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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
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10\pythonnote{wxPython uses wxGenericDragImage on all platforms, but
11uses the wxDragImage name.}
12
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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
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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
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25If you wish to draw the image yourself, use wxGenericDragImage and
26override \helpref{wxDragImage::DoDrawImage}{wxdragimagedodrawimage} and
27\helpref{wxDragImage::GetImageRect}{wxdragimagegetimagerect}.
28
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29Please see {\tt samples/dragimag} for an example.
30
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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
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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},
7af3ca16 57 \param{const wxPoint\& }{cursorHotspot = wxPoint(0, 0)}}
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58
59Constructs a drag image from a bitmap and optional cursor.
60
61\func{}{wxDragImage}{\param{const wxIcon\& }{image}, \param{const wxCursor\& }{cursor = wxNullCursor},
7af3ca16 62 \param{const wxPoint\& }{cursorHotspot = wxPoint(0, 0)}}
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63
64Constructs a drag image from an icon and optional cursor.
65
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66\pythonnote{This constructor is called wxDragIcon in wxPython.}
67
68be9f09 68\func{}{wxDragImage}{\param{const wxString\& }{text}, \param{const wxCursor\& }{cursor = wxNullCursor},
7af3ca16 69 \param{const wxPoint\& }{cursorHotspot = wxPoint(0, 0)}}
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70
71Constructs a drag image from a text string and optional cursor.
72
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73\pythonnote{This constructor is called wxDragString in wxPython.}
74
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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
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79\pythonnote{This constructor is called wxDragTreeItem in wxPython.}
80
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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
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85\pythonnote{This constructor is called wxDragListItem in wxPython.}
86
87\func{}{wxDragImage}{\param{const wxCursor\& }{cursor = wxNullCursor},
7af3ca16 88 \param{const wxPoint\& }{cursorHotspot = wxPoint(0, 0)}}
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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
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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
aa2d25a5 103\docparam{hotspot}{This parameter is deprecated.}
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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
cc81d32f 113\func{bool}{BeginDrag}{\param{const wxPoint\& }{hotspot}, \param{wxWindow* }{window}, \param{bool}{ fullScreen = false}, \param{wxRect*}{ rect = NULL}}
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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
cc81d32f 136is limited unless {\it fullScreen} is true.}
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137
138\docparam{boundingWindow}{In the second form of the function, specifies the
139area within which the drag occurs.}
140
cc81d32f 141\docparam{fullScreen}{If true, specifies that the drag will be visible over the full
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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
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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
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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
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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
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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
aa2d25a5 194{\it pt} is the position in client coordinates (relative to the window specified in BeginDrag).
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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
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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