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Signed-off-by: Peter Siegmund <mars3142@noreply.mars3142.dev>

libs/wxWidgets-3.3.1/docs/doxygen/overviews/scrolling.h

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+/////////////////////////////////////////////////////////////////////////////
+// Name:        scrolling.h
+// Purpose:     topic overview
+// Author:      wxWidgets team
+// Licence:     wxWindows licence
+/////////////////////////////////////////////////////////////////////////////
+
+/**
+
+@page overview_scrolling Scrolled Windows
+
+@tableofcontents
+
+Scrollbars come in various guises in wxWidgets. All windows have the potential
+to show a vertical scrollbar and/or a horizontal scrollbar: it is a basic
+capability of a window. However, in practice, not all windows do make use of
+scrollbars, such as a single-line wxTextCtrl.
+
+Because any class derived from wxWindow may have scrollbars, there are
+functions to manipulate the scrollbars and event handlers to intercept scroll
+events. But just because a window generates a scroll event, doesn't mean that
+the window necessarily handles it and physically scrolls the window. The base
+class wxWindow in fact doesn't have any default functionality to handle scroll
+events. If you created a wxWindow object with scrollbars, and then clicked on
+the scrollbars, nothing at all would happen. This is deliberate, because the
+@e interpretation of scroll events varies from one window class to another.
+
+::wxScrolledWindow (formerly wxCanvas) is an example of a window that adds
+functionality to make scrolling really work. It assumes that scrolling happens
+in consistent units, not different-sized jumps, and that page size is
+represented by the visible portion of the window. It is suited to drawing
+applications, but perhaps not so suitable for a sophisticated editor in which
+the amount scrolled may vary according to the size of text on a given line. For
+this, you would derive from wxWindow and implement scrolling yourself. wxGrid
+is an example of a class that implements its own scrolling, largely because
+columns and rows can vary in size.
+
+@see wxScrollBar
+
+
+@section overview_scrolling_model The Scrollbar Model
+
+The function wxWindow::SetScrollbar gives a clue about the way a scrollbar is
+modeled. This function takes the following arguments:
+
+@beginTable
+@row2col{ @c orientation , Which scrollbar: wxVERTICAL or wxHORIZONTAL. }
+@row2col{ @c position , The position of the scrollbar in scroll units. }
+@row2col{ @c visible , The size of the visible portion of the scrollbar,
+                       in scroll units. }
+@row2col{ @c range , The maximum position of the scrollbar. }
+@row2col{ @c refresh , Whether the scrollbar should be repainted. }
+@endTable
+
+@c orientation determines whether we're talking about the built-in horizontal
+or vertical scrollbar.
+
+@c position is simply the position of the 'thumb' (the bit you drag to scroll
+around). It is given in scroll units, and so is relative to the total range of
+the scrollbar.
+
+@c visible gives the number of scroll units that represents the portion of the
+window currently visible. Normally, a scrollbar is capable of indicating this
+visually by showing a different length of thumb.
+
+@c range is the maximum value of the scrollbar, where zero is the start
+position. You choose the units that suit you, so if you wanted to display text
+that has 100 lines, you would set this to 100. Note that this doesn't have to
+correspond to the number of pixels scrolled - it is up to you how you actually
+show the contents of the window.
+
+@c refresh just indicates whether the scrollbar should be repainted immediately
+or not.
+
+
+@section overview_scrolling_example An Example
+
+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:
+
+@code
+SetScrollbar(wxVERTICAL, 0, 16, 50);
+@endcode
+
+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 your wxSizeEvent
+handler function.
+
+*/