From: Carl Worth <cworth@cworth.org>
Date: Tue, 27 Jan 2009 16:12:39 +0000 (-0800)
Subject: Add minor ticks
X-Git-Url: https://git.cworth.org/git?p=acre;a=commitdiff_plain;h=4a5a4c8bad866e53298a1cdf47104c2711c139df;hp=5897f1f7f868e2fdfa51fc8e3bb9e02d49171b2b

Add minor ticks

For now, do 5 divisions of each major tick, regardless of whether the
major tick spacing is 1, 2.5, 5, or 10. Also, we don't yet fix the
axes to guarantee integer spacing of the minor ticks.
---

diff --git a/acre.c b/acre.c
index a01dbe5..6cd3a0b 100644
--- 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);