public static double ScrollBehavior(
Rect bgRect,
double contentSize,
double viewSize,
double viewPosition,
int id, bool horizontal,
out Rect gripRect,
out bool hovered, out bool held)
{
GUIContext g = Form.current.uiContext;
//grip size
var trackSize = horizontal ? bgRect.Width : bgRect.Height;
var contentRatio = viewSize / contentSize;
var gripSize = trackSize * contentRatio;
const double minGripSize = 20.0;
if (gripSize < minGripSize)
{
gripSize = minGripSize;
}
if (gripSize > trackSize)
{
gripSize = trackSize;
}
//grip position
var viewScrollAreaSize = contentSize - viewSize;
var viewPositionRatio = viewPosition / viewScrollAreaSize;
var trackScrollAreaSize = trackSize - gripSize;
var gripPositionOnTrack = trackScrollAreaSize * viewPositionRatio;
hovered = false;
held = false;
hovered = g.IsMouseHoveringRect(bgRect);
g.KeepAliveID(id);
if (hovered)
{
g.SetHoverID(id);
if (Mouse.Instance.LeftButtonPressed) //start track
{
g.SetActiveID(id);
}
}
if (g.ActiveId == id)
{
if (Mouse.Instance.LeftButtonState == KeyState.Down)
{
var v = Mouse.Instance.MouseDelta;
var mousePositionDelta = horizontal ? v.X : v.Y;
var newGripPosition = gripPositionOnTrack + mousePositionDelta;
newGripPosition = Math.Clamp(newGripPosition, 0, trackScrollAreaSize);
var newGripPositonRatio = newGripPosition / trackScrollAreaSize;
viewPosition = newGripPositonRatio * viewScrollAreaSize;
}
else //end track
{
g.SetActiveID(0);
}
}
if (g.ActiveId == id)
{
held = true;
}
if (horizontal)
{
gripRect = new Rect(bgRect.X + gripPositionOnTrack, bgRect.Y, gripSize, bgRect.Height);
}
else
{
gripRect = new Rect(bgRect.X, bgRect.Y + gripPositionOnTrack, bgRect.Width, gripSize);
}
return(viewPosition);
}