Bug 341481 - pangocairo kerning problem with nonidentity scaling

Finally fix this embarrassing bug.  The fix is a kludge, but it will
be redone for 1.28 (harfbuzz-ng) anyway.

1 files changed, 44 insertions, 0 deletions

diff --git a/pango/pangofc-private.h b/pango/pangofc-private.h
index 0612a692..e7c08bff 100644
--- a/pango/pangofc-private.h
+++ b/pango/pangofc-private.h
@@ -93,6 +93,50 @@ void            pango_fc_font_get_raw_extents    (PangoFcFont    *font,
 PangoFontMetrics *pango_fc_font_create_metrics_for_context (PangoFcFont   *font,
 							    PangoContext  *context);
 
+
+
+/* To be made public at some point */
+
+#include <math.h>
+
+static G_GNUC_UNUSED void
+pango_matrix_get_font_scale_factors (const PangoMatrix *matrix,
+				     double *xscale, double *yscale)
+{
+/*
+ * Based on cairo-matrix.c:_cairo_matrix_compute_scale_factors()
+ *
+ * Copyright 2005, Keith Packard
+ */
+  double major = 0, minor = 0;
+
+  if (matrix) {
+    double det = matrix->xx * matrix->yy - matrix->yx * matrix->xy;
+
+    if (det)
+      {
+	double x = matrix->xx;
+	double y = matrix->yx;
+
+	major = sqrt (x*x + y*y);
+
+	/*
+	 * ignore mirroring
+	 */
+	if (det < 0)
+	  det = - det;
+
+	if (major)
+	  minor = det / major;
+      }
+  }
+
+  if (xscale)
+    *xscale = major;
+  if (yscale)
+    *yscale = minor;
+}
+
 G_END_DECLS
 
 #endif /* __PANGOFC_PRIVATE_H__ */