+typedef void (*cairo_draw_func)(cairo_t *cr, double x, double y);
+
+static struct ScreenPoint to_screen(BVChartPrivate *priv,
+ GtkAllocation *allocation,
+ struct BVChartPoint *p) {
+ int margin = 3;
+ float xscale = (allocation->width - 2 * margin) / (priv->maxx - priv->minx);
+ float yscale = (allocation->height - 2 * margin) / (priv->miny - priv->maxy);
+ struct ScreenPoint screen_p = {
+ .x = xscale * (p->x - priv->minx) + margin,
+ .y = yscale * (p->y - priv->maxy) + margin,
+ };
+ return screen_p;
+}
+
+static void draw_data(BVChartPrivate *priv, cairo_t *cr,
+ GtkAllocation *allocation) {
+ cairo_set_source_rgb(cr, 0.0, 0.0, 1.0);
+ float gap_threshold = 3.0;
+ float prevx = 0.0;
+ for (guint i = 0; i < priv->points->len; i++) {
+ struct BVChartPoint *p =
+ &g_array_index(priv->points, struct BVChartPoint, i);
+ gboolean is_gap = p->x - prevx > gap_threshold;
+ cairo_draw_func f = is_gap ? cairo_move_to : cairo_line_to;
+ struct ScreenPoint screen_p = to_screen(priv, allocation, p);
+ f(cr, screen_p.x, screen_p.y);
+ prevx = p->x;
+ }
+ cairo_stroke(cr);
+}
+
+static void draw_axis(BVChartPrivate *priv, cairo_t *cr,
+ GtkAllocation *allocation) {
+ if (priv->miny < 0.0 && priv->maxy > 0.0) {
+ cairo_set_source_rgb(cr, 0.0, 0.0, 0.0);
+ struct BVChartPoint p = {.x = priv->minx, .y = 0.0};
+ struct ScreenPoint screen_p = to_screen(priv, allocation, &p);
+ cairo_move_to(cr, screen_p.x, screen_p.y);
+ p.x = priv->maxx;
+ screen_p = to_screen(priv, allocation, &p);
+ cairo_line_to(cr, screen_p.x, screen_p.y);
+ cairo_stroke(cr);
+ }
+}
+