A wxScrollBar is a control that represents a horizontal or vertical scrollbar. It is distinct from the two scrollbars that some windows provide automatically, but the two types of scrollbar share the way events are received.
A scrollbar has the following main attributes: range, thumb size, page size, and position.
The range is the total number of units associated with the view represented by the scrollbar. For a table with 15 columns, the range would be 15.
The thumb size is the number of units that are currently visible. For the table example, the window might be sized so that only 5 columns are currently visible, in which case the application would set the thumb size to 5. When the thumb size becomes the same as or greater than the range, the scrollbar will be automatically hidden on most platforms.
The page size is the number of units that the scrollbar should scroll by, when `paging' through the data. This value is normally the same as the thumb size length, because it is natural to assume that the visible window size defines a page.
The scrollbar position is the current thumb position.
Most applications will find it convenient to provide a function called AdjustScrollbars which can be called initially, from an OnSize event handler, and whenever the application data changes in size. It will adjust the view, object and page size according to the size of the window and the size of the data.
|wxSB_HORIZONTAL||Specifies a horizontal scrollbar.|
|wxSB_VERTICAL||Specifies a vertical scrollbar.|
See also window styles overview.
Event table macros
To process a scroll event, use these event handler macros to direct input to member functions that take a wxScrollEvent argument. You can use EVT_COMMAND_SCROLL... macros with window IDs for when intercepting scroll events from controls, or EVT_SCROLL... macros without window IDs for intercepting scroll events from the receiving window - except for this, the macros behave exactly the same.
|EVT_SCROLL(func)||Process all scroll events.|
|EVT_SCROLL_TOP(func)||Process wxEVT_SCROLL_TOP scroll-to-top events (minimum position).|
|EVT_SCROLL_BOTTOM(func)||Process wxEVT_SCROLL_TOP scroll-to-bottom events (maximum position).|
|EVT_SCROLL_LINEUP(func)||Process wxEVT_SCROLL_LINEUP line up events.|
|EVT_SCROLL_LINEDOWN(func)||Process wxEVT_SCROLL_LINEDOWN line down events.|
|EVT_SCROLL_PAGEUP(func)||Process wxEVT_SCROLL_PAGEUP page up events.|
|EVT_SCROLL_PAGEDOWN(func)||Process wxEVT_SCROLL_PAGEDOWN page down events.|
|EVT_SCROLL_THUMBTRACK(func)||Process wxEVT_SCROLL_THUMBTRACK thumbtrack events (frequent events sent as the user drags the thumbtrack).|
|EVT_SCROLL_THUMBRELEASE(func)||Process wxEVT_SCROLL_THUMBRELEASE thumb release events.|
|EVT_SCROLL_ENDSCROLL(func)||Process wxEVT_SCROLL_ENDSCROLL end of scrolling events (MSW only).|
|EVT_COMMAND_SCROLL(id, func)||Process all scroll events.|
|EVT_COMMAND_SCROLL_TOP(id, func)||Process wxEVT_SCROLL_TOP scroll-to-top events (minimum position).|
|EVT_COMMAND_SCROLL_BOTTOM(id, func)||Process wxEVT_SCROLL_TOP scroll-to-bottom events (maximum position).|
|EVT_COMMAND_SCROLL_LINEUP(id, func)||Process wxEVT_SCROLL_LINEUP line up events.|
|EVT_COMMAND_SCROLL_LINEDOWN(id, func)||Process wxEVT_SCROLL_LINEDOWN line down events.|
|EVT_COMMAND_SCROLL_PAGEUP(id, func)||Process wxEVT_SCROLL_PAGEUP page up events.|
|EVT_COMMAND_SCROLL_PAGEDOWN(id, func)||Process wxEVT_SCROLL_PAGEDOWN page down events.|
|EVT_COMMAND_SCROLL_THUMBTRACK(id, func)||Process wxEVT_SCROLL_THUMBTRACK thumbtrack events (frequent events sent as the user drags the thumbtrack).|
|EVT_COMMAND_SCROLL_THUMBRELEASE(func)||Process wxEVT_SCROLL_THUMBRELEASE thumb release events.|
|EVT_COMMAND_SCROLL_ENDSCROLL(func)||Process wxEVT_SCROLL_ENDSCROLL end of scrolling events (MSW only).|
The difference between EVT_SCROLL_THUMBRELEASE and EVT_SCROLL_ENDSCROLL
The EVT_SCROLL_THUMBRELEASE event is only emitted when actually dragging the thumb using the mouse and releasing it (This EVT_SCROLL_THUMBRELEASE event is also followed by an EVT_SCROLL_ENDSCROLL event).
The EVT_SCROLL_ENDSCROLL event also occurs when using the keyboard to change the thumb position, and when clicking next to the thumb (In all these cases the EVT_SCROLL_THUMBRELEASE event does not happen).
In short, the EVT_SCROLL_ENDSCROLL event is triggered when scrolling/ moving has finished. The only exception (unfortunately) is that changing the thumb position using the mousewheel does give a EVT_SCROLL_THUMBRELEASE event but NOT an EVT_SCROLL_ENDSCROLL event.
Please see the widgets sample ("Slider" page) to see the difference between EVT_SCROLL_THUMBRELEASE and EVT_SCROLL_ENDSCROLL in action.
Scrolling overview, Event handling overview, wxScrolledWindow
Constructor, creating and showing a scrollbar.
Destructor, destroying the scrollbar.
Scrollbar creation function called by the scrollbar constructor. See wxScrollBar::wxScrollBar for details.
int GetRange(void) const
Returns the length of the scrollbar.
int GetPageSize(void) const
Returns the page size of the scrollbar. This is the number of scroll units that will be scrolled when the user pages up or down. Often it is the same as the thumb size.
int GetThumbPosition(void) const
Returns the current position of the scrollbar thumb.
int GetThumbSize(void) const
Returns the thumb or `view' size.
Sets the position of the scrollbar.
Sets the scrollbar properties.
Let's say you wish to display 50 lines of text, using the same font. The window is sized so that you can only see 16 lines at a time.
You would use:
scrollbar->SetScrollbar(0, 16, 50, 15);
The page size is 1 less than the thumb size so that the last line of the previous page will be visible on the next page, to help orient the user.
Note that with the window at this size, the thumb position can never go above 50 minus 16, or 34.
You can determine how many lines are currently visible by dividing the current view size by the character height in pixels.
When defining your own scrollbar behaviour, you will always need to recalculate the scrollbar settings when the window size changes. You could therefore put your scrollbar calculations and SetScrollbar call into a function named AdjustScrollbars, which can be called initially and also from a wxSizeEvent event handler function.
Scrolling overview, wxWindow::SetScrollbar, wxScrolledWindow