Fix stacked bar column filling entire chart area when single element is present (#10)

* Initial plan

* Fix: Set moderate bar width for single-element stacked bar charts

Co-authored-by: rebelinux <1002783+rebelinux@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: rebelinux <1002783+rebelinux@users.noreply.github.com>

Author: Copilot

Sources/StackedBarChart.cs

@@ -85,6 +85,8 @@ public object Chart(List<double[]> values, string[] labels, string[] categoryNam
 
                 // create bars
                 var bars = new List<ScottPlot.Bar>();
+                // Set a moderate bar width when there is only one element to prevent it from filling the entire chart area
+                double barSize = values.Count == 1 ? 0.5 : 0.8;
                 // assign values and colors to each bar
                 for (int x = 0; x < values.Count; x++)
                 {
@@ -101,6 +103,7 @@ public object Chart(List<double[]> values, string[] labels, string[] categoryNam
                                 FillColor = colorPalette.GetColor(i),
                                 Label = $"{values[x][i]}",
                                 CenterLabel = true,
+                                Size = barSize,
                             });
                             nextBarBase += values[x][i];
                         }

Tests/AsBuiltReport.Chart.Functions.Tests.ps1

@@ -70,5 +70,13 @@ Describe 'AsBuiltReport.Chart Exported Functions' {
         It 'Should throw error for mismatched Values and LegendCategories' {
             { New-StackedBarChart -Title 'Test' -Values @(@(1, 2), @(3, 4)) -Labels @('A', 'B') -LegendCategories @('X') -Format 'png' -OutputFolderPath $TestDrive } | Should -Throw -ExpectedMessage "Error: Values and category names must be equal."
         }
+        It 'Should run without error with a single element (single-bar chart)' {
+            { New-StackedBarChart -Title 'Test' -Values @(,[double[]]@(1, 2)) -Labels @('A') -LegendCategories @('X', 'Y') -Format 'png' -OutputFolderPath $TestDrive } | Should -Not -Throw
+        }
+        It 'Should return a file path as output for a single element' {
+            $result = New-StackedBarChart -Title 'Test' -Values @(,[double[]]@(1, 2)) -Labels @('A') -LegendCategories @('X', 'Y') -Format 'png' -OutputFolderPath $TestDrive
+            $result | Should -BeOfType 'System.IO.FileSystemInfo'
+            Test-Path $result | Should -BeTrue
+        }
     }
 }