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mobile/profile: don't pan outside the actual profile

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When zooming and panning the profile, make sure we always show a subset
of the profile and don't end up showing the empty space outside of the
profile.

Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This commit is contained in:
Dirk Hohndel 2020-03-24 15:47:00 -07:00
parent f084852f5c
commit 577f713f1a
1 changed files with 19 additions and 0 deletions
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19
profile-widget/qmlprofile.cpp
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@ -62,6 +62,25 @@ void QMLProfile::paint(QPainter *painter)
// shift the painter (taking its existing transformation into account)
QTransform profileTransform = QTransform();
profileTransform.scale(sx, sy);
// this is a bit complex because of the interaction with the Qt widget scaling
// logic. We use the default setup where the scale happens with the center of the
// widget as transformation center.
// The QML code *should* already ensure that we don't shrink the profile, but for
// the math below to work, let's make sure
qreal profileScale = scale();
if (profileScale < 1.0) {
profileScale = 1.0;
setScale(profileScale);
}
// When zooming and panning we want to ensure that we always show a subset of the
// profile and not the "empty space" around the profile.
// a bit of math on a piece of paper shows that our offsets need to stay within +/- dx and dy
qreal dx = width() * (profileScale - 1) / (2 * dpr * profileScale);
qreal dy = height() * (profileScale - 1) / (2 * dpr * profileScale);
m_xOffset = std::max(-dx, std::min(m_xOffset, dx));
m_yOffset = std::max(-dy, std::min(m_yOffset, dy));
QTransform painterTransform = painter->transform();
painterTransform.translate(dpr * m_xOffset - painterRect.width() * magicShiftFactor, dpr * m_yOffset - painterRect.height() * magicShiftFactor);