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lottie: support for firstMargin < 0 in text follow path

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The first margin value shifts the starting point where the text
begins along the path. Now cases where firstMargin < 0 are handled,
for both closed and open paths.
This commit is contained in:
Mira Grudzinska 2025-04-09 23:05:31 +02:00 • committed by Hermet Park
parent 3fbb55440a
commit 97817bedfe
1 changed files with 52 additions and 23 deletions
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75
src/loaders/lottie/tvgLottieModel.cpp
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@ -80,36 +80,47 @@ float LottieTextFollowPath::prepare(LottieMask* mask, float frameNo, float scale
Point LottieTextFollowPath::position(float lenSearched, float& angle)
{
//position before the start of the curve
if (lenSearched <= 0.0f) {
//shape is closed -> wrapping
if (path.cmds.last() == PathCommand::Close) {
while (lenSearched < 0.0f) lenSearched += totalLen;
pts = path.pts.data;
cmds = path.cmds.data;
cmdsCnt = path.cmds.count;
currentLen = 0.0f;
//linear interpolation
} else {
if (cmds >= path.cmds.data + path.cmds.count - 1) return *start;
switch (*(cmds + 1)) {
case PathCommand::LineTo: {
auto dp = *(pts + 1) - *pts;
angle = tvg::atan2(dp.y, dp.x);
return {pts->x + lenSearched * cos(angle), pts->y + lenSearched * sin(angle)};
}
case PathCommand::CubicTo: {
angle = deg2rad(Bezier{*pts, *(pts + 1), *(pts + 2), *(pts + 3)}.angle(0.0001f));
return {pts->x + lenSearched * cos(angle), pts->y + lenSearched * sin(angle)};
}
default:
angle = 0.0f;
return *start;
}
}
}
auto shift = [&]() -> void {
switch (*cmds) {
case PathCommand::MoveTo:
start = pts;
++pts;
break;
case PathCommand::LineTo:
++pts;
break;
case PathCommand::CubicTo:
pts += 3;
break;
case PathCommand::Close:
break;
case PathCommand::MoveTo: start = pts; ++pts; break;
case PathCommand::LineTo: ++pts; break;
case PathCommand::CubicTo: pts += 3; break;
case PathCommand::Close: break;
}
++cmds;
--cmdsCnt;
};
auto length = [&]() -> float {
switch (*cmds) {
case PathCommand::MoveTo: return 0.0f;
case PathCommand::LineTo: return tvg::length(pts - 1, pts);
case PathCommand::CubicTo: return Bezier{*(pts - 1), *pts, *(pts + 1), *(pts + 2)}.length();
case PathCommand::Close: return tvg::length(pts - 1, start);
}
return 0.0f;
};
//beyond the curve
//position beyond the end of the curve
if (lenSearched >= totalLen) {
//shape is closed -> wrapping
if (path.cmds.last() == PathCommand::Close) {
@ -146,6 +157,24 @@ Point LottieTextFollowPath::position(float lenSearched, float& angle)
}
}
//reset required if text partially crosses curve start
if (lenSearched < currentLen) {
pts = path.pts.data;
cmds = path.cmds.data;
cmdsCnt = path.cmds.count;
currentLen = 0.0f;
}
auto length = [&]() -> float {
switch (*cmds) {
case PathCommand::MoveTo: return 0.0f;
case PathCommand::LineTo: return tvg::length(pts - 1, pts);
case PathCommand::CubicTo: return Bezier{*(pts - 1), *pts, *(pts + 1), *(pts + 2)}.length();
case PathCommand::Close: return tvg::length(pts - 1, start);
default: return 0.0f;
}
};
while (cmdsCnt > 0) {
auto dLen = length();
if (currentLen + dLen < lenSearched) {