Lottie: Animation Segment(Marker) Support

[hermet]

The concept of using markers in Lottie animations is known, where markers are used to control animation playback by specifying start and end points without needing to know the exact frame numbers.

Sample:
marker.json

API usage:

lottie->load("sample.json");

lottie->segment("sectionA") ;                    //specify the SectionA marked by Lottie spec.
auto frame = lottie->frameCnt();   //returns the "SectionA" frame count
auto duration = lottie->duration();  //returns the SectionA duration in seconds
...

lottie->segment(begin: 0.3, end: 0.7);        //specify the segment 0.3 ~ 0.7 ?
auto frame = lottie->frameCnt();       //returns the 0.3 ~ 0.7 frame count
auto duration = lottie->duration();    //returns the 0.3 ~ 0.7 duration in seconds
...

[hermet]

Acquire Marker List

uint32_t LottieAnimation::markerCnt();  //return the marker count
const char* LottieAnimation::markers(uint32_t idx); //return the marker name by a given index.

[fall2019]

Okay. I will add it.

[hermet]

@theashraf Hello, Could you please confirm whether those following APIs would be satisfied with the dotLottie?

Result LottieAnimation::segment(const char* marker) ;  //specify the SectionA marked by Lottie spec.
uint32_t LottieAnimation::markerCnt();  //return the marker count
const char* LottieAnimation::markers(uint32_t idx); //return the marker name by a given index.

Result LottieAnimation::segment(float begin, float end) ;  //Perhaps, this is not necessary by dotlottie?

Please suggest any missing features if dotlottie requires.

[theashraf]

@hermet

This would replace our current segment and marker management within the dotLottie player.

I believe these two APIs will be useful for dotLottie players:

Result LottieAnimation::segment(const char* marker);  // Specifies SectionA as marked by the Lottie specification.
Result LottieAnimation::segment(float begin, float end);  // Perhaps this is not necessary for dotLottie?

And I assume these two APIs are for retrieving all the markers available in a Lottie animation:

uint32_t LottieAnimation::markerCnt();  // Returns the count of markers.
const char* LottieAnimation::markers(uint32_t idx); // Returns the name of a marker by a given index.

I have two questions:

• Is there a way to determine the beginning and ending frame number of a given marker ? cause we have a use case where the user want to know the segment value for UI purposes

• Would applying a segment or a marker update the animation total_frames and duration information we get from tvg_get_total_frames and tvg_get_duration apis ?

[hermet]

@theashraf

• Is there a way to determine the beginning and ending frame number of a given marker ? cause we have a use case where the user want to know the segment value for UI purposes

Makes sense. Probably, thorvg could provide an extra api:

//Return the begin, end values of the given marker.
Result LottieAnimation::segment(const char* marker, float* begin, float* end)

• Would applying a segment or a marker update the animation total_frames and duration information we get from tvg_get_total_frames and tvg_get_duration apis ?

Yes.

I anticipate that dotLottie will replace the segment with the marker name. Could you please clarify in what scenarios dotLottie requires the use of this API?

Result LottieAnimation::segment(float begin, float end);  //Set the segment with a specific range.

[theashraf]

@hermet

In dotLottie, we offer support for both named segments (Markers) and standard segments. So, the following API would be beneficial:

Result LottieAnimation::segment(float begin, float end);

This is useful in scenarios where users want to specify a custom segment for playback that does not have an associated named marker within the Lottie JSON