TStringGrid provides the methods SaveToCSVFile/Stream for saving the grid content to a csv file or stream. This is very convenient for users, but it is not very flexible: The export works only for the csv data format, no html, no possibility to plug in other formats. It requires always a modification of the /grids /unit to extend these methods by additional options. And it works only with TStringGrid - there are other grid-like controls, such as custom "virtual" grids derived from TCustomDrawGrid, TListview in report mode, TKGrid and other third-party grids which are not supported: if they do not have such a method on their own the export code has to be re-written (often: duplicated).
The attached file contains code for a flexibile export system for 2D-data classes which is open and can easily be extended to other formats and other controls. It essentially consists of two parts:
* *TLazExporter *represents the file format. The class is abstract and provides the methods to write cells and rows to stream and file. I implemented an exporter for *csv *and *html *files for the lclbase package. But in addition there is also a dedicated SpreadsheetExporter which takes care of *Excel *and/or *Opendocument *file formats (using fpspreadsheet).
* *TLazExporterLink *provides the data to be exported. It is an abstract class between the control to be exported and the writer. It exposes methods to navigate from cell to cell and row to row, and to define the strings assigned to each cell. I implemented a TGridExporterLink (accessing *TCustomStringGrid*, in the long run: *TCustomDrawGrid*) and *TCustomListView*. The same principle works for any other classes with 2D data arrays (matrix).
The unit /GridExporter /exposes functions to write grid content to file and to stream. The exporter instance is passed as a parameter, i.e. it is very easy to switch from csv to hml or any other format provided the corresponding exporter is available.
procedure ExportGridToFile(AGrid: TCustomStringGrid;
AExporter: TLazExporter; const AFileName: String; AOptions:
TGridExportOptions); overload;
procedure ExportGridToStream(AGrid: TCustomStringGrid;
AExporter: TLazExporter; AStream: TStream; AOptions:
TGridExportOptions); overload;Similarly, there are also ExportListviewToFile/Stream procedures in the unit /ListViewExporter /for the export from a TListview.
Properties of the exporter can be used to fine-tune the export. In case of the html exporter, for example, a set of css statements can be specified to format the exported html table:
htmlexporter := THTMLExporter.Create;
with htmlexporter do
begin
CSS.Add('table { border: 1px solid #DDDDFF; }');
CSS.Add('th { background-color: #DDDDFF; }');
CSS.Add('h1 { font-family:Helvetica, Arial, sans-serif;
font-size:16pt; color:blue; background-color: #EEEEFF}; }');
end;
ExportGridToFile(StringGrid1, exporter, AFileNameForGrid,
[geoFixedRows, geoFixedCols, geoVisibleColsOnly]);
ExportListViewToFile(Listview1, exporter, AFileNameForListView,
[leoTitles, leoVisibleColsOnly]);In addition to these procedures there are overloaded versions taking the exporter class (instead of an exporter instance) as a parameter. In this way the default exporter parameters are applied during the export. Of course, these procedures can be added as methods to the classes referred to by the first parameter.
The attached demo shows the exporter requires no
modification of any LCL packages or units. In the long run, however, I'd propose to add unit /LazExporter /to package /LazUtils /and /GridExporter /and /ListviewExporter /to package /LclBase /(/SpreadsheetExporter /would go to /laz_//fpspreadsheet/), and to make these modifications to the /grids /unit:
* Extend the ExportGridToFile/Stream procedures to accept also TCustomDrawGrid descendants. This would be possible by introducing a virtual method GetCellText(Col,Row) to TCustomDrawGrid (or maybe even TCustomGrid) which would catch the cell text from a special event OnGetCellText; this would help to create "virtual" grids using TCustom(Draw)Grids. In case of the TStringGrid, of course, GetCellText would simply return the cell strings Cells[Col, Row].
* Replace the code in SaveToCSVFile/Stream by the csv exporter. I'd also vote to deprecate these methods because they are special cases of the csv exporter.
* Replace the copy-to-clipboard code (CopyCellRectToClipboard) by the csv exporter. In addition, a html format could be written to the clipboard with almost no extra code.
I would greatly appreciate any comments.
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