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 struct ScreenPoint {
  25   float x, y;
  26 };
  27
  28 G_DEFINE_TYPE_WITH_CODE(BVChart, bv_chart, GTK_TYPE_DRAWING_AREA,
  29                         G_ADD_PRIVATE(BVChart))
  30
  31 typedef void (*cairo_draw_func)(cairo_t *cr, double x, double y);
  32
  33 static struct ScreenPoint to_screen(BVChartPrivate *priv,
  34                                     GtkAllocation *allocation,
  35                                     struct BVChartPoint *p) {
  36   int margin = 3;
  37   float xscale = (allocation->width - 2 * margin) / (priv->maxx - priv->minx);
  38   float yscale = (allocation->height - 2 * margin) / (priv->miny - priv->maxy);
  39   struct ScreenPoint screen_p = {
  40       .x = xscale * (p->x - priv->minx) + margin,
  41       .y = yscale * (p->y - priv->maxy) + margin,
  42   };
  43   return screen_p;
  44 }
  45
  46 static gboolean bv_chart_draw(GtkWidget *widget, cairo_t *cr) {
  47   BVChart *chart = BV_CHART(widget);
  48   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
  49
  50   cairo_set_source_rgb(cr, 1.0, 1.0, 1.0);
  51   cairo_paint(cr);
  52
  53   if (priv->points->len < 2)
  54     return TRUE;
  55
  56   GtkAllocation allocation;
  57   gtk_widget_get_allocation(widget, &allocation);
  58
  59   cairo_set_source_rgb(cr, 0.0, 0.0, 1.0);
  60   float gap_threshold = 3.0;
  61   float prevx = 0.0;
  62   for (guint i = 0; i < priv->points->len; i++) {
  63     struct BVChartPoint *p =
  64         &g_array_index(priv->points, struct BVChartPoint, i);
  65     gboolean is_gap = p->x - prevx > gap_threshold;
  66     cairo_draw_func f = is_gap ? cairo_move_to : cairo_line_to;
  67     struct ScreenPoint screen_p = to_screen(priv, &allocation, p);
  68     f(cr, screen_p.x, screen_p.y);
  69     prevx = p->x;
  70   }
  71   cairo_stroke(cr);
  72
  73   return TRUE;
  74 }
  75
  76 static void bv_chart_class_init(BVChartClass *klass) {
  77   GtkWidgetClass *widget_class = GTK_WIDGET_CLASS(klass);
  78   widget_class->draw = bv_chart_draw;
  79 }
  80
  81 static void bv_chart_init(BVChart *chart) {
  82   gtk_widget_set_has_window(GTK_WIDGET(chart), FALSE);
  83   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
  84   gboolean zero_terminated = FALSE;
  85   gboolean clear_ = FALSE;
  86   priv->points =
  87       g_array_new(zero_terminated, clear_, sizeof(struct BVChartPoint));
  88   priv->minx = FLT_MAX;
  89   priv->miny = FLT_MAX;
  90   priv->maxx = FLT_MIN;
  91   priv->maxy = FLT_MIN;
  92 }
  93
  94 GtkWidget *bv_chart_new() {
  95   return GTK_WIDGET(g_object_new(bv_chart_get_type(), NULL));
  96 }
  97
  98 void bv_chart_add_point(BVChart *chart, float x, float y) {
  99   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
 100   if (x < priv->minx)
 101     priv->minx = x;
 102   if (y < priv->miny)
 103     priv->miny = y;
 104   if (x > priv->maxx)
 105     priv->maxx = x;
 106   if (y > priv->maxy)
 107     priv->maxy = y;
 108   struct BVChartPoint p = {.x = x, .y = y};
 109   g_array_append_val(priv->points, p);
 110 }