Gdk.Paintable

interface

An interface for 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 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 Snapshot 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 Paintable.invalidate_contents which will emit the Paintable.invalidate-contents signal. If a paintable is known to never change its contents, it will set the PaintableFlags.STATIC_CONTENTS flag. If a consumer cannot deal with changing contents, it may call 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 Paintable.invalidate_size which will emit the Paintable.invalidate-size signal. And just like for contents, if a paintable is known to never change its size, it will set the PaintableFlags.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: Paintable.invalidate_contents, Paintable.invalidate_size, Paintable.new_empty.

Methods

compute_concrete_size

def compute_concrete_size(self, specified_width: float, specified_height: float, default_width: float, default_height: float) -> tuple[float, float]

Compute a concrete size for the GdkPaintable.

Applies the sizing algorithm outlined in the CSS Image spec to the given paintable. See that link for more details.

It is not necessary to call this function when both specified_width and specified_height are known, but it is useful to call this function in GtkWidget:measure implementations to compute the other dimension when only one dimension is given.

Parameters:

• specified_width — the width paintable could be drawn into or 0.0 if unknown
• specified_height — the height paintable could be drawn into or 0.0 if unknown
• default_width — the width paintable would be drawn into if no other constraints were given
• default_height — the height paintable would be drawn into if no other constraints were given

get_current_image

def get_current_image(self) -> Paintable

Gets an immutable paintable for the current contents displayed by paintable.

This is useful when you want to retain the current state of an animation, for example to take a screenshot of a running animation.

If the paintable is already immutable, it will return itself.

get_flags

def get_flags(self) -> PaintableFlags

Get flags for the paintable.

This is oftentimes useful for optimizations.

See PaintableFlags for the flags and what they mean.

get_intrinsic_aspect_ratio

def get_intrinsic_aspect_ratio(self) -> float

Gets the preferred aspect ratio the paintable would like to be displayed at.

The aspect ratio is the width divided by the height, so a value of 0.5 means that the paintable prefers to be displayed twice as high as it is wide. Consumers of this interface can use this to preserve aspect ratio when displaying the paintable.

This is a purely informational value and does not in any way limit the values that may be passed to Paintable.snapshot.

Usually when a paintable returns nonzero values from Paintable.get_intrinsic_width and Paintable.get_intrinsic_height the aspect ratio should conform to those values, though that is not required.

If the paintable does not have a preferred aspect ratio, it returns 0. Negative values are never returned.

get_intrinsic_height

def get_intrinsic_height(self) -> int

Gets the preferred height the paintable would like to be displayed at.

Consumers of this interface can use this to reserve enough space to draw the paintable.

This is a purely informational value and does not in any way limit the values that may be passed to Paintable.snapshot.

If the paintable does not have a preferred height, it returns 0. Negative values are never returned.

get_intrinsic_width

def get_intrinsic_width(self) -> int

Gets the preferred width the paintable would like to be displayed at.

Consumers of this interface can use this to reserve enough space to draw the paintable.

This is a purely informational value and does not in any way limit the values that may be passed to Paintable.snapshot.

If the paintable does not have a preferred width, it returns 0. Negative values are never returned.

invalidate_contents

def invalidate_contents(self) -> None

Called by implementations of GdkPaintable to invalidate their contents.

Unless the contents are invalidated, implementations must guarantee that multiple calls of Paintable.snapshot produce the same output.

This function will emit the Paintable.invalidate-contents signal.

If a paintable reports the PaintableFlags.STATIC_CONTENTS flag, it must not call this function.

invalidate_size

def invalidate_size(self) -> None

Called by implementations of GdkPaintable to invalidate their size.

As long as the size is not invalidated, paintable must return the same values for its intrinsic width, height and aspect ratio.

This function will emit the Paintable.invalidate-size signal.

If a paintable reports the PaintableFlags.STATIC_SIZE flag, it must not call this function.

snapshot

def snapshot(self, snapshot: Snapshot, width: float, height: float) -> None

Snapshots the given paintable with the given width and height.

The paintable is drawn at the current (0,0) offset of the snapshot. If width and height are not larger than zero, this function will do nothing.

Parameters:

• snapshot — a GdkSnapshot to snapshot to
• width — width to snapshot in
• height — height to snapshot in

Static functions

new_empty

@staticmethod
def new_empty(intrinsic_width: int, intrinsic_height: int) -> Paintable

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

This is often useful for implementing the Paintable.get_current_image virtual function when the paintable is in an incomplete state (like a GtkMediaStream before receiving the first frame).

Parameters:

• intrinsic_width — The intrinsic width to report. Can be 0 for no width.
• intrinsic_height — The intrinsic height to report. Can be 0 for no height.

Virtual methods

do_get_current_image

def do_get_current_image(self) -> Paintable

Gets an immutable paintable for the current contents displayed by paintable.

This is useful when you want to retain the current state of an animation, for example to take a screenshot of a running animation.

If the paintable is already immutable, it will return itself.

do_get_flags

def do_get_flags(self) -> PaintableFlags

Get flags for the paintable.

This is oftentimes useful for optimizations.

See PaintableFlags for the flags and what they mean.

do_get_intrinsic_aspect_ratio

def do_get_intrinsic_aspect_ratio(self) -> float

Gets the preferred aspect ratio the paintable would like to be displayed at.

The aspect ratio is the width divided by the height, so a value of 0.5 means that the paintable prefers to be displayed twice as high as it is wide. Consumers of this interface can use this to preserve aspect ratio when displaying the paintable.

This is a purely informational value and does not in any way limit the values that may be passed to Paintable.snapshot.

Usually when a paintable returns nonzero values from Paintable.get_intrinsic_width and Paintable.get_intrinsic_height the aspect ratio should conform to those values, though that is not required.

If the paintable does not have a preferred aspect ratio, it returns 0. Negative values are never returned.

do_get_intrinsic_height

def do_get_intrinsic_height(self) -> int

Gets the preferred height the paintable would like to be displayed at.

Consumers of this interface can use this to reserve enough space to draw the paintable.

This is a purely informational value and does not in any way limit the values that may be passed to Paintable.snapshot.

If the paintable does not have a preferred height, it returns 0. Negative values are never returned.

do_get_intrinsic_width

def do_get_intrinsic_width(self) -> int

Gets the preferred width the paintable would like to be displayed at.

Consumers of this interface can use this to reserve enough space to draw the paintable.

This is a purely informational value and does not in any way limit the values that may be passed to Paintable.snapshot.

If the paintable does not have a preferred width, it returns 0. Negative values are never returned.

do_snapshot

def do_snapshot(self, snapshot: Snapshot, width: float, height: float) -> None

Snapshots the given paintable with the given width and height.

The paintable is drawn at the current (0,0) offset of the snapshot. If width and height are not larger than zero, this function will do nothing.

Parameters:

• snapshot — a GdkSnapshot to snapshot to
• width — width to snapshot in
• height — height to snapshot in

Signals

invalidate-contents

def on_invalidate_contents(self) -> None: ...

Emitted when the contents of the paintable change.

Examples for such an event would be videos changing to the next frame or the icon theme for an icon changing.

invalidate-size

def on_invalidate_size(self) -> None: ...

Emitted when the intrinsic size of the paintable changes.

This means the values reported by at least one of Paintable.get_intrinsic_width, Paintable.get_intrinsic_height or Paintable.get_intrinsic_aspect_ratio has changed.

Examples for such an event would be a paintable displaying the contents of a toplevel surface being resized.