tests: add CGLayer tests

Tests/opal/CGLayer/layer.m

@@ -0,0 +1,53 @@
+/* CGLayer size and context, and compositing a layer drawn green into a
+   destination context.  Expected values checked against Apple CoreGraphics. */
+#include "Testing.h"
+
+#include <CoreGraphics/CGLayer.h>
+#include <CoreGraphics/CGContext.h>
+#include <CoreGraphics/CGBitmapContext.h>
+#include <CoreGraphics/CGImage.h>
+#include <CoreGraphics/CGColorSpace.h>
+#include <CoreGraphics/CGColor.h>
+#include <math.h>
+#include <stdlib.h>
+
+int main(void)
+{
+  CGColorSpaceRef dev = CGColorSpaceCreateDeviceRGB();
+  unsigned char *dest = calloc(10 * 10 * 4, 1);
+  CGContextRef dctx = CGBitmapContextCreate(dest, 10, 10, 8, 40, dev,
+    kCGImageAlphaPremultipliedLast);
+
+  START_SET("CGLayer")
+
+  CGLayerRef layer = CGLayerCreateWithContext(dctx, CGSizeMake(4, 4), NULL);
+  PASS(layer != NULL, "creating a layer returns a layer");
+  CGSize sz = CGLayerGetSize(layer);
+  PASS(sz.width == 4 && sz.height == 4, "the layer reports its size");
+  PASS(CGLayerGetContext(layer) != NULL, "the layer has a drawing context");
+
+  /* Draw green into the layer, then composite it into the destination. */
+  CGContextRef lctx = CGLayerGetContext(layer);
+  CGFloat green[] = {0, 1, 0, 1};
+  CGColorRef gc = CGColorCreate(dev, green);
+  CGContextSetFillColorWithColor(lctx, gc);
+  CGContextFillRect(lctx, CGRectMake(0, 0, 4, 4));
+
+  CGContextDrawLayerAtPoint(dctx, CGPointMake(2, 2), layer);
+  unsigned char *d = (unsigned char *)CGBitmapContextGetData(dctx);
+  int in = (4 * 10 + 4) * 4, out = 0;
+  PASS(d[in] == 0 && d[in+1] == 255 && d[in+2] == 0 && d[in+3] == 255,
+       "a pixel where the layer was composited is the layer's colour");
+  PASS(d[out] == 0 && d[out+1] == 0 && d[out+2] == 0 && d[out+3] == 0,
+       "a pixel outside the composited layer is untouched");
+
+  CGColorRelease(gc);
+  CGLayerRelease(layer);
+
+  END_SET("CGLayer")
+
+  CGContextRelease(dctx);
+  CGColorSpaceRelease(dev);
+  free(dest);
+  return 0;
+}