Factor out drawing into Charts

lib/charts/BarChart.cpp

@@ -0,0 +1,92 @@
+#include "charts.h"
+
+void BarChart::reset()
+{
+    memset(ys, 0, width * sizeof(float));
+    memset(changed, false, width * sizeof(bool));
+    redraw_all = true;
+}
+
+int BarChart::updatePoint(float x, float y)
+{
+    if (x < min_x || x >= max_x)
+    {
+        return -1;
+    }
+
+    size_t idx = width * (x - min_x) / (max_x - min_x);
+    if (idx >= width)
+    {
+        idx = width - 1;
+    }
+
+    if (!changed[idx] || ys[idx] < y)
+    {
+        ys[idx] = y;
+        changed[idx] = true;
+    }
+
+    return idx;
+}
+
+void BarChart::draw()
+{
+    for (int x = 0; x < width; x++)
+    {
+        if (!changed[x] && !redraw_all)
+            continue;
+
+        drawOne(x);
+    }
+
+    redraw_all = false;
+}
+
+void BarChart::drawOne(int x)
+{
+    if (x < 0)
+        return;
+
+    int y = y2pos(ys[x]);
+
+    if (y < height)
+    {
+        display.setColor(BLACK);
+        display.drawVerticalLine(pos_x + x, pos_y, y);
+        display.setColor(WHITE);
+        display.drawVerticalLine(pos_x + x, pos_y + y, height - y);
+    }
+    else
+    {
+        display.setColor(BLACK);
+        display.drawVerticalLine(pos_x + x, pos_y, height);
+    }
+
+    if (x % 2 == 0)
+    {
+        display.setColor(INVERSE);
+        display.setPixel(pos_x + x, pos_y + y2pos(level_y));
+    }
+
+    changed[x] = false;
+}
+
+int BarChart::x2pos(float x)
+{
+    if (x < min_x)
+        x = min_x;
+    if (x > max_x)
+        x = max_x;
+
+    return width * (x - min_x) / (max_x - min_x);
+}
+
+int BarChart::y2pos(float y)
+{
+    if (y < min_y)
+        y = min_y;
+    if (y > max_y)
+        y = max_y;
+
+    return height - height * (y - min_y) / (max_y - min_y);
+}