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 void draw_data(BVChartPrivate *priv, cairo_t *cr,
  47                       GtkAllocation *allocation) {
  48   cairo_set_source_rgb(cr, 0.0, 0.0, 1.0);
  49   float gap_threshold = 3.0;
  50   float prevx = 0.0;
  51   for (guint i = 0; i < priv->points->len; i++) {
  52     struct BVChartPoint *p =
  53         &g_array_index(priv->points, struct BVChartPoint, i);
  54     gboolean is_gap = p->x - prevx > gap_threshold;
  55     cairo_draw_func f = is_gap ? cairo_move_to : cairo_line_to;
  56     struct ScreenPoint screen_p = to_screen(priv, allocation, p);
  57     f(cr, screen_p.x, screen_p.y);
  58     prevx = p->x;
  59   }
  60   cairo_stroke(cr);
  61 }
  62
  63 static void draw_axis(BVChartPrivate *priv, cairo_t *cr,
  64                       GtkAllocation *allocation) {
  65   if (priv->miny < 0.0 && priv->maxy > 0.0) {
  66     cairo_set_source_rgb(cr, 0.0, 0.0, 0.0);
  67     struct BVChartPoint p = {.x = priv->minx, .y = 0.0};
  68     struct ScreenPoint screen_p = to_screen(priv, allocation, &p);
  69     cairo_move_to(cr, screen_p.x, screen_p.y);
  70     p.x = priv->maxx;
  71     screen_p = to_screen(priv, allocation, &p);
  72     cairo_line_to(cr, screen_p.x, screen_p.y);
  73     cairo_stroke(cr);
  74   }
  75 }
  76
  77 static gboolean bv_chart_draw(GtkWidget *widget, cairo_t *cr) {
  78   BVChart *chart = BV_CHART(widget);
  79   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
  80
  81   cairo_set_source_rgb(cr, 1.0, 1.0, 1.0);
  82   cairo_paint(cr);
  83
  84   if (priv->points->len < 2)
  85     return TRUE;
  86
  87   GtkAllocation allocation;
  88   gtk_widget_get_allocation(widget, &allocation);
  89
  90   draw_axis(priv, cr, &allocation);
  91   draw_data(priv, cr, &allocation);
  92
  93   return TRUE;
  94 }
  95
  96 static void bv_chart_class_init(BVChartClass *klass) {
  97   GtkWidgetClass *widget_class = GTK_WIDGET_CLASS(klass);
  98   widget_class->draw = bv_chart_draw;
  99 }
 100
 101 static void bv_chart_init(BVChart *chart) {
 102   gtk_widget_set_has_window(GTK_WIDGET(chart), FALSE);
 103   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
 104   gboolean zero_terminated = FALSE;
 105   gboolean clear_ = FALSE;
 106   priv->points =
 107       g_array_new(zero_terminated, clear_, sizeof(struct BVChartPoint));
 108   priv->minx = FLT_MAX;
 109   priv->miny = FLT_MAX;
 110   priv->maxx = FLT_MIN;
 111   priv->maxy = FLT_MIN;
 112 }
 113
 114 GtkWidget *bv_chart_new() {
 115   return GTK_WIDGET(g_object_new(bv_chart_get_type(), NULL));
 116 }
 117
 118 void bv_chart_add_point(BVChart *chart, float x, float y) {
 119   BVChartPrivate *priv = bv_chart_get_instance_private(chart);
 120   if (x < priv->minx)
 121     priv->minx = x;
 122   if (y < priv->miny)
 123     priv->miny = y;
 124   if (x > priv->maxx)
 125     priv->maxx = x;
 126   if (y > priv->maxy)
 127     priv->maxy = y;
 128   struct BVChartPoint p = {.x = x, .y = y};
 129   g_array_append_val(priv->points, p);
 130 }