repository·master·Indexed 20 days ago
https://github.com/humbleui/skijaHand-crafted Java bindings for the Skia 2D graphics library, providing GPU-accelerated graphics capabilities for Java developers. Supports Bitmap, OpenGL, Direct3D, Metal, and Vulkan backends across Windows, Linux, macOS, and Android. The library is currently in Public Alpha and focuses on providing a natural, idiomatic Java API with automatic memory management.
Skija is currently in Public Alpha. Because the underlying Skia library changes frequently, the Skija API may change without notice.
Supported Backends:
Supported Platforms:
Skija aims to stay as close to the original Skia C++ API as possible, with a few specific adjustments to ensure idiomatic Java usage and avoid conflicts:
SkPath#close is renamed to Path#closePath to avoid clashing with Managed#close.io.github.humbleui.skija.* subpackages.void), Skija setters and updaters return this to allow for method chaining.Due to Java visibility limitations, many Skija fields are declared public and prefixed with an underscore (e.g., _r, _g).
Rule: Treat any field starting with _ as private. Do not access them directly as it breaches encapsulation. Instead, use the provided getter methods (e.g., getR()).
var color = new Color4f(1, 1, 1);
// BAD
float r = color._r;
// GOOD
float r = color.getR();Data classes in Skija (like LineMetrics) use a specific pattern to balance performance and Java idiomaticity:
final fields are prefixed with _ (e.g., public final long _startIndex).get..., is..., set..., with...). Setters return this.isBold()).@Data
public class LineMetrics {
public final long _startIndex;
public final long _endIndex;
// ... other fields
@Getter(AccessLevel.NONE)
public final int _flags;
public static final int _FLAG_IS_BOLD = 0b0001;
public static final int _FLAG_IS_ITALIC = 0b0010;
public boolean isBold() { return (_flags | _FLAG_IS_BOLD) != 0; }
public boolean isItalic() { return (_flags | _FLAG_IS_ITALIC) != 0; }
}Skija follows specific naming patterns to distinguish between different types of members:
_n (e.g., _nDrawRRect)._ (e.g., _startIndex).get.../is... for getters and set.../with... for setters.make... for static named constructors._FLAG_<TYPE>_<NAME> (e.g., _FLAG_IS_BOLD)....Mask.UPPER_CASE for values.count is used instead of size or length....Style is used instead of ...Config or ...Options....Mode is used instead of ...Type or ...Kind.serializeToData/makeFromData are used for data conversion.Text rendering in Skija involves two distinct concepts:
Typeface is expensive. You can load one from a file or match a family style via the OS using FontMgr.Font is built from a Typeface.Best Practice: For performance, cache Typeface and Font objects instead of recreating them every frame.
try (Typeface face = FontMgr.getDefault().matchFamilyStyle("Menlo", FontStyle.NORMAL);
Font font = new Font(face, 13);
Paint fill = new Paint().setColor(0xFF000000))
{
canvas.drawString("Hello, world", 0, 0, font, fill);
}Most Skija classes (extending RefCnt or Managed) are backed by native C++ pointers.
Automatic Management: Skija automatically frees C++ structures when the corresponding Java objects are collected by the Garbage Collector (GC). This makes Skija safe to use by default.
Manual Management: All Managed descendants implement AutoCloseable. To free memory more aggressively (e.g., for short-lived objects), use a try-with-resources block. This is not mandatory but can help reduce memory pressure.
Warning: Once a resource is closed via AutoCloseable, it can no longer be used.
// Automatic management (safe, but relies on GC)
void drawCircle(Canvas c) {
Paint p = new Paint();
c.drawCircle(0, 0, 10, p);
}
// Manual management (immediate cleanup)
void drawCircle(Canvas c) {
try (Paint p = new Paint()) {
c.drawCircle(0, 0, 10, p);
} // p is freed here
}Skija uses a permissive visibility model to ensure clients have access to necessary functionality, even if it's not part of the intended public surface:
public to prevent blocking client needs._ (e.g., _startIndex).@ApiStatus.Internal._ are considered effectively private. Skija provides no stability guarantees for these members.Unlike automatically generated bindings, Skija is hand-crafted to provide a natural Java API. Key characteristics include:
AutoCloseable) instead of wrapped C++ equivalents.Point, Rect, and FontMetrics are pure Java data classes and are not mirrored by native instances, reducing overhead.To use Skija, add the appropriate platform-specific dependency to your build system (Ant, Maven, Gradle, or Bazel). You must choose exactly ONE dependency based on your target architecture and operating system. Replace ${version} with the current Skija version.
Available dependencies:
io.github.humbleui:skija-windows-x64:${version}io.github.humbleui:skija-linux-x64:${version}io.github.humbleui:skija-linux-arm64:${version}io.github.humbleui:skija-macos-x64:${version}io.github.humbleui:skija-macos-arm64:${version}io.github.humbleui:skija-android-x64:${version}io.github.humbleui:skija-android-arm64:${version}io.github.humbleui:skija-windows-x64:${version}To run the kwinit example using a locally built version of Skija, first build the project using the build.py script from the root directory, then execute the example using run.py within the example directory.
python3 ../../script/build.py
python3 script/run.pyThe examples/scenes directory contains demo scenes that demonstrate most of the Skia and Skija APIs. These scenes serve as a learning resource for understanding how to use the library's capabilities in practice.
To run these demonstrations, you can use either the kwinit or lwjgl examples located in the adjacent directories.
# Run through kwinit
../kwinit
# Or run through lwjgl
../lwjgl