Module org.freedesktop.cairo

Package org.freedesktop.cairo

Interface UserScaledFontInitFunc

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface UserScaledFontInitFunc

UserScaledFontInitFunc is the type of function which is called when a scaled-font needs to be created for a user font-face.

The cairo context cr is not used by the caller, but is prepared in font space, similar to what the cairo contexts passed to the renderGlyph method will look like. The callback can use this context for extents computation for example. After the callback is called, cr is checked for any error status.

The extents argument is where the user font sets the font extents for scaledFont. It is in font space, which means that for most cases its ascent and descent members should add to 1.0. extents is preset to hold a value of 1.0 for ascent, height, and maxXAdvance, and 0.0 for descent and maxYAdvance members.

The callback is optional. If not set, default font extents as described in the previous paragraph will be used.

Note that scaledFont is not fully initialized at this point and trying to use it for text operations in the callback will result in deadlock.

Since:

1.8

Method Summary

Modifier and Type	Method	Description
void	init(UserScaledFont scaledFont, Context cr, FontExtents extents)	Called when a scaled-font needs to be created for a user font-face.
default MemorySegment	toCallback(Arena arena)	Generates an upcall stub, a C function pointer that will call upcall(java.lang.foreign.MemorySegment, java.lang.foreign.MemorySegment, java.lang.foreign.MemorySegment).
default int	upcall(MemorySegment scaledFont, MemorySegment cr, MemorySegment extents)	The callback that is executed by native code.

Method Details

init

void init(UserScaledFont scaledFont,
 Context cr,
 FontExtents extents)
   throws Exception

Called when a scaled-font needs to be created for a user font-face.

Parameters:

scaledFont - the scaled-font being created

cr - a cairo context, in font space

extents - font extents to fill in, in font space

Throws:

Exception - when an error occurs. Throwing an exception will trigger a Status.USER_FONT_ERROR return value to native code.

Since:

1.8

upcall

default int upcall(MemorySegment scaledFont,
 MemorySegment cr,
 MemorySegment extents)

The callback that is executed by native code. This method marshals the parameters and calls init(org.freedesktop.cairo.UserScaledFont, org.freedesktop.cairo.Context, org.freedesktop.cairo.FontExtents).

Parameters:

scaledFont - the scaled-font being created

cr - a cairo context, in font space

extents - font extents to fill in, in font space

Returns:

Status.SUCCESS upon success, or Status.USER_FONT_ERROR if an exception was thrown.

Since:

1.8

toCallback

default MemorySegment toCallback(Arena arena)

Generates an upcall stub, a C function pointer that will call upcall(java.lang.foreign.MemorySegment, java.lang.foreign.MemorySegment, java.lang.foreign.MemorySegment).

Parameters:

arena - the arena in which the upcall stub will be allocated

Returns:

the function pointer of the upcall stub

Since:

1.8