core_ui::Canvas Class Reference

A reusable canvas with support for logical coordinates and auto-scalling the content. More...

#include <canvas.h>

Inheritance diagram for core_ui::Canvas:

Public Member Functions
	Canvas (QWidget *parent)
	Creates a new Canvas.
int	borderSize () const
	Border size value (in pixels)
void	setBorderSize (int border_size)
	Sets a new border size (pixels)
const QRectF &	viewport () const
	Current viewport rectangle (in logical coordinates)
void	setViewport (const QRectF &viewport_rect)
	Sets the viewport rectangle (logical coordinates) More...
void	setViewport (const QPointF &top_left, const QPointF &bottom_right)
	Sets the viewport rectangle. More...
const QTransform &	transformFromViewport () const
	Logical viewport coordinates to client window coordinates.
const QTransform &	transformToViewport () const
	Client window coordinates to logical viewport coordinates.
double	scale () const
	Returns the current scale factor.

Detailed Description

A reusable canvas with support for logical coordinates and auto-scalling the content.

Once the logical viewport rectangle is defined, this class maintains the transformations to/from logical viewport coordinates such that the entire viewport is always visible.

Canvas supports both orientations of the y-axis:

• pointing down (default QPainter coordinates)
• pointing up (traditional math/physics Cartesian coordinates)

Using coordinates with y "pointing up" requires extra care, see Canvas::setViewport()

Member Function Documentation

setViewport() [1/2]

void core_ui::Canvas::setViewport

(

const QRectF &

viewport_rect

)

Sets the viewport rectangle (logical coordinates)

In order to use the traditional Cartesian coordinates, with the y-axis pointing up, the height of the viewport rectangle should have a negative value. The top_left viewport corner should still use the top y coordinate. For example, in order to define a (0,0) -> (10,5) viewport you would call:

setViewport(QRectF(0, 5, 10, -5));

Warning

When using coordinates where y "points up", the text will also be flipped upside down. To render text properly, the viewport transformation must be temporary modified to flip the y-coordinate.

setViewport() [2/2]

void core_ui::Canvas::setViewport	(	const QPointF &	top_left,
		const QPointF &	bottom_right
	)

Sets the viewport rectangle.

Note

Convenience overload, calls setViewport(const QRect&)

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

• C:/Users/lemo/work/darwin/core_ui/canvas.h
• C:/Users/lemo/work/darwin/core_ui/canvas.cpp