CRectTracker Class

Allows an item to be displayed, moved, and resized in different fashions.

Syntax

class CRectTracker

Members

Public Constructors

Name Description
CRectTracker::CRectTracker Constructs a CRectTracker object.

Public Methods

Name Description
CRectTracker::AdjustRect Called when the rectangle is resized.
CRectTracker::Draw Renders the rectangle.
CRectTracker::DrawTrackerRect Called when drawing the border of a CRectTracker object.
CRectTracker::GetHandleMask Called to get the mask of a CRectTracker item's resize handles.
CRectTracker::GetTrueRect Returns width and height of rectangle, including resize handles.
CRectTracker::HitTest Returns the current position of the cursor related to the CRectTracker object.
CRectTracker::NormalizeHit Normalizes a hit-test code.
CRectTracker::OnChangedRect Called when the rectangle has been resized or moved.
CRectTracker::SetCursor Sets the cursor, depending on its position over the rectangle.
CRectTracker::Track Allows the user to manipulate the rectangle.
CRectTracker::TrackRubberBand Allows the user to "rubber-band" the selection.

Public Data Members

Name Description
CRectTracker::m_nHandleSize Determines size of resize handles.
CRectTracker::m_nStyle Current style(s) of the tracker.
CRectTracker::m_rect Current position (in pixels) of the rectangle.
CRectTracker::m_sizeMin Determines minimum rectangle width and height.

Remarks

CRectTracker does not have a base class.

Although the CRectTracker class is designed to allow the user to interact with OLE items by using a graphical interface, its use is not restricted to OLE-enabled applications. It can be used anywhere such a user interface is required.

CRectTracker borders can be solid or dotted lines. The item can be given a hatched border or overlaid with a hatched pattern to indicate different states of the item. You can place eight resize handles on either the outside or the inside border of the item. (For an explanation of the resize handles, see GetHandleMask.) Finally, a CRectTracker allows you to change the orientation of an item during resizing.

To use CRectTracker, construct a CRectTracker object and specify which display states are initialized. You can then use this interface to give the user visual feedback on the current status of the OLE item associated with the CRectTracker object.

For more information on using CRectTracker, see the article Trackers.

Inheritance Hierarchy

CRectTracker

Requirements

Header: afxext.h

CRectTracker::AdjustRect

Called by the framework when the tracking rectangle is resized by using a resize handle.

virtual void AdjustRect(
    int nHandle,
    LPRECT lpRect);

Parameters

nHandle
Index of handle used.

lpRect
Pointer to the current size of the rectangle. (The size of a rectangle is given by its height and width.)

Remarks

The default behavior of this function allows the rectangle's orientation to change only when Track and TrackRubberBand are called with inverting allowed.

Override this function to control the adjustment of the tracking rectangle during a dragging operation. One method is to adjust the coordinates specified by lpRect before returning.

Special features that are not directly supported by CRectTracker, such as snap-to-grid or keep-aspect-ratio, can be implemented by overriding this function.

CRectTracker::CRectTracker

Creates and initializes a CRectTracker object.

CRectTracker();

CRectTracker(
    LPCRECT lpSrcRect,
    UINT nStyle);

Parameters

lpSrcRect
The coordinates of the rectangle object.

nStyle
Specifies the style of the CRectTracker object. The following styles are supported:

  • CRectTracker::solidLine Use a solid line for the rectangle border.

  • CRectTracker::dottedLine Use a dotted line for the rectangle border.

  • CRectTracker::hatchedBorder Use a hatched pattern for the rectangle border.

  • CRectTracker::resizeInside Resize handles located inside the rectangle.

  • CRectTracker::resizeOutside Resize handles located outside the rectangle.

  • CRectTracker::hatchInside Hatched pattern covers the entire rectangle.

Remarks

The default constructor initializes the CRectTracker object with the values from lpSrcRect and initializes other sizes to system defaults. If the object is created with no parameters, the m_rect and m_nStyle data members are uninitialized.

CRectTracker::Draw

Call this function to draw the rectangle's outer lines and inner region.

void Draw(CDC* pDC) const;

Parameters

pDC
Pointer to the device context on which to draw.

Remarks

The style of the tracker determines how the drawing is done. See the constructor for CRectTracker for more information on the styles available.

CRectTracker::DrawTrackerRect

Called by the framework whenever the position of the tracker has changed while inside the Track or TrackRubberBand member function.

virtual void DrawTrackerRect(
    LPCRECT lpRect,
    CWnd* pWndClipTo,
    CDC* pDC,
    CWnd* pWnd);

Parameters

lpRect
Pointer to the RECT that contains the rectangle to draw.

pWndClipTo
Pointer to the window to use in clipping the rectangle.

pDC
Pointer to the device context on which to draw.

pWnd
Pointer to the window on which the drawing will occur.

Remarks

The default implementation makes a call to CDC::DrawFocusRect, which draws a dotted rectangle.

Override this function to provide different feedback during the tracking operation.

CRectTracker::GetHandleMask

The framework calls this member function to retrieve the mask for a rectangle's resize handles.

virtual UINT GetHandleMask() const;

Return Value

The mask of a CRectTracker item's resize handles.

Remarks

The resize handles appear on the sides and corners of the rectangle and allow the user to control the shape and size of the rectangle.

A rectangle has 8 resize handles numbered 0-7. Each resize handle is represented by a bit in the mask; the value of that bit is 2^ n, where n is the resize handle number. Bits 0-3 correspond to the corner resize handles, starting at the top left moving clockwise. Bits 4-7 correspond to the side resize handles starting at the top moving clockwise. The following illustration shows a rectangle's resize handles and their corresponding resize handle numbers and values:

Resize handle numbers

The default implementation of GetHandleMask returns the mask of the bits so that the resize handles appear. If the single bit is on, the corresponding resize handle will be drawn.

Override this member function to hide or show the indicated resize handles.

CRectTracker::GetTrueRect

Call this function to retrieve the coordinates of the rectangle.

void GetTrueRect(LPRECT lpTrueRect) const;

Parameters

lpTrueRect
Pointer to the RECT structure that will contain the device coordinates of the CRectTracker object.

Remarks

The dimensions of the rectangle include the height and width of any resize handles located on the outer border. Upon returning, lpTrueRect is always a normalized rectangle in device coordinates.

CRectTracker::HitTest

Call this function to find out whether the user has grabbed a resize handle.

int HitTest(CPoint point) const;

Parameters

point
The point, in device coordinates, to test.

Return Value

The value returned is based on the enumerated type CRectTracker::TrackerHit and can have one of the following values:

  • CRectTracker::hitNothing -1

  • CRectTracker::hitTopLeft 0

  • CRectTracker::hitTopRight 1

  • CRectTracker::hitBottomRight 2

  • CRectTracker::hitBottomLeft 3

  • CRectTracker::hitTop 4

  • CRectTracker::hitRight 5

  • CRectTracker::hitBottom 6

  • CRectTracker::hitLeft 7

  • CRectTracker::hitMiddle 8

CRectTracker::m_nHandleSize

The size, in pixels, of the CRectTracker resize handles.

int m_nHandleSize;

Remarks

Initialized with the default system value.

CRectTracker::m_rect

The current position of the rectangle in client coordinates (pixels).

CRect m_rect;

CRectTracker::m_sizeMin

The minimum size of the rectangle.

CSize m_sizeMin;

Remarks

Both default values, cx and cy, are calculated from the default system value for the border width. This data member is used only by the AdjustRect member function.

CRectTracker::m_nStyle

Current style of the rectangle.

UINT m_nStyle;

Remarks

See CRectTracker::CRectTracker for a list of possible styles.

CRectTracker::NormalizeHit

Call this function to convert a potentially inverted handle.

int NormalizeHit(int nHandle) const;

Parameters

nHandle
Handle selected by the user.

Return Value

The index of the normalized handle.

Remarks

When CRectTracker::Track or CRectTracker::TrackRubberBand is called with inverting allowed, it is possible for the rectangle to be inverted on the x-axis, the y-axis, or both. When this happens, HitTest will return handles that are also inverted with respect to the rectangle. This is inappropriate for drawing cursor feedback because the feedback depends on the screen position of the rectangle, not the portion of the rectangle data structure that will be modified.

CRectTracker::OnChangedRect

Called by the framework whenever the tracker rectangle has changed during a call to Track.

virtual void OnChangedRect(const CRect& rectOld);

Parameters

rectOld
Contains the old device coordinates of the CRectTracker object.

Remarks

At the time this function is called, all feedback drawn with DrawTrackerRect has been removed. The default implementation of this function does nothing.

Override this function when you want to perform any actions after the rectangle has been resized.

CRectTracker::SetCursor

Call this function to change the cursor shape while it is over the CRectTracker object's region.

BOOL SetCursor(
    CWnd* pWnd,
    UINT nHitTest) const;

Parameters

pWnd
Points to the window that currently contains the cursor.

nHitTest
Results of the previous hit test, from the WM_SETCURSOR message.

Return Value

Nonzero if the previous hit was over the tracker rectangle; otherwise 0.

Remarks

Call this function from inside the function of your window that handles the WM_SETCURSOR message (typically OnSetCursor).

CRectTracker::Track

Call this function to display the user interface for resizing the rectangle.

BOOL Track(
    CWnd* pWnd,
    CPoint point,
    BOOL bAllowInvert = FALSE,
    CWnd* pWndClipTo = NULL);

Parameters

pWnd
The window object that contains the rectangle.

point
Device coordinates of the current mouse position relative to the client area.

bAllowInvert
If TRUE, the rectangle can be inverted along the x-axis or y-axis; otherwise FALSE.

pWndClipTo
The window that drawing operations will be clipped to. If NULL, pWnd is used as the clipping rectangle.

Return Value

If the ESC key is pressed, the tracking process is halted, the rectangle stored in the tracker is not altered, and 0 is returned. If the change is committed, by moving the mouse and releasing the left mouse button, the new position and/or size is recorded in the tracker's rectangle and nonzero is returned.

Remarks

This is usually called from inside the function of your application that handles the WM_LBUTTONDOWN message (typically OnLButtonDown).

This function will capture the mouse until the user releases the left mouse button, presses the ESC key, or presses the right mouse button. As the user moves the mouse cursor, the feedback is updated by calling DrawTrackerRect and OnChangedRect.

If bAllowInvert is TRUE, the tracking rectangle can be inverted on either the x-axis or y-axis.

CRectTracker::TrackRubberBand

Call this function to do rubber-band selection.

BOOL TrackRubberBand(
    CWnd* pWnd,
    CPoint point,
    BOOL bAllowInvert = TRUE);

Parameters

pWnd
The window object that contains the rectangle.

point
Device coordinates of the current mouse position relative to the client area.

bAllowInvert
If TRUE, the rectangle can be inverted along the x-axis or y-axis; otherwise FALSE.

Return Value

Nonzero if the mouse has moved and the rectangle is not empty; otherwise 0.

Remarks

It is usually called from inside the function of your application that handles the WM_LBUTTONDOWN message (typically OnLButtonDown).

This function will capture the mouse until the user releases the left mouse button, presses the ESC key, or presses the right mouse button. As the user moves the mouse cursor, the feedback is updated by calling DrawTrackerRect and OnChangedRect.

Tracking is performed with a rubber-band-type selection from the lower-right handle. If inverting is allowed, the rectangle can be sized by dragging either up and to the left or down and to the right.

See also

MFC Sample TRACKER
MFC Sample DRAWCLI
Hierarchy Chart
COleResizeBar Class
CRect Class