastFromMember(Linux_Object, timer.epoll_tag, tag);
                close(obj->timer.fd);
                obj->timer.fd = -1;
                linux_schedule_step();
            } break;
        }
    }

    return do_step;
}

int
main(int argc, char **argv){

    // NOTE(allen): context setup
    {
        Base_Allocator* alloc = get_base_allocator_system();
        thread_ctx_init(&linuxvars.tctx, ThreadKind_Main, alloc, alloc);
    }

    API_VTable_system system_vtable = {};
    system_api_fill_vtable(&system_vtable);

    API_VTable_graphics graphics_vtable = {};
    graphics_api_fill_vtable(&graphics_vtable);

    API_VTable_font font_vtable = {};
    font_api_fill_vtable(&font_vtable);

    // NOTE(allen): memory
    linuxvars.frame_arena = reserve_arena(&linuxvars.tctx);
    linuxvars.clipboard_arena = reserve_arena(&linuxvars.tctx);
    render_target.arena = make_arena_system(KB(256));

    linuxvars.fontconfig = FcInitLoadConfigAndFonts();

    linuxvars.cursor_show = MouseCursorShow_Always;
    linuxvars.prev_cursor_show = MouseCursorShow_Always;

    dll_init_sentinel(&linuxvars.free_linux_objects);
    dll_init_sentinel(&linuxvars.timer_objects);

    //InitializeCriticalSection(&win32vars.thread_launch_mutex);
    //InitializeConditionVariable(&win32vars.thread_launch_cv);

    linuxvars.clipboard_catch_all = true;

    // NOTE(allen): load core
    System_Library core_library = {};
    App_Functions app = {};
    {
        App_Get_Functions *get_funcs = 0;
        Scratch_Block scratch(&linuxvars.tctx, Scratch_Share);
        Path_Search_List search_list = {};
        search_list_add_system_path(scratch, &search_list, SystemPath_Binary);

        String_Const_u8 core_path = get_full_path(scratch, &search_list, SCu8("4ed_app.so"));
        if (system_load_library(scratch, core_path, &core_library)){
            get_funcs = (App_Get_Functions*)system_get_proc(core_library, "app_get_functions");
            if (get_funcs != 0){
                app = get_funcs();
            }
            else{
                char msg[] = "Failed to get application code from '4ed_app.so'.";
                system_error_box(msg);
            }
        }
        else{
            char msg[] = "Could not load '4ed_app.so'. This file should be in the same directory as the main '4ed' executable.";
            system_error_box(msg);
        }
    }

    // NOTE(allen): send system vtable to core
    app.load_vtables(&system_vtable, &font_vtable, &graphics_vtable);
    // get_logger calls log_init which is needed.
    app.get_logger();
    //linuxvars.log_string = app.get_logger();

    // NOTE(allen): init & command line parameters
    Plat_Settings plat_settings = {};
    void *base_ptr = 0;
    {
        Scratch_Block scratch(&linuxvars.tctx, Scratch_Share);
        String_Const_u8 curdir = system_get_path(scratch, SystemPath_CurrentDirectory);

        char **files = 0;
        i32 *file_count = 0;
        base_ptr = app.read_command_line(&linuxvars.tctx, curdir, &plat_settings, &files, &file_count, argc, argv);
        /* TODO(inso): what is this doing?
        {
            i32 end = *file_count;
            i32 i = 0, j = 0;
            for (; i < end; ++i){
                if (system_file_can_be_made(scratch, (u8*)files[i])){
                    files[j] = files[i];
                    ++j;
                }
            }
            *file_count = j;
        }*/
    }

    // NOTE(allen): load custom layer
    System_Library custom_library = {};
    Custom_API custom = {};
    {
        char custom_not_found_msg[] = "Did not find a library for the custom layer.";
        char custom_fail_version_msg[] = "Failed to load custom code due to missing version information or a version mismatch.  Try rebuilding with buildsuper.";
        char custom_fail_init_apis[] = "Failed to load custom code due to missing 'init_apis' symbol.  Try rebuilding with buildsuper";

        Scratch_Block scratch(&linuxvars.tctx, Scratch_Share);
        String_Const_u8 default_file_name = string_u8_litexpr("custom_4coder.so");
        Path_Search_List search_list = {};
        search_list_add_system_path(scratch, &search_list, SystemPath_CurrentDirectory);
        search_list_add_system_path(scratch, &search_list, SystemPath_Binary);
        String_Const_u8 custom_file_names[2] = {};
        i32 custom_file_count = 1;
        if (plat_settings.custom_dll != 0){
            custom_file_names[0] = SCu8(plat_settings.custom_dll);
            if (!plat_settings.custom_dll_is_strict){
                custom_file_names[1] = default_file_name;
                custom_file_count += 1;
            }
        }
        else{
            custom_file_names[0] = default_file_name;
        }
        String_Const_u8 custom_file_name = {};
        for (i32 i = 0; i < custom_file_count; i += 1){
            custom_file_name = get_full_path(scratch, &search_list, custom_file_names[i]);
            if (custom_file_name.size > 0){
                break;
            }
        }
        b32 has_library = false;
        if (custom_file_name.size > 0){
            if (system_load_library(scratch, custom_file_name, &custom_library)){
                has_library = true;
            }
        }

        if (!has_library){
            system_error_box(custom_not_found_msg);
        }
        custom.get_version = (_Get_Version_Type*)system_get_proc(custom_library, "get_version");
        if (custom.get_version == 0 || custom.get_version(MAJOR, MINOR, PATCH) == 0){
            system_error_box(custom_fail_version_msg);
        }
        custom.init_apis = (_Init_APIs_Type*)system_get_proc(custom_library, "init_apis");
        if (custom.init_apis == 0){
            system_error_box(custom_fail_init_apis);
        }
    }

    linux_x11_init(argc, argv, &plat_settings);
    linux_keycode_init(linuxvars.dpy);
    linux_epoll_init();

    // app init
    {
        Scratch_Block scratch(&linuxvars.tctx, Scratch_Share);
        String_Const_u8 curdir = system_get_path(scratch, SystemPath_CurrentDirectory);
        app.init(&linuxvars.tctx, &render_target, base_ptr, curdir, custom);
    }

    linuxvars.global_frame_mutex = system_mutex_make();
    system_mutex_acquire(linuxvars.global_frame_mutex);

    linux_schedule_step();
    b32 first_step = true;

    for (;;) {

        if (XEventsQueued(linuxvars.dpy, QueuedAlready)){
            linux_handle_x11_events();
        }

        system_mutex_release(linuxvars.global_frame_mutex);

        struct epoll_event events[16];
        int num_events = epoll_wait(linuxvars.epoll, events, ArrayCount(events), -1);

        system_mutex_acquire(linuxvars.global_frame_mutex);

        if (num_events == -1){
            if (errno != EINTR){
                perror("epoll_wait");
                //LOG("epoll_wait\n");
            }
            continue;
        }

        if(!linux_epoll_process(events, num_events)) {
            continue;
        }

        linuxvars.last_step_time = system_now_time();

        // NOTE(allen): Frame Clipboard Input
        // Request clipboard contents from X11 on first step, or every step if they don't have XFixes notification ability.
        if (first_step || (!linuxvars.has_xfixes && linuxvars.clipboard_catch_all)){
            XConvertSelection(linuxvars.dpy, linuxvars.atom_CLIPBOARD, linuxvars.atom_UTF8_STRING, linuxvars.atom_CLIPBOARD, linuxvars.win, CurrentTime);
        }

        Application_Step_Input input = {};

        if (linuxvars.received_new_clipboard){
            input.clipboard = linuxvars.clipboard_contents;
            linuxvars.received_new_clipboard = false;
        }

        input.first_step = first_step;
        input.dt = frame_useconds/1000000.f; // variable?
        input.events = linuxvars.input.trans.event_list;
        input.trying_to_kill = linuxvars.input.trans.trying_to_kill;

        input.mouse.out_of_window = linuxvars.input.pers.mouse_out_of_window;
        input.mouse.p = linuxvars.input.pers.mouse;
        input.mouse.l = linuxvars.input.pers.mouse_l;
        input.mouse.r = linuxvars.input.pers.mouse_r;
        input.mouse.press_l = linuxvars.input.trans.mouse_l_press;
        input.mouse.release_l = linuxvars.input.trans.mouse_l_release;
        input.mouse.press_r = linuxvars.input.trans.mouse_r_press;
        input.mouse.release_r = linuxvars.input.trans.mouse_r_release;
        input.mouse.wheel = linuxvars.input.trans.mouse_wheel;

        // NOTE(allen): Application Core Update
        Application_Step_Result result = {};
        if (app.step != 0){
            result = app.step(&linuxvars.tctx, &render_target, base_ptr, &input);
        }

        // NOTE(allen): Finish the Loop
        if (result.perform_kill){
            break;
        }

        // NOTE(NAME): Switch to New Title
        if (result.has_new_title){
            XStoreName(linuxvars.dpy, linuxvars.win, result.title_string);
        }

        // NOTE(allen): Switch to New Cursor
        if (result.mouse_cursor_type != linuxvars.cursor && !linuxvars.input.pers.mouse_l){
            XCursor c = linuxvars.xcursors[result.mouse_cursor_type];
            if (linuxvars.cursor_show){
                XDefineCursor(linuxvars.dpy, linuxvars.win, c);
            }
            linuxvars.cursor = result.mouse_cursor_type;
        }

        gl_render(&render_target);
        glXSwapBuffers(linuxvars.dpy, linuxvars.win);

        first_step = false;

        linalloc_clear(linuxvars.frame_arena);
        block_zero_struct(&linuxvars.input.trans);
        linuxvars.step_pending = false;
    }

    return 0;
}

// NOTE(inso): to prevent me continuously messing up indentation
// vim: et:ts=4:sts=4:sw=4