Get Warnings for Font Substitution while Rendering Excel File with Golang via C++

Sometimes, when rendering a Microsoft Excel file to PDF, Aspose.Cells substitutes fonts. Aspose.Cells provides a feature that lets developers know which particular font has been substituted by firing a warning. This is a useful feature that can help you identify why an Aspose.Cells‑rendered PDF looks different from the original Microsoft Excel file, so you can take appropriate actions. For example, installing the missing fonts so that rendering results look the same.

To get warnings for font substitution when rendering Excel files to PDF, implement the IWarningCallback interface and set the PdfSaveOptions.WarningCallback property with your implemented interface.

The screenshot below shows a source Excel file that we will use in the following code. It has some text in cells A6 and A7 in fonts that are not rendered correctly by Microsoft Excel.

Not all fonts are rendered correctly

Aspose.Cells will substitute the fonts in cells A6 and A7 with suitable fonts as shown below.

Substituted fonts

Download Source File and Output PDF

You can download the source Excel file and the output PDF from the following links:

• source.xlsx
• output.pdf

Code

The following code implements the IWarningCallback and sets the PdfSaveOptions.WarningCallback property with the implemented interface. Now, whenever any font is substituted in a cell, Aspose.Cells will fire a warning inside the WarningCallback.Warning() method.

Output

After converting the source Excel file to PDF, the warnings are output to the debug console like this:

WARNING INFO: Font substitution: Font [ Athene Logos; Regular ] has been substituted in Cell [ A6 ] in Sheet [ Sheet1 ].
WARNING INFO: Font substitution: Font [ B Traffic; Regular ] has been substituted in Cell [ A7 ] in Sheet [ Sheet1 ].

If your spreadsheet contains formulas, it is best to call the Workbook.CalculateFormula method just before rendering the spreadsheet to PDF format. Doing so will ensure that the formula‑dependent values are recalculated, and the correct values are rendered in the PDF.