Add minor ticks

[acre] / acre.c

diff --git a/acre.c b/acre.c
index a01dbe5c2f1275c0c4f77b049844c8220b2c69e8..6cd3a0b3c309fef4d49d5bffc05601e76f520e99 100644 (file)
--- a/acre.c
+++ b/acre.c
@@ -162,7 +162,8 @@ acre_add_data (acre_t *acre, acre_data_t *data)
 #define ACRE_FONT_SIZE 12
 #define ACRE_TITLE_FONT_SIZE 32
 #define ACRE_PAD (ACRE_FONT_SIZE)
-#define ACRE_TICK_SIZE 6
+#define ACRE_TICK_MAJOR_SIZE 6
+#define ACRE_TICK_MINOR_SIZE 3
 #define ACRE_X_TICK_VALUE_PAD 2
 #define ACRE_Y_TICK_VALUE_PAD 4
 
@@ -510,49 +511,63 @@ _draw_ticks (acre_t *acre,
             acre_ticks_t ticks)
 {
     cairo_t *cr = acre->cr;
-    double i, step;
+    double t, step, sub_step;
+    int minor_divisions = 5;
 
     cairo_save (cr);
 
     _set_transform_to_data_space (acre);
 
     step = _step_for_range (axis_max - axis_min);
-    i = (floor (axis_min / step) + 1) * step;
+    sub_step = step / minor_divisions;
 
-    while (i <= axis_max) {
-       if (ticks == ACRE_TICKS_X)
-           cairo_move_to (cr, i, acre->y_axis.min);
+    for (t = (floor (axis_min / sub_step) + 1) * sub_step;
+        t <= axis_max;
+        t += sub_step)
+    {
+       int tick_size;
+       if (fabs((t / step) - (int) (t / step)) < 0.5 * (sub_step / step))
+           tick_size = ACRE_TICK_MAJOR_SIZE;
        else
-           cairo_move_to (cr, acre->x_axis.min, i);
+           tick_size = ACRE_TICK_MINOR_SIZE;
 
        /* tick */
        cairo_save (cr);
        {
+           if (ticks == ACRE_TICKS_X)
+               cairo_move_to (cr, t, acre->y_axis.min);
+           else
+               cairo_move_to (cr, acre->x_axis.min, t);
+
            cairo_identity_matrix (cr);
+
            if (ticks == ACRE_TICKS_X) {
                cairo_rel_line_to (cr, 0, 0.5);
-               cairo_rel_line_to (cr, 0, -ACRE_TICK_SIZE-0.5);
+               cairo_rel_line_to (cr, 0, -tick_size - 0.5);
            } else {
                cairo_rel_line_to (cr, -0.5, 0);
-               cairo_rel_line_to (cr, ACRE_TICK_SIZE+0.5, 0);
+               cairo_rel_line_to (cr, tick_size + 0.5, 0);
            }
+
            cairo_set_line_width (cr, 1.0);
            cairo_stroke (cr);
        }
        cairo_restore (cr);
 
        /* label */
-       cairo_save (cr);
+       if (tick_size == ACRE_TICK_MAJOR_SIZE)
        {
            PangoLayout *layout;
            int width, height;
 
-           layout = _create_layout_printf (acre, "%g", i);
+           cairo_save (cr);
+
+           layout = _create_layout_printf (acre, "%g", t);
 
            if (ticks == ACRE_TICKS_X)
-               cairo_move_to (cr, i, acre->y_axis.min);
+               cairo_move_to (cr, t, acre->y_axis.min);
            else
-               cairo_move_to (cr, acre->x_axis.min, i);
+               cairo_move_to (cr, acre->x_axis.min, t);
 
            cairo_identity_matrix (cr);
            pango_layout_get_pixel_size (layout, &width, &height);
@@ -564,10 +579,9 @@ _draw_ticks (acre_t *acre,
                                   -height/2);
 
            _show_layout (cr, layout);
-       }
-       cairo_restore (cr);
 
-       i += step;
+           cairo_restore (cr);
+       }
     }
 
     cairo_restore (cr);