[vlc-devel] [PATCH 1/2] vout: add a resize acknowledgement callback
remi at remlab.net
remi at remlab.net
Tue Feb 9 17:04:42 UTC 2021
From: Rémi Denis-Courmont <remi at remlab.net>
For perfect rendering synchronisation, the change of window size must
be acknowledged after the last picture is rendered in the old size,
and before the first picture is rendered in the new size.
As of c9d6d95f291b1e2c0e4f374f87790af091282c1e, the window resize is
processed synchronously. This provides for the "after" requirement. But
it failed to address the "before" requirement: the video output thread
can end render a picture so soon after the resize so the window
callback thread has not had time to perform acknowledgement procedures.
This adds a callback to the window resize event which is called before
the display lock (or equivalent) is released. This is guaranteed to be
invoked before the video output thread has the opportunity to render
anything.
Other options were considered:
1) Invoking a callback to the window provider from the video output
thread code code.
-> This can delay the callback unreasonably.
-> Taking the window lock on the video output thread is undesirable
if at all possible.
2) Invoking a windowing system type-specific callback to the window
provider from every display of that windowing system.
-> Same delay and locking problems as 1.
-> Requires patching several display plugins.
3) Exposing the display lock to the window plugin, via new callbacks.
-> This leaks internal implementation of the core to window
providers.
-> This gets really confusing as some callbacks would need explicit
locking and others not.
In comparison, this patch seems like the least of evils.
The callback is passed a parameter rather than as a property of the
window to distinguish it from the existing window callbacks which are
not reentrant.
Refs #25112.
---
include/vlc_vout_window.h | 7 +++++--
modules/video_output/splitter.c | 6 +++++-
src/video_output/opengl.c | 6 +++++-
src/video_output/video_output.c | 6 +++++-
src/video_output/vout_internal.h | 3 ++-
src/video_output/window.c | 21 +++++++++++++++++++--
6 files changed, 41 insertions(+), 8 deletions(-)
diff --git a/include/vlc_vout_window.h b/include/vlc_vout_window.h
index ea16d4b414..7d0db591e5 100644
--- a/include/vlc_vout_window.h
+++ b/include/vlc_vout_window.h
@@ -173,6 +173,8 @@ typedef struct vout_window_cfg_t {
} vout_window_cfg_t;
+typedef void (*vout_window_ack_cb)(struct vout_window_t *, void *);
+
/**
* Window event callbacks structure.
*
@@ -200,7 +202,8 @@ struct vout_window_callbacks {
* of external events from the windowing system, or deferred processing of
* a size change request.
*/
- void (*resized)(struct vout_window_t *, unsigned width, unsigned height);
+ void (*resized)(struct vout_window_t *, unsigned width, unsigned height,
+ vout_window_ack_cb cb, void *opaque);
/**
* Callback for window closing.
@@ -543,7 +546,7 @@ void vout_window_Disable(vout_window_t *window);
static inline void vout_window_ReportSize(vout_window_t *window,
unsigned width, unsigned height)
{
- window->owner.cbs->resized(window, width, height);
+ window->owner.cbs->resized(window, width, height, NULL, NULL);
}
/**
diff --git a/modules/video_output/splitter.c b/modules/video_output/splitter.c
index 6ca82e34c1..9a2a1544e7 100644
--- a/modules/video_output/splitter.c
+++ b/modules/video_output/splitter.c
@@ -135,7 +135,8 @@ static void vlc_vidsplit_Close(vout_display_t *vd)
}
static void vlc_vidsplit_window_Resized(vout_window_t *wnd,
- unsigned width, unsigned height)
+ unsigned width, unsigned height,
+ vout_window_ack_cb cb, void *opaque)
{
struct vlc_vidsplit_part *part = wnd->owner.sys;
@@ -145,6 +146,9 @@ static void vlc_vidsplit_window_Resized(vout_window_t *wnd,
if (part->display != NULL)
vout_display_SetSize(part->display, width, height);
+
+ if (cb != NULL)
+ cb(wnd, opaque);
vlc_sem_post(&part->lock);
}
diff --git a/src/video_output/opengl.c b/src/video_output/opengl.c
index 8355c16135..bb10ca6302 100644
--- a/src/video_output/opengl.c
+++ b/src/video_output/opengl.c
@@ -124,7 +124,8 @@ typedef struct vlc_gl_surface
} vlc_gl_surface_t;
static void vlc_gl_surface_ResizeNotify(vout_window_t *surface,
- unsigned width, unsigned height)
+ unsigned width, unsigned height,
+ vout_window_ack_cb cb, void *opaque)
{
vlc_gl_surface_t *sys = surface->owner.sys;
@@ -133,6 +134,9 @@ static void vlc_gl_surface_ResizeNotify(vout_window_t *surface,
vlc_mutex_lock(&sys->lock);
sys->width = width;
sys->height = height;
+
+ if (cb != NULL)
+ cb(surface, opaque);
vlc_mutex_unlock(&sys->lock);
}
diff --git a/src/video_output/video_output.c b/src/video_output/video_output.c
index d04d3f4d11..fb7f54e385 100644
--- a/src/video_output/video_output.c
+++ b/src/video_output/video_output.c
@@ -543,7 +543,8 @@ void vout_ChangeWindowState(vout_thread_t *vout, unsigned st)
}
void vout_ChangeDisplaySize(vout_thread_t *vout,
- unsigned width, unsigned height)
+ unsigned width, unsigned height,
+ void (*cb)(void *), void *opaque)
{
vout_thread_sys_t *sys = VOUT_THREAD_TO_SYS(vout);
@@ -557,6 +558,9 @@ void vout_ChangeDisplaySize(vout_thread_t *vout,
if (sys->display != NULL)
vout_display_SetSize(sys->display, width, height);
+
+ if (cb != NULL)
+ cb(opaque);
vlc_mutex_unlock(&sys->display_lock);
}
diff --git a/src/video_output/vout_internal.h b/src/video_output/vout_internal.h
index fb24b51ee8..95274f2409 100644
--- a/src/video_output/vout_internal.h
+++ b/src/video_output/vout_internal.h
@@ -150,7 +150,8 @@ bool GetAspectRatio(const char *ar_str, unsigned *num, unsigned *den);
void vout_ChangeFullscreen(vout_thread_t *, const char *id);
void vout_ChangeWindowed(vout_thread_t *);
void vout_ChangeWindowState(vout_thread_t *, unsigned state);
-void vout_ChangeDisplaySize(vout_thread_t *, unsigned width, unsigned height);
+void vout_ChangeDisplaySize(vout_thread_t *, unsigned width, unsigned height,
+ void (*ack_cb)(void *), void *opaque);
void vout_ChangeDisplayFilled(vout_thread_t *, bool is_filled);
void vout_ChangeZoom(vout_thread_t *, unsigned num, unsigned den);
void vout_ChangeDisplayAspectRatio(vout_thread_t *, unsigned num, unsigned den);
diff --git a/src/video_output/window.c b/src/video_output/window.c
index 9c2df5c1e6..c866fe7af4 100644
--- a/src/video_output/window.c
+++ b/src/video_output/window.c
@@ -198,6 +198,20 @@ void vout_window_ReportFullscreen(vout_window_t *window, const char *id)
window->owner.cbs->fullscreened(window, id);
}
+struct vout_window_ack_data {
+ vout_window_t *window;
+ vout_window_ack_cb callback;
+ void *opaque;
+};
+
+static void vout_window_Ack(void *data)
+{
+ struct vout_window_ack_data *cb_data = data;
+
+ if (cb_data->callback != NULL)
+ cb_data->callback(cb_data->window, cb_data->opaque);
+}
+
/* Video output display integration */
#include <vlc_vout.h>
#include <vlc_vout_display.h>
@@ -214,13 +228,16 @@ typedef struct vout_display_window
} vout_display_window_t;
static void vout_display_window_ResizeNotify(vout_window_t *window,
- unsigned width, unsigned height)
+ unsigned width, unsigned height,
+ vout_window_ack_cb cb,
+ void *opaque)
{
vout_display_window_t *state = window->owner.sys;
vout_thread_t *vout = state->vout;
+ struct vout_window_ack_data data = { window, cb, opaque };
msg_Dbg(window, "resized to %ux%u", width, height);
- vout_ChangeDisplaySize(vout, width, height);
+ vout_ChangeDisplaySize(vout, width, height, vout_window_Ack, &data);
}
static void vout_display_window_CloseNotify(vout_window_t *window)
--
2.30.0
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