## 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.

Starting from version 2.4 of wxWidgets, there are several ways to use a wxScrolledWindow. In particular, there are now three ways to set the size of the scrolling area:

One way is to set the scrollbars directly using a call to wxScrolledWindow::SetScrollbars. This is the way it used to be in any previous version of wxWidgets and it will be kept for backwards compatibility.

An additional method of manual control, which requires a little less computation of your own, is to set the total size of the scrolling area by calling either wxWindow::SetVirtualSize, or wxWindow::FitInside, and setting the scrolling increments for it by calling wxScrolledWindow::SetScrollRate. Scrolling in some orientation is enabled by setting a non-zero increment for it.

The most automatic and newest way is to simply let sizers determine the scrolling area. This is now the default when you set an interior sizer into a wxScrolledWindow with wxWindow::SetSizer. The scrolling area will be set to the size requested by the sizer and the scrollbars will be assigned for each orientation according to the need for them and the scrolling increment set by wxScrolledWindow::SetScrollRate. As above, scrolling is only enabled in orientations with a non-zero increment. You can influence the minimum size of the scrolled area controlled by a sizer by calling wxWindow::SetVirtualSizeHints. (calling wxScrolledWindow::SetScrollbars has analogous effects in wxWidgets 2.4 -- in later versions it may not continue to override the sizer)

Note: if Maximum size hints are still supported by SetVirtualSizeHints, use them at your own dire risk. They may or may not have been removed for 2.4, but it really only makes sense to set minimum size hints here. We should probably replace SetVirtualSizeHints with SetMinVirtualSize or similar and remove it entirely in future.

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 DoPrepareDC).

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

A wxScrolledWindow will normally scroll itself and therefore its child windows as well. It might however be desired to scroll a different window than itself: e.g. when designing a spreadsheet, you will normally only have to scroll the (usually white) cell area, whereas the (usually grey) label area will scroll very differently. For this special purpose, you can call SetTargetWindow which means that pressing the scrollbars will scroll a different window.

Note that the underlying system knows nothing about scrolling coordinates, so that all system functions (mouse events, expose events, refresh calls etc) as well as the position of subwindows are relative to the "physical" origin of the scrolled window. If the user insert a child window at position (10,10) and scrolls the window down 100 pixels (moving the child window out of the visible area), the child window will report a position of (10,-90).

Derived from

wxPanel
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, wxVScrolledWindow

Members

wxScrolledWindow::wxScrolledWindow
wxScrolledWindow::~wxScrolledWindow
wxScrolledWindow::CalcScrolledPosition
wxScrolledWindow::CalcUnscrolledPosition
wxScrolledWindow::Create
wxScrolledWindow::EnableScrolling
wxScrolledWindow::GetScrollPixelsPerUnit
wxScrolledWindow::GetViewStart
wxScrolledWindow::GetVirtualSize
wxScrolledWindow::IsRetained
wxScrolledWindow::DoPrepareDC
wxScrolledWindow::OnDraw
wxScrolledWindow::PrepareDC
wxScrolledWindow::Scroll
wxScrolledWindow::SetScrollbars
wxScrolledWindow::SetScrollRate
wxScrolledWindow::SetTargetWindow

### 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

Parent window.

id

Window identifier. A value of -1 indicates a default value.

pos

Window position. If a position of (-1, -1) is specified then a default position is chosen.

size

Window size. If a size of (-1, -1) is specified then the window is sized appropriately.

style

Window style. See wxScrolledWindow.

name

Window 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::CalcScrolledPosition

void CalcScrolledPosition( int x, int y, int *xx int *yy) const

Translates the logical coordinates to the device ones. For example, if a window is scrolled 10 pixels to the bottom, the device coordinates of the origin are (0, 0) (as always), but the logical coordinates are (0, 10) and so the call to CalcScrolledPosition(0, 10, &xx, &yy) will return 0 in yy.

See also

CalcUnscrolledPosition

wxPython note: The wxPython version of this methods accepts only two parameters and returns xx and yy as a tuple of values.

### wxScrolledWindow::CalcUnscrolledPosition

void CalcUnscrolledPosition( int x, int y, int *xx int *yy) const

Translates the device coordinates to the logical ones. For example, if a window is scrolled 10 pixels to the bottom, the device coordinates of the origin are (0, 0) (as always), but the logical coordinates are (0, 10) and so the call to CalcUnscrolledPosition(0, 0, &xx, &yy) will return 10 in yy.

See also

CalcScrolledPosition

wxPython note: The wxPython version of this methods accepts only two parameters and returns xx and yy as a tuple of values.

### 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. Note that you will have to reposition child windows yourself, if physical scrolling is disabled.

Parameters

xScrolling

If true, enables physical scrolling in the x direction.

yScrolling

If true, enables physical scrolling in the y direction.

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

Receives the number of pixels per horizontal unit.

yUnit

Receives the number of pixels per vertical unit.

See also

wxScrolledWindow::SetScrollbars, wxScrolledWindow::GetVirtualSize

wxPython note: The wxPython version of this methods accepts no parameters and returns a tuple of values for xUnit and yUnit.

### wxScrolledWindow::GetViewStart

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

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

Parameters

x

Receives the first visible x position in scroll units.

y

Receives the first visible y position in scroll units.

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

wxPython note: The wxPython version of this methods accepts no parameters and returns a tuple of values for x and y.

### 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

Receives the length of the scrollable window, in pixels.

y

Receives the height of the scrollable window, in pixels.

Remarks

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

See also

wxScrolledWindow::SetScrollbars, wxScrolledWindow::GetScrollPixelsPerUnit

wxPython note: The wxPython version of this methods accepts no parameters and returns a tuple of values for x and y.

### wxScrolledWindow::IsRetained

bool IsRetained() const

Motif only: true if the window has a backing bitmap.

### wxScrolledWindow::DoPrepareDC

void DoPrepareDC(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.

DoPrepareDC 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);
      DoPrepareDC(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 paint event handler to allow the application to define painting behaviour without having to worry about calling wxScrolledWindow::DoPrepareDC.

Instead of overriding this function you may also just process the paint event in the derived class as usual, but then you will have to call DoPrepareDC() yourself.

### wxScrolledWindow::PrepareDC

void PrepareDC(wxDC& dc)

This function is for backwards compatibility only and simply calls DoPrepareDC now. Notice that it is not called by the default paint event handle (DoPrepareDC() is), so overriding this method in your derived class is useless.

### wxScrolledWindow::Scroll

void Scroll(int x, int y)

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

Parameters

x

The x position to scroll to, in scroll units.

y

The y position to scroll to, in scroll units.

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, bool noRefresh = false)

Sets up vertical and/or horizontal scrollbars.

Parameters

pixelsPerUnitX

Pixels per scroll unit in the horizontal direction.

pixelsPerUnitY

Pixels per scroll unit in the vertical direction.

noUnitsX

Number of units in the horizontal direction.

noUnitsY

Number of units in the vertical direction.

xPos

Position to initialize the scrollbars in the horizontal direction, in scroll units.

yPos

Position to initialize the scrollbars in the vertical direction, in scroll units.

noRefresh

Will not refresh window if true.

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.

See also

wxWindow::SetVirtualSize

### wxScrolledWindow::SetScrollRate

void SetScrollRate(int xstep, int ystep)

Set the horizontal and vertical scrolling increment only. See the pixelsPerUnit parameter in SetScrollbars.

### wxScrolledWindow::SetTargetWindow

void SetTargetWindow(wxWindow* window)

Call this function to tell wxScrolledWindow to perform the actual scrolling on a different window (and not on itself).