SpriteFont

This is a native Direct3D 12 implementation of a bitmap font renderer, similar to the SpriteFont type from XNA Game Studio, plus a command line tool (MakeSpriteFont) for building fonts into bitmap format. It is less fully featured than Direct2D and DirectWrite, but may be useful for those who want something simpler and lighter weight.

SpriteFont is particularly useful for the Xbox One XDK platform that lacks support for Direct2D and DirectWrite.

Related tutorial: Drawing text

Header

#include <SpriteFont.h>

Initialization

The SpriteFont class requires a SpriteBatch instance, a .spritefont bitmap file, a ResourceUploadBatch, and descriptor handles typically obtained from DescriptorHeap.

ResourceUploadBatch resourceUpload(device);

resourceUpload.Begin();

spriteFont = std::make_unique<SpriteFont>(device, resourceUpload,
    L"myfont.spritefont",
    resourceDescriptors->GetCpuHandle(Descriptors::MyFont),
    resourceDescriptors->GetGpuHandle(Descriptors::MyFont));

// Upload the resources to the GPU.
auto uploadResourcesFinished = resourceUpload.End(m_deviceResources->GetCommandQueue());

// Wait for the command list to finish executing
m_deviceResources->WaitForGpu();

// Wait for the upload thread to terminate
uploadResourcesFinished.wait();

For exception safety, it is recommended you make use of the C++ RAII pattern and use a std::unique_ptr or std::shared_ptr

You create one SpriteFont instance per font style & point-size you want to use to render with. You can use the same SpriteBatch or use several SpriteBatch instances if desired.

Simple drawing

The viewport needs to be set explicitly before drawing:

spriteBatch->SetViewport(viewPort);

And the resource descriptor heap for the font texture(s) need to be set (see DescriptorHeap for more information):

ID3D12DescriptorHeap* heaps[] = { resourceDescriptors->Heap() };
commandList->SetDescriptorHeaps(_countof(heaps), heaps);

Then use DrawString to output text:

spriteBatch->Begin(commandList);

spriteFont->DrawString(spriteBatch.get(), L"Hello, world!", XMFLOAT2(x, y));

spriteBatch->End();

The DrawString method has several overloads with parameters controlling color, rotation, origin point, scaling, horizontal or vertical mirroring, and layer depth. These work the same way as the equivalent SpriteBatch::Draw parameters. See SpriteBatch for more details.

To provide flexibility, setting the proper descriptor heaps to render with via SetDescriptorHeaps is left to the caller. You can create as many heaps as you wish in your application, but remember that you can have only a single texture descriptor heap and a single sampler descriptor heap active at a given time.

Constructors

SpriteFont has three constructors:

• Pass a filename string to read a binary file created by MakeSpriteFont
• Pass a buffer containing a MakeSpriteFont binary that was already loaded some other way
• Pass an array of Glyph structs if you prefer to entirely bypass MakeSpriteFont

Helpers

In addition to DrawString with various overloads, SpriteFont includes the following helpers:

• MeasureString which returns the size of the given string in pixels.

For example, XMVECTOR result = spriteFont->MeasureString( L"Measure" ); would be the pixel width in XMVectorGetX(result) and the pixel height in XMVectorGetY(result):

Note: The string size is computed from the origin to the rightmost pixel rendered by any character glyph. This has the effect of ignoring 'trailing spaces'.

• MeasureDrawBounds which returns a RECT bounding the string.

For example, RECT result = spriteFont->MeasureDrawBounds( L"Measure", XMFLOAT2(0.f, 0.f) ); would return a pixel rectangle as follows:

• ContainsCharacter tests to see if a given character is defined in the font

• FindGlyph can be used to obtain size and other metadata for a character in the font. Note if the character is not defined in the font and there is no default character, this function will throw a C++ exception.

• GetSpriteSheet / GetSpriteSheetSize returns the texture used for the sprite font for custom rendering.

Default character

If you try to DrawString or call MeasureString with a character that is not included in the font, by default you will get an exception. Use SetDefaultCharacter to specify some other character that will be automatically substituted in place of any that are missing. You can also use GetDefaultCharacter to obtain the current default which is also defined as part of the font.

Special characters

SpriteFont will respect new line characters (\n - ASCII character 10), and ignores carriage returns (\r - ASCII character 13). The distance moved for a new line is defined in the font and can be accessed with GetLineSpacing / SetLineSpacing.

There is no special handling for the bell character (\a - ASCII character 7), backspace (\b - ASCII character 8), horizontal tab (\t - ASCII character 9), vertical tab (ASCII character 11), form feed (\f - ASCII character 12), or escape (ASCII character 27). These are all treated as standard characters and if it is missing from the .spritefont, they will all render as the default character or generate an exception if there is no default character defined.

Localization

This implementation supports sparse fonts, so if you are localizing into languages such as Chinese, Japanese, or Korean, you can build a .spritefont including only the specific characters needed by your program. This is usually a good idea for CJK languages, as a complete CJK character set is too large to fit in a Direct3D texture! If you need full CJK support, DrectWrite would be a better choice if available on your target platform. SpriteFont does not support combining characters or right-to-left (RTL) layout, so it will not work for languages with complex layout requirements such as Arabic or Thai.

Note: This XNA Game Studio article How to: Create a Localized Game describes how to use the C# content pipeline to scan the game's strings and create a font from it. You have to use a different solution for DirectX Tool Kit but the idea is the same.

ASCII

The default character region for MakeSpriteFont from 32 to 127 covers the standard 7-bit ASCII range. For example, here is a C++ Unicode string for the printable characters (this would be an ASCII string if you remove the L prefix).

L" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`"
L"abcdefghijklmnopqrstuvwxyz{|}~"

Extended ASCII

If you are wanting to render an extended ASCII string with SpriteFont, you need to capture the full set of characters which are not contiguous in Unicode (see MakeSpriteFont for details). You then need to convert your 'extended ASCII' string to Unicode using Code page 437 before calling DrawString.

char ascii[...];
wchar_t unicode[...];
if (!MultiByteToWideChar(437, MB_PRECOMPOSED,
    ascii, length-of-ascii-string,
    unicode, length-of-unicode-string))
{
    // Error
}
spriteFont->DrawString(spriteBatch.get(), unicode, ...)

For example, here is a C++ Unicode string with the full extended ASCII IBM PC character set from 128 to 255:

L"\x00C7\x00FC\x00E9\x00E2\x00E4\x00E0\x00E5\x00E7\x00EA
\x00EB\x00E8\x00EF\x00EE\x00EC\x00C4\x00C5\x00C9\x00E6\x00C6\x00F4\x00F6\x00F2\x
00FB\x00F9\x00FF\x00D6\x00DC\x00A2\x00A3\x00A5\x20A7\x0192\x00E1\x00ED\x00F3\x00
FA\x00F1\x00D1\x00AA\x00BA\x00BF\x2310\x00AC\x00BD\x00BC\x00A1\x00AB\x00BB\x2591
\x2592\x2593\x2502\x2524\x2561\x2562\x2556\x2555\x2563\x2551\x2557\x255D\x255C\x
255B\x2510\x2514\x2534\x252C\x251C\x2500\x253C\x255E\x255F\x255A\x2554\x2569\x25
66\x2560\x2550\x256C\x2567\x2568\x2564\x2565\x2559\x2558\x2552\x2553\x256B\x256A
\x2518\x250C\x2588\x2584\x258C\x2590\x2580\x03B1\x00DF\x0393\x03C0\x03A3\x03C3\x
00B5\x03C4\x03A6\x0398\x03A9\x03B4\x221E\x03C6\x03B5\x2229\x2261\x00B1\x2265\x22
64\x2320\x2321\x00F7\x2248\x00B0\x2219\x00B7\x221A\x207F\x00B2\x25A0\x00A0"

The Xbox One exclusive apps version of MultiByteToWideChar does not support code page 437.

Further reading

Bitmap fonts in XNA
SpriteBatch billboards in a 3D world
Redistributable Font Pack