wx.DragImage

Inheritance diagram for wx.DragImage:

Description

This class is used when you wish to drag an object on the screen, and a simple cursor is not enough. On Windows, the WIN32 API is used to do achieve smooth dragging. On other platforms, wx.GenericDragImage is used. Applications may also prefer to use wx.GenericDragImage on Windows, too.

Note

wxPython note: wxPython uses wx.GenericDragImage on all platforms, but uses the wx.DragImage name.

To use this class, when you wish to start dragging an image, create a wx.DragImage object and store it somewhere you can access it as the drag progresses. Call BeginDrag to start, and EndDrag to stop the drag.

To move the image, initially call Show and then Move. If you wish to update the screen contents during the drag (for example, highlight an item as in the dragimag sample), first call Hide, update the screen, call Move, and then call Show.

You can drag within one window, or you can use full-screen dragging either across the whole screen, or just restricted to one area of the screen to save resources. If you want the user to drag between two windows, then you will need to use full-screen dragging.

If you wish to draw the image yourself, use wx.GenericDragImage and override DoDrawImage and GetImageRect.

Derived From

• wx.Object

Methods Summary

• __init__
• BeginDrag
• BeginDragBounded
• DoDrawImage
• EndDrag
• GetImageRect
• Hide
• Move
• RedrawImage
• SetBackingBitmap
• Show
• UpdateBackingFromWindow

Properties Summary

• ImageRect

Class API

Methods

__init__(image, cursor=wx.NullCursor)

Constructor.

Parameters:

• image (wx.Bitmap)
• cursor (wx.Cursor)

Returns:

wx.DragImage

---

BeginDrag(hotspot, window, fullScreen=None, rect=None)

Start dragging the image, using the first window to capture the mouse and the second to specify the bounding area.

You need to then call Show and Move to show the image on the screen. Call EndDrag when the drag has finished.

Parameters:

• hotspot (wx.Point): The location of the drag position relative to the upper-left corner of the image.
• window (wx.Window): The window that captures the mouse, and within which the dragging is limited unless fullScreen is True.
• fullScreen (int): If True, specifies that the drag will be visible over the full screen, or over as much of the screen as is specified by rect. Note that the mouse will still be captured in window.
• rect (wx.Rect)

Returns:

bool

Note

Note that this call automatically calls wx.Window.CaptureMouse.

---

BeginDragBounded(hotspot, window, boundingWindow)

Parameters:

• hotspot (wx.Point)
• window (wx.Window)
• boundingWindow (wx.Window)

Returns:

bool

---

DoDrawImage(dc, pos)

Draws the image on the device context with top-left corner at the given position.

If you override this function, you must also override GetImageRect.

Parameters:

• dc (wx.DC)
• pos (wx.Point)

Returns:

bool

---

EndDrag()

Call this when the drag has finished.

Returns:

bool

Note

Note that this call automatically calls wx.Window.ReleaseMouse.

---

GetImageRect(pos)

Returns the rectangle enclosing the image, assuming that the image is drawn with its top-left corner at the given point.

This function may be overridden (together with DoDrawImage) to provide a virtual drawing capability.

Parameters:

• pos (wx.Point)

Returns:

wx.Rect

---

Hide()

Hides the image. You may wish to call this before updating the window contents (perhaps highlighting an item). Then call Move and Show.

Returns:

bool

---

Move(pt)

Call this to move the image to a new position. The image will only be shown if Show has been called previously (for example at the start of the drag).

pt is the position in client coordinates (relative to the window specified in BeginDrag).

You can move the image either when the image is hidden or shown, but in general dragging will be smoother if you move the image when it is shown.

Parameters:

• pt (wx.Point)

Returns:

bool

---

RedrawImage(oldPos, newPos, eraseOld, drawNew)

Parameters:

• oldPos (wx.Point)
• newPos (wx.Point)
• eraseOld (bool)
• drawNew (bool)

Returns:

bool

---

SetBackingBitmap(bitmap)

Parameters:

• bitmap (wx.Bitmap)

---

Show()

Shows the image. Call this at least once when dragging.

Returns:

bool

---

UpdateBackingFromWindow(windowDC, destDC, sourceRect, destRect)

Override this if you wish to draw the window contents to the backing bitmap yourself. This can be desirable if you wish to avoid flicker by not having to redraw the updated window itself just before dragging, which can cause a flicker just as the drag starts. Instead, paint the drag image’s backing bitmap to show the appropriate graphic minus the objects to be dragged, and leave the window itself to be updated by the drag image. This can provide eerily smooth, flicker-free drag behaviour.

The default implementation copies the window contents to the backing bitmap. A new implementation will normally copy information from another source, such as from its own backing bitmap if it has one, or directly from internal data structures.

Parameters:

• windowDC (wx.DC)
• destDC (wx.MemoryDC)
• sourceRect (wx.Rect)
• destRect (wx.Rect)

Returns:

bool

---

Properties

ImageRect

See GetImageRect