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PegVScroll
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Examples |
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Overview |
Derived from class
PegThing
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The PegVScroll class provides vertical scroll bars.
The scroll bar elevator is proportional to the visible
area of the object being scrolled.
The PegVScroll scroll bar takes two forms.
The most common form is a non-client area scroll bar.
In this form, PegVScroll calls the parent window's
GetVScrollInfo() function to determine scroll bar position, size and
limit information. An instance of this form of PegVScroll scroll bar
has PSF_NONCLIENT system status.
The second form is a client area scroll bar.
This form does not have PSF_NONCLIENT system status.
A client area scroll bar controls its own position and operation. It does
not attempt to automatically determine position and limit information
from its parent.
Client area PegVScroll objects are very similar in operation to
PegSlider objects.
They are useful for allowing the end user to update a field on the
display by dragging the scroll elevator or selecting the directional
scroll buttons.
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How Scrolling Works
Scroll Structure (PegScrollInfo)
PegHScroll
PegSlider
The PegVScroll class generates
the following signals:
PSF_SCROLL_CHANGE | Sent by non-client PegHScroll and PegVScroll derived objects
when scroll bar changes occur. |
The signal message contains the following information:
Message.lData |
Current scroll position. |
Message.iData |
Last reported scroll position. |
Message.pSource |
Pointer to PegVScroll object. |
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Constructors:
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PegVScroll(void)
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This constructor
creates a non-client area scroll bar. The scroll bar will automatically
determine its position and size itself to the height of the parent window's
client area.
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PegVScroll(const PegRect &InRect,
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PegScrollInfo *si, WORD wId = 0)
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This constructor creates a client area
PegVScroll scroll bar at a specific location within a
rectangle specified by parameter Rect.
Parameter si is a pointer to a
PegScrollInfo scroll information structure which defines
the initial scrolling range and elevator position.
Parameter wId provides an optional scroll bar ID.
Public Functions:
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virtual void Draw(void)
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The PegVScroll class overrides
the Draw() function to fill the scroll bar background area.
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PegScrollInfo *GetScrollInfo(void)
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{return &mScrollInfo;}
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This inline function
can be called to retrieve the current scroll bar information.
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virtual SIGNED Message(const PegMessage &Mesg)
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The PegVScroll class catches
PM_SHOW, directional button selection and elevator drag messages.
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void Reset(void)
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void Reset(PegScrollInfo *si)
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These functions allow the scroll bar position to be recalculated or reset
at any time. The first form is used with non-client scroll bars.
The second form is used with client-area scroll bars that are under program
control.
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void Resize(PegRect Rect)
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The PegVScroll class overrides
the Resize() function to ensure that the elevator
remains proportional to the overall scroll bar size.
The following examples illustrate PegVScroll objects:
The following example
initializes a PegScrollInfo structure and creates a
client area scroll bar. The scroll bar will report values between
0 and 200 and will initially be positioned
at 100, the halfway point.
The height of the scroll bar elevator will be 25% of the height
of the entire scroll bar.
void MyWindow::AddVScroll(void)
{
PegScrollInfo si;
si.wMin = 0;
si.wMax = 200;
si.wCurrent = 100;
si.wStep = 1;
si.wVisible = 50;
PegRect ScrollRect;
ScrollRect.Set(10, 10, PEG_SCROLL_WIDTH + 10, 80);
Add(new PegVScroll(ScrollRect, &si));
}
