src/context.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * Copyright 2023 Mike Becker. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include "ascension/context.h"
#include "ascension/error.h"

#include <SDL3/SDL.h>
#include <SDL3_ttf/SDL_ttf.h>

#include <GL/glew.h>

#include <time.h>

AscContext asc_context;

static uint64_t asc_nanos(void) {
    struct timespec ts;
    clock_gettime(CLOCK_MONOTONIC, &ts);
    return 1000000000ull*(uint64_t)ts.tv_sec + (uint64_t)ts.tv_nsec;
}

// forward declare non-public font cache functions
void asc_font_cache_init(void);
void asc_font_cache_destroy(void);

void asc_context_initialize(void) {
    if (asc_test_flag(asc_context.flags, ASC_FLAG_INITIALIZED))
        return;
    memset(&asc_context, 0, sizeof(AscContext));

    // initialize default paths
    asc_context.font_path = cx_strdup(CX_STR("./fonts"));
    asc_context.shader_path = cx_strdup(CX_STR("./shader"));
    asc_context.texture_path = cx_strdup(CX_STR("./textures"));

    // initialize the font cache
    asc_font_cache_init();

    // no window, yet
    asc_context.active_window = ASC_MAX_WINDOWS;

    // initialize error buffer
    cxBufferInit(
            &asc_context.error_buffer,
            NULL,
            256,
            NULL,
            CX_BUFFER_AUTO_EXTEND
    );

    // initialize SDL
    if (!SDL_Init(SDL_INIT_VIDEO)) {
        asc_error("Failed to initialize SDL: %s", SDL_GetError());
    } else if (!TTF_Init()) {
        asc_error("Failed to initialize SDL_ttf: %s", SDL_GetError());
    }
    SDL_ClearError();
    asc_context.total_nanos = asc_nanos();
    asc_set_flag(asc_context.flags, ASC_FLAG_INITIALIZED);
    asc_dprintf("Ascension context initialized.");
}

void asc_context_destroy(void) {
    // destroy windows
    for (unsigned int i = 0 ; i < ASC_MAX_WINDOWS ; i++) {
        asc_window_destroy(i);
    }

    // destroy the font cache
    asc_font_cache_destroy();

    // quit SDL
    TTF_Quit();
    SDL_Quit();

    // destroy the error buffer
    cxBufferDestroy(&asc_context.error_buffer);
    asc_context.flags = 0;
    asc_dprintf("Ascension context destroyed.");

    // destroy the path information
    cx_strfree(&asc_context.font_path);
    cx_strfree(&asc_context.shader_path);
    cx_strfree(&asc_context.texture_path);
}

void asc_context_quit(void) {
    asc_set_flag(asc_context.flags, ASC_FLAG_QUIT);
}

AscWindow *asc_active_window_assert() {
    if (asc_context.active_window < ASC_MAX_WINDOWS) {
        return &asc_context.windows[asc_context.active_window];
    } else {
        asc_dprintf("Window access attempted without active window");
        abort();
    }
}

static void asc_event_window_resized(Uint32 id, Sint32 width, Sint32 height) {
    unsigned int i = asc_window_index(id);
    if (i < ASC_MAX_WINDOWS) {
        asc_context.windows[i].resized = true;
        asc_context.windows[i].dimensions.width = (unsigned) width;
        asc_context.windows[i].dimensions.height = (unsigned) height;
    }
}

bool asc_loop_next(void) {
    // reset mouse motion
    asc_context.input.mouse_xrel = 0;
    asc_context.input.mouse_yrel = 0;

    // reset key flags
    for (unsigned int i = 0 ; i < SDL_SCANCODE_COUNT ; i++) {
        asc_clear_flag(asc_context.input.keys[i], ASC_KEY_RELEASE_FLAG|ASC_KEY_PRESS_FLAG);
    }

    // dispatch SDL events
    SDL_Event event;
    while (SDL_PollEvent(&event)) {
        switch (event.type) {
            case SDL_EVENT_QUIT:
                asc_set_flag(asc_context.flags, ASC_FLAG_QUIT);
                break;
            case SDL_EVENT_WINDOW_RESIZED: {
                asc_event_window_resized(
                        event.window.windowID,
                        event.window.data1,
                        event.window.data2
                );
                break;
            }
            case SDL_EVENT_WINDOW_FOCUS_GAINED: {
                unsigned int idx = asc_window_index(event.window.windowID);
                asc_context.windows[idx].focused = true;
                break;
            }
            case SDL_EVENT_WINDOW_FOCUS_LOST: {
                unsigned int idx = asc_window_index(event.window.windowID);
                asc_context.windows[idx].focused = false;
                break;
            }
            case SDL_EVENT_MOUSE_MOTION: {
                // accumulate relative motion
                asc_context.input.mouse_xrel += event.motion.xrel;
                asc_context.input.mouse_yrel += event.motion.yrel;
                // update absolute position
                asc_context.input.mouse_x = event.motion.x;
                asc_context.input.mouse_y = event.motion.y;
                // update which window the mouse was seen in
                asc_context.input.mouse_window =
                        asc_window_index(event.motion.windowID);
                break;
            }
            case SDL_EVENT_KEY_DOWN:
                // we only set the down and press flags if the key is not already known to be down
                if (asc_key_up(event.key.scancode)) {
                    asc_context.input.keys[event.key.scancode] = ASC_KEY_DOWN_FLAG|ASC_KEY_PRESS_FLAG;
                }
                break;
            case SDL_EVENT_KEY_UP:
                // we can directly set the release flag - it will be cleared next round
                asc_context.input.keys[event.key.scancode] = ASC_KEY_RELEASE_FLAG;
                break;
        }
    }

    // compute frame time
    uint64_t frame_nanos, ns;
    do {
        ns = asc_nanos();
        frame_nanos = ns - asc_context.total_nanos;
    } while (frame_nanos == 0);
    asc_context.frame_nanos = frame_nanos;
    unsigned long long fps_1k = asc_seconds(1000) / frame_nanos;
    asc_context.frame_rate = (float)fps_1k / 1000.f;
    if (asc_context.frame_rate < 5) {
        // effectively stop the world when the frame rate drops too low
        asc_context.frame_factor = 0;
    } else {
        asc_context.frame_factor = 1.f / asc_context.frame_rate;
    }
    asc_context.total_nanos = ns;

    // sync the windows
    for (unsigned int i = 0 ; i < ASC_MAX_WINDOWS ; i++) {
        asc_window_sync(i);
    }

    return !asc_test_flag(asc_context.flags, ASC_FLAG_QUIT);
}

void asc_set_font_path(const char *path) {
    cx_strcpy(&asc_context.font_path, cx_str(path));
}

void asc_set_shader_path(const char *path) {
    cx_strcpy(&asc_context.shader_path, cx_str(path));
}

void asc_set_texture_path(const char *path) {
    cx_strcpy(&asc_context.texture_path, cx_str(path));
}