C# Stroke.UpdatedRanges方法代码示例

		// 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;
//.........这里部分代码省略.........

		public List<CGRect> DirtyRects (Stroke stroke)
		{
			var result = new List<CGRect> ();
			foreach (var range in stroke.UpdatedRanges ()) {
				var lowerBound = range.LowerBound;
				if (lowerBound > 0)
					lowerBound -= 1;

				var les = lastEstimatedSample;
				if (les != null) {
					if (les.Index < lowerBound)
						lowerBound = les.Index;
				}

				var samples = stroke.Samples;

				var upperBound = range.UpperBound;
				if (upperBound < samples.Count)
					upperBound += 1;

				var dirtyRect = DirtyRectForSampleStride (stroke.Samples.Skip (lowerBound).Take (upperBound - lowerBound));
				result.Add (dirtyRect);
			}

			var predictedSamples = stroke.PredictedSamples;
			if (predictedSamples != null && stroke.PredictedSamples.Count > 0) {
				var dirtyRect = DirtyRectForSampleStride (stroke.PredictedSamples);
				result.Add (dirtyRect);
			}

			var previousPredictedSamples = stroke.PreviousPredictedSamples;
			if (previousPredictedSamples != null && previousPredictedSamples.Count > 0) {
				var dirtyRect = DirtyRectForSampleStride (previousPredictedSamples);
				result.Add (dirtyRect);
			}

			return result;
		}