X-Git-Url: http://git.scottworley.com/batteryviewer/blobdiff_plain/4c6797b5290feab5d454bd2b53cf31c9c6e4d331..769fc186912381ce8528820bacfa7846a16bade2:/chart.c

diff --git a/chart.c b/chart.c
index e9b60fe..1813aa2 100644
--- a/chart.c
+++ b/chart.c
@@ -1,4 +1,20 @@
-/*
+/* batteryviewer: Display battery metrics
+ * Copyright (C) 2023 Scott Worley <scottworley@scottworley.com>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, version 3.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ *
+ *
+ *
  * h/t https://ptomato.name/advanced-gtk-techniques/html/custom-container.html
  * for examples of how to make GTK widgets
  */
@@ -60,6 +76,20 @@ static void draw_data(BVChartPrivate *priv, cairo_t *cr,
   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);
+  }
+}
+
 static gboolean bv_chart_draw(GtkWidget *widget, cairo_t *cr) {
   BVChart *chart = BV_CHART(widget);
   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
@@ -74,6 +104,7 @@ static gboolean bv_chart_draw(GtkWidget *widget, cairo_t *cr) {
   gtk_widget_get_allocation(widget, &allocation);
 
   draw_data(priv, cr, &allocation);
+  draw_axis(priv, cr, &allocation);
 
   return TRUE;
 }