Add support for character transformation

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

3 files changed, 50 insertions, 16 deletions

diff --git a/demo.c b/demo.c
index 60ba4bb..a4d998c 100644
--- a/demo.c
+++ b/demo.c
@@ -23,6 +23,12 @@ main(void)
 		perror("libskrift_open_font_file");
 		return -1;
 	}
+	rendering.char_transformation[0] = 1;
+	rendering.char_transformation[1] = 0.25;
+	rendering.char_transformation[2] = 0;
+	rendering.char_transformation[3] = 0;
+	rendering.char_transformation[4] = 1;
+	rendering.char_transformation[5] = 0;
 	height = libskrift_points_to_pixels(72, &rendering);
 	if (libskrift_create_context(&ctx, &font, 1, height, &rendering, NULL)) {
 		perror("libskrift_create_context");
diff --git a/libskrift.h b/libskrift.h
index aeeaad2..843de6e 100644
--- a/libskrift.h
+++ b/libskrift.h
@@ -89,21 +89,22 @@ enum libskrift_hinting {
 #define LIBSKRIFT_REMOVE_GAMMA         0x00000001L
 #define LIBSKRIFT_Y_INCREASES_UPWARDS  0x00000002L /* SFT_DOWNWARD_Y otherwise */
 #define LIBSKRIFT_FLIP_TEXT            0x00000004L
-#define LIBSKRIFT_MIRROR_TEXT          0x00000008L
-#define LIBSKRIFT_MIRROR_CHARS         0x00000010L
-#define LIBSKRIFT_TRANSPOSE_TEXT       0x00000020L
-#define LIBSKRIFT_TRANSPOSE_CHARS      0x00000040L
-#define LIBSKRIFT_NO_LIGATURES         0x00000080L
-#define LIBSKRIFT_ADVANCE_CHAR_TO_GRID 0x00000100L
-#define LIBSKRIFT_REGRESS_CHAR_TO_GRID 0x00000200L /* Combine with LIBSKRIFT_ADVANCE_CHAR_TO_GRID for closest alternative */
-#define LIBSKRIFT_ADVANCE_WORD_TO_GRID 0x00000400L
-#define LIBSKRIFT_REGRESS_WORD_TO_GRID 0x00000800L /* Combine with LIBSKRIFT_ADVANCE_WORD_TO_GRID for closest alternative */
-#define LIBSKRIFT_USE_SUBPIXEL_GRID    0x00001000L
-#define LIBSKRIFT_VERTICAL_TEXT        0x00002000L
-#define LIBSKRIFT_AUTOHINTING          0x00004000L /* Use autohinter even if hint information exists */
-#define LIBSKRIFT_NO_AUTOHINTING       0x00008000L /* Use autohinter if no hint information exist */
-#define LIBSKRIFT_AUTOKERNING          0x00010000L /* Use autokerner even if kerning information exists */
-#define LIBSKRIFT_NO_AUTOKERNING       0x00020000L /* Use autokerner if no kerning information exist */
+#define LIBSKRIFT_FLIP_CHARS           0x00000008L
+#define LIBSKRIFT_MIRROR_TEXT          0x00000010L
+#define LIBSKRIFT_MIRROR_CHARS         0x00000020L
+#define LIBSKRIFT_TRANSPOSE_TEXT       0x00000040L
+#define LIBSKRIFT_TRANSPOSE_CHARS      0x00000080L
+#define LIBSKRIFT_NO_LIGATURES         0x00000100L
+#define LIBSKRIFT_ADVANCE_CHAR_TO_GRID 0x00000200L
+#define LIBSKRIFT_REGRESS_CHAR_TO_GRID 0x00000400L /* Combine with LIBSKRIFT_ADVANCE_CHAR_TO_GRID for closest alternative */
+#define LIBSKRIFT_ADVANCE_WORD_TO_GRID 0x00000800L
+#define LIBSKRIFT_REGRESS_WORD_TO_GRID 0x00001000L /* Combine with LIBSKRIFT_ADVANCE_WORD_TO_GRID for closest alternative */
+#define LIBSKRIFT_USE_SUBPIXEL_GRID    0x00002000L
+#define LIBSKRIFT_VERTICAL_TEXT        0x00004000L
+#define LIBSKRIFT_AUTOHINTING          0x00008000L /* Use autohinter even if hint information exists */
+#define LIBSKRIFT_NO_AUTOHINTING       0x00010000L /* Use autohinter if no hint information exist */
+#define LIBSKRIFT_AUTOKERNING          0x00020000L /* Use autokerner even if kerning information exists */
+#define LIBSKRIFT_NO_AUTOKERNING       0x00040000L /* Use autokerner if no kerning information exist */
 
 struct libskrift_rendering {
 	int struct_version;
diff --git a/libskrift_create_context.c b/libskrift_create_context.c
index fd8d086..cf67826 100644
--- a/libskrift_create_context.c
+++ b/libskrift_create_context.c
@@ -13,6 +13,26 @@
 
 static const struct libskrift_rendering default_rendering = LIBSKRIFT_DEFAULT_RENDERING;
 
+static int
+transformation_hook(void *hook_data, double advance, double transform[6])
+{
+	LIBSKRIFT_CONTEXT *ctx = hook_data;
+	double r1c1b = ctx->rendering.char_transformation[0], r1c1a = transform[0];
+	double r1c2b = ctx->rendering.char_transformation[1], r1c2a = transform[2];
+	double r1c3b = ctx->rendering.char_transformation[2], r1c3a = transform[4];
+	double r2c1b = ctx->rendering.char_transformation[3], r2c1a = transform[1];
+	double r2c2b = ctx->rendering.char_transformation[4], r2c2a = transform[3];
+	double r2c3b = ctx->rendering.char_transformation[5], r2c3a = transform[5];
+	transform[0] = r1c1a * r1c1b + r1c2a * r2c1b;
+	transform[2] = r1c1a * r1c2b + r1c2a * r2c2b;
+	transform[4] = r1c1a * r1c3b + r1c2a * r2c3b + r1c3a;
+	transform[1] = r2c1a * r1c1b + r2c2a * r2c1b;
+	transform[3] = r2c1a * r1c2b + r2c2a * r2c2b;
+	transform[5] = r2c1a * r1c3b + r2c2a * r2c3b + r2c3a;
+	(void) advance;
+	return 0;
+}
+
 int
 libskrift_create_context(LIBSKRIFT_CONTEXT **ctxp, LIBSKRIFT_FONT **fonts, size_t nfonts, double height,
                          const struct libskrift_rendering *rendering, void *caching)
@@ -53,7 +73,6 @@ libskrift_create_context(LIBSKRIFT_CONTEXT **ctxp, LIBSKRIFT_FONT **fonts, size_
 		COPY_ARRAY((*ctxp)->rendering, default_rendering, top_transformation);
 		COPY_ARRAY((*ctxp)->rendering, default_rendering, bottom_transformation);
 		COPY_ARRAY((*ctxp)->rendering, default_rendering, poststroke_transformation_rotation);
-		COPY_ARRAY((*ctxp)->rendering, default_rendering, char_transformation);
 		COPY_ARRAY((*ctxp)->rendering, default_rendering, text_transformation);
 	} else {
 		memcpy(&(*ctxp)->rendering, &default_rendering, sizeof(default_rendering));
@@ -72,6 +91,14 @@ libskrift_create_context(LIBSKRIFT_CONTEXT **ctxp, LIBSKRIFT_FONT **fonts, size_
 
 	(*ctxp)->schrift_ctx.xScale = (*ctxp)->schrift_ctx.yScale;
 	(*ctxp)->schrift_ctx.xScale *= (*ctxp)->rendering.horizontal_dpi / (*ctxp)->rendering.vertical_dpi;
+	(*ctxp)->schrift_ctx.hook_data = (*ctxp);
+	if (fpclassify((*ctxp)->rendering.char_transformation[0] - 1) != FP_ZERO ||
+	    fpclassify((*ctxp)->rendering.char_transformation[1]) != FP_ZERO ||
+	    fpclassify((*ctxp)->rendering.char_transformation[2]) != FP_ZERO ||
+	    fpclassify((*ctxp)->rendering.char_transformation[3]) != FP_ZERO ||
+	    fpclassify((*ctxp)->rendering.char_transformation[4] - 1) != FP_ZERO ||
+	    fpclassify((*ctxp)->rendering.char_transformation[5]) != FP_ZERO)
+		(*ctxp)->schrift_ctx.transformation_hook = transformation_hook;
 
 	if ((*ctxp)->rendering.smoothing == LIBSKRIFT_SUBPIXEL) {
 		if ((*ctxp)->rendering.subpixel_order == LIBSKRIFT_RGB) {