ViewPort - Core geographic projection and coordinate transformation engine. More...

#include <viewport.h>

Public Member Functions
wxPoint	GetPixFromLL (double lat, double lon)
	Convert latitude and longitude on the ViewPort to physical pixel coordinates.

void	GetLLFromPix (const wxPoint &p, double lat, double lon)
	Convert physical pixel coordinates on the ViewPort to latitude and longitude.

void	GetLLFromPix (const wxPoint2DDouble &p, double lat, double lon)
	Convert physical pixel coordinates on the ViewPort to latitude and longitude using double precision.

wxPoint2DDouble	GetDoublePixFromLL (double lat, double lon)
	Convert latitude and longitude on the ViewPort to physical pixel coordinates with double precision.

LLRegion	GetLLRegion (const OCPNRegion &region)

OCPNRegion	GetVPRegionIntersect (const OCPNRegion &region, const LLRegion &llregion, int chart_native_scale)
	Get the intersection of the viewport with a given region.

OCPNRegion	GetVPRegionIntersect (const OCPNRegion &Region, int nPoints, float llpoints, int chart_native_scale, wxPoint ppoints)
	Get the intersection of the viewport with a polygon defined by lat/lon points.

wxRect	GetVPRectIntersect (size_t n, float *llpoints)
	Get the viewport rectangle intersecting with a set of lat/lon points.

ViewPort	BuildExpandedVP (int width, int height)

void	SetBoxes ()
	Computes the bounding box coordinates for the current viewport.

void	SetPixelScale (double scale)
	Set the physical to logical pixel ratio for the display.

void	Invalidate ()

void	Validate ()

bool	IsValid () const

void	SetRotationAngle (double angle_rad)

void	SetProjectionType (int type)

LLBBox &	GetBBox ()

void	SetBBoxDirect (const LLBBox &bbox)

void	SetBBoxDirect (double latmin, double lonmin, double latmax, double lonmax)

bool	ContainsIDL ()

void	InvalidateTransformCache ()

void	SetVPTransformMatrix ()

bool	operator== (const ViewPort &rhs) const

Public Attributes
double	clat
	Center latitude of the viewport in degrees.

double	clon
	Center longitude of the viewport in degrees.

double	view_scale_ppm
	Requested view scale in physical pixels per meter (ppm), before applying projections.

double	skew
	Angular distortion (shear transform) applied to the viewport in radians.

double	rotation
	Rotation angle of the viewport in radians.

double	tilt
	Tilt angle for perspective view in radians.

double	chart_scale
	Chart scale denominator (e.g., 50000 for a 1:50000 scale).

double	ref_scale
	The nominal scale of the "reference chart" for this view.

int	pix_width
	Width of the viewport in physical pixels.

int	pix_height
	Height of the viewport in physical pixels.

bool	b_quilt

bool	b_FullScreenQuilt

int	m_projection_type

bool	b_MercatorProjectionOverride

wxRect	rv_rect

float	vp_matrix_transform [16]

float	norm_transform [16]

Detailed Description

ViewPort - Core geographic projection and coordinate transformation engine.

Represents the fundamental viewing parameters and coordinate transformations for chart display. This class serves as the mathematical foundation for mapping between geographic coordinates (latitude/longitude) and screen coordinates (pixels). It encapsulates all parameters that define how a chart section is viewed, including position, scale, rotation, and projection.

ViewPort is designed to be a relatively lightweight, data-focused class that handles the complex mathematical operations needed for accurate chart rendering without direct dependencies on UI components.

Definition at line 56 of file viewport.h.

Constructor & Destructor Documentation

◆ ViewPort()

ViewPort::ViewPort ( )

Definition at line 107 of file viewport.cpp.

Member Function Documentation

◆ BuildExpandedVP()

ViewPort ViewPort::BuildExpandedVP	(	int	width,
		int	height
	)

Definition at line 965 of file viewport.cpp.

◆ ContainsIDL()

bool ViewPort::ContainsIDL ( )

Definition at line 958 of file viewport.cpp.

◆ GetBBox()

LLBBox & ViewPort::GetBBox ( )

inline

Definition at line 185 of file viewport.h.

◆ GetDoublePixFromLL()

wxPoint2DDouble ViewPort::GetDoublePixFromLL	(	double	lat,
		double	lon
	)

Convert latitude and longitude on the ViewPort to physical pixel coordinates with double precision.

Parameters

lat	Latitude in degrees.
lon	Longitude in degrees.

Returns: wxPoint2DDouble Physical pixel coordinates.

Definition at line 133 of file viewport.cpp.

◆ GetLLFromPix() [1/2]

void ViewPort::GetLLFromPix	(	const wxPoint &	p,
		double *	lat,
		double *	lon
	)

inline

Convert physical pixel coordinates on the ViewPort to latitude and longitude.

Parameters

p	Physical pixel coordinates.
lat	Pointer to store resulting latitude.
lon	Pointer to store resulting longitude.

See also: ChartCanvas::GetCanvasPixPoint() for the canvas-level implementation.

Definition at line 80 of file viewport.h.

◆ GetLLFromPix() [2/2]

void ViewPort::GetLLFromPix	(	const wxPoint2DDouble &	p,
		double *	lat,
		double *	lon
	)

Convert physical pixel coordinates on the ViewPort to latitude and longitude using double precision.

Parameters

p	Physical pixel coordinates as wxPoint2DDouble.
lat	Pointer to store resulting latitude.
lon	Pointer to store resulting longitude.

Definition at line 256 of file viewport.cpp.

◆ GetLLRegion()

LLRegion ViewPort::GetLLRegion ( const OCPNRegion & region )

Definition at line 333 of file viewport.cpp.

◆ GetPixFromLL()

wxPoint ViewPort::GetPixFromLL	(	double	lat,
		double	lon
	)

Convert latitude and longitude on the ViewPort to physical pixel coordinates.

Parameters

lat	Latitude in degrees.
lon	Longitude in degrees.

Returns: wxPoint Pixel coordinates.

See also: ChartCanvas::GetCanvasPointPix() for the canvas-level implementation.

Definition at line 124 of file viewport.cpp.

◆ GetVPRectIntersect()

wxRect ViewPort::GetVPRectIntersect	(	size_t	n,
		float *	llpoints
	)

Get the viewport rectangle intersecting with a set of lat/lon points.

Parameters

n	Number of points
llpoints	Array of lat/lon points

Returns: wxRect Intersecting rectangle

Definition at line 788 of file viewport.cpp.

◆ GetVPRegionIntersect() [1/2]

OCPNRegion ViewPort::GetVPRegionIntersect	(	const OCPNRegion &	region,
		const LLRegion &	llregion,
		int	chart_native_scale
	)

Get the intersection of the viewport with a given region.

Parameters

region	OCPNRegion to intersect with
llregion	LLRegion to use for the intersection
chart_native_scale	Native scale of the chart

Returns: OCPNRegion Resulting intersected region

Definition at line 409 of file viewport.cpp.

◆ GetVPRegionIntersect() [2/2]

OCPNRegion ViewPort::GetVPRegionIntersect	(	const OCPNRegion &	Region,
		int	nPoints,
		float *	llpoints,
		int	chart_native_scale,
		wxPoint *	ppoints
	)

Get the intersection of the viewport with a polygon defined by lat/lon points.

Parameters

Region	OCPNRegion to intersect with
nPoints	Number of points in the polygon
llpoints	Array of lat/lon points defining the polygon
chart_native_scale	Native scale of the chart
ppoints	Array to store resulting pixel coordinates

Returns: OCPNRegion Resulting intersected region

Definition at line 470 of file viewport.cpp.

◆ Invalidate()

void ViewPort::Invalidate ( )

inline

Definition at line 178 of file viewport.h.

◆ InvalidateTransformCache()

void ViewPort::InvalidateTransformCache ( )

inline

Definition at line 192 of file viewport.h.

◆ IsValid()

bool ViewPort::IsValid ( ) const

inline

Definition at line 180 of file viewport.h.

◆ operator==()

bool ViewPort::operator== ( const ViewPort & rhs ) const

inline

Definition at line 247 of file viewport.h.

◆ SetBBoxDirect() [1/2]

void ViewPort::SetBBoxDirect ( const LLBBox & bbox )

inline

Definition at line 187 of file viewport.h.

◆ SetBBoxDirect() [2/2]

void ViewPort::SetBBoxDirect	(	double	latmin,
		double	lonmin,
		double	latmax,
		double	lonmax
	)

Definition at line 954 of file viewport.cpp.

◆ SetBoxes()

void ViewPort::SetBoxes ( )

Computes the bounding box coordinates for the current viewport.

This function is responsible for determining the lat/lon boundaries of the current viewport, which are used for various purposes including plugin rendering.

The function calculates a larger "virtual" pixel window size when rotation is applied to ensure that enough chart data is fetched to fill the rotated screen. It then computes the viewport lat/lon reference points based on screen coordinates.

Different algorithms are used depending on the projection type (POLAR, ORTHOGRAPHIC, STEREOGRAPHIC, GNOMONIC, MERCATOR, EQUIRECTANGULAR).

Edge cases are handled such as:

IDL (International Date Line) crossings
Poles being visible on screen
Non-rectangular mappings between screen space and geographical coordinates

The computed bounding box is stored in vpBBox and is used by various parts of the program to determine which chart features should be rendered and which are outside the visible area.

Note: When rotation or skew is applied, the function creates a larger rectangle that encompasses the rotated viewport, which can lead to data being fetched and rendered for areas that may be just outside the visible part of the screen.

Definition at line 811 of file viewport.cpp.

◆ SetPixelScale()

void ViewPort::SetPixelScale ( double scale )

Set the physical to logical pixel ratio for the display.

On standard displays, one logical pixel equals one physical pixel, so this value is 1.0. On high-DPI/Retina displays, one logical pixel may equal multiple physical pixels:

MacBook Pro Retina: 2.0 (2x2 physical pixels per logical pixel)
Other HiDPI displays: May be 1.5, 1.75, etc.

Parameters

scale The ratio of physical pixels to logical pixels.

Definition at line 121 of file viewport.cpp.

◆ SetProjectionType()

void ViewPort::SetProjectionType ( int type )

inline

Definition at line 183 of file viewport.h.

◆ SetRotationAngle()

void ViewPort::SetRotationAngle ( double angle_rad )

inline

Definition at line 182 of file viewport.h.

◆ SetVPTransformMatrix()

void ViewPort::SetVPTransformMatrix ( )

Definition at line 975 of file viewport.cpp.

◆ Validate()

void ViewPort::Validate ( )

inline

Definition at line 179 of file viewport.h.

Member Data Documentation

◆ b_FullScreenQuilt

bool ViewPort::b_FullScreenQuilt

Definition at line 236 of file viewport.h.

◆ b_MercatorProjectionOverride

bool ViewPort::b_MercatorProjectionOverride

Definition at line 239 of file viewport.h.

◆ b_quilt

bool ViewPort::b_quilt

Definition at line 235 of file viewport.h.

◆ chart_scale

double ViewPort::chart_scale

Chart scale denominator (e.g., 50000 for a 1:50000 scale).

Definition at line 219 of file viewport.h.

◆ clat

double ViewPort::clat

Center latitude of the viewport in degrees.

Definition at line 197 of file viewport.h.

◆ clon

double ViewPort::clon

Center longitude of the viewport in degrees.

Definition at line 199 of file viewport.h.

◆ m_projection_type

int ViewPort::m_projection_type

Definition at line 238 of file viewport.h.

◆ norm_transform

float ViewPort::norm_transform[16]

Definition at line 244 of file viewport.h.

◆ pix_height

int ViewPort::pix_height

Height of the viewport in physical pixels.

Definition at line 233 of file viewport.h.

◆ pix_width

int ViewPort::pix_width

Width of the viewport in physical pixels.

This may be larger than the actual screen width if the viewport is expanded for operations like text rendering or to accommodate rotation.

See also: BuildExpandedVP() for how this is modified for text rendering

Definition at line 231 of file viewport.h.

◆ ref_scale

double ViewPort::ref_scale

The nominal scale of the "reference chart" for this view.

Definition at line 221 of file viewport.h.

◆ rotation

double ViewPort::rotation

Rotation angle of the viewport in radians.

Definition at line 214 of file viewport.h.

◆ rv_rect

wxRect ViewPort::rv_rect

Definition at line 240 of file viewport.h.

◆ skew

double ViewPort::skew

Angular distortion (shear transform) applied to the viewport in radians.

The skew parameter represents a shear transformation applied to the viewport, which maintains parallel lines while changing their angles relative to the axes.

Definition at line 212 of file viewport.h.

◆ tilt

double ViewPort::tilt

Tilt angle for perspective view in radians.

Definition at line 216 of file viewport.h.

◆ view_scale_ppm

double ViewPort::view_scale_ppm

Requested view scale in physical pixels per meter (ppm), before applying projections.

Definition at line 204 of file viewport.h.

◆ vp_matrix_transform

float ViewPort::vp_matrix_transform[16]

Definition at line 243 of file viewport.h.

The documentation for this class was generated from the following files:

/home/runner/work/main/main/opencpn/gui/include/gui/viewport.h
/home/runner/work/main/main/opencpn/gui/src/viewport.cpp

Public Member Functions

Public Attributes

Detailed Description

Constructor & Destructor Documentation

◆ ViewPort()

Member Function Documentation

◆ BuildExpandedVP()

◆ ContainsIDL()

◆ GetBBox()

◆ GetDoublePixFromLL()

◆ GetLLFromPix() [1/2]

◆ GetLLFromPix() [2/2]

◆ GetLLRegion()

◆ GetPixFromLL()

◆ GetVPRectIntersect()

◆ GetVPRegionIntersect() [1/2]

◆ GetVPRegionIntersect() [2/2]

◆ Invalidate()

◆ InvalidateTransformCache()

◆ IsValid()

◆ operator==()

◆ SetBBoxDirect() [1/2]

◆ SetBBoxDirect() [2/2]

◆ SetBoxes()

◆ SetPixelScale()

◆ SetProjectionType()

◆ SetRotationAngle()

◆ SetVPTransformMatrix()

◆ Validate()

Member Data Documentation

◆ b_FullScreenQuilt

◆ b_MercatorProjectionOverride

◆ b_quilt

◆ chart_scale

◆ clat

◆ clon

◆ m_projection_type

◆ norm_transform

◆ pix_height

◆ pix_width

◆ ref_scale

◆ rotation

◆ rv_rect

◆ skew

◆ tilt

◆ view_scale_ppm

◆ vp_matrix_transform