Stacking subsurface siblings
Jonas Ådahl
jadahl at gmail.com
Tue Jun 16 08:47:03 PDT 2015
On Tue, Jun 16, 2015 at 04:46:55PM +0200, Arnaud Vrac wrote:
> Hi,
>
> I'm wondering if a behaviour of weston related to subsurfaces is either a
> bug or intended. The protocol description is not clear on what happens in
> the following cases:
>
> Suppose I have a shell surface (BLUE) and two subsurfaces (RED, GREEN). I
> want to stack them to I get RED, GREEN, BLUE from bottom to top.
>
> If I do:
>
> wl_subsurface_place_below(GREEN->subsurface, BLUE->surface);
> wl_subsurface_place_below(RED->subsurface, GREEN->surface);
>
> It works, but if I do:
>
> wl_subsurface_place_below(RED->subsurface, GREEN->surface);
> wl_subsurface_place_below(GREEN->subsurface, BLUE->surface);
>
> The order is GREEN, RED, BLUE instead.
>
> Logically the sibling relative order should be kept in the second case, but
> it's not. The protocol is not clear on what should happen, what is the
> expected result ?
The protocol says "This sub-surface is taken from the stack, and put
back just above the reference surface, changing the z-order of the
sub-surfaces." Considering this, if you first placed a surface below
another, placing again, that relationship may have been broken by the
new operation. In other words, the "tree" is not moved, just the
subsurface you placed.
Jonas
>
> I have attached a small sample to test easily.
>
> --
> Arnaud
> #include <stdio.h>
> #include <stdlib.h>
> #include <stdint.h>
> #include <stdarg.h>
> #include <string.h>
> #include <assert.h>
> #include <unistd.h>
> #include <fcntl.h>
> #include <sys/mman.h>
>
> #include <wayland-client.h>
> #include <wayland-util.h>
>
> struct surface {
> struct context *context;
> struct wl_surface *surface;
> struct wl_subsurface *subsurface;
> struct wl_shell_surface *shell_surface;
> struct wl_buffer *buffer;
>
> int width;
> int height;
> int stride;
> int fd;
> uint32_t *data;
> uint32_t color;
>
> struct surface *parent;
> };
>
> struct context {
> struct wl_display *display;
> struct wl_registry *registry;
> struct wl_compositor *compositor;
> struct wl_subcompositor *subcompositor;
> struct wl_shell *shell;
> struct wl_shm *shm;
> };
>
> static void
> die(const char *fmt, ...)
> {
> va_list ap;
>
> va_start(ap, fmt);
> vfprintf(stderr, fmt, ap);
> fprintf(stderr, "\n");
> va_end(ap);
> exit(EXIT_FAILURE);
> }
>
> static int
> surface_alloc_data(struct surface *surface)
> {
> char filename[] = "/tmp/wayland-shm-XXXXXX";
> uint32_t *data;
> int stride;
> int size;
> int fd;
> int i;
>
> fd = mkstemp(filename);
> if (fd < 0)
> die("failed to create file for SHM buffer: %m");
>
> unlink(filename);
>
> stride = surface->width * 4;
> size = surface->height * stride;
>
> if (fallocate(fd, 0, 0, size) < 0)
> die("failed to allocate %d bytes for SHM buffer: %m", size);
>
> data = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
> if (data == MAP_FAILED)
> die("failed to map SHM buffer data: %m");
>
> for (i = 0; i < surface->width * surface->height; i++)
> data[i] = surface->color;
>
> surface->fd = fd;
> surface->data = data;
> surface->stride = stride;
>
> return 0;
> }
>
> static struct surface *
> surface_create(struct context *context, struct surface *parent,
> int width, int height, int x, int y, uint32_t color)
> {
> struct surface *surface;
> struct wl_shm_pool *pool;
>
> surface = calloc(1, sizeof *surface);
> if (!surface)
> return NULL;
>
> surface->fd = -1;
> surface->context = context;
> surface->width = width;
> surface->height = height;
> surface->color = color;
> surface->parent = parent;
>
> if (surface_alloc_data(surface)) {
> free(surface);
> return NULL;
> }
>
> pool = wl_shm_create_pool(context->shm, surface->fd,
> surface->stride * surface->height);
>
> surface->buffer = wl_shm_pool_create_buffer(pool, 0,
> surface->width,
> surface->height,
> surface->stride,
> WL_SHM_FORMAT_ARGB8888);
>
> wl_shm_pool_destroy(pool);
>
> surface->surface = wl_compositor_create_surface(context->compositor);
> if (surface->parent) {
> surface->subsurface = wl_subcompositor_get_subsurface(
> context->subcompositor, surface->surface,
> parent->surface);
>
> wl_subsurface_set_position(surface->subsurface, x, y);
> wl_subsurface_set_desync(surface->subsurface);
> } else {
> surface->shell_surface =
> wl_shell_get_shell_surface(context->shell,
> surface->surface);
> wl_shell_surface_set_toplevel(surface->shell_surface);
> }
>
> wl_surface_attach(surface->surface, surface->buffer, 0, 0);
> wl_surface_damage(surface->surface, 0, 0,
> surface->width, surface->height);
> wl_surface_commit(surface->surface);
>
> return surface;
> }
>
> static void
> registry_handle_global(void *data, struct wl_registry *registry,
> uint32_t id, const char *interface, uint32_t version)
> {
> struct context *ctx = data;
>
> if (!strcmp(interface, "wl_compositor")) {
> ctx->compositor =
> wl_registry_bind(registry, id,
> &wl_compositor_interface, 1);
> } else if (!strcmp(interface, "wl_subcompositor")) {
> ctx->subcompositor =
> wl_registry_bind(registry, id,
> &wl_subcompositor_interface, 1);
> } else if (!strcmp(interface, "wl_shell")) {
> ctx->shell =
> wl_registry_bind(registry, id, &wl_shell_interface, 1);
> } else if (!strcmp(interface, "wl_shm")) {
> ctx->shm = wl_registry_bind(registry, id, &wl_shm_interface, 1);
> }
> }
>
> static void
> registry_handle_global_remove(void *data, struct wl_registry *registry,
> uint32_t id)
> {
> }
>
> static const struct wl_registry_listener registry_listener = {
> registry_handle_global,
> registry_handle_global_remove
> };
>
> enum {
> RED,
> GREEN,
> BLUE,
> COUNT
> };
>
> static struct context *
> context_init(void)
> {
> struct context *ctx;
> struct surface *surf[COUNT];
>
> ctx = calloc(1, sizeof (*ctx));
> ctx->display = wl_display_connect(NULL);
> if (!ctx->display)
> die("failed to init wayland display");
>
> ctx->registry = wl_display_get_registry(ctx->display);
> wl_registry_add_listener(ctx->registry, ®istry_listener, ctx);
> wl_display_roundtrip(ctx->display);
>
> assert(ctx->compositor != NULL);
> assert(ctx->subcompositor != NULL);
> assert(ctx->shell != NULL);
>
> surf[BLUE] = surface_create(ctx, NULL, 100, 100, 0, 0, 0xff0000ff);
> if (!surf[BLUE])
> die("failed to create root surface");
>
> surf[RED] = surface_create(ctx, surf[BLUE], 100, 100, -100, -100,
> 0xffff0000);
>
> surf[GREEN] = surface_create(ctx, surf[BLUE], 100, 100, -50, -50,
> 0xff00ff00);
>
> #if 0
> wl_subsurface_place_below(surf[GREEN]->subsurface, surf[BLUE]->surface);
> wl_subsurface_place_below(surf[RED]->subsurface, surf[GREEN]->surface);
> #else
> wl_subsurface_place_below(surf[RED]->subsurface, surf[GREEN]->surface);
> wl_subsurface_place_below(surf[GREEN]->subsurface, surf[BLUE]->surface);
> #endif
>
> wl_surface_commit(surf[BLUE]->surface);
>
> return ctx;
> }
>
> static void
> context_destroy(struct context *ctx)
> {
> wl_display_disconnect(ctx->display);
>
> free(ctx);
> }
>
> static void
> seed(void)
> {
> int fd = open("/dev/urandom", O_RDONLY);
> unsigned int s;
>
> if (fd < 0)
> return;
>
> read(fd, &s, sizeof (s));
> srand(s);
> close(fd);
> }
>
> int main(int argc, char *argv[])
> {
> struct context *ctx;
>
> seed();
>
> ctx = context_init();
>
> while (wl_display_dispatch(ctx->display) >= 0)
> ;
>
> context_destroy(ctx);
>
> return 0;
> }
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