Initial commit

Can display a single PNG image scaled-to-fit on all outputs.

1 files changed, 192 insertions, 0 deletions

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);
+}