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Profile: attempt on better zoom and pan logic

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QGraphicsView::AnchorUnderMouse does not work for
Qt 4.8.1 on Ubuntu 12.04 and if the mouseMoveEvent
overload is disabled it practically can be seen that
the anchor point is [0, 0] instead of the mouse location.

After a suggestion found on the web this patch attempts
to use the hidden scroll bars to calculate reposition
on pan and zoom *near the mouse cursor.

On the other hand QAbstactSlider (QScrollBar) class
strangly uses negative offsets for minimum scroll
position, which makes the implementation even more
ugly.

[*near] because it's not that accurate!

Signed-off-by: Lubomir I. Ivanov <neolit123@gmail.com>
Signed-off-by: Dirk Hohndel <dirk@hohndel.org>
This commit is contained in:
Lubomir I. Ivanov 2013-07-04 23:55:27 +03:00 • committed by Dirk Hohndel
parent 1257adfd26
commit c7f8ada4ff
2 changed files with 25 additions and 5 deletions
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29
qt-ui/profilegraphics.cpp
View file

@ -6,6 +6,7 @@
#include <QGraphicsScene>
#include <QResizeEvent>
#include <QGraphicsLineItem>
#include <QScrollBar>
#include <QPen>
#include <QBrush>
#include <QDebug>
@ -67,12 +68,32 @@ ProfileGraphicsView::ProfileGraphicsView(QWidget* parent) : QGraphicsView(parent
}
/* since we cannot use translate() directly on the scene we hack on
* the scroll bars (hidden) functionality */
void ProfileGraphicsView::scrollViewTo(const QPoint pos)
{
if (!zoomLevel)
return;
QScrollBar *vs = verticalScrollBar();
QScrollBar *hs = horizontalScrollBar();
const qreal yRat = pos.y() / sceneRect().height();
const qreal xRat = pos.x() / sceneRect().width();
const int vMax = vs->maximum();
const int hMax = hs->maximum();
const int vMin = vs->minimum();
const int hMin = hs->minimum();
/* QScrollBar receives crazy negative values for minimum */
vs->setValue(yRat * (vMax - vMin) + vMin * 0.9);
hs->setValue(xRat * (hMax - hMin) + hMin * 0.9);
}
void ProfileGraphicsView::wheelEvent(QWheelEvent* event)
{
if (!toolTip)
return;
setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
// doesn't seem to work for Qt 4.8.1
// setTransformationAnchor(QGraphicsView::AnchorUnderMouse);
// Scale the view / do the zoom
QPoint toolTipPos = mapFromScene(toolTip->pos());
@ -86,6 +107,7 @@ void ProfileGraphicsView::wheelEvent(QWheelEvent* event)
scale(1.0 / scaleFactor, 1.0 / scaleFactor);
zoomLevel--;
}
scrollViewTo(event->pos());
toolTip->setPos(mapToScene(toolTipPos).x(), mapToScene(toolTipPos).y());
}
@ -98,10 +120,7 @@ void ProfileGraphicsView::mouseMoveEvent(QMouseEvent* event)
QPoint toolTipPos = mapFromScene(toolTip->pos());
double dx = sceneRect().x();
double dy = sceneRect().y();
ensureVisible(event->pos().x() + dx, event->pos().y() + dy, 1, 1);
scrollViewTo(event->pos());
if (zoomLevel == 0)
QGraphicsView::mouseMoveEvent(event);

1
qt-ui/profilegraphics.h
View file

@ -124,6 +124,7 @@ private:
void plot_depth_scale();
QColor get_sac_color(int sac, int avg_sac);
void scrollViewTo(const QPoint pos);
QPen defaultPen;
QBrush defaultBrush;