Weird behaviour of height and width options

[sintro]

For me, the default 400 for width and height is not applied when I try to render chart (tried for bar_chart).
My custom values are also does not applied directly, but applied in some weird modified states.
Here is origial (default) output code:

<canvas id="chart-0" class="chart" width="1064" height="1064" style="display: block; width: 1064px; height: 1064px;"></canvas>

Here is code with passed

    @chart_options = {
      :height => '20',
      :width => '100'
    }

<canvas id="chart-0" class="chart" width="1081" height="216" style="display: block; width: 1081px; height: 216px;"></canvas>

[XbandoleroX]

Same case in rails 5.2

[gloaec]

Same result using javascript and canvas :

<canvas id="chart" width="400" height="400"></canvas>

renders :

<canvas id="chart" width="895" height="895" style="display: block; width: 895px; height: 895px;" class="chartjs-render-monitor"></canvas>

would it come from Char.js lib itself ?

[gloaec]

This worked :

<div class="chart-container" style="width: 400px; height: 400px;">
  <canvas id="chart"></canvas>
</div>

Options :

options = {
  responsive: true,
  maintainAspectRatio: false
}

Or with ruby helpers :

<div class="chart-container">
  <%= line_chart data, {
    responsive: true,
    maintainAspectRatio: false,
  } %>
</div>