Add function to set axis labels alignment

include/xlsxwriter/chart.h

@@ -529,6 +529,20 @@ typedef enum lxw_chart_axis_label_position {
     LXW_CHART_AXIS_LABEL_POSITION_NONE
 } lxw_chart_axis_label_position;
 
+/**
+ * @brief Axis label alignments.
+ */
+typedef enum lxw_chart_axis_label_alignment {
+    /** Series data label alignment: center. */
+    LXW_CHART_AXIS_LABEL_ALIGNMENT_CENTER,
+
+    /** Series data label alignment: left. */
+    LXW_CHART_AXIS_LABEL_ALIGNMENT_LEFT,
+
+    /** Series data label alignment: right. */
+    LXW_CHART_AXIS_LABEL_ALIGNMENT_RIGHT
+} lxw_chart_axis_label_alignment;
+
 /**
  * @brief Display units for chart value axis.
  */
@@ -986,6 +1000,7 @@ typedef struct lxw_chart_axis {
     uint8_t is_value;
     uint8_t axis_position;
     uint8_t position_axis;
+    uint8_t label_alignment;
     uint8_t label_position;
     uint8_t hidden;
     uint8_t reverse;
@@ -2596,6 +2611,27 @@ void chart_axis_set_position(lxw_chart_axis *axis, uint8_t position);
  */
 void chart_axis_set_label_position(lxw_chart_axis *axis, uint8_t position);
 
+/**
+ * @brief Position the alignment of axis labels.
+ *
+ * @param axis     A pointer to a chart #lxw_chart_axis object.
+ * @param alignment A #lxw_chart_label_alignment value.
+ *
+ * Position the axis labels for the chart. The labels are the numbers, or
+ * strings or dates, on the axis that indicate the categories or values of
+ * the axis. * The allowable values:
+ *
+ * - #LXW_CHART_AXIS_LABEL_ALIGNMENT_CENTER - Align label center (default).
+ * - #LXW_CHART_AXIS_LABEL_ALIGNMENT_LEFT - Align label left.
+ * - #LXW_CHART_AXIS_LABEL_ALIGNMENT_RIGHT - Align label right.
+ *
+ * @image html chart_label_alignment1.png
+ *
+ * **Axis types**: This function is applicable to to all axes types.
+ *                 See @ref ww_charts_axes.
+ */
+void chart_axis_set_label_alignment(lxw_chart_axis *axis, uint8_t alignment);
+
 /**
  * @brief Set the minimum value for a chart axis.
  *

src/chart.c

@@ -3201,13 +3201,19 @@ _chart_write_auto(lxw_chart *self)
  * Write the <c:lblAlgn> element.
  */
 STATIC void
-_chart_write_label_align(lxw_chart *self)
+_chart_write_label_align(lxw_chart *self, lxw_chart_axis *axis)
 {
     struct xml_attribute_list attributes;
     struct xml_attribute *attribute;
 
     LXW_INIT_ATTRIBUTES();
-    LXW_PUSH_ATTRIBUTES_STR("val", "ctr");
+
+    if (axis->label_alignment == LXW_CHART_AXIS_LABEL_ALIGNMENT_LEFT)
+        LXW_PUSH_ATTRIBUTES_STR("val", "l");
+    else if (axis->label_alignment == LXW_CHART_AXIS_LABEL_ALIGNMENT_RIGHT)
+        LXW_PUSH_ATTRIBUTES_STR("val", "r");
+    else
+        LXW_PUSH_ATTRIBUTES_STR("val", "ctr");
 
     lxw_xml_empty_tag(self->file, "c:lblAlgn", &attributes);
 
@@ -4098,7 +4104,7 @@ _chart_write_cat_axis(lxw_chart *self)
     _chart_write_auto(self);
 
     /* Write the c:lblAlgn element. */
-    _chart_write_label_align(self);
+    _chart_write_label_align(self, self->x_axis);
 
     /* Write the c:lblOffset element. */
     _chart_write_label_offset(self);
@@ -6047,6 +6053,15 @@ chart_axis_minor_gridlines_set_line(lxw_chart_axis *axis,
         axis->minor_gridlines.visible = LXW_TRUE;
 }
 
+/*
+ * Set the labels alignement.
+ */
+void
+chart_axis_set_label_alignment(lxw_chart_axis *axis, uint8_t alignment)
+{
+    axis->label_alignment = alignment;
+}
+
 /*
  * Set the chart title.
  */

test/functional/src/test_chart_axis42.c

@@ -0,0 +1,47 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2018, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = new_workbook("test_chart_axis42.xlsx");
+    lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
+    lxw_chart     *chart     = workbook_add_chart(workbook, LXW_CHART_COLUMN);
+
+    /* For testing, copy the randomly generated axis ids in the target file. */
+    chart->axis_id_1 = 43704320;
+    chart->axis_id_2 = 43706624;
+
+    uint8_t data[5][3] = {
+        {1, 2,  3},
+        {2, 4,  6},
+        {3, 6,  9},
+        {4, 8,  12},
+        {5, 10, 15}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 3; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    chart_axis_set_name(chart->x_axis, "XXX");
+    chart_axis_set_name(chart->y_axis, "YYY");
+
+    chart_axis_set_label_alignment(chart->x_axis, LXW_CHART_AXIS_LABEL_ALIGNMENT_RIGHT);
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/test_chart_axis.py

@@ -130,3 +130,6 @@ class TestCompareXLSXFiles(base_test_class.XLSXBaseTest):
 
     def test_chart_axis41(self):
         self.run_exe_test('test_chart_axis41')
+
+    def test_chart_axis42(self):
+        self.run_exe_test('test_chart_axis42')