1\section{\class{wxDragImage}}\label{wxdragimage} 2 3This class is used when you wish to drag an object on the screen, 4and a simple cursor is not enough. 5 6On Windows, the WIN32 API is used to do achieve smooth dragging. On other platforms, 7wxGenericDragImage is used. Applications may also prefer to use 8wxGenericDragImage on Windows, too. 9 10\pythonnote{wxPython uses wxGenericDragImage on all platforms, but 11uses the wxDragImage name.} 12 13To use this class, when you wish to start dragging an image, create a wxDragImage 14object and store it somewhere you can access it as the drag progresses. 15Call BeginDrag to start, and EndDrag to stop the drag. To move the image, 16initially call Show and then Move. If you wish to update the screen contents 17during the drag (for example, highlight an item as in the dragimag sample), first call Hide, 18update the screen, call Move, and then call Show. 19 20You can drag within one window, or you can use full-screen dragging 21either across the whole screen, or just restricted to one area 22of the screen to save resources. If you want the user to drag between 23two windows, then you will need to use full-screen dragging. 24 25If you wish to draw the image yourself, use wxGenericDragImage and 26override \helpref{wxDragImage::DoDrawImage}{wxdragimagedodrawimage} and 27\helpref{wxDragImage::GetImageRect}{wxdragimagegetimagerect}. 28 29Please see {\tt samples/dragimag} for an example. 30 31%\wxheading{Notes} 32% 33%Using the native Windows implementation, you must supply an image with a mask, or 34%the image will not show when dragged. It is not clear if this is a bug 35%in Windows or in the wxDragImage implementation. You can add a mask 36%with a call to wxImage::SetMaskColour, passing RGB values not likely 37%to be in the image. [CURED by creating the ImageList with ILC_MASK] 38 39\wxheading{Derived from} 40 41\helpref{wxObject}{wxobject} 42 43\wxheading{Include files} 44 45<wx/dragimag.h>\\ 46<wx/generic/dragimgg.h> 47 48\latexignore{\rtfignore{\wxheading{Members}}} 49 50\membersection{wxDragImage::wxDragImage}\label{wxdragimageconstr} 51 52\func{}{wxDragImage}{\void} 53 54Default constructor. 55 56\func{}{wxDragImage}{\param{const wxBitmap\& }{image}, \param{const wxCursor\& }{cursor = wxNullCursor}, 57 \param{const wxPoint\& }{cursorHotspot = wxPoint(0, 0)}} 58 59Constructs a drag image from a bitmap and optional cursor. 60 61\func{}{wxDragImage}{\param{const wxIcon\& }{image}, \param{const wxCursor\& }{cursor = wxNullCursor}, 62 \param{const wxPoint\& }{cursorHotspot = wxPoint(0, 0)}} 63 64Constructs a drag image from an icon and optional cursor. 65 66\pythonnote{This constructor is called wxDragIcon in wxPython.} 67 68\func{}{wxDragImage}{\param{const wxString\& }{text}, \param{const wxCursor\& }{cursor = wxNullCursor}, 69 \param{const wxPoint\& }{cursorHotspot = wxPoint(0, 0)}} 70 71Constructs a drag image from a text string and optional cursor. 72 73\pythonnote{This constructor is called wxDragString in wxPython.} 74 75\func{}{wxDragImage}{\param{const wxTreeCtrl\& }{treeCtrl}, \param{wxTreeItemId\& }{id}} 76 77Constructs a drag image from the text in the given tree control item, and optional cursor. 78 79\pythonnote{This constructor is called wxDragTreeItem in wxPython.} 80 81\func{}{wxDragImage}{\param{const wxListCtrl\& }{treeCtrl}, \param{long }{id}} 82 83Constructs a drag image from the text in the given tree control item, and optional cursor. 84 85\pythonnote{This constructor is called wxDragListItem in wxPython.} 86 87\func{}{wxDragImage}{\param{const wxCursor\& }{cursor = wxNullCursor}, 88 \param{const wxPoint\& }{cursorHotspot = wxPoint(0, 0)}} 89 90Constructs a drag image an optional cursor. This constructor is only available for 91wxGenericDragImage, and can be used when the application 92supplies \helpref{wxDragImage::DoDrawImage}{wxdragimagedodrawimage} and \helpref{wxDragImage::GetImageRect}{wxdragimagegetimagerect}. 93 94\wxheading{Parameters} 95 96\docparam{image}{Icon or bitmap to be used as the drag image. The bitmap can 97have a mask.} 98 99\docparam{text}{Text used to construct a drag image.} 100 101\docparam{cursor}{Optional cursor to combine with the image.} 102 103\docparam{hotspot}{This parameter is deprecated.} 104 105\docparam{treeCtrl}{Tree control for constructing a tree drag image.} 106 107\docparam{listCtrl}{List control for constructing a list drag image.} 108 109\docparam{id}{Tree or list control item id.} 110 111\membersection{wxDragImage::BeginDrag}\label{wxdragimagebegindrag} 112 113\func{bool}{BeginDrag}{\param{const wxPoint\& }{hotspot}, \param{wxWindow* }{window}, \param{bool}{ fullScreen = false}, \param{wxRect*}{ rect = NULL}} 114 115Start dragging the image, in a window or full screen. 116 117\func{bool}{BeginDrag}{\param{const wxPoint\& }{hotspot}, \param{wxWindow* }{window}, \param{wxWindow*}{ boundingWindow}} 118 119Start dragging the image, using the first window to capture the mouse and the second 120to specify the bounding area. This form is equivalent to using the first form, 121but more convenient than working out the bounding rectangle explicitly. 122 123You need to then call \helpref{wxDragImage::Show}{wxdragimageshow} 124and \helpref{wxDragImage::Move}{wxdragimagemove} to show the image on the screen. 125 126Call \helpref{wxDragImage::EndDrag}{wxdragimageenddrag} when the drag has finished. 127 128Note that this call automatically calls CaptureMouse. 129 130\wxheading{Parameters} 131 132\docparam{hotspot}{The location of the drag position relative to the upper-left corner 133of the image.} 134 135\docparam{window}{The window that captures the mouse, and within which the dragging 136is limited unless {\it fullScreen} is true.} 137 138\docparam{boundingWindow}{In the second form of the function, specifies the 139area within which the drag occurs.} 140 141\docparam{fullScreen}{If true, specifies that the drag will be visible over the full 142screen, or over as much of the screen as is specified by {\it rect}. Note that the mouse will 143still be captured in {\it window}.} 144 145\docparam{rect}{If non-NULL, specifies the rectangle (in screen coordinates) that 146bounds the dragging operation. Specifying this can make the operation more efficient 147by cutting down on the area under consideration, and it can also make a visual difference 148since the drag is clipped to this area.} 149 150\membersection{wxDragImage::DoDrawImage}\label{wxdragimagedodrawimage} 151 152\func{virtual bool}{DoDrawImage}{\param{wxDC\&}{ dc}, \param{const wxPoint\&}{ pos}} 153 154Draws the image on the device context with top-left corner at the given position. 155 156This function is only available with wxGenericDragImage, to allow applications to 157draw their own image instead of using an actual bitmap. If you override this function, 158you must also override \helpref{wxDragImage::GetImageRect}{wxdragimagegetimagerect}. 159 160\membersection{wxDragImage::EndDrag}\label{wxdragimageenddrag} 161 162\func{bool}{EndDrag}{\void} 163 164Call this when the drag has finished. 165 166Note that this call automatically calls ReleaseMouse. 167 168\membersection{wxDragImage::GetImageRect}\label{wxdragimagegetimagerect} 169 170\constfunc{virtual wxRect}{GetImageRect}{\param{const wxPoint\&}{ pos}} 171 172Returns the rectangle enclosing the image, assuming that the image is drawn with its 173top-left corner at the given point. 174 175This function is available in wxGenericDragImage only, and may be overridden (together with 176\helpref{wxDragImage::DoDrawImage}{wxdragimagedodrawimage}) to provide a virtual drawing capability. 177 178\membersection{wxDragImage::Hide}\label{wxdragimagehide} 179 180\func{bool}{Hide}{\void} 181 182Hides the image. You may wish to call this before updating the window 183contents (perhaps highlighting an item). Then call \helpref{wxDragImage::Move}{wxdragimagemove} 184and \helpref{wxDragImage::Show}{wxdragimageshow}. 185 186\membersection{wxDragImage::Move}\label{wxdragimagemove} 187 188\func{bool}{Move}{\param{const wxPoint\& }{pt}} 189 190Call this to move the image to a new position. The image will only be shown if 191\helpref{wxDragImage::Show}{wxdragimageshow} has been called previously (for example 192at the start of the drag). 193 194{\it pt} is the position in client coordinates (relative to the window specified in BeginDrag). 195 196You can move the image either when the image is hidden or shown, but in general dragging 197will be smoother if you move the image when it is shown. 198 199\membersection{wxDragImage::Show}\label{wxdragimageshow} 200 201\func{bool}{Show}{\void} 202 203Shows the image. Call this at least once when dragging. 204 205\membersection{wxDragImage::UpdateBackingFromWindow}\label{wxdragimageupdatebackingfromwindow} 206 207\constfunc{bool}{UpdateBackingFromWindow}{\param{wxDC\&}{ windowDC}, \param{wxMemoryDC\&}{ destDC}, 208 \param{const wxRect\&}{ sourceRect}, \param{const wxRect\&}{ destRect}} 209 210Override this if you wish to draw the window contents to the backing bitmap 211yourself. This can be desirable if you wish to avoid flicker by not having to 212redraw the updated window itself just before dragging, which can cause a flicker just 213as the drag starts. Instead, paint the drag image's backing bitmap to show the appropriate 214graphic {\it minus the objects to be dragged}, and leave the window itself to be updated 215by the drag image. This can provide eerily smooth, flicker-free drag behaviour. 216 217The default implementation copies the window contents to the backing bitmap. A new 218implementation will normally copy information from another source, such as from its 219own backing bitmap if it has one, or directly from internal data structures. 220 221This function is available in wxGenericDragImage only. 222 223