#include <e32std.h>
| class TRegion |
| Protected Attributes | |
|---|---|
| TInt | iAllocedRects |
| TInt | iCount |
| TBool | iError |
| Protected Member Enumerations | |
|---|---|
| enum | anonymous { ERRegionBuf } |
| Public Member Functions | |
|---|---|
| IMPORT_C void | AddRect(const TRect &) |
| IMPORT_C TRect | BoundingRect() |
| TBool | CheckError() |
| IMPORT_C void | Clear() |
| IMPORT_C void | ClipRect(const TRect &) |
| IMPORT_C TBool | Contains(const TPoint &) |
| IMPORT_C void | Copy(const TRegion &) |
| TInt | Count() |
| IMPORT_C void | ForceError() |
| IMPORT_C void | Intersect(const TRegion &) |
| IMPORT_C void | Intersection(const TRegion &, const TRegion &) |
| IMPORT_C TBool | Intersects(const TRect &) |
| IMPORT_C TBool | IsContainedBy(const TRect &) |
| IMPORT_C TBool | IsEmpty() |
| IMPORT_C void | Offset(TInt, TInt) |
| IMPORT_C void | Offset(const TPoint &) |
| const TRect * | RectangleList() |
| IMPORT_C TInt | Sort() |
| IMPORT_C TInt | Sort(const TPoint &) |
| IMPORT_C void | SubRect(const TRect &, TRegion *) |
| IMPORT_C void | SubRegion(const TRegion &, TRegion *) |
| IMPORT_C void | Tidy() |
| IMPORT_C void | Union(const TRegion &) |
| IMPORT_C const TRect & | operator[](TInt) |
| Protected Member Functions | |
|---|---|
| TRegion(TInt) | |
| TRegion() | |
| void | AppendRect(const TRect &) |
| void | AppendRegion(TRegion &) |
| void | DeleteRect(TRect *) |
| TRect * | ExpandRegion(TInt) |
| void | MergeRect(const TRect &, TBool) |
| IMPORT_C TRect * | RectangleListW() |
| TBool | SetListSize(TInt) |
| void | ShrinkRegion() |
| void | SubtractRegion(const TRegion &, TRegion *) |
Clipping region - abstract base class.
This abstract base class represents a 2-dimensional area which is used by Graphics, the graphics window server, and the text window server to define regions of the display which need to be updated, or regions within which all operations must occur.
A TRegion is defined in terms of an array of TRects and the more complex the region, the more TRects are required to represent it.
A clipping region initially has space allocated for five rectangles. If manipulations result in a region which requires more than this, an attempt is made to allocate more rectangles. If this cannot be done, an error flag is set, and all subsequent operations involving the region have no effect (except possibly to propagate the error flag to other regions). The CheckError() member function allows the error flag to be tested; Clear() can be used to clear it.
The redraw logic of application programs may use the TRegion in various ways:
1. minimally, they pass it to the graphics context as the clipping region; when a graphics context is activated to a window, the clipping region is set up automatically
2. if they wish to avoid redrawing objects which are outside the general area of the region, they may use TRegion::BoundingRect() to return the rectangle which bounds the clipping region, and draw only primitives that lie within that rectangle
3. if they wish to exercise finer control, they may extract the individual rectangles that comprise the clipping region using Operator[]().
Application programs may also manipulate clipping regions in order to constrain parts of their redrawing to narrower areas of the screen than the clipping region offered by the window server. To do this, functions that allow clipping region manipulation may be used; for example, adding or removing rectangles or finding the intersection or union of two regions.
| IMPORT_C void | AddRect | ( | const TRect & | aRect | ) |
Adds a rectangle to this region.
Notes:
1. If this region's error flag is already set, this function has no effect.
2. If the operation causes the capacity of this region to be exceeded, or if memory allocation fails, the region is cleared, freeing up any memory which has been allocated; its error flag is also set.
| Parameter | Description |
|---|---|
| aRect | The rectangle to be added to this region. |
| IMPORT_C TRect | BoundingRect | ( | ) | const |
Gets the minimal rectangle that bounds the entire region.
Returns: The region's minimal bounding rectangle.
| TBool | CheckError | ( | ) | const [inline] |
Tests whether the region's error flag is set.
The error flag may be set:
1. when an attempt to allocate more memory for the region fails
2. if an attempt is made to expand a fixed size region beyond its allocated size
3. if ForceError() has been called.
Use Clear() to unset the error flag, clear the region and free all allocated memory.
See also: TRegion::ForceError TRegion::Clear
Returns: True, if the error flag is set; false, otherwise.
| IMPORT_C void | Clear | ( | ) |
Clears this region.
This frees up any memory which has been allocated and unsets the error flag.
| IMPORT_C void | ClipRect | ( | const TRect & | aRect | ) |
Clips the region to the specified rectangle.
The resulting region is the area of overlap between the region and the rectangle. If there is no overlap, all rectangles within this region are deleted and the resulting region is empty.
| Parameter | Description |
|---|---|
| aRect | The rectangle to which this region is to be clipped. |
Tests whether a point is located within the region.
If the point is located on the top or left hand side of any rectangle in the region, it is considered to be within that rectangle and within the region.
If the point is located on the right hand side or bottom of a rectangle, it is considered to be outside that rectangle, and may be outside the region.
| Parameter | Description |
|---|---|
| aPoint | The specified point. |
Returns: True, if the point is within the region; false, otherwise.
| IMPORT_C void | Copy | ( | const TRegion & | aRegion | ) |
Copies another region to this region.
The state of the specified region's error flag is also copied.
| Parameter | Description |
|---|---|
| aRegion | The region to be copied. |
| TInt | Count | ( | ) | const [inline] |
Gets the number of rectangles in this region.
Returns: The number of rectangles.
Ensure that the region is big enough to hold aCount rectangles. Any allocation increase is for at least the granularity count of rectangles. Similar to SetListSize, but always preserves existing iCount rectangles.
| Parameter | Description |
|---|---|
| aCount | number of rectangles the region is expected to hold |
Returns: NULL if region is not big enough, otherwise pointer to the Rect array.
| IMPORT_C void | ForceError | ( | ) |
Sets the error flag, and clears the region.
This frees up memory allocated to the region.
| IMPORT_C void | Intersect | ( | const TRegion & | aRegion | ) |
Replaces this region with the area of intersection between it and the specified region.
Note that if the error flag of either this region or the specified region is set, then this region is cleared and its error flag is set. This frees up allocated memory.
| Parameter | Description |
|---|---|
| aRegion | The region to be intersected with this region. |
Replaces this region with the area of intersection between two specified regions.
Notes:
1. If the error flag of either of the two specified regions is set, then this region is cleared and its error flag is set. This frees up allocated memory.
2. If this region's error flag is already set, then the function has no effect.
| Parameter | Description |
|---|---|
| aRegion | The first region. |
| aRegion2 | The second region. |
| IMPORT_C TBool | IsEmpty | ( | ) | const |
Tests whether the region is empty.
Returns: True, if the region is empty and its error flag is unset; false, otherwise.
Merges a rectangle with this region.
If requested it looks for a rectangle in the region that covers the new rectangle, if found method returns immediately. Otherwise, or if an enclosing rectangle is not found, the new aRect is subtracted from all intersecting rectangles, and then aRect is appended to the region.
| Parameter | Description |
|---|---|
| aRect | The rectangular area to be added to this region. |
| aEnclosed | Whether to look for a rectangle in the region that covers the new aRect. |
Moves the region by adding X and Y offsets to the co-ordinates of its corners.
The size of the region is not changed.
| Parameter | Description |
|---|---|
| aXoffset | The number of pixels by which to move the region horizontally. If negative, the region moves leftwards. |
| aYoffset | The number of pixels by which to move the region vertically. If negative, the region moves upwards. |
| IMPORT_C void | Offset | ( | const TPoint & | aOffset | ) |
Moves the region by adding a TPoint offset to the co-ordinates of its corners.
The size of the region is not changed.
| Parameter | Description |
|---|---|
| aOffset | The offset by which the region is moved. The region is moved horizontally by aOffset.iX pixels and vertically by aOffset.iY pixels. |
| const TRect * | RectangleList | ( | ) | const [inline] |
Gets a pointer to the array of rectangles defining this region.
See also: TRegion::Count
Returns: Pointer to the array of rectangles. Note that array is a standard C++ array, i.e. a concatenated set of TRect objects. Use Count() to get the number of rectangles.
| void | ShrinkRegion | ( | ) | [protected] |
After an RRegion's iCount has reduced try to release some memory. Hysteresis rule: reduce allocated memory to iCount, but only if the released memory will also be at least the granularity.
| IMPORT_C TInt | Sort | ( | ) |
Sorts the region's array of rectangles according to their vertical position on the screen.
The sort uses the bottom right hand corner co-ordinates of the rectangles. The co-ordinates of the top and left hand sides are irrelevant to the sort operation.
Higher rectangles take precedence over lower ones. For rectangles at the same vertical position, the leftmost takes priority.
Note that the sort order may need to be different from the default if, for example, a region is moved downwards so that lower non-overlapping rectangles need to be redrawn (and sorted) before higher ones. In this case, use the second overload of this function.
Returns: KErrNone, if the operation is successful; KErrGeneral, otherwise.
Sorts the region's array of rectangles according to a specified sort order.
The sort uses the bottom right hand co-ordinates of the rectangles. The co-ordinates of the top and left hand sides are irrelevant to the sort operation
The order of the sort is determined by whether the iX and iY members of aOffset are positive, or zero or less. If aOffset.iY is greater than zero, lower rectangles take precedence over higher rectangles in the list order. Otherwise, higher rectangles take precedence. For rectangles of equal height, aOffset.iX becomes relevant to the sort. If is greater than zero, rightmost rectangles take precedence. Otherwise, leftmost rectangles take precedence.
Note that the sort order may need to be different from the default if, for example, a region is moved downwards so that lower non-overlapping rectangles need to be redrawn (and sorted) before higher ones.
| Parameter | Description |
|---|---|
| aOffset | A point whose iX and iY members determine the order of the sort. |
Returns: KErrNone, if the operation is successful; KErrGeneral, otherwise.
Removes a rectangle from this region.
If there is no intersection between the rectangle and this region, then this region is unaffected.
| Parameter | Description |
|---|---|
| aRect | The rectangular area to be removed from this region. |
| aSubtractedRegion | A pointer to a region. If this is supplied, the removed rectangle is added to it. By default this pointer is NULL. |
Removes a region.
If there is no area of intersection between the two regions, this region is unaffected.
| Parameter | Description |
|---|---|
| aRegion | The region to be removed from this region. If aRegion's error flag is set, then this region is cleared, freeing up any allocated memory, and the error flag is set. |
| aSubtractedRegion | If specified, then on return contains the area removed from this region. |
Removes a region.
If there is no area of intersection between the two regions, this region is unaffected.
| Parameter | Description |
|---|---|
| aRegion | The region to be removed from this region. If aRegion's error flag is set, then this region is cleared, freeing up any allocated memory, and the error flag is set. |
| aSubtractedRegion | If specified, then on return contains the area removed from this region. |
| IMPORT_C void | Tidy | ( | ) |
Merges all rectangles within this region which share an adjacent edge of the same length.
The function subsequently checks for allocated but unused memory, if this memory is at least as large as the granularity it is released to the system.
| IMPORT_C void | Union | ( | const TRegion & | aRegion | ) |
Replaces this region with the union of it and the specified region.
Note that if the error flag of either this region or the specified region is set, then this region is cleared and its error flag is set. This frees up allocated memory.
| Parameter | Description |
|---|---|
| aRegion | The region to be joined to this region. |
Gets a rectangle from the region.
| Parameter | Description |
|---|---|
| aIndex | The index of a rectangle within the region's array of rectangles. Indexes are relative to zero. |
Returns: The specified rectangle.