// Note: this is not a particularily efficient way to draw a great stroke path
// with CoreGraphics.It is just a way to produce an interesting looking result.
// For a real world example you would reuse and cache CGPaths and draw longer
// paths instead of an aweful lot of tiny ones, etc.You would also respect the
// draw rect to cull your draw requests.And you would use bezier paths to
// interpolate between the points to get a smooother curve.
void Draw (Stroke stroke)
{
var updateRanges = stroke.UpdatedRanges ();
if (DisplayOptions == StrokeViewDisplayOptions.Debug) {
for (int index = 0; index < DirtyRectViews.Count; index++) {
var dirtyRectView = DirtyRectViews [index];
dirtyRectView.Alpha = 0;
if (index < updateRanges.Length) {
dirtyRectView.Alpha = 1;
var range = updateRanges [index];
var strokes = stroke.Samples.Skip (range.LowerBound)
.Take (range.UpperBound - range.LowerBound + 1);
dirtyRectView.Frame = DirtyRectForSampleStride (strokes);
}
}
}
lastEstimatedSample = null;
stroke.ClearUpdateInfo ();
var sampleCount = stroke.Samples.Count;
if (sampleCount <= 0)
return;
var context = UIGraphics.GetCurrentContext ();
if (context == null)
return;
var strokeColor = UIColor.Black;
Action lineSettings;
Action forceEstimatedLineSettings;
if (displayOptions == StrokeViewDisplayOptions.Debug) {
lineSettings = () => {
context.SetLineWidth (0.5f);
context.SetStrokeColor (UIColor.White.CGColor);
};
forceEstimatedLineSettings = () => {
context.SetLineWidth (0.5f);
context.SetStrokeColor (UIColor.Blue.CGColor);
};
} else {
lineSettings = () => {
context.SetLineWidth (0.25f);
context.SetStrokeColor (strokeColor.CGColor);
};
forceEstimatedLineSettings = lineSettings;
}
Action azimuthSettings = () => {
context.SetLineWidth (1.5f);
context.SetStrokeColor (UIColor.Orange.CGColor);
};
Action altitudeSettings = () => {
context.SetLineWidth (0.5f);
context.SetStrokeColor (strokeColor.CGColor);
};
var forceMultiplier = 2f;
var forceOffset = 0.1f;
var fillColorRegular = UIColor.Black.CGColor;
var fillColorCoalesced = UIColor.LightGray.CGColor;
var fillColorPredicted = UIColor.Red.CGColor;
CGVector? lockedAzimuthUnitVector = null;
var azimuthLockAltitudeThreshold = NMath.PI / 2 * 0.8f; // locking azimuth at 80% altitude
lineSettings ();
Func<StrokeSample, nfloat> forceAccessBlock = sample => {
return sample.ForceWithDefault ();
};
if (DisplayOptions == StrokeViewDisplayOptions.Ink) {
forceAccessBlock = sample => {
return sample.PerpendicularForce ();
};
}
// Make the force influence less pronounced for the calligraphy pen.
if (DisplayOptions == StrokeViewDisplayOptions.Calligraphy) {
var prevGetter = forceAccessBlock;
forceAccessBlock = sample => {
return NMath.Max (prevGetter (sample), 1);
};
// make force value less pronounced
forceMultiplier = 1;
forceOffset = 10;
}
var previousGetter = forceAccessBlock;
forceAccessBlock = sample => {
return previousGetter (sample) * forceMultiplier + forceOffset;
};
StrokeSample heldFromSample = null;
CGVector? heldFromSampleUnitVector = null;
Action<StrokeSegment> draw = segment => {
var toSample = segment.ToSample;
if (toSample != null) {
StrokeSample fromSample = heldFromSample ?? segment.FromSample;
// Skip line segments that are too short.
var dist = Vector (fromSample.Location, toSample.Location).Quadrance ();
if (dist < 0.003f) {
if (heldFromSample == null) {
heldFromSample = fromSample;
heldFromSampleUnitVector = segment.FromSampleUnitNormal;
}
return;
}
if (toSample.Predicted) {
if (displayOptions == StrokeViewDisplayOptions.Debug)
context.SetFillColor (fillColorPredicted);
} else {
bool coalesced = displayOptions == StrokeViewDisplayOptions.Debug && fromSample.Coalesced;
context.SetFillColor (coalesced ? fillColorCoalesced : fillColorRegular);
}
if (displayOptions == StrokeViewDisplayOptions.Calligraphy) {
var fromAzimuthUnitVector = Stroke.CalligraphyFallbackAzimuthUnitVector;
var toAzimuthUnitVector = Stroke.CalligraphyFallbackAzimuthUnitVector;
if (fromSample.Azimuth.HasValue) {
if (!lockedAzimuthUnitVector.HasValue)
lockedAzimuthUnitVector = fromSample.GetAzimuthUnitVector ();
fromAzimuthUnitVector = fromSample.GetAzimuthUnitVector ();
toAzimuthUnitVector = toSample.GetAzimuthUnitVector ();
if (fromSample.Altitude.Value > azimuthLockAltitudeThreshold)
fromAzimuthUnitVector = lockedAzimuthUnitVector.Value;
if (toSample.Altitude.Value > azimuthLockAltitudeThreshold)
toAzimuthUnitVector = lockedAzimuthUnitVector.Value;
else
lockedAzimuthUnitVector = toAzimuthUnitVector;
}
// Rotate 90 degrees
var calligraphyTransform = CGAffineTransform.MakeRotation (NMath.PI / 2);
fromAzimuthUnitVector = fromAzimuthUnitVector.Apply (calligraphyTransform);
toAzimuthUnitVector = toAzimuthUnitVector.Apply (calligraphyTransform);
var fromUnitVector = fromAzimuthUnitVector.Mult (forceAccessBlock (fromSample));
var toUnitVector = toAzimuthUnitVector.Mult (forceAccessBlock (toSample));
context.BeginPath ();
context.Move (fromSample.Location.Add (fromUnitVector));
context.AddLine (toSample.Location.Add (toUnitVector));
context.AddLine (toSample.Location.Sub (toUnitVector));
context.AddLine (fromSample.Location.Sub (fromUnitVector));
context.ClosePath ();
context.DrawPath (CGPathDrawingMode.FillStroke);
} else {
var fromUnitVector = (heldFromSampleUnitVector.HasValue ? heldFromSampleUnitVector.Value : segment.FromSampleUnitNormal).Mult (forceAccessBlock (fromSample));
var toUnitVector = segment.ToSampleUnitNormal.Mult (forceAccessBlock (toSample));
var isForceEstimated = fromSample.EstimatedProperties.HasFlag (UITouchProperties.Force)
|| toSample.EstimatedProperties.HasFlag (UITouchProperties.Force);
if (isForceEstimated) {
if (lastEstimatedSample == null)
lastEstimatedSample = new EstimatedSample { Index = segment.FromSampleIndex + 1, Sample = toSample };
forceEstimatedLineSettings ();
} else {
lineSettings ();
}
context.BeginPath ();
context.Move (fromSample.Location.Add (fromUnitVector));
context.AddLine (toSample.Location.Add (toUnitVector));
context.AddLine (toSample.Location.Sub (toUnitVector));
context.AddLine (fromSample.Location.Sub (fromUnitVector));
context.ClosePath ();
context.DrawPath (CGPathDrawingMode.FillStroke);
}
var isEstimated = fromSample.EstimatedProperties.HasFlag (UITouchProperties.Azimuth);
if (fromSample.Azimuth.HasValue && (!fromSample.Coalesced || isEstimated) && !fromSample.Predicted && displayOptions == StrokeViewDisplayOptions.Debug) {
var length = 20f;
var azimuthUnitVector = fromSample.GetAzimuthUnitVector ();
var azimuthTarget = fromSample.Location.Add (azimuthUnitVector.Mult (length));
var altitudeStart = azimuthTarget.Add (azimuthUnitVector.Mult (length / -2));
var altitudeTarget = altitudeStart.Add ((azimuthUnitVector.Mult (length / 2)).Apply (CGAffineTransform.MakeRotation (fromSample.Altitude.Value)));
// Draw altitude as black line coming from the center of the azimuth.
altitudeSettings ();
context.BeginPath ();
context.Move (altitudeStart);
context.AddLine (altitudeTarget);
context.StrokePath ();
// Draw azimuth as orange (or blue if estimated) line.
azimuthSettings ();
if (isEstimated)
context.SetStrokeColor (UIColor.Blue.CGColor);
context.BeginPath ();
context.Move (fromSample.Location);
context.AddLine (azimuthTarget);
context.StrokePath ();
}
heldFromSample = null;
heldFromSampleUnitVector = null;
}
};
if (stroke.Samples.Count == 1) {
// Construct a face segment to draw for a stroke that is only one point.
var sample = stroke.Samples [0];
var tempSampleFrom = new StrokeSample {
Timestamp = sample.Timestamp,
Location = sample.Location.Add (new CGVector (-0.5f, 0)),
Coalesced = false,
Predicted = false,
Force = sample.Force,
Azimuth = sample.Azimuth,
Altitude = sample.Altitude,
EstimatedProperties = sample.EstimatedProperties
};
var tempSampleTo = new StrokeSample {
Timestamp = sample.Timestamp,
Location = sample.Location.Add (new CGVector (0.5f, 0)),
Coalesced = false,
Predicted = false,
Force = sample.Force,
Azimuth = sample.Azimuth,
Altitude = sample.Altitude,
EstimatedProperties = sample.EstimatedProperties
};
var segment = new StrokeSegment (tempSampleFrom);
segment.AdvanceWithSample (tempSampleTo);
segment.AdvanceWithSample (null);
draw (segment);
} else {
foreach (var segment in stroke)
draw (segment);
}
}
// Note: this is not a particularily efficient way to draw a great stroke path
// with CoreGraphics.It is just a way to produce an interesting looking result.
// For a real world example you would reuse and cache CGPaths and draw longer
// paths instead of an aweful lot of tiny ones, etc.You would also respect the
// draw rect to cull your draw requests.And you would use bezier paths to
// interpolate between the points to get a smooother curve.
void Draw(Stroke stroke)
{
var updateRanges = stroke.UpdatedRanges();
if (DisplayOptions == StrokeViewDisplayOptions.Debug)
{
for (int index = 0; index < DirtyRectViews.Count; index++)
{
var dirtyRectView = DirtyRectViews [index];
dirtyRectView.Alpha = 0;
if (index < updateRanges.Length)
{
dirtyRectView.Alpha = 1;
var range = updateRanges [index];
var strokes = stroke.Samples.Skip(range.LowerBound)
.Take(range.UpperBound - range.LowerBound + 1);
dirtyRectView.Frame = DirtyRectForSampleStride(strokes);
}
}
}
lastEstimatedSample = null;
stroke.ClearUpdateInfo();
var sampleCount = stroke.Samples.Count;
if (sampleCount <= 0)
{
return;
}
var context = UIGraphics.GetCurrentContext();
if (context == null)
{
return;
}
var strokeColor = UIColor.Black;
Action lineSettings;
Action forceEstimatedLineSettings;
if (displayOptions == StrokeViewDisplayOptions.Debug)
{
lineSettings = () => {
context.SetLineWidth(0.5f);
context.SetStrokeColor(UIColor.White.CGColor);
};
forceEstimatedLineSettings = () => {
context.SetLineWidth(0.5f);
context.SetStrokeColor(UIColor.Blue.CGColor);
};
}
else
{
lineSettings = () => {
context.SetLineWidth(0.25f);
context.SetStrokeColor(strokeColor.CGColor);
};
forceEstimatedLineSettings = lineSettings;
}
Action azimuthSettings = () => {
context.SetLineWidth(1.5f);
context.SetStrokeColor(UIColor.Orange.CGColor);
};
Action altitudeSettings = () => {
context.SetLineWidth(0.5f);
context.SetStrokeColor(strokeColor.CGColor);
};
var forceMultiplier = 2f;
var forceOffset = 0.1f;
var fillColorRegular = UIColor.Black.CGColor;
var fillColorCoalesced = UIColor.LightGray.CGColor;
var fillColorPredicted = UIColor.Red.CGColor;
CGVector?lockedAzimuthUnitVector = null;
var azimuthLockAltitudeThreshold = NMath.PI / 2 * 0.8f; // locking azimuth at 80% altitude
lineSettings();
Func <StrokeSample, nfloat> forceAccessBlock = sample => {
return(sample.ForceWithDefault());
};
if (DisplayOptions == StrokeViewDisplayOptions.Ink)
{
forceAccessBlock = sample => {
return(sample.PerpendicularForce());
};
}
// Make the force influence less pronounced for the calligraphy pen.
if (DisplayOptions == StrokeViewDisplayOptions.Calligraphy)
{
var prevGetter = forceAccessBlock;
forceAccessBlock = sample => {
return(NMath.Max(prevGetter(sample), 1));
};
// make force value less pronounced
forceMultiplier = 1;
forceOffset = 10;
}
var previousGetter = forceAccessBlock;
forceAccessBlock = sample => {
return(previousGetter(sample) * forceMultiplier + forceOffset);
};
StrokeSample heldFromSample = null;
CGVector? heldFromSampleUnitVector = null;
Action <StrokeSegment> draw = segment => {
var toSample = segment.ToSample;
if (toSample != null)
{
StrokeSample fromSample = heldFromSample ?? segment.FromSample;
// Skip line segments that are too short.
var dist = Vector(fromSample.Location, toSample.Location).Quadrance();
if (dist < 0.003f)
{
if (heldFromSample == null)
{
heldFromSample = fromSample;
heldFromSampleUnitVector = segment.FromSampleUnitNormal;
}
return;
}
if (toSample.Predicted)
{
if (displayOptions == StrokeViewDisplayOptions.Debug)
{
context.SetFillColor(fillColorPredicted);
}
}
else
{
bool coalesced = displayOptions == StrokeViewDisplayOptions.Debug && fromSample.Coalesced;
context.SetFillColor(coalesced ? fillColorCoalesced : fillColorRegular);
}
if (displayOptions == StrokeViewDisplayOptions.Calligraphy)
{
var fromAzimuthUnitVector = Stroke.CalligraphyFallbackAzimuthUnitVector;
var toAzimuthUnitVector = Stroke.CalligraphyFallbackAzimuthUnitVector;
if (fromSample.Azimuth.HasValue)
{
if (!lockedAzimuthUnitVector.HasValue)
{
lockedAzimuthUnitVector = fromSample.GetAzimuthUnitVector();
}
fromAzimuthUnitVector = fromSample.GetAzimuthUnitVector();
toAzimuthUnitVector = toSample.GetAzimuthUnitVector();
if (fromSample.Altitude.Value > azimuthLockAltitudeThreshold)
{
fromAzimuthUnitVector = lockedAzimuthUnitVector.Value;
}
if (toSample.Altitude.Value > azimuthLockAltitudeThreshold)
{
toAzimuthUnitVector = lockedAzimuthUnitVector.Value;
}
else
{
lockedAzimuthUnitVector = toAzimuthUnitVector;
}
}
// Rotate 90 degrees
var calligraphyTransform = CGAffineTransform.MakeRotation(NMath.PI / 2);
fromAzimuthUnitVector = fromAzimuthUnitVector.Apply(calligraphyTransform);
toAzimuthUnitVector = toAzimuthUnitVector.Apply(calligraphyTransform);
var fromUnitVector = fromAzimuthUnitVector.Mult(forceAccessBlock(fromSample));
var toUnitVector = toAzimuthUnitVector.Mult(forceAccessBlock(toSample));
context.BeginPath();
context.Move(fromSample.Location.Add(fromUnitVector));
context.AddLine(toSample.Location.Add(toUnitVector));
context.AddLine(toSample.Location.Sub(toUnitVector));
context.AddLine(fromSample.Location.Sub(fromUnitVector));
context.ClosePath();
context.DrawPath(CGPathDrawingMode.FillStroke);
}
else
{
var fromUnitVector = (heldFromSampleUnitVector.HasValue ? heldFromSampleUnitVector.Value : segment.FromSampleUnitNormal).Mult(forceAccessBlock(fromSample));
var toUnitVector = segment.ToSampleUnitNormal.Mult(forceAccessBlock(toSample));
var isForceEstimated = fromSample.EstimatedProperties.HasFlag(UITouchProperties.Force) ||
toSample.EstimatedProperties.HasFlag(UITouchProperties.Force);
if (isForceEstimated)
{
if (lastEstimatedSample == null)
{
lastEstimatedSample = new EstimatedSample {
Index = segment.FromSampleIndex + 1, Sample = toSample
}
}
;
forceEstimatedLineSettings();
}
else
{
lineSettings();
}
context.BeginPath();
context.Move(fromSample.Location.Add(fromUnitVector));
context.AddLine(toSample.Location.Add(toUnitVector));
context.AddLine(toSample.Location.Sub(toUnitVector));
context.AddLine(fromSample.Location.Sub(fromUnitVector));
context.ClosePath();
context.DrawPath(CGPathDrawingMode.FillStroke);
}
var isEstimated = fromSample.EstimatedProperties.HasFlag(UITouchProperties.Azimuth);
if (fromSample.Azimuth.HasValue && (!fromSample.Coalesced || isEstimated) && !fromSample.Predicted && displayOptions == StrokeViewDisplayOptions.Debug)
{
var length = 20f;
var azimuthUnitVector = fromSample.GetAzimuthUnitVector();
var azimuthTarget = fromSample.Location.Add(azimuthUnitVector.Mult(length));
var altitudeStart = azimuthTarget.Add(azimuthUnitVector.Mult(length / -2));
var altitudeTarget = altitudeStart.Add((azimuthUnitVector.Mult(length / 2)).Apply(CGAffineTransform.MakeRotation(fromSample.Altitude.Value)));
// Draw altitude as black line coming from the center of the azimuth.
altitudeSettings();
context.BeginPath();
context.Move(altitudeStart);
context.AddLine(altitudeTarget);
context.StrokePath();
// Draw azimuth as orange (or blue if estimated) line.
azimuthSettings();
if (isEstimated)
{
context.SetStrokeColor(UIColor.Blue.CGColor);
}
context.BeginPath();
context.Move(fromSample.Location);
context.AddLine(azimuthTarget);
context.StrokePath();
}
heldFromSample = null;
heldFromSampleUnitVector = null;
}
};
if (stroke.Samples.Count == 1)
{
// Construct a face segment to draw for a stroke that is only one point.
var sample = stroke.Samples [0];
var tempSampleFrom = new StrokeSample {
Timestamp = sample.Timestamp,
Location = sample.Location.Add(new CGVector(-0.5f, 0)),
Coalesced = false,
Predicted = false,
Force = sample.Force,
Azimuth = sample.Azimuth,
Altitude = sample.Altitude,
EstimatedProperties = sample.EstimatedProperties
};
var tempSampleTo = new StrokeSample {
Timestamp = sample.Timestamp,
Location = sample.Location.Add(new CGVector(0.5f, 0)),
Coalesced = false,
Predicted = false,
Force = sample.Force,
Azimuth = sample.Azimuth,
Altitude = sample.Altitude,
EstimatedProperties = sample.EstimatedProperties
};
var segment = new StrokeSegment(tempSampleFrom);
segment.AdvanceWithSample(tempSampleTo);
segment.AdvanceWithSample(null);
draw(segment);
}
else
{
foreach (var segment in stroke)
{
draw(segment);
}
}
}
