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[batteryviewer] / 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 gboolean bv_chart_draw(GtkWidget *widget, cairo_t *cr) {
64 BVChart *chart = BV_CHART(widget);
65 BVChartPrivate *priv = bv_chart_get_instance_private(chart);
66
67 cairo_set_source_rgb(cr, 1.0, 1.0, 1.0);
68 cairo_paint(cr);
69
70 if (priv->points->len < 2)
71 return TRUE;
72
73 GtkAllocation allocation;
74 gtk_widget_get_allocation(widget, &allocation);
75
76 draw_data(priv, cr, &allocation);
77
78 return TRUE;
79 }
80
81 static void bv_chart_class_init(BVChartClass *klass) {
82 GtkWidgetClass *widget_class = GTK_WIDGET_CLASS(klass);
83 widget_class->draw = bv_chart_draw;
84 }
85
86 static void bv_chart_init(BVChart *chart) {
87 gtk_widget_set_has_window(GTK_WIDGET(chart), FALSE);
88 BVChartPrivate *priv = bv_chart_get_instance_private(chart);
89 gboolean zero_terminated = FALSE;
90 gboolean clear_ = FALSE;
91 priv->points =
92 g_array_new(zero_terminated, clear_, sizeof(struct BVChartPoint));
93 priv->minx = FLT_MAX;
94 priv->miny = FLT_MAX;
95 priv->maxx = FLT_MIN;
96 priv->maxy = FLT_MIN;
97 }
98
99 GtkWidget *bv_chart_new() {
100 return GTK_WIDGET(g_object_new(bv_chart_get_type(), NULL));
101 }
102
103 void bv_chart_add_point(BVChart *chart, float x, float y) {
104 BVChartPrivate *priv = bv_chart_get_instance_private(chart);
105 if (x < priv->minx)
106 priv->minx = x;
107 if (y < priv->miny)
108 priv->miny = y;
109 if (x > priv->maxx)
110 priv->maxx = x;
111 if (y > priv->maxy)
112 priv->maxy = y;
113 struct BVChartPoint p = {.x = x, .y = y};
114 g_array_append_val(priv->points, p);
115 }