Paintable

class Paintable(*args, **kwargs)

Implementations: DmabufTexture, GLTexture, MemoryTexture, Texture

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 <https://www.w3.org/TR/css-images-4/``paint`-source>`_, or SVG Paint Servers.

A GdkPaintable can be snapshot at any time and size using 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 invalidate_contents which will emit the invalidate_contents signal. If a paintable is known to never change its contents, it will set the CONTENTS flag. If a consumer cannot deal with changing contents, it may call 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 invalidate_size which will emit the invalidate_size signal. And just like for contents, if a paintable is known to never change its size, it will set the SIZE flag.

Besides API for applications, there are some functions that are only useful for implementing subclasses and should not be used by applications: invalidate_contents, invalidate_size, new_empty.

Methods

class Paintable
compute_concrete_size(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 <https://drafts.csswg.org/css-images-3/``default`-sizing>`_ 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() → 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() → 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() → 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 snapshot.

Usually when a paintable returns nonzero values from get_intrinsic_width and 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() → 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 snapshot.

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

get_intrinsic_width() → 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 snapshot.

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

invalidate_contents() → None

Called by implementations of GdkPaintable to invalidate their contents.

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

This function will emit the invalidate_contents signal.

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

invalidate_size() → 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 invalidate_size signal.

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

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 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.

snapshot(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

class Paintable.signals
invalidate_contents() → 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() → None

Emitted when the intrinsic size of the paintable changes.

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

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

Virtual Methods

class Paintable
do_get_current_image() → 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() → 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() → 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 snapshot.

Usually when a paintable returns nonzero values from get_intrinsic_width and 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() → 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 snapshot.

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

do_get_intrinsic_width() → 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 snapshot.

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

do_snapshot(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