[vlc-devel] [PATCH 02/17] video_output: translate the mouse coordinates to display coordinates early

[Steve Lhomme]

It seems the issue is that code in macosx.m

     @synchronized(self) {
         _hasPendingReshape = NO;
     }

It might use an atomic bool for this variable. Using less locks is 
always a good idea when possible. I don't know if/how Objective-C can 
handle atomics.

On the other hand the original patch is not mandatory and doesn't 
improve anything much. So if necessary I'm OK with reverting it.

On 2020-10-31 17:49, Zhao Zhili wrote:
> Hi Steve,
> 
>> On Sep 14, 2020, at 10:03 PM, Steve Lhomme <robux4 at ycbcr.xyz> wrote:
>>
>> We can do this in the UI thread, the processing is light.
>> Locking the display_lock doesn't have a big impact on lag as it's only taking
>> time when reloading a display module, which is very rare.
>> ---
>> src/video_output/video_output.c | 21 ++++++++++++---------
>> 1 file changed, 12 insertions(+), 9 deletions(-)
>>
>> diff --git a/src/video_output/video_output.c b/src/video_output/video_output.c
>> index cbc66b9dbc0..ed1e3bfcb07 100644
>> --- a/src/video_output/video_output.c
>> +++ b/src/video_output/video_output.c
>> @@ -389,7 +389,14 @@ void vout_MouseState(vout_thread_t *vout, const vlc_mouse_t *mouse)
>>      assert(mouse);
>>      vout_control_cmd_t cmd;
>>      vout_control_cmd_Init(&cmd, VOUT_CONTROL_MOUSE_STATE);
>> -    cmd.mouse = *mouse;
>> +
>> +    /* Translate window coordinates to video coordinates */
>> +    vlc_mutex_lock(&sys->display_lock);
> 
> This change leads to a deadlock on macOS.
> 
> * thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
>    * frame #0: 0x00007fff6dcdd882 libsystem_kernel.dylib`__psynch_cvwait + 10
>      frame #1: 0x00007fff6dd9e425 libsystem_pthread.dylib`_pthread_cond_wait + 698
>      frame #2: 0x000000010023d27c libvlccore.dylib`vlc_atomic_wait(addr=0x000000010ef31ff0, value=2) at wait.c:84:9
>      frame #3: 0x0000000100226d4e libvlccore.dylib`vlc_mutex_lock(mtx=0x000000010ef31ff0) at threads.c:175:9
>      frame #4: 0x00000001001eb968 libvlccore.dylib`vout_MouseState(vout=0x000000010ef31d50, mouse=0x000000010ed8e4a8) at video_output.c:389:5
>      frame #5: 0x00000001002005f4 libvlccore.dylib`vout_display_window_MouseEvent(window=0x000000010ed8e370, ev=0x00007ffeefbfdd80) at window.c:321:5
>      frame #6: 0x0000000107fc11b9 libvout_macosx_plugin.dylib`vout_window_SendMouseEvent(window=0x000000010ed8e370, mouse=0x00007ffeefbfdd80) at vlc_vout_window.h:595:9
>      frame #7: 0x0000000107fc1239 libvout_macosx_plugin.dylib`vout_window_ReportMouseMoved(window=0x000000010ed8e370, x=2038, y=943) at vlc_vout_window.h:614:5
>      frame #8: 0x0000000107fc05b8 libvout_macosx_plugin.dylib`vout_display_SendMouseMovedDisplayCoordinates(vd=0x0000000110911340, m_x=2038, m_y=943) at vlc_vout_display.h:467:5
>      frame #9: 0x0000000107fc0507 libvout_macosx_plugin.dylib`-[VLCOpenGLVideoView mouseMoved:](self=0x0000000110911da0, _cmd="mouseMoved:", o_event=0x0000000100676520) at macosx.m:778:17
> 
> 
>    thread #42
>      frame #0: 0x00007fff6dcdc55e libsystem_kernel.dylib`__ulock_wait + 10
>      frame #1: 0x00007fff6dd909c3 libsystem_platform.dylib`_os_unfair_lock_lock_slow + 160
>      frame #2: 0x00007fff6c9e8dc7 libobjc.A.dylib`objc_sync_enter + 27
>      frame #3: 0x0000000107fbf4e4 libvout_macosx_plugin.dylib`-[VLCOpenGLVideoView setVoutFlushing:](self=0x0000000110911da0, _cmd="setVoutFlushing:", flushing=YES) at macosx.m:550:5
>      frame #4: 0x0000000107fc0cf0 libvout_macosx_plugin.dylib`PictureDisplay(vd=0x0000000110911340, pic=0x000000010ae1d640) at macosx.m:331:5
>      frame #5: 0x00000001001f2b09 libvlccore.dylib`vout_display_Display(vd=0x0000000110911340, picture=0x000000010ae1d640) at vlc_vout_display.h:431:9
>      frame #6: 0x00000001001f2127 libvlccore.dylib`ThreadDisplayRenderPicture(vout=0x000000010ef31d50, render_now=false) at video_output.c:1446:5
>      frame #7: 0x00000001001edf69 libvlccore.dylib`ThreadDisplayPicture(vout=0x000000010ef31d50, deadline=0x00007000061d6fa0) at video_output.c:1572:15
>      frame #8: 0x00000001001f0409 libvlccore.dylib`Thread(object=0x000000010ef31d50) at video_output.c:1914:16
>      frame #9: 0x00007fff6dd9e109 libsystem_pthread.dylib`_pthread_start + 148
>      frame #10: 0x00007fff6dd99b8b libsystem_pthread.dylib`thread_start + 15
> 
> 
> 
>> +    if (sys->display)
>> +        vout_display_TranslateMouseState(sys->display, &cmd.mouse, mouse);
>> +    else
>> +        cmd.mouse = *mouse;
>> +    vlc_mutex_unlock(&sys->display_lock);
>>
>>      vout_control_Push(&sys->control, &cmd);
>> }
>> @@ -1678,17 +1685,13 @@ void vout_ChangeSpuRate(vout_thread_t *vout, size_t channel_id, float rate)
>> static void ThreadProcessMouseState(vout_thread_sys_t *p_vout,
>>                                      const vlc_mouse_t *win_mouse)
>> {
>> -    vlc_mouse_t vid_mouse, tmp1, tmp2, *m;
>> +    vlc_mouse_t tmp1, tmp2;
>> +    const vlc_mouse_t *m;
>>      vout_thread_t *vout = &p_vout->obj;
>>      vout_thread_sys_t *sys = p_vout;
>>
>> -    /* Translate window coordinates to video coordinates */
>> -    vlc_mutex_lock(&sys->display_lock);
>> -    vout_display_TranslateMouseState(sys->display, &vid_mouse, win_mouse);
>> -    vlc_mutex_unlock(&sys->display_lock);
>> -
>> -    /* Then pass up the filter chains. */
>> -    m = &vid_mouse;
>> +    /* pass mouse coordinates in the filter chains. */
>> +    m = win_mouse;
>>      vlc_mutex_lock(&sys->filter.lock);
>>      if (sys->filter.chain_static && sys->filter.chain_interactive) {
>>          if (!filter_chain_MouseFilter(sys->filter.chain_interactive,
>> -- 
>> 2.26.2
>>
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