Interface

GdkPaintable

Description [src]

interface Gdk.Paintable : GObject.Object

GdkPaintable is a simple interface used by GTK to represent content that can be painted.

The content of a GdkPaintable can be painted anywhere at any size without requiring any sort of layout. The interface is inspired by similar concepts elsewhere, such as ClutterContent, HTML/CSS Paint Sources, or SVG Paint Servers.

A GdkPaintable can be snapshot at any time and size using gdk_paintable_snapshot(). How the paintable interprets that size and if it scales or centers itself into the given rectangle is implementation defined, though if you are implementing a GdkPaintable and don’t know what to do, it is suggested that you scale your paintable ignoring any potential aspect ratio.

The contents that a GdkPaintable produces may depend on the GdkSnapshot passed to it. For example, paintables may decide to use more detailed images on higher resolution screens or when OpenGL is available. A GdkPaintable will however always produce the same output for the same snapshot.

A GdkPaintable may change its contents, meaning that it will now produce a different output with the same snapshot. Once that happens, it will call gdk_paintable_invalidate_contents() which will emit the GdkPaintable::invalidate-contents signal. If a paintable is known to never change its contents, it will set the GDK_PAINTABLE_STATIC_CONTENTS flag. If a consumer cannot deal with changing contents, it may call gdk_paintable_get_current_image() which will return a static paintable and use that.

A paintable can report an intrinsic (or preferred) size or aspect ratio it wishes to be rendered at, though it doesn’t have to. Consumers of the interface can use this information to layout thepaintable appropriately. Just like the contents, the size of a paintable can change. A paintable will indicate this by calling gdk_paintable_invalidate_size() which will emit the GdkPaintable::invalidate-size signal. And just like for contents, if a paintable is known to never change its size, it will set the GDK_PAINTABLE_STATIC_SIZE flag.

Besides API for applications, there are some functions that are only useful for implementing subclasses and should not be used by applications: gdk_paintable_invalidate_contents(), gdk_paintable_invalidate_size(), gdk_paintable_new_empty().

Prerequisite

In order to implement Paintable, your type must inherit fromGObject.

Implementations

Functions

gdk_paintable_new_empty

Returns a paintable that has the given intrinsic size and draws nothing.

Signals

Gdk.Paintable::invalidate-contents

Emitted when the contents of the paintable change.

Gdk.Paintable::invalidate-size

Emitted when the intrinsic size of the paintable changes.

Interface structure

struct GdkPaintableInterface {
  void (* snapshot) (
    GdkPaintable* paintable,
    GdkSnapshot* snapshot,
    double width,
    double height
  );
  GdkPaintable* (* get_current_image) (
    GdkPaintable* paintable
  );
  GdkPaintableFlags (* get_flags) (
    GdkPaintable* paintable
  );
  int (* get_intrinsic_width) (
    GdkPaintable* paintable
  );
  int (* get_intrinsic_height) (
    GdkPaintable* paintable
  );
  double (* get_intrinsic_aspect_ratio) (
    GdkPaintable* paintable
  );
  
}

The list of functions that can be implemented for the GdkPaintable interface.

Note that apart from the Gdk.PaintableInterface.snapshot function, no virtual function of this interface is mandatory to implement, though it is a good idea to implement Gdk.PaintableInterface.get_current_image for non-static paintables and Gdk.PaintableInterface.get_flags if the image is not dynamic as the default implementation returns no flags and that will make the implementation likely quite slow.

Interface members

`snapshot`	`void (* snapshot) ( GdkPaintable* paintable, GdkSnapshot* snapshot, double width, double height )`
	Snapshot the paintable. The given `width` and `height` are guaranteed to be larger than 0.0. The resulting snapshot must modify only the area in the rectangle from (0,0) to (width, height). This is the only function that must be implemented for this interface.
`get_current_image`	`GdkPaintable* (* get_current_image) ( GdkPaintable* paintable )`
	Return a `GdkPaintable` that does not change over time. This means the `GDK_PAINTABLE_STATIC_SIZE` and `GDK_PAINTABLE_STATIC_CONTENTS` flag are set.
`get_flags`	`GdkPaintableFlags (* get_flags) ( GdkPaintable* paintable )`
	Get the flags for this instance. See `GdkPaintableFlags` for details.
`get_intrinsic_width`	`int (* get_intrinsic_width) ( GdkPaintable* paintable )`
	The preferred width for this object to be snapshot at or 0 if none. This is purely a hint. The object must still be able to render at any size.
`get_intrinsic_height`	`int (* get_intrinsic_height) ( GdkPaintable* paintable )`
	The preferred height for this object to be snapshot at or 0 if none. This is purely a hint. The object must still be able to render at any size.
`get_intrinsic_aspect_ratio`	`double (* get_intrinsic_aspect_ratio) ( GdkPaintable* paintable )`
	The preferred aspect ratio for this object or 0 if none. If both `Gdk.PaintableInterface.get_intrinsic_width` and `Gdk.PaintableInterface.get_intrinsic_height` return non-zero values, this function should return the aspect ratio computed from those.

Interface

GdkPaintable

Description [src]

Prerequisite

Implementations

Functions

gdk_paintable_new_empty

Instance methods

gdk_paintable_compute_concrete_size

gdk_paintable_get_current_image

gdk_paintable_get_flags

gdk_paintable_get_intrinsic_aspect_ratio

gdk_paintable_get_intrinsic_height

gdk_paintable_get_intrinsic_width

gdk_paintable_invalidate_contents

gdk_paintable_invalidate_size

gdk_paintable_snapshot

Signals

Gdk.Paintable::invalidate-contents

Gdk.Paintable::invalidate-size

Interface structure

Interface members

Virtual methods

Gdk.Paintable.get_current_image

Gdk.Paintable.get_flags

Gdk.Paintable.get_intrinsic_aspect_ratio

Gdk.Paintable.get_intrinsic_height

Gdk.Paintable.get_intrinsic_width

Gdk.Paintable.snapshot