Allow custom cell_fill_mode in tables

CHANGELOG.md

@@ -18,6 +18,7 @@ This can also be enabled programmatically with `warnings.simplefilter('default',
 
 ## [2.7.9] - Not released yet
 ### Added
+* allow to define custom `cell_fill_mode` logic for tables: [_Set cells background_ - documentation section](https://py-pdf.github.io/fpdf2/Tables.html#set-cells-background)
 
 ### Fixed
 
@@ -47,7 +48,7 @@ This can also be enabled programmatically with `warnings.simplefilter('default',
 * outer table borders are now drawn continuously for nonzero `gutter_width`/`gutter_height`, with spacing applied inside the border similar to HTML tables - thanks to @mjasperse - cf. [#1071](https://github.com/py-pdf/fpdf2/issues/1071)
 * removed the requirement that all rows in a `Table` have the same number of columns - thanks to @mjasperse
 ### Deprecated
-- font aliases (`Arial` → `Helvetica`, `CourierNew` → `Courer`, `TimesNewRoman` → `Times`). They will be removed in a later release.
+- font aliases (`Arial` → `Helvetica`, `CourierNew` → `Courier`, `TimesNewRoman` → `Times`). They will be removed in a later release.
 
 ## [2.7.7] - 2023-12-10
 ### Added

docs/Tables.md

@@ -208,6 +208,18 @@ The cell color is set following those settings, ordered by priority:
 4. The table setting `cell_fill_color`, if `cell_fill_mode` indicates to fill a cell
 5. The document `.fill_color` set before rendering the table
 
+Finally, it is possible to define your own cell-filling logic:
+
+```python
+class EvenOddCellFillMode():
+    def should_fill_cell(self, i, j):
+        return i % 2 and j % 2
+
+...
+with pdf.table(cell_fill_color=lightblue, cell_fill_mode=EvenOddCellFillMode()) as table:
+    ...
+```
+
 
 ## Set borders layout
 

fpdf/enums.py

@@ -54,7 +54,7 @@ def coerce(cls, value):
 
             raise ValueError(f"{value} is not a valid {cls.__name__}")
 
-        raise TypeError(f"{value} cannot convert to a {cls.__name__}")
+        raise TypeError(f"{value} cannot be converted to a {cls.__name__}")
 
 
 class CoerciveIntEnum(IntEnum):
@@ -314,6 +314,13 @@ class TableCellFillMode(CoerciveEnum):
     COLUMNS = intern("COLUMNS")
     "Fill only table cells in odd columns"
 
+    @classmethod
+    def coerce(cls, value):
+        "Any class that has a .should_fill_cell() method is considered a valid 'TableCellFillMode' (duck-typing)"
+        if callable(getattr(value, "should_fill_cell", None)):
+            return value
+        return super().coerce(value)
+
     def should_fill_cell(self, i, j):
         if self is self.NONE:
             return False

test/table/test_table.py

@@ -267,6 +267,24 @@ def test_table_with_cell_fill(tmp_path):
     assert_pdf_equal(pdf, HERE / "table_with_cell_fill.pdf", tmp_path)
 
 
+class EvenOddCellFillMode():
+    def should_fill_cell(self, i, j):
+        return i % 2 and j % 2
+
+
+def test_table_with_cell_fill_custom_class(tmp_path):
+    pdf = FPDF()
+    pdf.add_page()
+    pdf.set_font("Times", size=16)
+    lightblue = (173, 216, 230)
+    with pdf.table(cell_fill_color=lightblue, cell_fill_mode=EvenOddCellFillMode()) as table:
+        for data_row in TABLE_DATA:
+            row = table.row()
+            for datum in data_row:
+                row.cell(datum)
+    assert_pdf_equal(pdf, HERE / "table_with_cell_fill_custom_class.pdf", tmp_path, generate=True)
+
+
 def test_table_with_internal_layout(tmp_path):
     pdf = FPDF()
     pdf.add_page()