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wxScrolledWindow

The wxScrolledWindow class manages scrolling for its client area, transforming the coordinates according to the scrollbar positions, and setting the scroll positions, thumb sizes and ranges according to the area in view.

As with all windows, an application can draw onto a wxScrolledWindow using a device context.

You have the option of handling the OnPaint handler or overriding the OnDraw function, which is passed a pre-scrolled device context (prepared by PrepareDC).

If you don't wish to calculate your own scrolling, you must call PrepareDC when not drawing from within OnDraw, to set the device origin for the device context according to the current scroll position.

Derived from

wxWindow
wxEvtHandler
wxObject

Include files

<wx/scrolwin.h>

Window styles

wxRETAINED Uses a backing pixmap to speed refreshes. Motif only.

See also window styles overview.

Remarks

Use wxScrolledWindow for applications where the user scrolls by a fixed amount, and where a 'page' can be interpreted to be the current visible portion of the window. For more sophisticated applications, use the wxScrolledWindow implementation as a guide to build your own scroll behaviour.

See also

wxScrollBar, wxClientDC, wxPaintDC

Members

wxScrolledWindow::wxScrolledWindow
wxScrolledWindow::~wxScrolledWindow
wxScrolledWindow::Create
wxScrolledWindow::EnableScrolling
wxScrolledWindow::GetScrollPixelsPerUnit
wxScrolledWindow::GetVirtualSize
wxScrolledWindow::IsRetained
wxScrolledWindow::PrepareDC
wxScrolledWindow::OnDraw
wxScrolledWindow::OnPaint
wxScrolledWindow::OnScroll
wxScrolledWindow::Scroll
wxScrolledWindow::SetScrollbars
wxScrolledWindow::ViewStart


wxScrolledWindow::wxScrolledWindow

wxScrolledWindow()

Default constructor.

wxScrolledWindow(wxWindow* parent, wxWindowID id = -1, const wxPoint& pos = wxDefaultPosition, const wxSize& size = wxDefaultSize, long style = wxHSCROLL | wxVSCROLL, const wxString& name = "scrolledWindow")

Constructor.

Parameters

parent

id

pos

size

style

name

Remarks

The window is initially created without visible scrollbars. Call wxScrolledWindow::SetScrollbars to specify how big the virtual window size should be.


wxScrolledWindow::~wxScrolledWindow

~wxScrolledWindow()

Destructor.


wxScrolledWindow::Create

bool Create(wxWindow* parent, wxWindowID id = -1, const wxPoint& pos = wxDefaultPosition, const wxSize& size = wxDefaultSize, long style = wxHSCROLL | wxVSCROLL, const wxString& name = "scrolledWindow")

Creates the window for two-step construction. Derived classes should call or replace this function. See wxScrolledWindow::wxScrolledWindow for details.


wxScrolledWindow::EnableScrolling

void EnableScrolling(const bool xScrolling, const bool yScrolling)

Enable or disable physical scrolling in the given direction. Physical scrolling is the physical transfer of bits up or down the screen when a scroll event occurs. If the application scrolls by a variable amount (e.g. if there are different font sizes) then physical scrolling will not work, and you should switch it off.

Parameters

xScrolling

yScrolling

Remarks

Physical scrolling may not be available on all platforms. Where it is available, it is enabled by default.


wxScrolledWindow::GetScrollPixelsPerUnit

void GetScrollPixelsPerUnit(int* xUnit, int* yUnit) const

Get the number of pixels per scroll unit (line), in each direction, as set by wxScrolledWindow::SetScrollbars. A value of zero indicates no scrolling in that direction.

Parameters

xUnit

yUnit

See also

wxScrolledWindow::SetScrollbars, wxScrolledWindow::GetVirtualSize


wxScrolledWindow::GetVirtualSize

void GetVirtualSize(int* x, int* y) const

Gets the size in device units of the scrollable window area (as opposed to the client size, which is the area of the window currently visible).

Parameters

x

y

Remarks

Use wxDC::DeviceToLogicalX and wxDC::DeviceToLogicalY to translate these units to logical units.

See also

wxScrolledWindow::SetScrollbars, wxScrolledWindow::GetScrollPixelsPerUnit


wxScrolledWindow::IsRetained

bool IsRetained() const

TRUE if the window has a backing bitmap.


wxScrolledWindow::PrepareDC

void PrepareDC(wxDC& dc)

Call this function to prepare the device context for drawing a scrolled image. It sets the device origin according to the current scroll position.

PrepareDC is called automatically within the default wxScrolledWindow::OnPaint event handler, so your wxScrolledWindow::OnDraw override will be passed a 'pre-scrolled' device context. However, if you wish to draw from outside of OnDraw (via OnPaint), or you wish to implement OnPaint yourself, you must call this function yourself. For example:

void MyWindow::OnEvent(wxMouseEvent& event)
{
  wxClientDC dc(this);
  PrepareDC(dc);

  dc.SetPen(*wxBLACK_PEN);
  float x, y;
  event.Position(&x, &y);
  if (xpos > -1 && ypos > -1 && event.Dragging())
  {
    dc.DrawLine(xpos, ypos, x, y);
  }
  xpos = x;
  ypos = y;
}

wxScrolledWindow::OnDraw

virtual void OnDraw(wxDC& dc)

Called by the default wxScrolledWindow::OnPaint implementation to allow the application to define painting behaviour without having to worry about calling wxScrolledWindow::PrepareDC.


wxScrolledWindow::OnPaint

void OnPaint(wxPaintEvent& event)

Sent to the window when the window must be refreshed.

For more details, see wxWindow::OnPaint.

The default implementation for wxScrolledWindow's OnPaint handler is simply:

void wxScrolledWindow::OnPaint(wxPaintEvent& event)
{
	wxPaintDC dc(this);
	PrepareDC(dc);

	OnDraw(dc);
}

wxScrolledWindow::OnScroll

void OnScroll(wxScrollEvent& event)

Override this function to intercept scroll events. This member function implements the default scroll behaviour. If you do not call the default function, you will have to manage all scrolling behaviour including drawing the window contents at an appropriate position relative to the scrollbars.

For more details, see wxWindow::OnScroll.

See also

wxScrollEvent


wxScrolledWindow::Scroll

void Scroll(int x, int y)

Scrolls a window so the view start is at the given point.

Parameters

x

y

Remarks

The positions are in scroll units, not pixels, so to convert to pixels you will have to multiply by the number of pixels per scroll increment. If either parameter is -1, that position will be ignored (no change in that direction).

See also

wxScrolledWindow::SetScrollbars, wxScrolledWindow::GetScrollPixelsPerUnit


wxScrolledWindow::SetScrollbars

void SetScrollbars(int pixelsPerUnitX, int pixelsPerUnitY, int noUnitsX, int noUnitsY, int xPos = 0, int yPos = 0)

Sets up vertical and/or horizontal scrollbars.

Parameters

pixelsPerUnitX

pixelsPerUnitY

noUnitsX

noUnitsY

xPos

yPos

Remarks

The first pair of parameters give the number of pixels per 'scroll step', i.e. amount moved when the up or down scroll arrows are pressed. The second pair gives the length of scrollbar in scroll steps, which sets the size of the virtual window.

xPos and yPos optionally specify a position to scroll to immediately.

For example, the following gives a window horizontal and vertical scrollbars with 20 pixels per scroll step, and a size of 50 steps (1000 pixels) in each direction.

  window->SetScrollbars(20, 20, 50, 50);
wxScrolledWindow manages the page size itself, using the current client window size as the page size.

Note that for more sophisticated scrolling applications, for example where scroll steps may be variable according to the position in the document, it will be necessary to derive a new class from wxWindow, overriding OnSize and adjusting the scrollbars appropriately.


wxScrolledWindow::ViewStart

void ViewStart(int* x, int* y) const

Get the position at which the visible portion of the window starts.

Parameters

x

y

Remarks

If either of the scrollbars is not at the home position, x and/or y will be greater than zero. Combined with wxWindow::GetClientSize, the application can use this function to efficiently redraw only the visible portion of the window. The positions are in logical scroll units, not pixels, so to convert to pixels you will have to multiply by the number of pixels per scroll increment.

See also

wxScrolledWindow::SetScrollbars