wayland_viewport_t - Man Page

crop and scale interface to a wl_surface

Synopsis

#include <wayland-client-protocol-extra.hpp>

Inherits wayland::proxy_t.

Public Types

enum class wrapper_type { standard, display, foreign, proxy_wrapper }

void set_source (double x, double y, double width, double height)
set the source rectangle for cropping
void set_destination (int32_t width, int32_t height)
set the surface size for scaling
uint32_t get_id () const
Get the id of a proxy object.
std::string get_class () const
Get the interface name (class) of a proxy object.
uint32_t get_version () const
Get the protocol object version of a proxy object.
wrapper_type get_wrapper_type () const
Get the type of a proxy object.
void set_queue (event_queue_t queue)
Assign a proxy to an event queue.
wl_proxy * c_ptr () const
Get a pointer to the underlying C struct.
bool proxy_has_object () const
Check whether this wrapper actually wraps an object.
operator bool () const
Check whether this wrapper actually wraps an object.
bool operator== (const proxy_t &right) const
Check whether two wrappers refer to the same object.
bool operator!= (const proxy_t &right) const
Check whether two wrappers refer to different objects.
void proxy_release ()
Release the wrapped object (if any), making this an empty wrapper.

Static Public Attributes

static constexpr std::uint32_t set_source_since_version = 1
Minimum protocol version required for the set_source function.
static constexpr std::uint32_t set_destination_since_version = 1
Minimum protocol version required for the set_destination function.

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:

buffer_transform (wl_surface.set_buffer_transform)
buffer_scale (wl_surface.set_buffer_scale)
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 437 of file wayland-client-protocol-extra.hpp.

Member Enumeration Documentation

enum class wayland::proxy_t::wrapper_type [strong], [inherited]

Underlying wl_proxy type and properties of a proxy_t that affect construction, destruction, and event handling

Enumerator

standard: C pointer is a standard type compatible with wl_proxy*. Events are dispatched and it is destructed when the proxy_t is destructed. User data is set.
display: C pointer is a wl_display*. No events are dispatched, wl_display_disconnect is called when the proxy_t is destructed. User data is set.
foreign: C pointer is a standard type compatible with wl_proxy*, but another library owns it and it should not be touched in a way that could affect the operation of the other library. No events are dispatched, wl_proxy_destroy is not called when the proxy_t is destructed, user data is not touched. Consequently, there is no reference counting for the proxy_t. Lifetime of such wrappers should preferably be short to minimize the chance that the owning library decides to destroy the wl_proxy.
proxy_wrapper: C pointer is a wl_proxy* that was constructed with wl_proxy_create_wrapper. No events are dispatched, wl_proxy_wrapper_destroy is called when the proxy_t is destroyed. Reference counting is active. A reference to the proxy_t creating this proxy wrapper is held to extend its lifetime until after the proxy wrapper is destroyed.

Definition at line 116 of file wayland-client.hpp.

Member Function Documentation

wl_proxy * wayland::proxy_t::c_ptr () const [inherited]

Get a pointer to the underlying C struct.

Returns: The underlying wl_proxy wrapped by this proxy_t if it exists, otherwise an exception is thrown

std::string wayland::proxy_t::get_class () const [inherited]

Get the interface name (class) of a proxy object.

Returns: The interface name of the object associated with the proxy

uint32_t wayland::proxy_t::get_id () const [inherited]

Get the id of a proxy object.

Returns: The id the object associated with the proxy

uint32_t wayland::proxy_t::get_version () const [inherited]

Get the protocol object version of a proxy object. Gets the protocol object version of a proxy object, or 0 if the proxy was created with unversioned API.

A returned value of 0 means that no version information is available, so the caller must make safe assumptions about the object's real version.

display_t will always return version 0.

Returns: The protocol object version of the proxy or 0

wrapper_type wayland::proxy_t::get_wrapper_type () const [inline], [inherited]

Get the type of a proxy object.

Definition at line 302 of file wayland-client.hpp.

wayland::proxy_t::operator bool () const [inherited]

Check whether this wrapper actually wraps an object.

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

bool wayland::proxy_t::operator!= (const proxy_t & right) const [inherited]

Check whether two wrappers refer to different objects.

bool wayland::proxy_t::operator== (const proxy_t & right) const [inherited]

Check whether two wrappers refer to the same object.

bool wayland::proxy_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

void wayland::proxy_t::proxy_release () [inherited]

Release the wrapped object (if any), making this an empty wrapper. Note that display_t instances cannot be released this way. Attempts to do so are ignored.

Examples foreign_display.cpp.

void viewport_t::set_destination (int32_t width, int32_t height)

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 953 of file wayland-client-protocol-extra.cpp.

void wayland::proxy_t::set_queue (event_queue_t queue) [inherited]

Assign a proxy to an event queue.

Parameters: queue The event queue that will handle this proxy

Assign proxy to event queue. Events coming from proxy will be queued in queue instead of the display's main queue.

See also: display_t::dispatch_queue().

Examples proxy_wrapper.cpp.

void viewport_t::set_source (double x, double y, double width, double height)

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.