1 files changed, 49 insertions, 9 deletions

diff --git a/excanvas.js b/excanvas.js
index 73963d8..367764b 100644
--- a/excanvas.js
+++ b/excanvas.js
@@ -797,6 +797,33 @@ if (!document.createElement('canvas').getContext) {
     this.m_ = this.mStack_.pop();
   };
 
+  function matrixIsFinite(m) {
+    for (var j = 0; j < 3; j++) {
+      for (var k = 0; k < 2; k++) {
+        if (!isFinite(m[j][k]) || isNaN(m[j][k])) {
+          return false;
+        }
+      }
+    }
+    return true;
+  }
+
+  function setM(ctx, m, updateLineScale) {
+    if (!matrixIsFinite(m)) {
+      return;
+    }
+    ctx.m_ = m;
+
+    if (updateLineScale) {
+      // Get the line scale.
+      // Determinant of this.m_ means how much the area is enlarged by the
+      // transformation. So its square root can be used as a scale factor
+      // for width.
+      var det = m[0][0] * m[1][1] - m[0][1] * m[1][0];
+      ctx.lineScale_ = sqrt(abs(det));
+    }
+  }
+
   contextPrototype.translate = function(aX, aY) {
     var m1 = [
       [1,  0,  0],
@@ -804,7 +831,7 @@ if (!document.createElement('canvas').getContext) {
       [aX, aY, 1]
     ];
 
-    this.m_ = matrixMultiply(m1, this.m_);
+    setM(this, matrixMultiply(m1, this.m_), false);
   };
 
   contextPrototype.rotate = function(aRot) {
@@ -817,7 +844,7 @@ if (!document.createElement('canvas').getContext) {
       [0,  0, 1]
     ];
 
-    this.m_ = matrixMultiply(m1, this.m_);
+    setM(this, matrixMultiply(m1, this.m_), false);
   };
 
   contextPrototype.scale = function(aX, aY) {
@@ -829,14 +856,27 @@ if (!document.createElement('canvas').getContext) {
       [0,  0,  1]
     ];
 
-    var m = this.m_ = matrixMultiply(m1, this.m_);
+    setM(this, matrixMultiply(m1, this.m_), true);
+  };
+
+  contextPrototype.transform = function(m11, m12, m21, m22, dx, dy) {
+    var m1 = [
+      [m11, m12, 0],
+      [m21, m22, 0],
+      [dx,  dy,  1]
+    ];
+
+    setM(this, matrixMultiply(m1, this.m_), true);
+  };
+
+  contextPrototype.setTransform = function(m11, m12, m21, m22, dx, dy) {
+    var m = [
+      [m11, m12, 0],
+      [m21, m22, 0],
+      [dx,  dy,  1]
+    ];
 
-    // Get the line scale.
-    // Determinant of this.m_ means how much the area is enlarged by the
-    // transformation. So its square root can be used as a scale factor
-    // for width.
-    var det = m[0][0] * m[1][1] - m[0][1] * m[1][0];
-    this.lineScale_ = sqrt(abs(det));
+    setM(this, m, true);
   };
 
   /******** STUBS ********/