Merge pull request #625 from telerik/new-kb-auto-font-size-form-fields-pdfprocessing-bb4fa243e78d48fa9c2785015ede054e

Added new kb article auto-font-size-form-fields-pdfprocessing

Author: YoanKar

knowledge-base/auto-font-size-form-fields-pdfprocessing.md

@@ -0,0 +1,143 @@
+---
+title: Adjust Font Size and Flatten Form Fields in PDFs with PdfProcessing
+description: Learn how to calculate and adjust the font size of text fields when flattening form fields of a PDF document with PdfProcessing.
+type: how-to
+page_title: Adjust Font Size and Flatten Form Fields in PDFs with PdfProcessing
+meta_title: Adjust Font Size and Flatten Form Fields in PDFs with PdfProcessing
+slug: auto-font-size-form-fields-pdfprocessing
+tags: pdf, processing, text, box, field, flatten, font, size, recalculation, acroform, fixed, calculate, auto, fit
+res_type: kb
+ticketid: 1697695
+---
+
+<style>
+img[alt$="><"] {
+  border: 1px solid lightgrey;
+}
+</style>
+
+## Environment
+
+| Version | Product | Author | 
+| ---- | ---- | ---- | 
+| 2025.3.806| RadPdfProcessing |[Desislava Yordanova](https://www.telerik.com/blogs/author/desislava-yordanova)| 
+
+## Description
+
+Learn how to adjust the font size of textbox fields to fit the whole text content while processing a PDF form.
+
+![Adjust TextBox Font Size ><](images/textboxfield-calculculate-font-size.gif)   
+
+## Solution
+
+To auto-size text in [TextBoxFields]({%slug radpdfprocessing-model-interactive-forms-form-fields-textboxfield%}), set the `TextBoxField.TextProperties.FontSize` property to `0`. This enables the font size to adjust automatically to fit the content when the document is **displayed** in a viewer. 
+
+```csharp
+TextBoxField textBoxField = new TextBoxField("AutoSizeTextBox");
+textBoxField.TextProperties.FontSize = 0; // Auto-size when displayed in a PDF viewer
+textBoxField.TextProperties.Font = FontsRepository.HelveticaBold;
+textBoxField.Value = "Sample text for auto-sizing.";
+```
+
+However, if you want to adjust the font size and flatten the [form fields]({%slug radpdfprocessing-model-interactive-forms-form-fields%}) to produce a non-editable PDF document, it would be necessary to calculate the appropriate font size according to the rectangle occupied by the [widget]({%slug radpdfprocessing-model-annotations-widgets%}).
+
+The following code snippet shows how to calculate the font size manually to fit the content using the following approach:
+
+```csharp
+public static double CalculateFontSizeForRectangle(string text, Rect rect, FontBase font)
+{
+    double fontSize = 0;
+    Size measuredSize = new Size(0, 0);
+    Size availableSize = rect.Size;
+
+    while (measuredSize.Width < availableSize.Width && measuredSize.Height < availableSize.Height)
+    {
+        fontSize++;
+        Block block = new Block();
+        block.TextProperties.FontSize = fontSize;
+        block.TextProperties.Font = font;
+        block.InsertText(text);
+        measuredSize = block.Measure();
+    }
+
+    return fontSize - 1;
+}
+```
+
+Use this calculated font size to create the textbox field:
+
+```csharp
+        static void Main(string[] args)
+        {
+            RadFixedDocument document = new RadFixedDocument();
+            RadFixedPage page = document.Pages.AddPage(); 
+            FontBase font = FontsRepository.Helvetica;
+            string wideText = "This is a wide textbox that demonstrates horizontal fitting of text content.";
+            Rect wideRect = new Rect(200, 500, 400, 30);
+            double wideFontSize = CalculateFontSizeForRectangle(wideText, wideRect, font);
+
+            TextBoxField wideTextBoxField = CreateTextBoxWithCalculatedFont("WideTextBox", wideText, wideRect, wideFontSize, font);
+            document.AcroForm.FormFields.Add(wideTextBoxField);
+            var wideWidget = wideTextBoxField.Widgets.First();
+            page.Annotations.Add(wideWidget);
+            wideWidget.RecalculateContent();
+            string outputPath = "AutoSizeTextBoxForm.pdf";
+            using (FileStream output = File.Create(outputPath))
+            {
+                PdfFormatProvider provider = new PdfFormatProvider();
+                provider.Export(document, output, TimeSpan.FromSeconds(10));
+            }
+
+            Process.Start(new ProcessStartInfo() { FileName = outputPath, UseShellExecute = true });
+          
+        }
+
+        /// <summary>
+        /// Creates a TextBoxField with calculated font size for the given rectangle
+        /// </summary>
+        private static TextBoxField CreateTextBoxWithCalculatedFont(string name, string text, Rect rect, double fontSize, FontBase font)
+        {
+            TextBoxField field = new TextBoxField(name);
+       
+            field.TextProperties.FontSize = Unit.DipToPoint(fontSize);
+            field.TextProperties.Font = font;
+            field.Value = text;
+
+            var widget = field.Widgets.AddWidget();
+            widget.Rect = rect;
+            widget.Border.Width = 0;
+            widget.TextProperties.FontSize = Unit.DipToPoint(fontSize); ;
+            widget.TextProperties.Font = font;
+
+            return field;
+        }
+
+        /// <summary>
+        /// Calculates the optimal font size for text to fit within a specific rectangle
+        /// </summary>
+        public static double CalculateFontSizeForRectangle(string text, Rect rect, FontBase font)
+        {
+            double fontSize = 0;
+            Size measuredSize = new Size(0, 0);
+            Size availableSize = rect.Size;
+            while (measuredSize.Width<availableSize.Width && measuredSize.Height< availableSize.Height)
+            {
+                fontSize++;
+                Block block = new Block();
+                block.TextProperties.FontSize = fontSize;
+                block.TextProperties.Font = font;
+                block.InsertText(text);
+                measuredSize = block.Measure();
+            }
+
+            return fontSize-1;
+        }
+```
+ 
+
+## See Also
+
+- [PdfProcessing Overview]({%slug radpdfprocessing-overview%})
+- [Flatten Form Fields]({%slug radpdfprocessing-flatten-form-fields%})
+- [TextBoxFields]({%slug radpdfprocessing-model-interactive-forms-form-fields-textboxfield%})
+- [Widget]({%slug radpdfprocessing-model-annotations-widgets%})

knowledge-base/images/textboxfield-calculculate-font-size.gif

@@ -91,3 +91,4 @@ TextBoxField exposes the following properties:
 * [Create Interactive Forms SDK example](https://github.com/telerik/document-processing-sdk/tree/master/PdfProcessing/CreateInteractiveForms) 
 * [Modifying Forms SDK example](https://github.com/telerik/document-processing-sdk/tree/master/PdfProcessing/ModifyForms) 
 * [Customizing Text and Border Colors to Highlight a TextBoxField with RadPdfProcessing]({%slug radpdfprocessing-customize-textboxfield-colors%})
+* [Adjusting Widgets' Font Size to Fit the Whole Content in Form Fields Using PdfProcessing]({%slug auto-font-size-form-fields-pdfprocessing%})