Tweak x-axis labels of charts

* Avoid overlapping of labels

Signed-off-by: Holger Friedrich <[email protected]>

Author: holgerfriedrich

bundles/org.openhab.core.ui/src/main/java/org/openhab/core/ui/internal/chart/defaultchartprovider/DefaultChartProvider.java

@@ -206,6 +206,11 @@ public BufferedImage createChart(@Nullable String serviceId, @Nullable String th
         }
         styler.setYAxisTickMarkSpacingHint(yAxisSpacing);
         styler.setYAxisLabelAlignment(TextAlignment.Right);
+        // avoid overlapping labels on x-axis;
+        // Font.getSize() is related to font height, but will also give an indication of the width;
+        // pattern is not the actual label, but also gives a rough estimation of the width of the label
+        int xAxisSpacing = Math.max(width / 15, chartTheme.getAxisTickLabelsFont(dpi).getSize() * pattern.length());
+        styler.setXAxisTickMarkSpacingHint(xAxisSpacing);
         // chart
         styler.setChartBackgroundColor(chartTheme.getChartBackgroundColor());
         styler.setChartFontColor(chartTheme.getChartFontColor());