Fix potential file corrupted and change worksheet name case-insensitive

- Using sheet ID instead of sheet index when delete the cell in calculation chain
- Update documentation for exported functions
- Using `sheet` represent the sheet name in the function parameters

1 files changed, 2 insertions, 1 deletions

diff --git a/shape.go b/shape.go
index ddf9e31..58751b2 100644
--- a/shape.go
+++ b/shape.go
@@ -300,7 +300,8 @@ func (f *File) AddShape(sheet, cell, format string) error {
 		drawingXML = strings.ReplaceAll(sheetRelationshipsDrawingXML, "..", "xl")
 	} else {
 		// Add first shape for given sheet.
-		sheetRels := "xl/worksheets/_rels/" + strings.TrimPrefix(f.sheetMap[trimSheetName(sheet)], "xl/worksheets/") + ".rels"
+		sheetXMLPath, _ := f.getSheetXMLPath(sheet)
+		sheetRels := "xl/worksheets/_rels/" + strings.TrimPrefix(sheetXMLPath, "xl/worksheets/") + ".rels"
 		rID := f.addRels(sheetRels, SourceRelationshipDrawingML, sheetRelationshipsDrawingXML, "")
 		f.addSheetDrawing(sheet, rID)
 		f.addSheetNameSpace(sheet, SourceRelationship)