i made a swapchain

Makefile

@@ -2,12 +2,13 @@ CC = gcc
 
 INCFLAGS  = -Isrc
 
-CCFLAGS  = -std=c99 -Wall -Wextra -pedantic -O2
+CCFLAGS  = -std=gnu99 -Wall -Wextra -pedantic -O2
 CCFLAGS += $(INCFLAGS)
 
 LDFLAGS += $(INCFLAGS)
 LDFLAGS += -lX11
 LDFLAGS += -lm
+LDFLAGS += -lpthread
 
 BIN = bin
 APP = $(BIN)/app

src/renderer.c

@@ -3,6 +3,8 @@
 #include "ray.h"
 
 #include <math.h>
+#include <pthread.h>
+#include <stdio.h>
 #include <string.h>
 
 
@@ -80,10 +82,11 @@ void update_camera(Camera* camera, Screen* screen) {
     if (movey) camera->pos.y += move.y * MOVE_SPEED * screen->delta;
 }
 
-static void verline(Screen* screen, int x, int y0, int y1, uint32_t color) {
+static void verline(Swapchain* swapchain, int x, int y0, int y1, uint32_t color) {
     for (int y = y0; y <= y1; y++) {
-        screen->pixels[(y * screen->width) + x] = color;
+        swapchain->images[swapchain->image_current][(y * swapchain->width) + x] = color;
     }
+
 }
 
 void render(Screen* screen, const Camera* camera) {
@@ -93,9 +96,13 @@ void render(Screen* screen, const Camera* camera) {
         cos(camera->angle)
     };
 
-    for (int x = 0; x < screen->width; x++) {
+    Swapchain* swapchain = &screen->swapchain;
 
-        const float xcam = (2 * (x / (float) (screen->width))) - 1;
+    swapchain_next(swapchain);
+    
+    for (int x = 0; x < screen->swapchain.width; x++) {
+
+        const float xcam = (2 * (x / (float) (swapchain->width))) - 1;
         const float change = fov * atan(xcam);
         const float theta = camera->angle + change;
 
@@ -126,15 +133,18 @@ void render(Screen* screen, const Camera* camera) {
         // }
 
         const int
-            h = (int) (screen->height / len),
+            h = (int) (swapchain->height / len),
-            y0 = max((screen->height / 2) - (h / 2), 0),
+            y0 = max((swapchain->height / 2) - (h / 2), 0),
-            y1 = min((screen->height / 2) + (h / 2), screen->height - 1);
+            y1 = min((swapchain->height / 2) + (h / 2), swapchain->height - 1);
+        
+        verline(swapchain, x, 0, y0, 0xFF202020);
+        verline(swapchain, x, y0, y1, color);
+        verline(swapchain, x, y1, swapchain->height - 1, 0xFF505050);
 
-        verline(screen, x, 0, y0, 0xFF202020);
-        verline(screen, x, y0, y1, color);
-        verline(screen, x, y1, screen->height - 1, 0xFF505050);
         // verline(screen, x, 0, y0, 0x202020FF);
         // verline(screen, x, y0, y1, color);
         // verline(screen, x, y1, screen->height - 1, 0x505050FF);
     }
+
+    swapchain_submit(swapchain);
 }

src/screen.c

@@ -1,4 +1,5 @@
 #include "screen.h"
+#include <sched.h>
 #undef Screen
 
 #include <math.h>
@@ -7,6 +8,8 @@
 #include <string.h>
 #include <time.h>
 #include <sys/select.h>
+#include <pthread.h>
+#include <unistd.h>
 
 #define XLIB_ILLEGAL_ACCESS
 #include <X11/X.h>
@@ -28,8 +31,9 @@ typedef struct {
     Window window;
     GC graphics_ctx;
     Pixmap pixel_map;
-    XImage* image;
+    XImage** images;
-    int width, height;
+    pthread_t update_thread;
+    pthread_mutex_t recreate_lock;
 } WindowState;
 
 static void init_x() {
@@ -89,6 +93,126 @@ static XImage* create_image(int width, int height, void* data) {
     );
 }
 
+static Swapchain create_swapchain(int width, int height, int frames, int bit_depth, WindowState* state) {
+    Swapchain swapchain;
+    swapchain.width = width;
+    swapchain.height = height;
+    swapchain.image_count = frames;
+    swapchain.image_front = 0;
+    swapchain.image_recent = 0;
+    swapchain.image_current = 0;
+    swapchain.images = malloc(sizeof(uint32_t*) * frames);
+    
+    state->images = malloc(sizeof(XImage*) * frames);
+    state->pixel_map = XCreatePixmap(dpy, state->window, width, height, bit_depth);
+    state->graphics_ctx = XCreateGC(dpy, state->pixel_map, 0, NULL);
+    
+    size_t pixel_count = width * height;
+    for (int i = 0; i < frames; i++) {
+        uint32_t* data = malloc(pixel_count * bit_depth / 8);
+        memset(data, 0, pixel_count * bit_depth / 8);
+
+        swapchain.images[i] = data;
+        state->images[i] = create_image(width, height, data);
+
+    }
+
+    pthread_mutex_init(&state->recreate_lock, NULL);
+    pthread_mutex_init(&swapchain.lock, NULL);
+
+    return swapchain;
+}
+
+static void free_swapchain(Swapchain swapchain, WindowState* state) {
+    for (uint8_t i = 0; i < swapchain.image_count; i++) {
+        XDestroyImage(state->images[i]); // also frees pixel buffer :3
+    }
+    
+    free(swapchain.images);
+    free(state->images);
+    
+    XFreePixmap(dpy, state->pixel_map);
+    XFreeGC(dpy, state->graphics_ctx);
+}
+
+static void recreate_swapchain(int width, int height, int bit_depth, Swapchain* swapchain, WindowState* state) {
+    pthread_mutex_lock(&state->recreate_lock);
+
+    swapchain->width = width;
+    swapchain->height = height;
+    
+    XFreePixmap(dpy, state->pixel_map);
+    XFreeGC(dpy, state->graphics_ctx);
+
+    state->pixel_map = XCreatePixmap(dpy, state->window, width, height, bit_depth);
+    state->graphics_ctx = XCreateGC(dpy, state->pixel_map, 0, NULL);
+   
+    size_t pixel_count = width * height;
+    for (uint8_t i = 0; i < swapchain->image_count; i++) {
+        XDestroyImage(state->images[i]); // also frees pixel buffer :3
+        
+        uint32_t* data = malloc(pixel_count * bit_depth / 8);
+        memset(data, 0, pixel_count * bit_depth / 8);
+
+        swapchain->images[i] = data;
+        state->images[i] = create_image(width, height, data);
+    }
+
+    pthread_mutex_unlock(&state->recreate_lock);
+}
+
+void swapchain_next(Swapchain* swapchain) {
+    pthread_mutex_lock(&swapchain->lock);
+    uint8_t next = swapchain->image_current + 1;
+    next %= swapchain->image_count;
+
+    if (next == swapchain->image_front) {
+        next += 1;
+        next %= 3;
+    }
+
+    swapchain->image_current = next;
+    pthread_mutex_unlock(&swapchain->lock);
+}
+
+void swapchain_submit(Swapchain* swapchain) {
+    pthread_mutex_lock(&swapchain->lock);
+    swapchain->image_recent = swapchain->image_current;
+    pthread_mutex_unlock(&swapchain->lock);
+}
+
+static void* swapchain_thread(void* arg) {
+    struct Screen* screen = (struct Screen*) arg;
+    WindowState* state = (WindowState*) screen->internal;
+
+    while (1) {
+        pthread_mutex_lock(&state->recreate_lock);
+        
+        pthread_mutex_lock(&screen->swapchain.lock);
+        int index = screen->swapchain.image_recent;
+        screen->swapchain.image_front = index;
+        pthread_mutex_unlock(&screen->swapchain.lock);
+        
+        XPutImage(
+            dpy,
+            state->window,
+            state->graphics_ctx,
+            state->images[index],
+            0, 0, 0, 0,
+            screen->swapchain.width,
+            screen->swapchain.height
+        );
+        XSync(dpy, 0);
+        
+        pthread_mutex_unlock(&state->recreate_lock);
+
+        usleep(1000 * 1000 / 60);
+    }
+
+    return NULL;
+}
+
+#define FRAMES 3
 
 void init_screen(struct Screen* screen, uint16_t width, uint16_t height, const char* title) {
 
@@ -96,36 +220,17 @@ void init_screen(struct Screen* screen, uint16_t width, uint16_t height, const c
         init_x();
     }
     
-    screen->width = width;
-    screen->height = height;
-    screen->delta = 0;
-    
-    size_t pixel_count = screen->width * screen->height;
-
-    screen->pixels = malloc(pixel_count * bit_depth / 8);
-    memset(screen->pixels, 0, pixel_count * bit_depth / 8);
-
     Window window = create_window(0, 0, width, height, bit_depth, title);
     XMapWindow(dpy, window);
 
-    Pixmap pixel_map = XCreatePixmap(dpy, window, width, height, bit_depth);
-
-    GC gc = XCreateGC(dpy, pixel_map, 0, NULL);
-
     WindowState* state = malloc(sizeof(WindowState));
     state->window = window;
-    state->graphics_ctx = gc;
-    state->pixel_map = pixel_map;
 
-    XWindowAttributes xwa;
+    screen->swapchain = create_swapchain(width, height, FRAMES, bit_depth, state);
-    XGetWindowAttributes(dpy, window, &xwa);
+    pthread_create(&state->update_thread, NULL, &swapchain_thread, screen);
-    state->width = xwa.width;
+
-    state->height = xwa.height;
+    screen->delta = 0;
     screen->internal = state;
-
-    XImage* image = create_image(state->width, state->height, screen->pixels);
-    state->image = image;
-
     count++;
 }
 
@@ -147,27 +252,10 @@ static void update_delta(struct Screen* screen) {
     last = now;
 }
 
-static void draw_screen(struct Screen* screen) {
+static void handle_event(struct Screen* screen) {
-    WindowState* state = (WindowState*) screen->internal;
-
-    XPutImage(
-        dpy,
-        state->window,
-        state->graphics_ctx,
-        state->image,
-        0, 0, 0, 0,
-        state->width,
-        state->height
-    );
-}
-
-
-static void handle_event(WindowState* state) {
     XEvent event;
     XNextEvent(dpy, &event);
-    
     switch(event.type) {
-        
         case KeyPress: {
             XKeyEvent xkpe = event.xkey;
             uint32_t code = xkpe.keycode - dpy->min_keycode;
@@ -185,9 +273,8 @@ static void handle_event(WindowState* state) {
 
         case ConfigureNotify: {
             XConfigureEvent xce = event.xconfigure;
-            state->width = xce.width;
+            if (xce.width != screen->swapchain.width || xce.height != screen->swapchain.height)
-            state->height = xce.height;
+                recreate_swapchain(xce.width, xce.height, bit_depth, &screen->swapchain, (WindowState*) screen->internal);
-
             break;
         }
 
@@ -197,12 +284,8 @@ static void handle_event(WindowState* state) {
 
 bool poll_screen(struct Screen* screen) {
     
-    draw_screen(screen);
-    
-    WindowState* state = (WindowState*) screen->internal;
-
     while (XPending(dpy))
-        handle_event(state);
+        handle_event(screen);
 
     update_delta(screen);
     return true;
@@ -211,10 +294,9 @@ bool poll_screen(struct Screen* screen) {
 void free_screen(struct Screen* screen) {
     WindowState* state = (WindowState*) screen->internal;
 
+    pthread_exit(&state->update_thread);
     XUnmapWindow(dpy, state->window);
-    XFreePixmap(dpy, state->pixel_map);
+    free_swapchain(screen->swapchain, state);
-    XDestroyImage(state->image);
-    XFreeGC(dpy, state->graphics_ctx);
     XDestroyWindow(dpy, state->window);
     free(screen->internal);
 

src/screen.h

@@ -1,13 +1,28 @@
 #pragma once
 
-#define _POSIX_C_SOURCE 200809L
+#define _XOPEN_SOURCE   600
+#define _POSIX_C_SOURCE 200112L
+// #define _POSIX_C_SOURCE 200809L
 #include <stdint.h>
 #include <stdbool.h>
+#include <pthread.h>
 
-struct Screen {
+typedef struct {
     uint16_t width;
     uint16_t height;
-    uint32_t* pixels;
+    uint8_t image_count; // amount of frames in flight
+    uint8_t image_front; // image being drawn to screen
+    uint8_t image_recent; // last image that finished drawing
+    uint8_t image_current; // current image being drawn
+    pthread_mutex_t lock;
+    uint32_t** images;
+} Swapchain;
+
+void swapchain_next(Swapchain* swapchain);
+void swapchain_submit(Swapchain* swapchain);
+
+struct Screen {
+    Swapchain swapchain;
     float delta;
     void* internal;
 };