Added docs and example for worksheet macro buttons.

Feature request #39

.gitignore

@@ -41,6 +41,7 @@ examples/*
 !examples/logo.png
 !examples/logo_small.png
 !examples/Makefile
+!examples/vbaProject.bin
 cov-int
 libxlsxwriter-coverity.tgz
 build

docs/src/working_with_macros.dox

@@ -82,6 +82,33 @@ or else Excel will complain and possibly not open the file:
     lxw_workbook *workbook = new_workbook("macro.xlsm");
 @endcode
 
+It is also possible to assign a macro to a button that is inserted into a
+worksheet using the `worksheet_insert_button()` function:
+
+@code
+    lxw_button_options options = {.caption = "Press Me",
+                                  .macro   = "say_hello"};
+
+     worksheet_insert_button(worksheet, 2, 1, &options);
+@endcode
+
+See the full example at @ref macro.c.
+
+It may be necessary to specify a more explicit macro name prefixed by the
+workbook VBA name as follows:
+
+
+@code
+    lxw_button_options options = {.caption = "Press Me",
+                                  .macro   = "ThisWorkbook.say_hello"};
+
+     worksheet_insert_button(worksheet, 2, 1, &options);
+@endcode
+
+@note Button is the only VBA Control supported by libxlsxwriter and due to the
+implementation effort required it is unlikely that any other form elements
+will be added in the future.
+
 
 @section ww_macros_codenames Setting the VBA codenames
 
@@ -113,6 +140,8 @@ clarity:
       <workbookPr codeName="MyWorkbook" defaultThemeVersion="124226"/>
       <sheetPr codeName="MySheet1"/>
 
+@note This step is particularly important for macros created with non-English
+versions of Excel.
 
 @section ww_macros_debugging What to do if it doesn't work
 

examples/macro.c

@@ -6,20 +6,33 @@
  * The vba_extract.py utility from the libxlsxwriter examples directory can be
  * used to extract the vbaProject.bin file.
  *
+ * This example connects the macro to a button (the only Excel/VBA form object
+ * supported by libxlsxwriter) but that isn't a requirement for adding a macro
+ * file to the workbook.
+ *
  * Copyright 2014-2021, John McNamara, [email protected]
  */
 
 #include "xlsxwriter.h"
 
 int main() {
 
+    /* Note the xlsm extension of the filename */
     lxw_workbook  *workbook  = workbook_new("macro.xlsm");
     lxw_worksheet *worksheet = workbook_add_worksheet(workbook, NULL);
 
-    /* Add a macro that will execute when the file is opened. */
+    worksheet_set_column(worksheet, COLS("A:A"), 30, NULL);
+
+    /* Add a macro file extracted from an Excel workbook. */
     workbook_add_vba_project(workbook, "vbaProject.bin");
 
-    worksheet_write_string(worksheet, 0, 0, "Overwrite this", NULL);
+    worksheet_write_string(worksheet, 2, 0, "Press the button to say hello.", NULL);
+
+    lxw_button_options options = {.caption = "Press Me", .macro = "say_hello",
+                                  .width = 80, .height = 30};
+
+     worksheet_insert_button(worksheet, 2, 1, &options);
+
 
     return workbook_close(workbook);
 }

include/xlsxwriter/worksheet.h

@@ -4306,10 +4306,36 @@ lxw_error worksheet_conditional_format_range(lxw_worksheet *worksheet,
                                              lxw_col_t last_col,
                                              lxw_conditional_format
                                              *conditional_format);
-
-lxw_error worksheet_insert_button(lxw_worksheet *worksheet, lxw_row_t row_num,
-                                  lxw_col_t col_num,
-                                  lxw_button_options *options);
+/**
+ * @brief Insert a button object into a worksheet.
+ *
+ * @param worksheet  Pointer to a lxw_worksheet instance to be updated.
+ * @param row        The zero indexed row number.
+ * @param col        The zero indexed column number.
+ * @param options    A #lxw_button_options object to set the button properties.
+ *
+ * @return A #lxw_error code.
+ *
+ * The `%worksheet_insert_button()` function can be used to insert an Excel
+ * form button into a worksheet. This function is generally only useful when
+ * used in conjunction with the `workbook_add_vba_project()` function to tie
+ * the button to a macro from an embedded VBA project:
+ *
+ * @code
+ *     lxw_button_options options = {.caption = "Press Me",
+ *                                   .macro   = "say_hello"};
+ *
+ *     worksheet_insert_button(worksheet, 2, 1, &options);
+ * @endcode
+ *
+ * @image html macros.png
+ *
+ * The button properties are set using the lxw_button_options struct.
+ *
+ * See also @ref working_with_macros
+ */
+lxw_error worksheet_insert_button(lxw_worksheet *worksheet, lxw_row_t row,
+                                  lxw_col_t col, lxw_button_options *options);
 
 /**
  * @brief Add an Excel table to a worksheet.