Implement libfonts_calculate_subpixel_order

Signed-off-by: Mattias Andrée <maandree@kth.se>

3 files changed, 63 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index 28289b7..2ea54db 100644
--- a/Makefile
+++ b/Makefile
@@ -16,7 +16,8 @@ LIB_VERSION = $(LIB_MAJOR).$(LIB_MINOR)
 LIB_NAME = fonts
 
 
-OBJ =
+OBJ =\
+	libfonts_calculate_subpixel_order.o
 
 HDR =\
 	libfonts.h
diff --git a/libfonts.h b/libfonts.h
index 211e391..6a988a5 100644
--- a/libfonts.h
+++ b/libfonts.h
@@ -20,7 +20,7 @@ enum libfonts_subpixel_order {
 
 	/* For any value V, a rotation of 90⋅R degrees, R integer,
 	 * clockwise, of the physical output, will yeild a subpixel
-	 * order represented with the value (V + R) Mod 4 + ⌊V / 4⌋,
+	 * order represented with the value (V + R) Mod 4 + 4⋅⌊V / 4⌋,
 	 * if V ≥ 4, otherwise V asis. A rotation that is not
 	 * divisible by 90 degrees, will yeild the subpixel order
 	 * LIBFONTS_SUBPIXEL_ORDER_NONLINEAR if V is greater or equal
diff --git a/libfonts_calculate_subpixel_order.c b/libfonts_calculate_subpixel_order.c
new file mode 100644
index 0000000..6d26921
--- /dev/null
+++ b/libfonts_calculate_subpixel_order.c
@@ -0,0 +1,60 @@
+/* See LICENSE file for copyright and license details. */
+#include "libfonts.h"
+
+
+enum libfonts_subpixel_order
+libfonts_calculate_subpixel_order(enum libfonts_subpixel_order unrotated, enum libfonts_orientation rotation)
+{
+	int rot;
+
+	switch (rotation) {
+	case LIBFONTS_ORIENTATION_UNKNOWN:
+	default:
+		switch (unrotated) {
+		case LIBFONTS_SUBPIXEL_ORDER_UNKNOWN:
+		case LIBFONTS_SUBPIXEL_ORDER_NONRGB:
+		case LIBFONTS_SUBPIXEL_ORDER_NONLINEAR:
+		case LIBFONTS_SUBPIXEL_ORDER_OTHER:
+			return unrotated;
+		default:
+			return LIBFONTS_SUBPIXEL_ORDER_UNKNOWN;
+		}
+		break;
+
+	case LIBFONTS_ORIENTATION_0_DEGREES_CLOCKWISE:
+		return unrotated;
+
+	case LIBFONTS_ORIENTATION_90_DEGREES_CLOCKWISE:
+		rot = 1;
+		break;
+
+	case LIBFONTS_ORIENTATION_180_DEGREES_CLOCKWISE:
+		rot = 2;
+		break;
+
+	case LIBFONTS_ORIENTATION_270_DEGREES_CLOCKWISE:
+		rot = 3;
+		break;
+
+	case LIBFONTS_ORIENTATION_OTHER:
+		switch (unrotated) {
+		case LIBFONTS_SUBPIXEL_ORDER_UNKNOWN:
+		case LIBFONTS_SUBPIXEL_ORDER_NONRGB:
+		case LIBFONTS_SUBPIXEL_ORDER_NONLINEAR:
+			return unrotated;
+		default:
+			return LIBFONTS_SUBPIXEL_ORDER_NONLINEAR;
+		}
+		break;
+	}
+
+	switch (unrotated) {
+	case LIBFONTS_SUBPIXEL_ORDER_UNKNOWN:
+	case LIBFONTS_SUBPIXEL_ORDER_NONRGB:
+	case LIBFONTS_SUBPIXEL_ORDER_NONLINEAR:
+	case LIBFONTS_SUBPIXEL_ORDER_OTHER:
+		return unrotated;
+	default:
+		return ((unrotated + rot) & 3) + (unrotated & ~3);
+	}
+}