Scrolled¶The Scrolled 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.
There are two commonly used (but not the only possible!) specializations of this class:
Starting from version 2.4 of wxWidgets, there are several ways to use a ScrolledWindow (and now Scrolled). In particular, there are three ways to set the size of the scrolling area:
One way is to set the scrollbars directly using a call to 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 Window.SetVirtualSize , or Window.FitInside , and setting the scrolling increments for it by calling 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 Scrolled with Window.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 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 Window.SetVirtualSizeHints(). (Calling SetScrollbars has analogous effects in wxWidgets 2.4 – in later versions it may not continue to override the sizer.)
Note that if maximum size hints are still supported by Window.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 Window.SetVirtualSizeHints() with Window.SetMinVirtualSize() or similar and remove it entirely in future.
As with all windows, an application can draw onto a Scrolled using a device context.
You have the option of handling the OnPaint handler or overriding the Scrolled.OnDraw function, which is passed a pre-scrolled device context (prepared by Scrolled.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 Scrolled 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).
Window Styles¶This class supports the following styles:
Events Emitted by this Class¶Handlers bound for the following event types will receive a ScrollWinEvent parameter.
New in version The: :r ef:Scrolled template exists since version 2.9.0. In older versions, only ScrolledWindow (equivalent of Scrolled<wxPanel>) was available.
Note
Use Scrolled 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 Scrolled implementation as a guide to build your own scroll behaviour or use VScrolledWindow or its variants.
Note
Don’t confuse ScrollWinEvents generated by this class with ScrollEvent objects generated by ScrollBar and Slider.
See also
ScrollBar, ClientDC, PaintDC, VScrolledWindow, HScrolledWindow, HVScrolledWindow,
Todo
review docs for this class replacing SetVirtualSizeHints() with SetMinClientSize().
Methods Summary¶| __init__ | Default constructor. |
| AdjustScrollbars | |
| CalcScrolledPosition | Translates the logical coordinates to the device ones. |
| CalcUnscrolledPosition | Translates the device coordinates to the logical ones. |
| Create | Creates the window for two-step construction. |
| DisableKeyboardScrolling | Disable use of keyboard keys for scrolling. |
| DoPrepareDC | Call this function to prepare the device context for drawing a scrolled image. |
| EnableScrolling | Enable or disable physical scrolling in the given direction. |
| GetScaleX | |
| GetScaleY | |
| GetScrollLines | |
| GetScrollPageSize | |
| GetScrollPixelsPerUnit | Get the number of pixels per scroll unit (line), in each direction, as set by SetScrollbars . |
| GetSizeAvailableForScrollTarget | Function which must be overridden to implement the size available for the scroll target for the given size of the main window. |
| GetTargetRect | |
| GetTargetWindow | |
| GetViewStart | Get the position at which the visible portion of the window starts. |
| GetVirtualSize | 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). |
| IsAutoScrolling | |
| IsRetained | Motif only: True if the window has a backing bitmap. |
| OnDraw | Called by the default paint event handler to allow the application to define painting behaviour without having to worry about calling DoPrepareDC . |
| PrepareDC | This function is for backwards compatibility only and simply calls DoPrepareDC now. |
| Scroll | Scrolls a window so the view start is at the given point. |
| SetScale | |
| SetScrollPageSize | |
| SetScrollRate | Set the horizontal and vertical scrolling increment only. |
| SetScrollbars | Sets up vertical and/or horizontal scrollbars. |
| SetTargetRect | |
| SetTargetWindow | Call this function to tell Scrolled to perform the actual scrolling on a different window (and not on itself). |
| ShowScrollbars | Set the scrollbar visibility. |
| StopAutoScrolling |
Properties Summary¶| ScaleX | See GetScaleX |
| ScaleY | See GetScaleY |
| TargetRect | See GetTargetRect and SetTargetRect |
| TargetWindow | See GetTargetWindow and SetTargetWindow |
Class API¶The Scrolled 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.
Possible constructors:
Inheritance Diagram
Known SubclassesScrolled()
Scrolled(parent, id=ID_ANY, pos=DefaultPosition, size=DefaultSize,
style=HSCROLL|VSCROLL, name="scrolledWindow")
Overloaded Implementations:
__init__ (self)
Default constructor.
__init__ (self, parent, id=ID_ANY, pos=DefaultPosition, size=DefaultSize, style=HSCROLL|VSCROLL, name=”scrolledWindow”)
Constructor.
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Note
The window is initially created without visible scrollbars. Call SetScrollbars to specify how big the virtual window size should be.
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.
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| Return type: | tuple |
| Returns: | ( xx, yy ) |
See also
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.
| Parameters: |
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| Return type: | tuple |
| Returns: | ( xx, yy ) |
See also
Creates the window for two-step construction.
Derived classes should call or replace this function. See Scrolled.__init__ for details.
| Parameters: | |
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| Return type: | bool |
Disable use of keyboard keys for scrolling.
By default cursor movement keys (including Home, End, Page Up and Down) are used to scroll the window appropriately. If the derived class uses these keys for something else, e.g. changing the currently selected item, this function can be used to disable this behaviour as it’s not only not necessary then but can actually be actively harmful if another object forwards a keyboard event corresponding to one of the above keys to us using ProcessWindowEvent() because the event will always be processed which can be undesirable.
New in version 2.9.1.
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 wxEVT_PAINT event handler, so your OnDraw override will be passed an already ‘pre-scrolled’ device context. However, if you wish to draw from outside of OnDraw (e.g. from your own wxEVT_PAINT handler), you must call this function yourself.
For example:
def OnEvent(self, event):
dc = wx.ClientDC(self)
self.DoPrepareDC(dc)
dc.SetPen(wx.BLACK_PEN)
x, y = event.GetPosition()
if (xpos > -1 and ypos > -1 and event.Dragging()):
dc.DrawLine(xpos, ypos, x, y)
xpos = x
ypos = y
Notice that the function sets the origin by moving it relatively to the current origin position, so you shouldn’t change the origin before calling DoPrepareDC or, if you do, reset it to (0, 0) later. If you call DoPrepareDC immediately after device context creation, as in the example above, this problem doesn’t arise, of course, so it is customary to do it like this.
| Parameters: | dc (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.
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Note
Physical scrolling may not be available on all platforms. Where it is available, it is enabled by default.
| Return type: | float |
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| Return type: | float |
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| Parameters: | orient (int) – |
|---|---|
| Return type: | int |
| Parameters: | orient (int) – |
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| Return type: | int |
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.
Receives the number of pixels per horizontal unit.
Receives the number of pixels per vertical unit.
| Return type: | tuple |
|---|---|
| Returns: | ( xUnit, yUnit ) |
See also
Function which must be overridden to implement the size available for the scroll target for the given size of the main window.
This method must be overridden if SetTargetWindow is used (it is never called otherwise). The implementation should decrease the size to account for the size of the non-scrollable parts of the main window and return only the size available for the scrollable window itself. E.g. in the example given in SetTargetWindow documentation the function would subtract the height of the header window from the vertical component of size.
| Parameters: | size (Size) – |
|---|---|
| Return type: | Size |
Get the position at which the visible portion of the window starts.
Receives the first visible x position in scroll units.
Receives the first visible y position in scroll units.
Note
If either of the scrollbars is not at the home position, x and/or y will be greater than zero. Combined with Window.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
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).
Receives the length of the scrollable window, in pixels.
Receives the height of the scrollable window, in pixels.
| Return type: | tuple |
|---|---|
| Returns: | ( x, y ) |
Note
Use DC.DeviceToLogicalX and DC.DeviceToLogicalY to translate these units to logical units.
See also
| Return type: | bool |
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Motif only: True if the window has a backing bitmap.
| Return type: | bool |
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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.
| Parameters: | dc (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.
| Parameters: | dc (DC) – |
|---|
Overloaded Implementations:
Scroll (self, x, y)
Scrolls a window so the view start is at the given point.
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Note
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 DefaultCoord (-1), that position will be ignored (no change in that direction).
See also
Scroll (self, pt)
This is an overload of Scroll ; see that function for more info.
| Parameters: | pt (Point) – |
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Set the horizontal and vertical scrolling increment only.
See the pixelsPerUnit parameter in SetScrollbars .
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Sets up vertical and/or horizontal scrollbars.
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)
Scrolled 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 Window, overriding OnSize() and adjusting the scrollbars appropriately.
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See also
Call this function to tell Scrolled to perform the actual scrolling on a different window (and not on itself).
This method is useful when only a part of the window should be scrolled. A typical example is a control consisting of a fixed header and the scrollable contents window: the scrollbars are attached to the main window itself, hence it, and not the contents window must be derived from Scrolled, but only the contents window scrolls when the scrollbars are used. To implement such setup, you need to call this method with the contents window as argument.
Notice that if this method is used, GetSizeAvailableForScrollTarget method must be overridden.
| Parameters: | window (Window) – |
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Set the scrollbar visibility.
By default the scrollbar in the corresponding direction is only shown if it is needed, i.e. if the virtual size of the scrolled window in this direction is greater than the current physical window size. Using this function the scrollbar visibility can be changed to be:
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New in version 2.9.0.
See GetTargetRect and SetTargetRect
See GetTargetWindow and SetTargetWindow