feat: vsync and double buffer for framebuffer

sww/source/platform/fb.c

@@ -49,6 +49,8 @@ struct swwApp
 {
     struct termios term;
 
+    uint8_t* fb;
+
     int fbfd;
     int xres;
     int yres;
@@ -68,12 +70,15 @@ struct swwWindow
 {
     swwImage* surface;
 
+    /* Poistion on display(framebuffer) */
+    uint32_t x, y;
+
     /* common data */
     swwWindowCallback callback;
     void* userdata;
 };
 
-swwApp g_app = {{0}, 0, 0, 0, 0, 0, NULL, {-1}, 0, {0}, {0}};
+swwApp g_app = {{0}, NULL, 0, 0, 0, 0, 0, NULL, {-1}, 0, {0}, {0}};
 
 /* Signal Handler */
 typedef enum
@@ -291,8 +296,6 @@ void swwApp_Initialize()
     // EnableRawMode();
     struct fb_var_screeninfo vinfo;
     struct fb_fix_screeninfo finfo;
-    long int screensize = 0;
-    char* fbp = 0;
 
     g_app.fbfd = open("/dev/fb0", O_RDWR);
     if (g_app.fbfd == -1) {
@@ -315,6 +318,13 @@ void swwApp_Initialize()
         exit(4);
     }
 
+    g_app.fb = (uint8_t*)mmap(0, g_app.xres * g_app.yres * 4, PROT_READ | PROT_WRITE, MAP_SHARED,
+                              g_app.fbfd, 0);
+    if (g_app.fb == (void*)-1) {
+        perror("Error: failed to map framebuffer device to memory");
+        exit(5);
+    }
+
     g_app.xres = vinfo.xres;
     g_app.yres = vinfo.yres;
 
@@ -354,6 +364,8 @@ void swwApp_Cleanup()
             close(g_app.event_source[i].fd);
         }
     }
+
+    munmap(g_app.fb, g_app.xres * g_app.yres * 4);
     close(g_app.fbfd);
     // DisableRawMode();
 }
@@ -391,22 +403,11 @@ swwWindow* swwWindow_Create(const char* title, uint32_t width, uint32_t height)
 
     assert(width > 0 && height > 0 && width < g_app.xres && height < g_app.yres);
 
-    int screensize = g_app.xres * g_app.yres * 4;
-
-    uint8_t* fbp = (uint8_t*)mmap(0, screensize, PROT_READ | PROT_WRITE, MAP_SHARED, g_app.fbfd, 0);
-    if (fbp == (void*)-1) {
-        perror("Error: failed to map framebuffer device to memory");
-        exit(5);
-    }
-
     o = (swwWindow*)malloc(sizeof(swwWindow));
     memset(o, 0, sizeof(swwWindow));
-    o->surface = swwImage_Create(10, 10, 4);
-    // NOTE(donkey): An guly patch, the buffer will be allocated by mmap
-    free(o->surface->buffer);
-    o->surface->buffer = fbp;
-    o->surface->width = g_app.xres;
-    o->surface->height = g_app.yres;
+    o->surface = swwImage_Create(width, height, 4);
+    o->x = (g_app.xres - width) >> 1;  // divided by 2
+    o->y = (g_app.yres - height) >> 1; // divided by 2
 
     g_app.window = o;
     ++g_app.window_count;
@@ -417,15 +418,34 @@ swwWindow* swwWindow_Create(const char* title, uint32_t width, uint32_t height)
 void swwWindow_Destroy(swwWindow* o)
 {
     if (o != NULL) {
-        munmap(o->surface->buffer, o->surface->width * o->surface->height * 4);
+        swwImage_Destroy(o->surface);
         free(o);
         --g_app.window_count;
         g_app.window = NULL;
     }
 }
 
-void swwWindow_Present(swwWindow* window)
-{}
+void swwWindow_Present(swwWindow* o)
+{
+    int i = 0;
+    /* Start position: <fb4pixels>[y][x] */
+    uint8_t* start = g_app.fb + (((o->y * g_app.xres) + o->x) << 2);
+    uint8_t* buf = o->surface->buffer;
+    size_t line_size = o->o->surface->width << 2;
+
+    // VSYNC
+    int zero = 0;
+    int ret = ioctl(g_app.fbfd, FBIO_WAITFORVSYNC, &zero);
+
+    if (ret != 0) {
+        perror("Failed to do VSYNC!");
+    }
+
+    /* Copy the window buffer to framebuffer line by line */
+    for (; i < o->height; ++i, start += (g_app.xres << 2), buf += line_size) {
+        memcpy(start, buf, line_size);
+    }
+}
 
 uint8_t* swwWindow_LockBuffer(swwWindow* o)
 {