Resource Management

Skija is a Java wrapper around the C++ Skia library. This means that many Java objects are backed by native C++ resources. Understanding how these resources are managed is crucial for building stable and efficient applications.

Automatic Memory Management

By default, Skija manages memory automatically. Most Skija objects extend the Managed class. When a Java object is garbage collected, Skija ensures that the corresponding native C++ resource is also released.

void drawSomething(Canvas canvas) {
    Paint paint = new Paint(); // Native resource allocated
    canvas.drawCircle(50, 50, 20, paint);
} // paint goes out of scope, will be cleaned up by GC eventually

For most use cases, this "safe by default" behavior is exactly what you want.

Manual Resource Release

In performance-critical applications or when dealing with many short-lived objects, you might want to release native resources immediately rather than waiting for the Garbage Collector.

All Managed objects implement AutoCloseable, so you can use the try-with-resources pattern:

void drawCircle(Canvas canvas) {
    try (Paint p = new Paint()) {
        canvas.drawCircle(50, 50, 20, p);
    } // Native resource is freed IMMEDIATELY here
}

Warning: Once an object is closed, it cannot be used again. Attempting to use a closed object will result in an exception or a crash.

Reusing Objects

Because creating native objects can have some overhead, it is often better to reuse them, especially in a render loop.

class MyApp {
    private final Paint paint = new Paint().setColor(0xFFFF0000);

    void onRender(Canvas canvas) {
        canvas.drawCircle(100, 100, 50, paint); // Reuse the same paint object
    }
}

Encapsulation and Getters

Skija uses a specific convention for its data classes (like Rect, Color4f). You will often see public fields starting with an underscore (e.g., _r, _g, _b in Color4f).

Convention:

• Fields starting with _ should be treated as private/internal.
• Always use the provided getters (e.g., getR(), getG()) for public API access.

Color4f color = new Color4f(1f, 0f, 0f);

float r = color._r;    // AVOID: Accessing internal field
float r2 = color.getR(); // RECOMMENDED: Using public getter

This approach allows Skija to maintain a stable API even if the internal implementation of these data classes changes in future versions.