[matrix] Improve bbox finding for translation matrix

If the matrix is a pure translation matrix than we can skip determination
of the extents and just translate the input bbox.

1 files changed, 29 insertions, 27 deletions

diff --git a/src/cairo-matrix.c b/src/cairo-matrix.c
index 94ed0e915..bf20ee4fc 100644
--- a/src/cairo-matrix.c
+++ b/src/cairo-matrix.c
@@ -371,37 +371,39 @@ _cairo_matrix_transform_bounding_box (const cairo_matrix_t *matrix,
     double min_x, max_x;
     double min_y, max_y;
 
-    if (_cairo_matrix_is_identity (matrix)) {
-	if (is_tight)
-	    *is_tight = TRUE;
-
-	return;
-    }
-
     if (matrix->xy == 0. && matrix->yx == 0.) {
 	/* non-rotation/skew matrix, just map the two extreme points */
-	quad_x[0] = *x1;
-	quad_y[0] = *y1;
-	cairo_matrix_transform_distance (matrix, &quad_x[0], &quad_y[0]);
-
-	quad_x[1] = *x2;
-	quad_y[1] = *y2;
-	cairo_matrix_transform_distance (matrix, &quad_x[1], &quad_y[1]);
-
-	if (quad_x[0] < quad_x[1]) {
-	    *x1 = quad_x[0] + matrix->x0;
-	    *x2 = quad_x[1] + matrix->x0;
-	} else {
-	    *x1 = quad_x[1] + matrix->x0;
-	    *x2 = quad_x[0] + matrix->x0;
+
+	if (matrix->xx != 1.) {
+	    quad_x[0] = *x1 * matrix->xx;
+	    quad_x[1] = *x2 * matrix->xx;
+	    if (quad_x[0] < quad_x[1]) {
+		*x1 = quad_x[0];
+		*x2 = quad_x[1];
+	    } else {
+		*x1 = quad_x[1];
+		*x2 = quad_x[0];
+	    }
+	}
+	if (matrix->x0 != 0.) {
+	    *x1 += matrix->x0;
+	    *x2 += matrix->x0;
 	}
 
-	if (quad_y[0] < quad_y[1]) {
-	    *y1 = quad_y[0] + matrix->y0;
-	    *y2 = quad_y[1] + matrix->y0;
-	} else {
-	    *y1 = quad_y[1] + matrix->y0;
-	    *y2 = quad_y[0] + matrix->y0;
+	if (matrix->yy != 1.) {
+	    quad_y[0] = *y1 * matrix->yy;
+	    quad_y[1] = *y2 * matrix->yy;
+	    if (quad_y[0] < quad_y[1]) {
+		*y1 = quad_y[0];
+		*y2 = quad_y[1];
+	    } else {
+		*y1 = quad_y[1];
+		*y2 = quad_y[0];
+	    }
+	}
+	if (matrix->y0 != 0.) {
+	    *y1 += matrix->y0;
+	    *y2 += matrix->y0;
 	}
 
 	if (is_tight)