125 lines
4.6 KiB
Python
125 lines
4.6 KiB
Python
import display_driver
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import lvgl as lv
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# A class is used to keep track of the series list because later we
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# need to draw to the series in the reverse order to which they were initialised.
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class StackedAreaChart:
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def __init__(self):
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self.obj = None
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self.series_list = [None, None, None]
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stacked_area_chart = StackedAreaChart()
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#
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# Callback which draws the blocks of colour under the lines
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#
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def draw_event_cb(e):
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obj = e.get_target()
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cont_a = lv.area_t()
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obj.get_coords(cont_a)
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#Add the faded area before the lines are drawn
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dsc = e.get_draw_part_dsc()
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if dsc.part == lv.PART.ITEMS:
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if not dsc.p1 or not dsc.p2:
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return
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# Add a line mask that keeps the area below the line
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line_mask_param = lv.draw_mask_line_param_t()
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line_mask_param.points_init(dsc.p1.x, dsc.p1.y, dsc.p2.x, dsc.p2.y, lv.DRAW_MASK_LINE_SIDE.BOTTOM)
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line_mask_id = lv.draw_mask_add(line_mask_param, None)
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#Draw a rectangle that will be affected by the mask
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draw_rect_dsc = lv.draw_rect_dsc_t()
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draw_rect_dsc.init()
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draw_rect_dsc.bg_opa = lv.OPA.COVER
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draw_rect_dsc.bg_color = dsc.line_dsc.color
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a = lv.area_t()
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a.x1 = dsc.p1.x
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a.x2 = dsc.p2.x
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a.y1 = min(dsc.p1.y, dsc.p2.y)
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a.y2 = cont_a.y2 - 13 # -13 cuts off where the rectangle draws over the chart margin. Without this an area of 0 doesn't look like 0
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dsc.draw_ctx.rect(draw_rect_dsc, a)
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# Remove the mask
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lv.draw_mask_free_param(line_mask_param)
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lv.draw_mask_remove_id(line_mask_id)
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#
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# Helper function to round a fixed point number
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#
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def round_fixed_point(n, shift):
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# Create a bitmask to isolates the decimal part of the fixed point number
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mask = 1
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for bit_pos in range(shift):
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mask = (mask << 1) + 1
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decimal_part = n & mask
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# Get 0.5 as fixed point
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rounding_boundary = 1 << (shift - 1)
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# Return either the integer part of n or the integer part + 1
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if decimal_part < rounding_boundary:
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return (n & ~mask)
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return ((n >> shift) + 1) << shift
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#
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# Stacked area chart
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#
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def lv_example_chart_8():
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#Create a stacked_area_chart.obj
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stacked_area_chart.obj = lv.chart(lv.scr_act())
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stacked_area_chart.obj.set_size(200, 150)
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stacked_area_chart.obj.center()
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stacked_area_chart.obj.set_type( lv.chart.TYPE.LINE)
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stacked_area_chart.obj.set_div_line_count(5, 7)
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stacked_area_chart.obj.add_event_cb( draw_event_cb, lv.EVENT.DRAW_PART_BEGIN, None)
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# Set range to 0 to 100 for percentages. Draw ticks
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stacked_area_chart.obj.set_range(lv.chart.AXIS.PRIMARY_Y,0,100)
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stacked_area_chart.obj.set_axis_tick(lv.chart.AXIS.PRIMARY_Y, 3, 0, 5, 1, True, 30)
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#Set point size to 0 so the lines are smooth
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stacked_area_chart.obj.set_style_size(0, lv.PART.INDICATOR)
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# Add some data series
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stacked_area_chart.series_list[0] = stacked_area_chart.obj.add_series(lv.palette_main(lv.PALETTE.RED), lv.chart.AXIS.PRIMARY_Y)
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stacked_area_chart.series_list[1] = stacked_area_chart.obj.add_series(lv.palette_main(lv.PALETTE.BLUE), lv.chart.AXIS.PRIMARY_Y)
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stacked_area_chart.series_list[2] = stacked_area_chart.obj.add_series(lv.palette_main(lv.PALETTE.GREEN), lv.chart.AXIS.PRIMARY_Y)
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for point in range(10):
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# Make some random data
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vals = [lv.rand(10, 20), lv.rand(20, 30), lv.rand(20, 30)]
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fixed_point_shift = 5
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total = vals[0] + vals[1] + vals[2]
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draw_heights = [0, 0, 0]
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int_sum = 0
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decimal_sum = 0
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# Fixed point cascade rounding ensures percentages add to 100
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for series_index in range(3):
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decimal_sum += int(((vals[series_index] * 100) << fixed_point_shift) // total)
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int_sum += int((vals[series_index] * 100) / total)
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modifier = (round_fixed_point(decimal_sum, fixed_point_shift) >> fixed_point_shift) - int_sum
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# The draw heights are equal to the percentage of the total each value is + the cumulative sum of the previous percentages.
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# The accumulation is how the values get "stacked"
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draw_heights[series_index] = int(int_sum + modifier)
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# Draw to the series in the reverse order to which they were initialised.
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# Without this the higher values will draw on top of the lower ones.
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# This is because the Z-height of a series matches the order it was initialised
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stacked_area_chart.obj.set_next_value( stacked_area_chart.series_list[3 - series_index - 1], draw_heights[series_index])
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stacked_area_chart.obj.refresh()
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lv_example_chart_8()
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