From: Scott Worley Date: Fri, 24 Feb 2023 05:14:24 +0000 (-0800) Subject: Draw axis if data crosses zero X-Git-Url: http://git.scottworley.com/batteryviewer/commitdiff_plain/ad6194dafdb57ad332f1d29bc505c605dea9bc57?ds=sidebyside Draw axis if data crosses zero --- diff --git a/chart.c b/chart.c index e9b60fe..2d255e0 100644 --- a/chart.c +++ b/chart.c @@ -60,6 +60,20 @@ 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); @@ -73,6 +87,7 @@ static gboolean bv_chart_draw(GtkWidget *widget, cairo_t *cr) { GtkAllocation allocation; gtk_widget_get_allocation(widget, &allocation); + draw_axis(priv, cr, &allocation); draw_data(priv, cr, &allocation); return TRUE;