git.scottworley.com Git - batteryviewer/blob - chart.c

   1 /*
   2  * h/t https://ptomato.name/advanced-gtk-techniques/html/custom-container.html
   3  * for examples of how to make GTK widgets
   4  */
   5
   6 #include "chart.h"
   7 #include <float.h>
   8 #include <gtk/gtk.h>
   9
  10 #define BV_CHART_PRIVATE(obj)                                                  \
  11   (G_TYPE_INSTANCE_GET_PRIVATE((obj), BV_CHART_TYPE, BVChartPrivate))
  12
  13 typedef struct _BVChartPrivate BVChartPrivate;
  14
  15 struct _BVChartPrivate {
  16   GArray *points;
  17   float minx, miny, maxx, maxy;
  18 };
  19
  20 struct BVChartPoint {
  21   float x, y;
  22 };
  23
  24 G_DEFINE_TYPE_WITH_CODE(BVChart, bv_chart, GTK_TYPE_DRAWING_AREA,
  25                         G_ADD_PRIVATE(BVChart))
  26
  27 typedef void (*cairo_draw_func)(cairo_t *cr, double x, double y);
  28
  29 static gboolean bv_chart_draw(GtkWidget *widget, cairo_t *cr) {
  30   BVChart *chart = BV_CHART(widget);
  31   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
  32
  33   cairo_set_source_rgb(cr, 1.0, 1.0, 1.0);
  34   cairo_paint(cr);
  35
  36   if (priv->points->len < 2)
  37     return TRUE;
  38
  39   GtkAllocation allocation;
  40   gtk_widget_get_allocation(widget, &allocation);
  41
  42   int margin = 3;
  43   float xscale = (allocation.width - 2 * margin) / (priv->maxx - priv->minx);
  44   float yscale = (allocation.height - 2 * margin) / (priv->miny - priv->maxy);
  45   cairo_set_source_rgb(cr, 0.0, 0.0, 1.0);
  46   float gap_threshold = 3.0;
  47   float prevx = 0.0;
  48   for (guint i = 0; i < priv->points->len; i++) {
  49     struct BVChartPoint *p =
  50         &g_array_index(priv->points, struct BVChartPoint, i);
  51     gboolean is_gap = p->x - prevx > gap_threshold;
  52     cairo_draw_func f = is_gap ? cairo_move_to : cairo_line_to;
  53     float screen_x = xscale * (p->x - priv->minx) + margin;
  54     float screen_y = yscale * (p->y - priv->maxy) + margin;
  55     f(cr, screen_x, screen_y);
  56     prevx = p->x;
  57   }
  58   cairo_stroke(cr);
  59
  60   return TRUE;
  61 }
  62
  63 static void bv_chart_class_init(BVChartClass *klass) {
  64   GtkWidgetClass *widget_class = GTK_WIDGET_CLASS(klass);
  65   widget_class->draw = bv_chart_draw;
  66 }
  67
  68 static void bv_chart_init(BVChart *chart) {
  69   gtk_widget_set_has_window(GTK_WIDGET(chart), FALSE);
  70   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
  71   gboolean zero_terminated = FALSE;
  72   gboolean clear_ = FALSE;
  73   priv->points =
  74       g_array_new(zero_terminated, clear_, sizeof(struct BVChartPoint));
  75   priv->minx = FLT_MAX;
  76   priv->miny = FLT_MAX;
  77   priv->maxx = FLT_MIN;
  78   priv->maxy = FLT_MIN;
  79 }
  80
  81 GtkWidget *bv_chart_new() {
  82   return GTK_WIDGET(g_object_new(bv_chart_get_type(), NULL));
  83 }
  84
  85 void bv_chart_add_point(BVChart *chart, float x, float y) {
  86   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
  87   if (x < priv->minx)
  88     priv->minx = x;
  89   if (y < priv->miny)
  90     priv->miny = y;
  91   if (x > priv->maxx)
  92     priv->maxx = x;
  93   if (y > priv->maxy)
  94     priv->maxy = y;
  95   struct BVChartPoint p = {.x = x, .y = y};
  96   g_array_append_val(priv->points, p);
  97 }