https://bugs.freedesktop.org/show_bug.cgi?id=51358
Bug #: 51358
Summary: SVG: Add support for more slide transitions to svg
documents exported by Impress
Classification: Unclassified
Product: LibreOffice
Version: 3.7.0.0.alpha0+ Master
Platform: Other
OS/Version: All
Status: NEW
Severity: normal
Priority: medium
Component: Presentation
AssignedTo: libreoffice-bugs@lists.freedesktop.org
ReportedBy: mrcek...@gmail.com
In order to add a slide transition you need to work with the JavaScript
presentation engine:
http://cgit.freedesktop.org/libreoffice/core/tree/filter/source/svg/presentation_engine.js
Don't be scared by the fact the file is really large you need to work only on
small portions of it.
We use the barWipe slide transition for illustrating the steps to follows for
adding a slide transition:
1) Choose the slide transition from here:
http://cgit.freedesktop.org/libreoffice/core/tree/sd/xml/transitions.xml
For a visual description of the effect go here:
http://www.w3.org/TR/2005/REC-SMIL2-20050107/smil-transitions.html#TransitionEffects-Appendix
2) For a list of transition type constant look at:
http://cgit.freedesktop.org/libreoffice/core/tree/offapi/com/sun/star/animations/TransitionType.idl.
For a list of transition subtype constant look at:
http://cgit.freedesktop.org/libreoffice/core/tree/offapi/com/sun/star/animations/TransitionSubType.idl.
If not present add the constants related to the transition you want to
implement to the JavaScript engine: search for the BARWIPE_TRANSITION constant
in the JavaScript file, the list of transition types is there; then search for
DEFAULT_TRANS_SUBTYPE constant the list of transition subtypes is there.
Near to some type or subtype constant you can see a number commented out that
number is the value of the constant in the C++ file, please keep such constants
in the correct order.
You need to update aTransitionTypeInMap, aTransitionTypeOutMap,
aTransitionSubtypeInMap and aTransitionSubtypeOutMap accordingly.
3) You can get the transition parameters to be used here:
http://cgit.freedesktop.org/libreoffice/core/tree/slideshow/source/engine/transitions/transitionfactorytab.cxx
For the BARWIPE transition type with subtype LEFTTORIGHT we have:
{
// mapped to BarWipePolyPolygon:
animations::TransitionType::BARWIPE,
animations::TransitionSubType::LEFTTORIGHT, // (1)
TransitionInfo::TRANSITION_CLIP_POLYPOLYGON,
0.0, // no rotation
1.0, // no scaling
1.0, // no scaling
TransitionInfo::REVERSEMETHOD_FLIP_X,
false, // 'out' by subtraction
false // scale isotrophically to target size
},
You need to port such transition info to the JavaScript engine: search for
aTransitionInfoTable, and create the correct info entry for your transition
effect. For the barWipe transition effect we have:
aTransitionInfoTable[BARWIPE_TRANSITION][LEFTTORIGHT_TRANS_SUBTYPE] =
{
'class' : TRANSITION_CLIP_POLYPOLYGON,
'rotationAngle' : 0.0,
'scaleX' : 1.0,
'scaleY' : 1.0,
'reverseMethod' : REVERSEMETHOD_FLIP_X,
'outInvertsSweep' : false,
'scaleIsotropically' : false
};
Note that there is no need to port the first two info entries (type and
subtype).
4) Now we need to modify the createClipPolyPolygon method. First off look at
the C++ implementation here:
http://cgit.freedesktop.org/libreoffice/core/tree/slideshow/source/engine/transitions/parametricpolypolygonfactory.cxx.
Then search for the JavaScript createClipPolyPolygon function: you will find
the lines:
case BARWIPE_TRANSITION:
return new BarWipePath( 1 );
For the transition effect you want to implement you need to add the related
"case" for the transition type and if it is needed also for the transition
subtype (look at the pinWheelWipe transition case).
Now the final implementation step.
5) Create the class that implements the transition effect you have chosen.
Transition effect classes can be found here:
http://cgit.freedesktop.org/libreoffice/core/tree/slideshow/source/engine/transitions.
For instance barwipepolypolygon.hpp and barwipepolypolygon.cxx implements the
barWipe effect.
You need to port the class related to the transition effect you want to
implement to JavaScript.
For the barWipe effect the JavaScript class is named BarWipePath.
In order to create or precompute the initial base path you can utilize helper
functions such as PathTools.normalizePath and PathTools.createPathFromEllipse,
give a glance to the EllipseWipePath class.
You can read more on how slide and shape transition has been ported/implemented
here:
https://docs.google.com/document/d/1GSLPSIWRGSDTSi69dT9Te8tRyTJcAekxT7scoCoGO2M/edit?pli=1#heading=h.zak45bwtec07.
6) Now you need to create a presentation with Impress that utilizes the
transition effect you have ported. Please be sure that the presentation has at
least 2 slides or the JavaScript engine will not be embedded into the exported
svg document. Open the exported svg document with a browser and look how it
works. Maybe you'll need to install some debug tool. For instance for Firefox
there is the Firebug extension.
For a working example you can look at:
http://users.freedesktop.org/~thorsten/gsoc-2012/slide_transitions-week3/
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