Added support for custom chart data labels.

.indent.pro

@@ -57,6 +57,8 @@
 -T lxw_chart_axis_tick_position
 -T lxw_chart_axis_type
 -T lxw_chart_blank
+-T lxw_chart_custom_label
+-T lxw_chart_data_label
 -T lxw_chart_error_bar_axis
 -T lxw_chart_error_bar_cap
 -T lxw_chart_error_bar_direction

include/xlsxwriter/chart.h

@@ -787,6 +787,29 @@ typedef struct lxw_chart_point {
 
 } lxw_chart_point;
 
+typedef struct lxw_chart_data_label {
+
+    char *value;
+    uint8_t delete;
+    lxw_chart_font *font;
+
+} lxw_chart_data_label;
+
+/* Internal version of lxw_chart_data_label with more metadata. */
+typedef struct lxw_chart_custom_label {
+
+    char *value;
+    uint8_t delete;
+    lxw_chart_font *font;
+
+    /* We use a range to hold the label formula properties even though it
+     * will only have 1 point in order to re-use similar functions.*/
+    lxw_series_range *range;
+
+    struct lxw_series_data_point data_point;
+
+} lxw_chart_custom_label;
+
 /**
  * @brief Define how blank values are displayed in a chart.
  */
@@ -916,7 +939,9 @@ typedef struct lxw_chart_series {
     lxw_chart_pattern *pattern;
     lxw_chart_marker *marker;
     lxw_chart_point *points;
+    lxw_chart_custom_label *data_labels;
     uint16_t point_count;
+    uint16_t data_label_count;
 
     uint8_t smooth;
     uint8_t invert_if_negative;
@@ -1659,6 +1684,9 @@ void chart_series_set_labels_options(lxw_chart_series *series,
                                      uint8_t show_name, uint8_t show_category,
                                      uint8_t show_value);
 
+lxw_error chart_series_set_labels_custom(lxw_chart_series *series, lxw_chart_data_label
+                                         *data_labels[]);
+
 /**
  * @brief Set the separator for the data label captions.
  *

src/chart.c

@@ -82,6 +82,23 @@ _chart_free_font(lxw_chart_font *font)
     free(font);
 }
 
+STATIC void
+_chart_free_data_labels(lxw_chart_series *series)
+{
+    uint16_t index;
+
+    for (index = 0; index < series->data_label_count; index++) {
+        lxw_chart_custom_label *data_label = &series->data_labels[index];
+
+        free(data_label->value);
+        _chart_free_range(data_label->range);
+        _chart_free_font(data_label->font);
+    }
+
+    series->data_label_count = 0;
+    free(series->data_labels);
+}
+
 /*
  * Free a series object.
  */
@@ -109,6 +126,7 @@ _chart_series_free(lxw_chart_series *series)
     _chart_free_range(series->values);
     _chart_free_range(series->title.range);
     _chart_free_points(series);
+    _chart_free_data_labels(series);
 
     if (series->x_error_bars) {
         free(series->x_error_bars->line);
@@ -1067,12 +1085,14 @@ _chart_write_a_p_pie(lxw_chart *self, lxw_chart_font *font)
  * Write the <a:p> element.
  */
 STATIC void
-_chart_write_a_p_rich(lxw_chart *self, char *name, lxw_chart_font *font)
+_chart_write_a_p_rich(lxw_chart *self, char *name, lxw_chart_font *font,
+                      uint8_t is_data_label)
 {
     lxw_xml_start_tag(self->file, "a:p", NULL);
 
     /* Write the a:pPr element. */
-    _chart_write_a_p_pr_rich(self, font);
+    if (!is_data_label)
+        _chart_write_a_p_pr_rich(self, font);
 
     /* Write the a:r element. */
     _chart_write_a_r(self, name, font);
@@ -1454,8 +1474,8 @@ _chart_write_axis_font(lxw_chart *self, lxw_chart_font *font)
  * Write the <c:rich> element.
  */
 STATIC void
-_chart_write_rich(lxw_chart *self, char *name, uint8_t is_horizontal,
-                  lxw_chart_font *font)
+_chart_write_rich(lxw_chart *self, char *name, lxw_chart_font *font,
+                  uint8_t is_horizontal, uint8_t is_data_label)
 {
     int32_t rotation = 0;
 
@@ -1471,7 +1491,7 @@ _chart_write_rich(lxw_chart *self, char *name, uint8_t is_horizontal,
     _chart_write_a_lst_style(self);
 
     /* Write the a:p element. */
-    _chart_write_a_p_rich(self, name, font);
+    _chart_write_a_p_rich(self, name, font, is_data_label);
 
     lxw_xml_end_tag(self->file, "c:rich");
 }
@@ -1487,7 +1507,7 @@ _chart_write_tx_rich(lxw_chart *self, char *name, uint8_t is_horizontal,
     lxw_xml_start_tag(self->file, "c:tx", NULL);
 
     /* Write the c:rich element. */
-    _chart_write_rich(self, name, is_horizontal, font);
+    _chart_write_rich(self, name, font, is_horizontal, LXW_FALSE);
 
     lxw_xml_end_tag(self->file, "c:tx");
 }
@@ -2256,6 +2276,110 @@ _chart_write_label_num_fmt(lxw_chart *self, char *format)
     LXW_FREE_ATTRIBUTES();
 }
 
+/*
+ * Write parts of the <c:dLbl> elements for formula custom labels.
+ */
+STATIC void
+_chart_write_custom_label_formula(lxw_chart *self, lxw_chart_series *series,
+                                  lxw_chart_custom_label *data_label)
+{
+    lxw_xml_empty_tag(self->file, "c:layout", NULL);
+    lxw_xml_start_tag(self->file, "c:tx", NULL);
+
+    _chart_write_str_ref(self, data_label->range);
+
+    lxw_xml_end_tag(self->file, "c:tx");
+
+    if (data_label->font) {
+        lxw_xml_empty_tag(self->file, "c:spPr", NULL);
+        _chart_write_tx_pr(self, LXW_FALSE, data_label->font);
+    }
+
+    /* Write the c:showVal element. */
+    if (series->show_labels_value)
+        _chart_write_show_val(self);
+
+    /* Write the c:showCatName element. */
+    if (series->show_labels_category)
+        _chart_write_show_cat_name(self);
+
+    /* Write the c:showSerName element. */
+    if (series->show_labels_name)
+        _chart_write_show_ser_name(self);
+
+}
+
+/*
+ * Write parts of the <c:dLbl> elements for string custom labels.
+ */
+STATIC void
+_chart_write_custom_label_str(lxw_chart *self, lxw_chart_series *series,
+                              lxw_chart_custom_label *data_label)
+{
+    lxw_xml_empty_tag(self->file, "c:layout", NULL);
+    lxw_xml_start_tag(self->file, "c:tx", NULL);
+
+    /* Write the c:rich element. */
+    _chart_write_rich(self, data_label->value, data_label->font,
+                      LXW_FALSE, LXW_TRUE);
+
+    lxw_xml_end_tag(self->file, "c:tx");
+
+    /* Write the c:showVal element. */
+    if (series->show_labels_value)
+        _chart_write_show_val(self);
+
+    /* Write the c:showCatName element. */
+    if (series->show_labels_category)
+        _chart_write_show_cat_name(self);
+
+    /* Write the c:showSerName element. */
+    if (series->show_labels_name)
+        _chart_write_show_ser_name(self);
+
+}
+
+/*
+ * Write the <c:dLbl> elements for custom labels.
+ */
+STATIC void
+_chart_write_custom_labels(lxw_chart *self, lxw_chart_series *series)
+{
+    uint16_t index = 0;
+
+    for (index = 0; index < series->data_label_count; index++) {
+        lxw_chart_custom_label *data_label = &series->data_labels[index];
+
+        if (!data_label->value && !data_label->range && !data_label->delete
+            && !data_label->font) {
+
+            continue;
+        }
+
+        lxw_xml_start_tag(self->file, "c:dLbl", NULL);
+
+        /* Write the c:idx element. */
+        _chart_write_idx(self, index);
+
+        if (data_label->delete) {
+            /* Write the c:delete element. */
+            _chart_write_delete(self);
+        }
+        else if (data_label->value) {
+            _chart_write_custom_label_str(self, series, data_label);
+        }
+        else if (data_label->range) {
+            _chart_write_custom_label_formula(self, series, data_label);
+        }
+        else if (data_label->font) {
+            lxw_xml_empty_tag(self->file, "c:spPr", NULL);
+            _chart_write_tx_pr(self, LXW_FALSE, data_label->font);
+        }
+
+        lxw_xml_end_tag(self->file, "c:dLbl");
+    }
+}
+
 /*
  * Write the <c:dLbls> element.
  */
@@ -2267,6 +2391,9 @@ _chart_write_d_lbls(lxw_chart *self, lxw_chart_series *series)
 
     lxw_xml_start_tag(self->file, "c:dLbls", NULL);
 
+    if (series->data_labels)
+        _chart_write_custom_labels(self, series);
+
     /* Write the c:numFmt element. */
     if (series->label_num_format)
         _chart_write_label_num_fmt(self, series->label_num_format);
@@ -3557,7 +3684,7 @@ _chart_write_legend_entry(lxw_chart *self, uint16_t index)
     /* Write the c:idx element. */
     _chart_write_idx(self, self->delete_series[index]);
 
-    /* Write the c:delete element. */
+    /* Write the c:dst_label element. */
     _chart_write_delete(self);
 
     lxw_xml_end_tag(self->file, "c:legendEntry");
@@ -4999,7 +5126,7 @@ lxw_chart_add_data_cache(lxw_series_range *range, uint8_t *data,
 }
 
 /*
- * Insert an image into the worksheet.
+ * Add a series to the chart.
  */
 lxw_chart_series *
 chart_add_series(lxw_chart *self, const char *categories, const char *values)
@@ -5306,7 +5433,7 @@ chart_series_set_marker_pattern(lxw_chart_series *series,
 }
 
 /*
- * Store the horizontal page breaks on a worksheet.
+ * Store the points for a chart.
  */
 lxw_error
 chart_series_set_points(lxw_chart_series *series, lxw_chart_point *points[])
@@ -5375,6 +5502,81 @@ chart_series_set_labels_options(lxw_chart_series *series, uint8_t show_name,
     series->show_labels_value = show_value;
 }
 
+/*
+ * Store the custom data_labels for a chart.
+ */
+lxw_error
+chart_series_set_labels_custom(lxw_chart_series *series,
+                               lxw_chart_data_label *data_labels[])
+{
+    uint16_t i = 0;
+    uint16_t data_label_count = 0;
+
+    if (data_labels == NULL)
+        return LXW_ERROR_NULL_PARAMETER_IGNORED;
+
+    while (data_labels[data_label_count])
+        data_label_count++;
+
+    if (data_label_count == 0)
+        return LXW_ERROR_NULL_PARAMETER_IGNORED;
+
+    series->has_labels = LXW_TRUE;
+
+    /* Set the Value label type if no other type is set. */
+    if (!series->show_labels_name && !series->show_labels_category
+        && !series->show_labels_value) {
+        series->show_labels_value = LXW_TRUE;
+    }
+
+    /* Free any existing resource. */
+    _chart_free_data_labels(series);
+
+    series->data_labels = calloc(data_label_count,
+                                 sizeof(lxw_chart_custom_label));
+    RETURN_ON_MEM_ERROR(series->data_labels, LXW_ERROR_MEMORY_MALLOC_FAILED);
+
+    /* Copy the user data into the array of new structs. The struct types
+     * are different since the internal version has more fields. */
+    for (i = 0; i < data_label_count; i++) {
+        lxw_chart_data_label *user_data_label = data_labels[i];
+        lxw_chart_custom_label *data_label = &series->data_labels[i];
+
+        char *src_value = user_data_label->value;
+
+        data_label->delete = user_data_label->delete;
+
+        data_label->font = _chart_convert_font_args(user_data_label->font);
+
+        if (src_value) {
+            if (*src_value == '=') {
+                /* The value is a formula. Handle like other chart ranges. */
+                data_label->range = calloc(1, sizeof(lxw_series_range));
+                GOTO_LABEL_ON_MEM_ERROR(data_label->range, mem_error);
+
+                data_label->range->formula = lxw_strdup(src_value + 1);
+
+                /* Add the formula to the data cache to allow value to be looked
+                 * up and filled in when the file is closed. */
+                if (_chart_init_data_cache(data_label->range) != LXW_NO_ERROR)
+                    goto mem_error;
+            }
+            else {
+                /* The value is a simple string. */
+                data_label->value = lxw_strdup(src_value);
+            }
+        }
+    }
+
+    series->data_label_count = data_label_count;
+
+    return LXW_NO_ERROR;
+
+mem_error:
+    _chart_free_data_labels(series);
+    return LXW_ERROR_MEMORY_MALLOC_FAILED;
+}
+
 /*
  * Set the data labels separator for a series.
  */

src/workbook.c

@@ -879,6 +879,9 @@ _populate_range_dimensions(lxw_workbook *self, lxw_series_range *range)
 STATIC void
 _populate_range(lxw_workbook *self, lxw_series_range *range)
 {
+    if (!range)
+        return;
+
     _populate_range_dimensions(self, range);
     _populate_range_data_cache(self, range);
 }
@@ -892,6 +895,7 @@ _add_chart_cache_data(lxw_workbook *self)
 {
     lxw_chart *chart;
     lxw_chart_series *series;
+    uint16_t i;
 
     STAILQ_FOREACH(chart, self->ordered_charts, ordered_list_pointers) {
 
@@ -906,6 +910,11 @@ _add_chart_cache_data(lxw_workbook *self)
             _populate_range(self, series->categories);
             _populate_range(self, series->values);
             _populate_range(self, series->title.range);
+
+            for (i = 0; i < series->data_label_count; i++) {
+                lxw_chart_custom_label *data_label = &series->data_labels[i];
+                _populate_range(self, data_label->range);
+            }
         }
     }
 }

test/functional/src/test_chart_data_labels26.c

@@ -0,0 +1,48 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2020, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_chart_data_labels26.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 = 48514944;
+    chart->axis_id_2 = 48516480;
+
+    uint8_t data[5][4] = {
+        {1, 2,  3,  10},
+        {2, 4,  6,  20},
+        {3, 6,  9,  30},
+        {4, 8,  12, 40},
+        {5, 10, 15, 50}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 4; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+
+    lxw_chart_data_label data_label1 = {.value = "33"};
+    lxw_chart_data_label *data_labels[] = {&data_label1, NULL};
+
+    chart_series_set_labels_custom(series, data_labels);
+
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_data_labels27.c

@@ -0,0 +1,48 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2020, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_chart_data_labels27.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 = 48514944;
+    chart->axis_id_2 = 48516480;
+
+    uint8_t data[5][4] = {
+        {1, 2,  3,  10},
+        {2, 4,  6,  20},
+        {3, 6,  9,  30},
+        {4, 8,  12, 40},
+        {5, 10, 15, 50}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 4; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+
+    lxw_chart_data_label data_label1 = {.value = "=Sheet1!$D$1"};
+    lxw_chart_data_label *data_labels[] = {&data_label1, NULL};
+
+    chart_series_set_labels_custom(series, data_labels);
+
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_data_labels28.c

@@ -0,0 +1,64 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2020, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_chart_data_labels28.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 = 48514944;
+    chart->axis_id_2 = 48516480;
+
+    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);
+
+    worksheet_write_string(worksheet, CELL("D1"), "foo" , NULL);
+    worksheet_write_string(worksheet, CELL("D2"), "bar" , NULL);
+
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+
+
+    lxw_chart_data_label data_label1 = {.value = "123"};
+    lxw_chart_data_label data_label2 = {.value = "abc"};
+    lxw_chart_data_label data_label3 = {0};
+    lxw_chart_data_label data_label4 = {.value = "=Sheet1!$D$1"};
+    lxw_chart_data_label data_label5 = {.value = "=Sheet1!$D$2"};
+
+    lxw_chart_data_label *data_labels[] = {
+        &data_label1,
+        &data_label2,
+        &data_label3,
+        &data_label4,
+        &data_label5,
+        NULL
+    };
+
+    chart_series_set_labels_custom(series, data_labels);
+
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_data_labels29.c

@@ -0,0 +1,49 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2020, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_chart_data_labels29.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 = 67858816;
+    chart->axis_id_2 = 67863296;
+
+    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);
+
+
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+
+    lxw_chart_data_label data_label1 = {.delete = LXW_TRUE};
+    lxw_chart_data_label *data_labels[] = {&data_label1, NULL};
+
+    chart_series_set_labels_custom(series, data_labels);
+
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_data_labels30.c

@@ -0,0 +1,49 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2020, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_chart_data_labels30.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 = 67858816;
+    chart->axis_id_2 = 67863296;
+
+    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);
+
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+
+    lxw_chart_data_label data_label1 = {.delete = LXW_TRUE};
+    lxw_chart_data_label data_label2 = {0};
+    lxw_chart_data_label *data_labels[] = {&data_label1, &data_label2, &data_label1, &data_label2, &data_label1, NULL};
+
+    chart_series_set_labels_custom(series, data_labels);
+
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_data_labels31.c

@@ -0,0 +1,49 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2020, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_chart_data_labels31.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 = 71248896;
+    chart->axis_id_2 = 71373568;
+
+    uint8_t data[5][4] = {
+        {1, 2,  3,  10},
+        {2, 4,  6,  20},
+        {3, 6,  9,  30},
+        {4, 8,  12, 40},
+        {5, 10, 15, 50}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 4; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+
+    lxw_chart_data_label data_label1 = {.value = "33"};
+    lxw_chart_data_label *data_labels[] = {&data_label1, NULL};
+
+    chart_series_set_labels_custom(series, data_labels);
+    chart_series_set_labels_options(series, LXW_TRUE, LXW_TRUE, LXW_TRUE);
+
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_data_labels32.c

@@ -0,0 +1,49 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2020, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_chart_data_labels32.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 = 71374336;
+    chart->axis_id_2 = 71414144;
+
+    uint8_t data[5][4] = {
+        {1, 2,  3,  10},
+        {2, 4,  6,  20},
+        {3, 6,  9,  30},
+        {4, 8,  12, 40},
+        {5, 10, 15, 50}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 4; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+
+    lxw_chart_font font1 = {.bold = LXW_TRUE, .italic = LXW_TRUE, .color = LXW_COLOR_RED, .baseline = -1};
+    lxw_chart_data_label data_label1 = {.value = "33", .font = &font1};
+    lxw_chart_data_label *data_labels[] = {&data_label1, NULL};
+
+    chart_series_set_labels_custom(series, data_labels);
+
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_data_labels33.c

@@ -0,0 +1,49 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2020, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_chart_data_labels33.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 = 65546112;
+    chart->axis_id_2 = 70217728;
+
+    uint8_t data[5][4] = {
+        {1, 2,  3,  10},
+        {2, 4,  6,  20},
+        {3, 6,  9,  30},
+        {4, 8,  12, 40},
+        {5, 10, 15, 50}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 4; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+
+    lxw_chart_font font1 = {.bold = LXW_TRUE, .italic = LXW_TRUE, .baseline = -1};
+    lxw_chart_data_label data_label1 = {.font = &font1};
+    lxw_chart_data_label *data_labels[] = {&data_label1, NULL};
+
+    chart_series_set_labels_custom(series, data_labels);
+
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/src/test_chart_data_labels34.c

@@ -0,0 +1,49 @@
+/*****************************************************************************
+ * Test cases for libxlsxwriter.
+ *
+ * Test to compare output against Excel files.
+ *
+ * Copyright 2014-2020, John McNamara, jmcnamara@cpan.org
+ *
+ */
+
+#include "xlsxwriter.h"
+
+int main() {
+
+    lxw_workbook  *workbook  = workbook_new("test_chart_data_labels34.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 = 48497792;
+    chart->axis_id_2 = 48499712;
+
+    uint8_t data[5][4] = {
+        {1, 2,  3,  10},
+        {2, 4,  6,  20},
+        {3, 6,  9,  30},
+        {4, 8,  12, 40},
+        {5, 10, 15, 50}
+    };
+
+    int row, col;
+    for (row = 0; row < 5; row++)
+        for (col = 0; col < 4; col++)
+            worksheet_write_number(worksheet, row, col, data[row][col], NULL);
+
+    lxw_chart_series *series = chart_add_series(chart, NULL, "=Sheet1!$A$1:$A$5");
+
+    lxw_chart_font font1 = {.bold = LXW_TRUE, .italic = LXW_TRUE, .color = LXW_COLOR_RED, .baseline = -1};
+    lxw_chart_data_label data_label1 = {. value = "=Sheet1!$D$1", .font = &font1};
+    lxw_chart_data_label *data_labels[] = {&data_label1, NULL};
+
+    chart_series_set_labels_custom(series, data_labels);
+
+    chart_add_series(chart, NULL, "=Sheet1!$B$1:$B$5");
+    chart_add_series(chart, NULL, "=Sheet1!$C$1:$C$5");
+
+    worksheet_insert_chart(worksheet, CELL("E9"), chart);
+
+    return workbook_close(workbook);
+}

test/functional/test_chart_data_labels.py

@@ -86,3 +86,30 @@ class TestCompareXLSXFiles(base_test_class.XLSXBaseTest):
 
     def test_chart_data_labels25(self):
         self.run_exe_test('test_chart_data_labels25')
+
+    def test_chart_data_labels26(self):
+        self.run_exe_test('test_chart_data_labels26')
+
+    def test_chart_data_labels27(self):
+        self.run_exe_test('test_chart_data_labels27')
+
+    def test_chart_data_labels28(self):
+        self.run_exe_test('test_chart_data_labels28')
+
+    def test_chart_data_labels29(self):
+        self.run_exe_test('test_chart_data_labels29')
+
+    def test_chart_data_labels30(self):
+        self.run_exe_test('test_chart_data_labels30')
+
+    def test_chart_data_labels31(self):
+        self.run_exe_test('test_chart_data_labels31')
+
+    def test_chart_data_labels32(self):
+        self.run_exe_test('test_chart_data_labels32')
+
+    def test_chart_data_labels33(self):
+        self.run_exe_test('test_chart_data_labels33')
+
+    def test_chart_data_labels34(self):
+        self.run_exe_test('test_chart_data_labels34')