Improve re-use of client/compositor shared memory by Wayland buffers

1 files changed, 38 insertions, 30 deletions

diff --git a/src/drivers/Wayland/Fl_Wayland_Graphics_Driver.cxx b/src/drivers/Wayland/Fl_Wayland_Graphics_Driver.cxx
index cfe1ff494..4a5351701 100644
--- a/src/drivers/Wayland/Fl_Wayland_Graphics_Driver.cxx
+++ b/src/drivers/Wayland/Fl_Wayland_Graphics_Driver.cxx
@@ -27,53 +27,56 @@ extern "C" {
 #  include "../../../libdecor/src/os-compatibility.h" // for os_create_anonymous_file()
 }
 
+// used by create_shm_buffer and buffer_release
+static struct wl_shm_pool *pool = NULL; // the current pool
+
 
 struct fl_wld_buffer *Fl_Wayland_Graphics_Driver::create_shm_buffer(int width, int height)
 {
   struct fl_wld_buffer *buffer;
   int stride = cairo_format_stride_for_width(Fl_Cairo_Graphics_Driver::cairo_format, width);
   int size = stride * height;
-  static int pool_size = 10000000; // gets increased if necessary
-  static int chunk_offset = pool_size;
-  static int fd = -1;
-  static struct wl_shm_pool *pool = NULL;
-  if (chunk_offset + size > pool_size) {
+  const int default_pool_size = 10000000; // larger pools are possible if needed
+  int chunk_offset = 0; // offset to start of available memory in pool
+  struct wld_shm_pool_data *pool_data = pool ? // data record attached to current pool
+    (struct wld_shm_pool_data *)wl_shm_pool_get_user_data(pool) : NULL;
+  int pool_size = pool ? pool_data->pool_size : default_pool_size; // current pool size
+  if (pool) {
+    // last fl_wld_buffer created from current pool
+    struct fl_wld_buffer *record = wl_container_of(pool_data->buffers.next, record, link);
+    chunk_offset = ((char*)record->data - pool_data->pool_memory) + record->data_size;
+  }
+  if (!pool || chunk_offset + size > pool_size) { // if true, a new pool is needed
     chunk_offset = 0;
-    if (pool) {
-      struct wld_shm_pool_data *pool_data =
-        (struct wld_shm_pool_data *)wl_shm_pool_get_user_data(pool);
-      wl_shm_pool_destroy(pool);
-      close(fd);
-      pool_data->destroyed = true;
-      if (pool_data->use_count == 0) {
-        /*int err =*/ munmap(pool_data->pool_memory, pool_data->pool_size);
-//printf("munmap(%p)->%d\n", pool_data->pool_memory, err);
-        free(pool_data);
-      }
+    pool_size = default_pool_size;
+    if (size > pool_size) pool_size = 2 * size; // a larger pool is needed
+    int fd = os_create_anonymous_file(pool_size);
+    if (fd < 0) {
+      Fl::fatal("os_create_anonymous_file failed: %s\n", strerror(errno));
     }
-    if (size > pool_size) pool_size = 2 * size;
-    fd = os_create_anonymous_file(pool_size);
-    struct wld_shm_pool_data *pool_data = (struct wld_shm_pool_data*)
-        calloc(1, sizeof(struct wld_shm_pool_data));
-    pool_data->pool_memory = (char*)mmap(NULL, pool_size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+    pool_data = (struct wld_shm_pool_data*)calloc(1, sizeof(struct wld_shm_pool_data));
+    pool_data->pool_memory = (char*)mmap(NULL, pool_size, PROT_READ | PROT_WRITE,
+                                         MAP_SHARED, fd, 0);
     if (pool_data->pool_memory == MAP_FAILED) {
       close(fd);
       Fl::fatal("mmap failed: %s\n", strerror(errno));
     }
     Fl_Wayland_Screen_Driver *scr_driver = (Fl_Wayland_Screen_Driver*)Fl::screen_driver();
     pool = wl_shm_create_pool(scr_driver->wl_shm, fd, pool_size);
+    close(fd); // does not prevent the mmap'ed memory from being used
+//puts("wl_shm_create_pool");
     pool_data->pool_size = pool_size;
+    wl_list_init(&pool_data->buffers);
     wl_shm_pool_set_user_data(pool, pool_data);
   }
   buffer = (struct fl_wld_buffer*)calloc(1, sizeof(struct fl_wld_buffer));
   buffer->stride = stride;
   buffer->wl_buffer = wl_shm_pool_create_buffer(pool, chunk_offset, width, height, stride, Fl_Wayland_Graphics_Driver::wld_format);
-  struct wld_shm_pool_data *pool_data =
-    (struct wld_shm_pool_data *)wl_shm_pool_get_user_data(pool);
-  pool_data->use_count++;
-  wl_buffer_set_user_data(buffer->wl_buffer, pool_data);
+  // add this buffer to head of list of current pool's buffers
+  wl_list_insert(&pool_data->buffers, &buffer->link);
+  buffer->shm_pool = pool;
   buffer->data = (void*)(pool_data->pool_memory + chunk_offset);
-  chunk_offset += size;
+//fprintf(stderr, "last=%p chunk_offset=%d ", pool_data->buffers.next, chunk_offset);
   buffer->data_size = size;
   buffer->width = width;
   buffer->draw_buffer = new uchar[buffer->data_size];
@@ -174,15 +177,20 @@ void Fl_Wayland_Graphics_Driver::buffer_release(struct wld_window *window)
 {
   if (window->buffer) {
     if (window->buffer->cb) wl_callback_destroy(window->buffer->cb);
+    struct wl_shm_pool *my_pool = window->buffer->shm_pool;
     struct wld_shm_pool_data *pool_data =
-      (struct wld_shm_pool_data *)wl_buffer_get_user_data(window->buffer->wl_buffer);
+      (struct wld_shm_pool_data*)wl_shm_pool_get_user_data(my_pool);
     wl_buffer_destroy(window->buffer->wl_buffer);
 //printf("wl_buffer_destroy(%p)\n",window->buffer->wl_buffer);
-    pool_data->use_count--;
-    if (pool_data->destroyed && pool_data->use_count == 0) {
-      /*int err =*/ munmap(pool_data->pool_memory, pool_data->pool_size);
+    // remove fl_wld_buffer from list of pool's buffers
+    wl_list_remove(&window->buffer->link);
+//printf("last=%p\n", wl_list_empty(&pool_data->buffers) ? NULL : pool_data->buffers.next);
+    if (wl_list_empty(&pool_data->buffers)) { // all buffers from pool are gone
+      wl_shm_pool_destroy(my_pool);
+      /*int err = */munmap(pool_data->pool_memory, pool_data->pool_size);
 //printf("munmap(%p)->%d\n", pool_data->pool_memory, err);
       free(pool_data);
+      if (my_pool == pool) pool = NULL;
     }
     delete[] window->buffer->draw_buffer;
     window->buffer->draw_buffer = NULL;