From b947448795d604f169246b0c3191028ae6a0ab83 Mon Sep 17 00:00:00 2001
From: Daniel Eklöf <daniel@ekloef.se>
Date: Sat, 1 Aug 2020 15:32:48 +0200
Subject: Initial commit
Can display a single PNG image scaled-to-fit on all outputs.
---
shm.c | 192 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 192 insertions(+)
create mode 100644 shm.c
(limited to 'shm.c')
diff --git a/shm.c b/shm.c
new file mode 100644
index 0000000..0fff7b0
--- /dev/null
+++ b/shm.c
@@ -0,0 +1,192 @@
+#include "shm.h"
+
+#include <unistd.h>
+#include <assert.h>
+
+#include <sys/types.h>
+#include <sys/mman.h>
+#include <linux/memfd.h>
+
+#include <tllist.h>
+
+#define LOG_MODULE "shm"
+#include "log.h"
+#include "stride.h"
+
+static tll(struct buffer) buffers;
+
+static void
+buffer_destroy(struct buffer *buf)
+{
+ pixman_image_unref(buf->pix);
+ wl_buffer_destroy(buf->wl_buf);
+ munmap(buf->mmapped, buf->size);
+}
+
+static void
+buffer_release(void *data, struct wl_buffer *wl_buffer)
+{
+ //printf("buffer release\n");
+ struct buffer *buffer = data;
+ assert(buffer->wl_buf == wl_buffer);
+ assert(buffer->busy);
+ buffer->busy = false;
+}
+
+static const struct wl_buffer_listener buffer_listener = {
+ .release = &buffer_release,
+};
+
+struct buffer *
+shm_get_buffer(struct wl_shm *shm, int width, int height, unsigned long cookie)
+{
+ /* Purge buffers marked for purging */
+ tll_foreach(buffers, it) {
+ if (it->item.cookie != cookie)
+ continue;
+
+ if (!it->item.purge)
+ continue;
+
+ assert(!it->item.busy);
+
+ LOG_DBG("cookie=%lx: purging buffer %p (width=%d, height=%d): %zu KB",
+ cookie, &it->item, it->item.width, it->item.height,
+ it->item.size / 1024);
+
+ buffer_destroy(&it->item);
+ tll_remove(buffers, it);
+ }
+
+ tll_foreach(buffers, it) {
+ if (!it->item.busy &&
+ it->item.width == width &&
+ it->item.height == height &&
+ it->item.cookie == cookie)
+ {
+ it->item.busy = true;
+ it->item.purge = false;
+ return &it->item;
+ }
+ }
+
+ /* Purge old buffers associated with this cookie */
+ tll_foreach(buffers, it) {
+ if (it->item.cookie != cookie)
+ continue;
+
+ if (it->item.busy)
+ continue;
+
+ if (it->item.width == width && it->item.height == height)
+ continue;
+
+ LOG_DBG("cookie=%lx: marking buffer %p for purging", cookie, &it->item);
+ it->item.purge = true;
+ }
+
+ /*
+ * No existing buffer available. Create a new one by:
+ *
+ * 1. open a memory backed "file" with memfd_create()
+ * 2. mmap() the memory file, to be used by the pixman image
+ * 3. create a wayland shm buffer for the same memory file
+ *
+ * The pixman image and the wayland buffer are now sharing memory.
+ */
+
+ int pool_fd = -1;
+ void *mmapped = NULL;
+ size_t size = 0;
+
+ struct wl_shm_pool *pool = NULL;
+ struct wl_buffer *buf = NULL;
+ pixman_image_t *pix = NULL;
+
+ /* Backing memory for SHM */
+ pool_fd = memfd_create("fuzzel-wayland-shm-buffer-pool", MFD_CLOEXEC);
+ if (pool_fd == -1) {
+ LOG_ERRNO("failed to create SHM backing memory file");
+ goto err;
+ }
+
+ /* Total size */
+ const uint32_t stride = stride_for_format_and_width(PIXMAN_a8r8g8b8, width);
+ size = stride * height;
+ if (ftruncate(pool_fd, size) == -1) {
+ LOG_ERRNO("failed to truncate SHM pool");
+ goto err;
+ }
+
+ mmapped = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, pool_fd, 0);
+ if (mmapped == MAP_FAILED) {
+ LOG_ERR("failed to mmap SHM backing memory file");
+ goto err;
+ }
+
+ pool = wl_shm_create_pool(shm, pool_fd, size);
+ if (pool == NULL) {
+ LOG_ERR("failed to create SHM pool");
+ goto err;
+ }
+
+ buf = wl_shm_pool_create_buffer(
+ pool, 0, width, height, stride, WL_SHM_FORMAT_ARGB8888);
+ if (buf == NULL) {
+ LOG_ERR("failed to create SHM buffer");
+ goto err;
+ }
+
+ /* We use the entire pool for our single buffer */
+ wl_shm_pool_destroy(pool); pool = NULL;
+ close(pool_fd); pool_fd = -1;
+
+ pix = pixman_image_create_bits_no_clear(
+ PIXMAN_a8r8g8b8, width, height, mmapped, stride);
+ if (pix == NULL) {
+ LOG_ERR("failed to create pixman image");
+ goto err;
+ }
+
+ /* Push to list of available buffers, but marked as 'busy' */
+ tll_push_back(
+ buffers,
+ ((struct buffer){
+ .width = width,
+ .height = height,
+ .stride = stride,
+ .cookie = cookie,
+ .busy = true,
+ .size = size,
+ .mmapped = mmapped,
+ .wl_buf = buf,
+ .pix = pix,
+ })
+ );
+
+ struct buffer *ret = &tll_back(buffers);
+ wl_buffer_add_listener(ret->wl_buf, &buffer_listener, ret);
+ return ret;
+
+err:
+ if (pix != NULL)
+ pixman_image_unref(pix);
+ if (buf != NULL)
+ wl_buffer_destroy(buf);
+ if (pool != NULL)
+ wl_shm_pool_destroy(pool);
+ if (pool_fd != -1)
+ close(pool_fd);
+ if (mmapped != NULL)
+ munmap(mmapped, size);
+
+ return NULL;
+}
+
+void
+shm_fini(void)
+{
+ tll_foreach(buffers, it)
+ buffer_destroy(&it->item);
+ tll_free(buffers);
+}
--
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