+#define ACRE_FONT_FAMILY "sans"
+#define ACRE_FONT_SIZE 12
+#define ACRE_TITLE_FONT_SIZE 20
+#define ACRE_PAD (ACRE_FONT_SIZE)
+#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
+#define ACRE_LEGEND_PAD 4
+#define ACRE_LEGEND_LINE_SIZE 10
+
+static PangoLayout *
+_create_layout (acre_t *acre, const char *text)
+{
+ PangoLayout *layout;
+
+ layout = pango_cairo_create_layout (acre->cr);
+ pango_layout_set_font_description (layout, acre->font);
+ pango_layout_set_text (layout, text, -1);
+ pango_layout_set_alignment (layout, PANGO_ALIGN_CENTER);
+
+ return layout;
+}
+
+#define PRINTF_FORMAT(fmt_index, va_index) __attribute__ ((__format__(__printf__, fmt_index, va_index)))
+
+static PangoLayout *
+_create_layout_vprintf (acre_t *acre, const char *fmt, va_list ap)
+{
+ PangoLayout *layout;
+ char *text;
+
+ vasprintf (&text, fmt, ap);
+
+ layout = _create_layout (acre, text);
+
+ free (text);
+
+ return layout;
+}
+
+static PangoLayout *
+_create_layout_printf (acre_t *acre, const char *fmt, ...)
+ PRINTF_FORMAT (2, 3);
+
+static PangoLayout *
+_create_layout_printf (acre_t *acre, const char *fmt, ...)
+{
+ va_list ap;
+ PangoLayout *layout;
+
+ va_start (ap, fmt);
+
+ layout = _create_layout_vprintf (acre, fmt, ap);
+
+ va_end (ap);
+
+ return layout;
+}
+
+static void
+_destroy_layout (PangoLayout *layout)
+{
+ g_object_unref (layout);
+}
+
+static void
+_show_layout (cairo_t *cr, PangoLayout *layout)
+{
+ pango_cairo_show_layout (cr, layout);
+
+ _destroy_layout (layout);
+}
+
+static void
+_draw_title_and_labels (acre_t *acre)
+{
+ cairo_t *cr = acre->cr;
+ PangoFontDescription *title_font;
+ PangoLayout *title_layout, *x_axis_layout, *y_axis_layout;
+ PangoLayout *min_y, *max_y;
+ int min_y_width, max_y_width, y_axis_value_width;
+ int title_width, title_height;
+ int x_axis_width, x_axis_height;
+ int y_axis_width, y_axis_height;
+ PangoRectangle new_chart;
+
+ cairo_save (cr);
+
+ acre->font = pango_font_description_new ();
+ pango_font_description_set_family (acre->font, ACRE_FONT_FAMILY);
+ pango_font_description_set_absolute_size (acre->font,
+ ACRE_FONT_SIZE * PANGO_SCALE);
+
+ title_font = pango_font_description_new ();
+ pango_font_description_set_family (title_font, ACRE_FONT_FAMILY);
+ pango_font_description_set_absolute_size (title_font,
+ ACRE_TITLE_FONT_SIZE * PANGO_SCALE);
+
+ title_layout = _create_layout (acre, acre->title);
+ pango_layout_set_font_description (title_layout, title_font);
+
+ x_axis_layout = _create_layout (acre, acre->x_axis.label);
+ y_axis_layout = _create_layout (acre, acre->y_axis.label);
+
+ min_y = _create_layout_printf (acre, "%g",
+ round (acre->y_axis.view_min));
+ max_y = _create_layout_printf (acre, "%g",
+ round (acre->y_axis.view_max));
+
+ pango_layout_get_pixel_size (min_y, &min_y_width, NULL);
+ pango_layout_get_pixel_size (max_y, &max_y_width, NULL);
+ y_axis_value_width = MAX (min_y_width, max_y_width);
+
+ _destroy_layout (min_y);
+ _destroy_layout (max_y);
+
+ /* Iterate with the layout of the title and axis labels until they
+ * are stable, (this requires iteration since we don't know what
+ * to set their widths to in advance due to the wrapping of the
+ * other elements). */
+ while (1) {
+ pango_layout_set_width (title_layout, acre->chart.width * PANGO_SCALE);
+ pango_layout_set_width (x_axis_layout, acre->chart.width * PANGO_SCALE);
+ pango_layout_set_width (y_axis_layout, acre->chart.height * PANGO_SCALE);
+
+ pango_layout_get_pixel_size (title_layout, &title_width, &title_height);
+ pango_layout_get_pixel_size (x_axis_layout, &x_axis_width, &x_axis_height);
+ pango_layout_get_pixel_size (y_axis_layout, &y_axis_width, &y_axis_height);
+
+ new_chart.x = ACRE_PAD + y_axis_height +
+ ACRE_PAD + y_axis_value_width + ACRE_Y_TICK_VALUE_PAD;
+ new_chart.width = acre->width - acre->chart.x - ACRE_PAD;
+
+ new_chart.y = ACRE_PAD + title_height + ACRE_PAD;
+ new_chart.height = acre->height - acre->chart.y -
+ (ACRE_X_TICK_VALUE_PAD + ACRE_FONT_SIZE +
+ ACRE_PAD + x_axis_height + ACRE_PAD);
+
+ if (new_chart.x == acre->chart.x &&
+ new_chart.y == acre->chart.y &&
+ new_chart.width == acre->chart.width &&
+ new_chart.height == acre->chart.height)
+ {
+ break;
+ }
+
+ acre->chart.x = new_chart.x;
+ acre->chart.y = new_chart.y;
+ acre->chart.width = new_chart.width;
+ acre->chart.height = new_chart.height;
+ }
+
+ cairo_set_source_rgb (cr, 0, 0, 0);
+
+ cairo_move_to (cr, acre->chart.x, ACRE_PAD);
+ _show_layout (cr, title_layout);
+
+ cairo_save (cr);
+ {
+ cairo_translate (cr, ACRE_PAD, acre->chart.y + acre->chart.height);
+ cairo_rotate (cr, - M_PI / 2.0);
+ cairo_move_to (cr, 0, 0);
+ _show_layout (cr, y_axis_layout);
+ }
+ cairo_restore (cr);
+
+ cairo_move_to (cr, acre->chart.x,
+ acre->chart.y + acre->chart.height +
+ ACRE_FONT_SIZE + ACRE_PAD);
+ _show_layout (cr, x_axis_layout);
+
+ cairo_restore (cr);
+}
+
+/* For a given axis range, compute a step size (in data space) to
+ * generate a suitable number of ticks (5 or so). */
+static double
+_step_for_range (double range, int *minor_divisions)
+{
+ double step, scale_factor;
+
+ /* We want roughly 5 major ticks for the chart. */
+ step = range / 5;
+
+ /* Normalize the step so we can easily snap it to a desirable
+ * value. */
+ scale_factor = pow (10.0, floor (log10 (step)));
+ step /= scale_factor;
+
+ /* We want increments of 1, 2.5, 5, or 10 (times some power of
+ * 10). The threshold values between these are computed
+ * logarithmically. */
+ if (step < 3.535533905932738) {
+ if (step < 1.58113883008419) {
+ step = 1.0;
+ *minor_divisions = 4;
+ } else {
+ step = 2.5;
+ *minor_divisions = 5;
+ }
+ } else {
+ if (step < 7.071067811865475) {
+ step = 5.0;
+ *minor_divisions = 5;
+ } else {
+ step = 10.0;
+ *minor_divisions = 4;
+ }
+ }
+
+ /* Un-normalize and we now have the data value that we want to
+ * step at. */
+ return step * scale_factor;
+}
+
+/* Given an axis range, we can compute a desired data-space step
+ * amount for the major ticks (see _step_for_range). To get
+ * nice-looking pixel-snapped ticks we want to expand the range
+ * slightly. */
+static void
+_expand_range_for_width (double *axis_min, double *axis_max, int pixel_range)
+{
+ double range, new_range, step, step_minor, pixel_step;
+ int minor_divisions;
+
+ range = *axis_max - *axis_min;
+
+ step = _step_for_range (range, &minor_divisions);
+ step_minor = step / minor_divisions;
+
+ pixel_step = step_minor * (pixel_range / range);
+
+ /* We expand the range by the ratio of the pixel step to the floor
+ * of the 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.view_max - acre->x_axis.view_min),
+ - acre->chart.height /(acre->y_axis.view_max - acre->y_axis.view_min));
+ cairo_translate (cr, -acre->x_axis.view_min, -acre->y_axis.view_min);
+}
+
+static void
+_compute_axis_ranges (acre_t *acre)
+{
+ double x_adjust, y_adjust;
+ cairo_t *cr = acre->cr;
+
+ /* First, simply set view ranges to data ranges. */
+ acre->x_axis.view_min = acre->x_axis.data_min;
+ acre->x_axis.view_max = acre->x_axis.data_max;
+
+ acre->y_axis.view_min = acre->y_axis.data_min;
+ acre->y_axis.view_max = acre->y_axis.data_max;
+
+ /* Next, we want to ensure that the data never collides with the
+ * ticks. So we expand each axis on its minimum side as needed. */
+ cairo_save (cr);
+ {
+ double x, y;
+
+ _set_transform_to_data_space (acre);
+
+ x = ACRE_TICK_MAJOR_SIZE + 2.0;
+ y = ACRE_TICK_MAJOR_SIZE + 2.0;
+ cairo_device_to_user_distance (cr, &x, &y);
+
+ acre->x_axis.view_min -= x;
+ acre->y_axis.view_min += y;
+ }
+ cairo_restore (cr);
+
+ /* Then, increase the axis ranges just enough so that the step
+ * sizes for the ticks will be integers.
+ */
+ _expand_range_for_width (&acre->x_axis.view_min,
+ &acre->x_axis.view_max,
+ acre->chart.width);
+
+ _expand_range_for_width (&acre->y_axis.view_min,
+ &acre->y_axis.view_max,
+ acre->chart.height);
+
+ /* 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);
+
+ 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);
+
+ acre->x_axis.view_min -= x_adjust;
+ acre->x_axis.view_max -= x_adjust;
+
+ acre->y_axis.view_min -= y_adjust;
+ acre->y_axis.view_max -= y_adjust;
+ }
+ cairo_restore (cr);
+}
+
+static void
+_acre_color_from_hsv (acre_color_t *color,
+ double hue,
+ double saturation,
+ double value)
+{
+ double f, p, q, t;
+ int hmod6;
+
+ hmod6 = (int) floor (hue / 60) % 6;
+ f = hue / 60 - floor (hue / 60);
+ p = value * (1 - saturation);
+ q = value * (1 - f * saturation);
+ t = value * (1 - (1 - f) * saturation);
+
+ switch (hmod6) {
+ case 0:
+ color->red = value;
+ color->green = t;
+ color->blue = p;
+ break;
+ case 1:
+ color->red = q;
+ color->green = value;
+ color->blue = p;
+ break;
+ case 2:
+ color->red = p;
+ color->green = value;
+ color->blue = t;
+ break;
+ case 3:
+ color->red = p;
+ color->green = q;
+ color->blue = value;
+ break;
+ case 4:
+ color->red = t;
+ color->green = p;
+ color->blue = value;
+ break;
+ case 5:
+ color->red = value;
+ color->green = p;
+ color->blue = q;
+ break;
+ }
+}
+
+static void
+_choose_colors (acre_t *acre)
+{
+ cmsHPROFILE lab_profile, srgb_profile;
+ cmsHTRANSFORM lab_to_srgb;
+ int i;
+ double theta, radius, srgb[3];
+ cmsCIELab lab;
+
+ lab_profile = cmsCreateLabProfile (NULL); /* D50 */
+ srgb_profile = cmsCreate_sRGBProfile ();
+
+ lab_to_srgb = cmsCreateTransform (lab_profile, TYPE_Lab_DBL,
+ srgb_profile, TYPE_RGB_DBL,
+ INTENT_PERCEPTUAL, 0);
+
+ acre->num_colors = acre->num_data;
+
+ if (acre->num_colors > acre->colors_size) {
+ acre->colors_size = acre->num_colors;
+ acre->colors = xrealloc (acre->colors,
+ acre->colors_size * sizeof (acre_color_t));
+ }
+
+ lab.L = 36;
+ radius = 130;
+ for (i = 0; i < acre->num_colors; i++) {
+ theta = 0.713 + 2 * M_PI * (double) i / acre->num_colors;
+ lab.a = radius * cos (theta);
+ lab.b = radius * sin (theta);
+
+ cmsDoTransform (lab_to_srgb, &lab, srgb, 1);
+
+ acre->colors[i].red = srgb[0];
+ acre->colors[i].green = srgb[1];
+ acre->colors[i].blue = srgb[2];
+ }
+
+ cmsDeleteTransform (lab_to_srgb);
+ cmsCloseProfile (lab_profile);
+ cmsCloseProfile (srgb_profile);
+}
+
+static void
+_draw_data (acre_t *acre)
+{
+ cairo_t *cr = acre->cr;
+ unsigned int d, i;
+ acre_data_t *data;
+
+ cairo_save (cr);
+
+ cairo_set_source_rgb (cr, 0, 0, 0);
+
+ _set_transform_to_data_space (acre);
+
+ for (d = 0; d < acre->num_data; d++) {
+ int color = d % acre->num_colors;
+ cairo_set_source_rgb (cr,
+ acre->colors[color].red,
+ acre->colors[color].green,
+ acre->colors[color].blue);
+ data = acre->data[d];
+ cairo_new_path (cr);
+ for (i = 0; i < data->num_points; i++) {
+ cairo_line_to (cr,
+ data->points[i].x,
+ data->points[i].y);
+ }
+ cairo_save (cr);
+ {
+ cairo_identity_matrix (cr);
+ cairo_set_line_width (cr, 1.0);
+ cairo_stroke (cr);
+ }
+ cairo_restore (cr);
+ }
+
+ cairo_restore (cr);
+}
+
+typedef enum _ticks { ACRE_TICKS_X, ACRE_TICKS_Y } acre_ticks_t;
+
+static void
+_draw_ticks (acre_t *acre,
+ double axis_min, double axis_max,
+ acre_ticks_t ticks)
+{
+ cairo_t *cr = acre->cr;
+ double t, step, sub_step;
+ int minor_divisions;
+
+ cairo_save (cr);
+
+ _set_transform_to_data_space (acre);
+
+ step = _step_for_range (axis_max - axis_min, &minor_divisions);
+ sub_step = step / minor_divisions;
+
+ for (t = (floor (axis_min / sub_step) + 1) * sub_step;
+ t <= axis_max;
+ t += sub_step)
+ {
+ int tick_size;
+ if (fabs((t / step) - round (t / step)) < 0.5 * (sub_step / step))
+ tick_size = ACRE_TICK_MAJOR_SIZE;
+ else
+ tick_size = ACRE_TICK_MINOR_SIZE;
+
+ /* tick */
+ cairo_save (cr);
+ {
+ if (ticks == ACRE_TICKS_X)
+ cairo_move_to (cr, t, acre->y_axis.view_min);
+ else
+ cairo_move_to (cr, acre->x_axis.view_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, -tick_size - 0.5);
+ } else {
+ cairo_rel_line_to (cr, -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 */
+ if (tick_size == ACRE_TICK_MAJOR_SIZE)
+ {
+ PangoLayout *layout;
+ int width, height;
+
+ cairo_save (cr);
+
+ layout = _create_layout_printf (acre, "%g", t);
+
+ if (ticks == ACRE_TICKS_X)
+ cairo_move_to (cr, t, acre->y_axis.view_min);
+ else
+ cairo_move_to (cr, acre->x_axis.view_min, t);
+
+ cairo_identity_matrix (cr);
+ pango_layout_get_pixel_size (layout, &width, &height);
+
+ if (ticks == ACRE_TICKS_X)
+ cairo_rel_move_to (cr, -width / 2, ACRE_X_TICK_VALUE_PAD);
+ else
+ cairo_rel_move_to (cr, -width - ACRE_Y_TICK_VALUE_PAD,
+ -height/2);
+
+ _show_layout (cr, layout);
+
+ cairo_restore (cr);
+ }
+ }
+
+ cairo_restore (cr);
+}
+
+static void
+_draw_legend (acre_t *acre)
+{
+ PangoLayout *layout;
+ int label_width, max_label_width = 0;
+ int width, height;
+ unsigned int i;
+ cairo_t *cr = acre->cr;
+
+ cairo_save (cr);
+
+ for (i = 0; i < acre->num_data; i++) {
+ layout = _create_layout (acre, acre->data[i]->name);
+ pango_layout_get_pixel_size (layout, &label_width, NULL);
+ _destroy_layout (layout);
+ if (label_width > max_label_width)
+ max_label_width = label_width;
+ }
+
+ width = ACRE_LEGEND_PAD + ACRE_LEGEND_LINE_SIZE + ACRE_LEGEND_PAD +
+ max_label_width + ACRE_LEGEND_PAD;
+ height = ACRE_LEGEND_PAD +
+ acre->num_data * (ACRE_FONT_SIZE + ACRE_LEGEND_PAD);
+
+ cairo_translate (cr, acre->chart.x, acre->chart.y);
+
+ cairo_translate (cr,
+ acre->chart.width - ACRE_LEGEND_PAD - width,
+ ACRE_LEGEND_PAD);
+
+ cairo_rectangle (cr, -0.5, -0.5, width + 1.0, height + 1.0);
+ cairo_set_source_rgb (cr, 0, 0, 0);
+ cairo_set_line_width (cr, 1.0);
+ cairo_stroke (cr);
+
+ cairo_translate (cr, ACRE_LEGEND_PAD, ACRE_LEGEND_PAD);
+
+ for (i = 0; i < acre->num_data; i++) {
+ cairo_rectangle (cr,
+ 0, ACRE_LEGEND_LINE_SIZE / 2,
+ ACRE_LEGEND_LINE_SIZE, ACRE_LEGEND_LINE_SIZE / 2);
+ cairo_set_source_rgb (cr,
+ acre->colors[i % acre->num_colors].red,
+ acre->colors[i % acre->num_colors].green,
+ acre->colors[i % acre->num_colors].blue);
+ cairo_fill (cr);
+
+ layout = _create_layout (acre, acre->data[i]->name);
+ cairo_move_to (cr, ACRE_LEGEND_LINE_SIZE + ACRE_LEGEND_PAD, 0);
+ cairo_set_source_rgb (cr, 0, 0, 0);
+ _show_layout (cr, layout);
+
+ cairo_translate (cr, 0, ACRE_LEGEND_PAD + ACRE_FONT_SIZE);
+ }
+
+ cairo_restore (cr);
+}
+
+static void
+_draw_frame_and_ticks (acre_t *acre)
+{
+ cairo_t *cr = acre->cr;
+
+ cairo_save (cr);
+
+ cairo_set_source_rgb (cr, 0, 0, 0); /* black */
+
+ /* ticks */
+ _draw_ticks (acre, acre->x_axis.view_min, acre->x_axis.view_max, ACRE_TICKS_X);
+ _draw_ticks (acre, acre->y_axis.view_min, acre->y_axis.view_max, ACRE_TICKS_Y);
+
+ /* frame */
+ cairo_rectangle (cr,
+ acre->chart.x - 0.5, acre->chart.y - 0.5,
+ acre->chart.width + 1.0, acre->chart.height + 1.0);
+ cairo_set_line_width (cr, 1.0);
+ cairo_stroke (cr);
+
+ cairo_restore (cr);
+}
+