* 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
*/
+#define _ISOC99_SOURCE /* for round() */
+#define _XOPEN_SOURCE 500
+
#include "acre.h"
#include "xmalloc.h"
* amount for the major ticks (see _step_for_range). To get
* nice-looking pixel-snapped ticks we want to expand the range
* slightly. */
-static double
-_expand_range (double data_range, int pixel_size)
+static void
+_expand_range_for_width (double *axis_min, double *axis_max, int pixel_size)
{
- double step, pixel_step;
+ double range, new_range, step, pixel_step;
- step = _step_for_range (data_range);
- pixel_step = step * pixel_size / data_range;
+ range = *axis_max - *axis_min;
+
+ step = _step_for_range (range);
+ pixel_step = step * pixel_size / range;
/* We expand the range by the ratio of the pixel step to the floor
* of the pixel_step.
*/
- return data_range * pixel_step / floor (pixel_step);
+ new_range = range * pixel_step / floor (pixel_step);
+
+ /* And spread the increase out on either side of the range. */
+ *axis_min -= (new_range - range) / 2.0;
+ *axis_max += (new_range - range) / 2.0;
+}
+
+/* Setup a transformation in acre->cr such that data values plotted
+ * will appear where they should within the chart.
+ */
+static void
+_set_transform_to_data_space (acre_t *acre)
+{
+ cairo_t *cr = acre->cr;
+
+ cairo_translate (cr,
+ acre->chart.x,
+ acre->chart.y + acre->chart.height);
+ cairo_scale (cr,
+ acre->chart.width / (acre->x_axis.max - acre->x_axis.min),
+ - acre->chart.height /(acre->y_axis.max - acre->y_axis.min));
+ cairo_translate (cr, -acre->x_axis.min, -acre->y_axis.min);
}
static void
{
unsigned int d, i;
acre_data_t *data;
- double x_range, new_x_range;
- double y_range, new_y_range;
+ double x_adjust, y_adjust;
+ cairo_t *cr = acre->cr;
/* First, simply find the extrema of the data. */
for (d = 0; d < acre->num_data; d++) {
/* Next, increase the axis ranges just enough so that the step
* sizes for the ticks will be integers.
*/
- x_range = acre->x_axis.max - acre->x_axis.min;
- new_x_range = _expand_range (x_range, acre->chart.width);
+ _expand_range_for_width (&acre->x_axis.min,
+ &acre->x_axis.max,
+ acre->chart.width);
- y_range = acre->y_axis.max - acre->y_axis.min;
- new_y_range = _expand_range (y_range, acre->chart.height);
+ _expand_range_for_width (&acre->y_axis.min,
+ &acre->y_axis.max,
+ acre->chart.height);
- /* And spread the increase out on either side of the range. */
- acre->x_axis.min -= (new_x_range - x_range) / 2.0;
- acre->x_axis.max += (new_x_range - x_range) / 2.0;
+ /* Finally, we also translate the axis ranges slightly so that the
+ * ticks land on half-integer device-pixel positions.
+ */
+ cairo_save (cr);
+ {
+ _set_transform_to_data_space (acre);
- acre->y_axis.min -= (new_y_range - y_range) / 2.0;
- acre->y_axis.max += (new_y_range - y_range) / 2.0;
-}
+ x_adjust = 0.0;
+ y_adjust = 0.0;
+ cairo_user_to_device (cr, &x_adjust, &y_adjust);
+ x_adjust = (round (x_adjust + 0.5) - 0.5) - x_adjust;
+ y_adjust = (round (y_adjust + 0.5) - 0.5) - y_adjust;
+ cairo_device_to_user_distance (cr, &x_adjust, &y_adjust);
-/* Setup a transformation in acre->cr such that data values plotted
- * will appear where they should within the chart.
- */
-static void
-_set_transform_to_data_space (acre_t *acre)
-{
- cairo_t *cr = acre->cr;
+ acre->x_axis.min -= x_adjust;
+ acre->x_axis.max -= x_adjust;
- cairo_translate (cr,
- acre->chart.x,
- acre->chart.y + acre->chart.height);
- cairo_scale (cr,
- acre->chart.width / (acre->x_axis.max - acre->x_axis.min),
- - acre->chart.height /(acre->y_axis.max - acre->y_axis.min));
- cairo_translate (cr, -acre->x_axis.min, -acre->y_axis.min);
+ acre->y_axis.min -= y_adjust;
+ acre->y_axis.max -= y_adjust;
+ }
+ cairo_restore (cr);
}
static void
{
cairo_identity_matrix (cr);
cairo_rel_line_to (cr, 0, 0.5);
- cairo_rel_line_to (cr, 0, -ACRE_TICK_SIZE);
+ cairo_rel_line_to (cr, 0, -ACRE_TICK_SIZE-0.5);
cairo_set_line_width (cr, 1.0);
cairo_stroke (cr);
}
{
cairo_identity_matrix (cr);
cairo_rel_line_to (cr, -0.5, 0);
- cairo_rel_line_to (cr, ACRE_TICK_SIZE, 0);
+ cairo_rel_line_to (cr, ACRE_TICK_SIZE+0.5, 0);
cairo_set_line_width (cr, 1.0);
cairo_stroke (cr);
}