Draw title and axis labels with pango

[acre] / acre.c

diff --git a/acre.c b/acre.c
index 672ba62bf776aaba82a4d966fc057a80ddcbe53d..e7b4a0f82b1984dfe47a093ad0252a6d7bb3539a 100644 (file)
--- a/acre.c
+++ b/acre.c
@@ -21,6 +21,7 @@
 #include "xmalloc.h"
 
 #include <string.h>
+#include <math.h>
 
 typedef struct _acre_data_point_2d {
     double x;
@@ -124,6 +125,12 @@ acre_add_data (acre_t *acre, acre_data_t *data)
     acre->num_data++;
 }
 
+#define ACRE_FONT_FAMILY "sans"
+#define ACRE_FONT_SIZE 12
+#define ACRE_TITLE_FONT_SIZE 32
+#define ACRE_PAD (ACRE_FONT_SIZE)
+#define ACRE_TICK_SIZE 4
+
 /* Draw the plot to the given cairo context within a user-space
  * rectangle from (0, 0) to (width, height). This size includes all
  * space for extra-plot elements (such as the title, the axis labels,
@@ -132,13 +139,105 @@ acre_add_data (acre_t *acre, acre_data_t *data)
 void
 acre_draw (acre_t *acre, cairo_t *cr, double width, double height)
 {
-    cairo_save (cr);
+    PangoFontDescription *acre_font, *title_font;
+    PangoLayout *title_layout, *x_axis_layout, *y_axis_layout;
+    int title_width, title_height;
+    int x_axis_width, x_axis_height;
+    int y_axis_width, y_axis_height;
+    PangoRectangle chart, new_chart;
 
-    cairo_rectangle (cr, 0, 0, width, height);
+    cairo_save (cr);
 
-    cairo_set_source_rgb (cr, 1, 0, 1);
+    cairo_set_source_rgb (cr, 1, 1, 1);
 
     cairo_paint (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 = pango_cairo_create_layout (cr);
+    pango_layout_set_font_description (title_layout, title_font);
+    pango_layout_set_text (title_layout, acre->title, -1);
+    pango_layout_set_alignment (title_layout, PANGO_ALIGN_CENTER);
+
+    x_axis_layout = pango_cairo_create_layout (cr);
+    pango_layout_set_font_description (x_axis_layout, acre_font);
+    pango_layout_set_text (x_axis_layout, acre->x_axis_label, -1);
+    pango_layout_set_alignment (x_axis_layout, PANGO_ALIGN_CENTER);
+
+    y_axis_layout = pango_cairo_create_layout (cr);
+    pango_layout_set_font_description (y_axis_layout, acre_font);
+    pango_layout_set_text (y_axis_layout, acre->y_axis_label, -1);
+    pango_layout_set_alignment (y_axis_layout, PANGO_ALIGN_CENTER);
+
+    /* 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). */
+    chart.x = 0;
+    chart.y = 0;
+    chart.width = width;
+    chart.height = height;
+    while (1) {
+       pango_layout_set_width (title_layout, chart.width * PANGO_SCALE);
+       pango_layout_set_width (x_axis_layout, chart.width * PANGO_SCALE);
+       pango_layout_set_width (y_axis_layout, 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 + ACRE_FONT_SIZE;
+       new_chart.width = width - chart.x - ACRE_PAD;
+
+       new_chart.y = ACRE_PAD + title_height + ACRE_PAD;
+       new_chart.height = height - chart.y - (ACRE_FONT_SIZE + ACRE_PAD + x_axis_height + ACRE_PAD);
+
+       if (new_chart.x == chart.x &&
+           new_chart.y == chart.y &&
+           new_chart.width == chart.width &&
+           new_chart.height == chart.height)
+       {
+           break;
+       }
+
+       chart.x = new_chart.x;
+       chart.y = new_chart.y;
+       chart.width = new_chart.width;
+       chart.height = new_chart.height;
+    }
+
+    cairo_set_source_rgb (cr, 0, 0, 0);
+
+    cairo_move_to (cr, chart.x, ACRE_PAD);
+    pango_cairo_show_layout (cr, title_layout);
+
+    cairo_save (cr);
+    {
+       cairo_translate (cr, ACRE_PAD, chart.y + chart.height);
+       cairo_rotate (cr, - M_PI / 2.0);
+       cairo_move_to (cr, 0, 0);
+       pango_cairo_show_layout (cr, y_axis_layout);
+    }
+    cairo_restore (cr);
+
+    cairo_move_to (cr, chart.x,
+                  chart.y + chart.height + ACRE_FONT_SIZE + ACRE_PAD);
+    pango_cairo_show_layout (cr, x_axis_layout);
+
+    cairo_rectangle (cr,
+                    chart.x - 0.5, chart.y - 0.5,
+                    chart.width + 1.0, chart.height + 1.0);
+    cairo_set_line_width (cr, 1.0);
+    cairo_stroke (cr);
 }
 
 /* Create a new dataset---a collection of (x, y) datapoints. A single