---
name: "wayland_server_viewport_t"
section: "3"
platform: "linux"
package: "waylandpp-dev"
version: "1.0.0-6+b2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/wayland_server_viewport_t"
---

# wayland\_server\_viewport\_t(3)

crop and scale interface to a wl\_surface

## NAME

wayland::server::viewport\_t - crop and scale interface to a wl\_surface

## SYNOPSIS

`#include <wayland-server-protocol-extra.hpp>`

Inherits wayland::server::resource\_t.

### Public Member Functions

std::function\< void()\> & **on\_destroy** ()\
 remove scaling and cropping from the surface  std::function\< void(double, double, double, double)\> & **on\_set\_source** ()\
 set the source rectangle for cropping  std::function\< void(int32\_t, int32\_t)\> & **on\_set\_destination** ()\
 set the surface size for scaling  void **post\_bad\_value** (std::string const &msg)\
 Post error: negative or zero values in width or height.  void **post\_bad\_size** (std::string const &msg)\
 Post error: destination size is not integer.  void **post\_out\_of\_buffer** (std::string const &msg)\
 Post error: source rectangle extends outside of the content area.  void **post\_no\_surface** (std::string const &msg)\
 Post error: the wl\_surface was destroyed.  bool **proxy\_has\_object** () const\
 Check whether this wrapper actually wraps an object.  void **post\_no\_memory** () const\
 uint32\_t **get\_id** () const\
 client\_t **get\_client** () const\
 unsigned int **get\_version** () const\
 std::string **get\_class** ()\

## Detailed Description

crop and scale interface to a wl\_surface

An additional interface to a wl\_surface object, which allows the client to specify the cropping and scaling of the surface contents.

This interface works with two concepts: the source rectangle (src\_x, src\_y, src\_width, src\_height), and the destination size (dst\_width, dst\_height). The contents of the source rectangle are scaled to the destination size, and content outside the source rectangle is ignored. This state is double-buffered, and is applied on the next wl\_surface.commit.

The two parts of crop and scale state are independent: the source rectangle, and the destination size. Initially both are unset, that is, no scaling is applied. The whole of the current wl\_buffer is used as the source, and the surface size is as defined in wl\_surface.attach.

If the destination size is set, it causes the surface size to become dst\_width, dst\_height. The source (rectangle) is scaled to exactly this size. This overrides whatever the attached wl\_buffer size is, unless the wl\_buffer is NULL. If the wl\_buffer is NULL, the surface has no content and therefore no size. Otherwise, the size is always at least 1x1 in surface local coordinates.

If the source rectangle is set, it defines what area of the wl\_buffer is taken as the source. If the source rectangle is set and the destination size is not set, then src\_width and src\_height must be integers, and the surface size becomes the source rectangle size. This results in cropping without scaling. If src\_width or src\_height are not integers and destination size is not set, the bad\_size protocol error is raised when the surface state is applied.

The coordinate transformations from buffer pixel coordinates up to the surface-local coordinates happen in the following order:

- 1\.

  buffer\_transform (wl\_surface.set\_buffer\_transform)

- 2\.

  buffer\_scale (wl\_surface.set\_buffer\_scale)

- 3\.

  crop and scale (wp\_viewport.set\*) This means, that the source rectangle coordinates of crop and scale are given in the coordinates after the buffer transform and scale, i.e. in the coordinates that would be the surface-local coordinates if the crop and scale was not applied.

If src\_x or src\_y are negative, the bad\_value protocol error is raised. Otherwise, if the source rectangle is partially or completely outside of the non-NULL wl\_buffer, then the out\_of\_buffer protocol error is raised when the surface state is applied. A NULL wl\_buffer does not raise the out\_of\_buffer error.

The x, y arguments of wl\_surface.attach are applied as normal to the surface. They indicate how many pixels to remove from the surface size from the left and the top. In other words, they are still in the surface-local coordinate system, just like dst\_width and dst\_height are.

If the wl\_surface associated with the wp\_viewport is destroyed, all wp\_viewport requests except 'destroy' raise the protocol error no\_surface.

If the wp\_viewport object is destroyed, the crop and scale state is removed from the wl\_surface. The change will be applied on the next wl\_surface.commit.

Definition at line **492** of file **wayland-server-protocol-extra.hpp**.

## Member Function Documentation

### std::string wayland::server::resource\_t::get\_class ()` [inherited]`

Retrieve the interface name (class) of a resource object.

**Returns**

Interface name of the resource object.

### client\_t wayland::server::resource\_t::get\_client () const` [inherited]`

Get the associated client

**Returns**

the client that owns the resource.

### uint32\_t wayland::server::resource\_t::get\_id () const` [inherited]`

Get the internal ID of the resource

**Returns**

the internal ID of the resource

### unsigned int wayland::server::resource\_t::get\_version () const` [inherited]`

Get interface version

**Returns**

Interface version this resource has been constructed with.

### std::function\< void()\> & viewport\_t::on\_destroy ()

remove scaling and cropping from the surface The associated wl\_surface's crop and scale state is removed. The change is applied on the next wl\_surface.commit.

Definition at line **848** of file **wayland-server-protocol-extra.cpp**.

### std::function\< void(int32\_t, int32\_t)\> & viewport\_t::on\_set\_destination ()

set the surface size for scaling

**Parameters**

*width* surface width \
 *height* surface height

Set the destination size of the associated wl\_surface. See wp\_viewport for the description, and relation to the wl\_buffer size.

If width is -1 and height is -1, the destination size is unset instead. Any other pair of values for width and height that contains zero or negative values raises the bad\_value protocol error.

The crop and scale state is double-buffered state, and will be applied on the next wl\_surface.commit.

Definition at line **860** of file **wayland-server-protocol-extra.cpp**.

### std::function\< void(double, double, double, double)\> & viewport\_t::on\_set\_source ()

set the source rectangle for cropping

**Parameters**

*x* source rectangle x \
 *y* source rectangle y \
 *width* source rectangle width \
 *height* source rectangle height

Set the source rectangle of the associated wl\_surface. See wp\_viewport for the description, and relation to the wl\_buffer size.

If all of x, y, width and height are -1.0, the source rectangle is unset instead. Any other set of values where width or height are zero or negative, or x or y are negative, raise the bad\_value protocol error.

The crop and scale state is double-buffered state, and will be applied on the next wl\_surface.commit.

Definition at line **854** of file **wayland-server-protocol-extra.cpp**.

### void viewport\_t::post\_bad\_size (std::string const & msg)

Post error: destination size is not integer.

Definition at line **871** of file **wayland-server-protocol-extra.cpp**.

### void viewport\_t::post\_bad\_value (std::string const & msg)

Post error: negative or zero values in width or height.

Definition at line **866** of file **wayland-server-protocol-extra.cpp**.

### void wayland::server::resource\_t::post\_no\_memory () const` [inherited]`

Post 'not enough memory' error to the client

If the compositor has not enough memory to fulfill a certail request of the client, this function can be called to notify the client of this circumstance.

### void viewport\_t::post\_no\_surface (std::string const & msg)

Post error: the wl\_surface was destroyed.

Definition at line **881** of file **wayland-server-protocol-extra.cpp**.

### void viewport\_t::post\_out\_of\_buffer (std::string const & msg)

Post error: source rectangle extends outside of the content area.

Definition at line **876** of file **wayland-server-protocol-extra.cpp**.

### bool wayland::server::resource\_t::proxy\_has\_object () const` [inherited]`

Check whether this wrapper actually wraps an object.

**Returns**

true if there is an underlying object, false if this wrapper is empty

## Author

Generated automatically by Doxygen for Wayland++ from the source code.