wxWidgets/interface/scrolwin.h

/////////////////////////////////////////////////////////////////////////////
// Name:        scrolwin.h
// Purpose:     documentation for wxScrolledWindow class
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

/**
    @class wxScrolledWindow
    @wxheader{scrolwin.h}

    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 @ref overview_dcoverview "device context".

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

    @beginStyleTable
    @style{wxRETAINED}:
           Uses a backing pixmap to speed refreshes. Motif only.
    @endStyleTable

    @library{wxcore}
    @category{miscwnd}

    @seealso
    wxScrollBar, wxClientDC, wxPaintDC, wxVScrolledWindow
*/
class wxScrolledWindow : public wxPanel
{
public:
    //@{
    /**
        Constructor.
        
        @param parent
            Parent window.
        @param id
            Window identifier. The value wxID_ANY indicates a default value.
        @param pos
            Window position. If a position of (-1, -1) is specified then a default
        position
            is chosen.
        @param size
            Window size. If a size of (-1, -1) is specified then the window is sized
            appropriately.
        @param style
            Window style. See wxScrolledWindow.
        @param name
            Window name.
        
        @remarks The window is initially created without visible scrollbars. Call
                 SetScrollbars() to specify how big the
                 virtual window size should be.
    */
    wxScrolledWindow();
    wxScrolledWindow(wxWindow* parent, wxWindowID id = -1,
                     const wxPoint& pos = wxDefaultPosition,
                     const wxSize& size = wxDefaultSize,
                     long style = wxHSCROLL | wxVSCROLL,
                     const wxString& name = "scrolledWindow");
    //@}

    /**
        Destructor.
    */
    ~wxScrolledWindow();

    /**
        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 CalcUnscrolledPosition()
    */
    void CalcScrolledPosition(int x, int y, int* xx, int* yy);

    /**
        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 CalcScrolledPosition()
    */
    void CalcUnscrolledPosition(int x, int y, int* xx, int* yy);

    /**
        Creates the window for two-step construction. Derived classes
        should call or replace this function. See wxScrolledWindow()
        for details.
    */
    bool Create(wxWindow* parent, wxWindowID id = -1,
                const wxPoint& pos = wxDefaultPosition,
                const wxSize& size = wxDefaultSize,
                long style = wxHSCROLL | wxVSCROLL,
                const wxString& name = "scrolledWindow");

    /**
        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 OnPaint() event
        handler, so your 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 DoPrepareDC(wxDC& dc);

    /**
        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.
        
        @param xScrolling
            If @true, enables physical scrolling in the x direction.
        @param 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.
    */
    void EnableScrolling(bool xScrolling, bool yScrolling);

    /**
        Get the number of pixels per scroll unit (line), in each direction, as set
        by SetScrollbars(). A value of zero indicates no
        scrolling in that direction.
        
        @param xUnit
            Receives the number of pixels per horizontal unit.
        @param yUnit
            Receives the number of pixels per vertical unit.
        
        @see SetScrollbars(), GetVirtualSize()
    */
    void GetScrollPixelsPerUnit(int* xUnit, int* yUnit);

    /**
        Get the position at which the visible portion of the window starts.
        
        @param x
            Receives the first visible x position in scroll units.
        @param 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 SetScrollbars()
    */
    void GetViewStart(int* x, int* y);

    /**
        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).
        
        @param x
            Receives the length of the scrollable window, in pixels.
        @param 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 SetScrollbars(), GetScrollPixelsPerUnit()
    */
    void GetVirtualSize(int* x, int* y);

    /**
        Motif only: @true if the window has a backing bitmap.
    */
    bool IsRetained();

    /**
        Called by the default paint event handler to allow the application to define
        painting behaviour without having to worry about calling
        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.
    */
    virtual void OnDraw(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.
    */
    void PrepareDC(wxDC& dc);

    /**
        Scrolls a window so the view start is at the given point.
        
        @param x
            The x position to scroll to, in scroll units.
        @param 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 SetScrollbars(), GetScrollPixelsPerUnit()
    */
    void Scroll(int x, int y);

    /**
        Set the horizontal and vertical scrolling increment only. See the pixelsPerUnit
        parameter in SetScrollbars.
    */
    void SetScrollRate(int xstep, int ystep);

    /**
        Sets up vertical and/or horizontal scrollbars.
        
        @param pixelsPerUnitX
            Pixels per scroll unit in the horizontal direction.
        @param pixelsPerUnitY
            Pixels per scroll unit in the vertical direction.
        @param noUnitsX
            Number of units in the horizontal direction.
        @param noUnitsY
            Number of units in the vertical direction.
        @param xPos
            Position to initialize the scrollbars in the horizontal direction, in
        scroll units.
        @param yPos
            Position to initialize the scrollbars in the vertical direction, in scroll
        units.
        @param 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.
        
        @see wxWindow::SetVirtualSize
    */
    void SetScrollbars(int pixelsPerUnitX, int pixelsPerUnitY,
                       int noUnitsX,
                       int noUnitsY,
                       int xPos = 0,
                       int yPos = 0,
                       bool noRefresh = false);

    /**
        Call this function to tell wxScrolledWindow to perform the actual scrolling on
        a different window (and not on itself).
    */
    void SetTargetWindow(wxWindow* window);
};