Render Presentations with Fallback Fonts in С++

Overview

Aspose.Slides allows you to render presentations using fallback font rules. This article shows how to create a fallback font rules collection, modify its rules by removing or adding fallback fonts, and assign the collection using the FontsManager::set_FontFallBackRulesCollection method.

Once the fallback font rules collection is assigned to the presentation’s FontsManager, the rules are applied during operations such as saving, rendering, and converting the presentation. The example demonstrates how to use the configured rules when rendering a slide thumbnail and saving it as a PNG image.

Render a Slide Using Fallback Font Rules

The following example includes these steps:

  1. We create fallback font rules collection.
  2. Remove() a fallback font rule and AddFallBackFonts() to another rule.
  3. Pass the rules collection to FontsManager::set_FontFallBackRulesCollection() method.
  4. With Presentation::Save() method we can save presentation in the same format, or save it in another one. After fallback font rules collection is set to FontsManager, these rules are applied during any operations over the presentation: save, render, convert, etc.
// Create new instance of a rules collection
auto rulesList = MakeObject<FontFallBackRulesCollection>();

// Create a number of rules
rulesList->Add(MakeObject<FontFallBackRule>(static_cast<uint32_t>(0x400), static_cast<uint32_t>(0x4FF), u"Times New Roman"));
//rulesList.Add(new FontFallBackRule(...));

for (const auto& fallBackRule : rulesList)
{
	// Trying to remove FallBack font "Tahoma" from loaded rules
	fallBackRule->Remove(u"Tahoma");

	// And to update of rules for specified range
	if ((fallBackRule->get_RangeEndIndex() >= static_cast<uint32_t>(0x4000)) && 
		(fallBackRule->get_RangeStartIndex() < static_cast<uint32_t>(0x5000)))
	{
		fallBackRule->AddFallBackFonts(u"Verdana");
	}
}

// Also we can remove any existing rules from list
if (rulesList->get_Count() > 0)
{
	rulesList->Remove(rulesList->idx_get(0));
}

auto pres = System::MakeObject<Presentation>(u"input.pptx");
// Assigning a prepared rules list for using
pres->get_FontsManager()->set_FontFallBackRulesCollection(rulesList);

// Rendering of thumbnail with using of initialized rules collection and saving to PNG
auto image = pres->get_Slide(0)->GetImage(1.f, 1.f);
image->Save(u"Slide_0.png", ImageFormat::Png);
image->Dispose();

pres->Dispose();
Configure Fallback Font Collections in С++