[Drawing API] Add ModifyCTM (Matrix m) to Xwt.Drawing.Context API

This provides the link between the Matrix transforms facilities and Drawing.Contexts
An sample of using this for specialised transforms has been added to DrawingTransforms.cs
and unit tests hve been aded to Testing/Tests/TransformTests.cs

1 files changed, 87 insertions, 13 deletions

diff --git a/Testing/Tests/TransformTests.cs b/Testing/Tests/TransformTests.cs
index 54b06616..b2243b93 100644
--- a/Testing/Tests/TransformTests.cs
+++ b/Testing/Tests/TransformTests.cs
@@ -41,6 +41,9 @@ namespace Xwt
 	[TestFixture]
 	public class TransformTests
 	{
+		// There is only a single context used in all tests,
+		// so it MUST be Saved and Restored for each test.
+
 		const double DELTA = 0.000000001d;
 
 		ImageBuilder ib = null;
@@ -49,8 +52,11 @@ namespace Xwt
 		[TestFixtureSetUp]
 		public void Init ()
 		{
-			ib = new ImageBuilder (10, 10);
+			ib = new ImageBuilder (1, 1);
 			context = ib.Context;
+			Matrix m1 = Matrix.Identity;
+			Matrix m2 = context.GetCTM ();
+			CheckMatrix (m1, m2);
 		}
 
 		[TestFixtureTearDown]
@@ -58,12 +64,11 @@ namespace Xwt
 		{
 			if (context != null)
 				context.Dispose ();
-
 			if (ib != null)
 				ib.Dispose ();
 		}
 
-		private Context NewContext {
+		private Context Context {
 			get { return context; }
 		}
 
@@ -77,19 +82,14 @@ namespace Xwt
 			Assert.AreEqual (expected.OffsetY, actual.OffsetY, DELTA);
 		}
 
-		[Test]
-		public void NewCTM ()
-		{
-			Matrix mI = Matrix.Identity;
-			Context ctx = NewContext;
-			CheckMatrix (mI, ctx.GetCTM ());
-		}
+
 
 		[Test]
 		public void Translate ()
 		{
 			Matrix m1, m2;
-			Context ctx = NewContext;
+			Context ctx = Context;
+			ctx.Save ();
 
 			// Check with a range of -ve and +ve offsets
 			for (double tx = -1; tx <= 1; tx += 0.25) {
@@ -110,13 +110,15 @@ namespace Xwt
 				CheckMatrix (m1, m2);
 				ctx.Restore ();
 			}
+			ctx.Restore ();
 		}
 
 		[Test]
 		public void Scale ()
 		{
 			Matrix m1, m2;
-			Context ctx = NewContext;
+			Context ctx = Context;
+			ctx.Save ();
 
 			// Scaling with a zero scale-factor results in a non-invertible matrix
 			// This fails with Cairo, so avoid zero as one of the test values
@@ -138,13 +140,15 @@ namespace Xwt
 				CheckMatrix (m1, m2);
 				ctx.Restore ();
 			}
+			ctx.Restore ();
 		}
 
 		[Test]
 		public void Rotate ()
 		{
 			Matrix m1, m2;
-			Context ctx = NewContext;
+			Context ctx = Context;
+			ctx.Save ();
 
 			for (double theta = 0; theta <= 360; theta += 30) {
 				ctx.Save ();
@@ -155,6 +159,76 @@ namespace Xwt
 				CheckMatrix (m1, m2);
 				ctx.Restore ();
 			}
+			ctx.Restore ();
+		}
+
+		[Test]
+		public void RotateAndTranslate ()
+		{
+			// Transforms are Prepended to the CTM, so they are done in reverse order.
+			// At present, this must be stated explicitly in the Matrix calls, but may
+			// be worth changing so that Prepend is the default (to match the Backends).
+
+			Matrix m1, m2;
+			Context ctx = Context;
+			ctx.Save ();
+
+			for (double theta = 30; theta <= 360; theta += 30) {
+				ctx.Save ();
+				ctx.Translate (100, 0);		// done last
+				ctx.Rotate (theta);			// done first (about the origin)
+
+				m1 = Matrix.Identity;
+				m1.TranslatePrepend (100, 0);
+				m1.RotatePrepend (theta);
+				m2 = ctx.GetCTM ();
+
+				CheckMatrix (m1, m2);
+				ctx.Restore ();
+			}
+			ctx.Restore ();
+		}
+
+		[Test]
+		public void ModifyCTM ()
+		{
+			// Checks that Matrix and Context transforms match, and that applying
+			// a matrix transform to the Context CTM produces the expected result
+
+			double theta = 30;
+			double x = 50;
+			double y = 30;
+
+			Context ctx = Context;
+			ctx.Save ();
+
+			Matrix m1 = Matrix.Identity;
+			Matrix ctm;
+
+			// Apply and compare several transforms
+			ctx.Save ();
+			ctx.Scale (2, 3);
+			m1.ScalePrepend (2, 3);
+			ctm = ctx.GetCTM ();
+			CheckMatrix (m1, ctm);
+
+			ctx.Translate (x, y);
+			m1.TranslatePrepend (x, y);
+			ctm = ctx.GetCTM ();
+			CheckMatrix (m1, ctm);
+
+			ctx.Rotate (theta);
+			m1.RotatePrepend (theta);
+			ctm = ctx.GetCTM ();
+			CheckMatrix (m1, ctm);
+
+			// Check ModifyCTM matches combined Matrix Transform
+			ctx.Restore ();
+			ctx.ModifyCTM (m1);
+			ctm = ctx.GetCTM ();
+			CheckMatrix (m1, ctm);
+
+			ctx.Restore ();
 		}
 
 	}