/// <summary>
/// Overrides the default arrangement of a Canvas.
/// </summary>
/// <param name="arrangeSize">The largest possible size for the canvas.</param>
/// <returns>The actual size used by this canvas.</returns>
protected override Size MeasureOverride(Size constraint)
{
// The base class does the hard work of building the visible part of the report on the canvas.
Size size = base.MeasureOverride(constraint);
// This creates a group of geometries around all the selected cells.
GeometryGroup geometryGroup = new GeometryGroup();
foreach (UIElement uiElement in this.Children)
{
if (uiElement is FrameworkElement)
{
FrameworkElement frameworkElement = uiElement as FrameworkElement;
ReportCell reportCell = DynamicReport.GetCell(frameworkElement);
if (reportCell != null)
{
if (reportCell.IsSelected)
{
geometryGroup.Children.Add(new RectangleGeometry(reportCell.Rect));
}
}
}
}
// An path around all the selected cells is created from the aggregation of all the selected cells. This path was
// roughly backward engineered arond the one used for Microsoft Excel.
this.selectedOutline.Data = geometryGroup.GetOutlinedPathGeometry();
// This is the size of the canvas as measured by the base class.
return(size);
}
/// <summary>
/// Invoked when an unhandled PreviewGotKeyboardFocus attached event reaches an element in the route derived from this class.
/// This will place a border around the cell.
/// </summary>
/// <param name="e">The arguments describing the focus change.</param>
//protected override void OnPreviewGotKeyboardFocus(KeyboardFocusChangedEventArgs e)
//{
// // If the visual element that received the focus is associated with a virtual cell, then a distinctive border is drawn
// // around it to indicate that it is selected. This is roughly engineered around the Excel user interface.
// ReportCell reportCell = DynamicReport.GetCell(e.NewFocus as DependencyObject);
// bool isShiftKeyPressed = ((Keyboard.Modifiers & ModifierKeys.Shift) == ModifierKeys.Shift);
// if (reportCell != null)
// {
// //if ((!isShiftKeyPressed) || (e.RightButton != MouseButtonState.Pressed))
// if (!isShiftKeyPressed)
// {
// this.selectedRanges.Clear();
// }
// this.selectedRanges.Add(Rect.Inflate(reportCell.Rect, -1.0, -1.0));
// SelectCells();
// }
// // Allow the base class to handle the rest of the keyboard focus event.
// base.OnPreviewGotKeyboardFocus(e);
//}
/// <summary>
/// Invoked when an unhandled PreviewLostKeyboardFocus attached event reaches an element in the route derived from this class.
/// </summary>
/// <param name="e">The arguments describing the focus change.</param>
protected override void OnPreviewLostKeyboardFocus(KeyboardFocusChangedEventArgs e)
{
// If the visual element that lost the focus was associated with a virtual cell, then all the distinctive borders are
// removed from the report.
DependencyObject dependencyObject = Keyboard.FocusedElement as DependencyObject;
Boolean isChildOfCell = false;
while (dependencyObject != null)
{
if (DynamicReport.GetCell(dependencyObject) != null)
{
isChildOfCell = true;
break;
}
dependencyObject = VisualTreeHelper.GetParent(dependencyObject);
}
if (!isChildOfCell)
{
this.selectedRanges.Clear();
SelectCells();
}
// Allow the base class to handle the rest of the keyboard focus event.
base.OnPreviewLostKeyboardFocus(e);
}
/// <summary>
/// Handles a change to the XAML source code property for this report.
/// </summary>
/// <param name="dependencyObject">The target object of the property change.</param>
/// <param name="dependencyPropertyChangedEventArgs">The property change event arguments.</param>
private static void OnSourceChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
{
// Changing the source code involves compiling a new core for the report. This operation will require access to some
// of the protected properties of the class and so an instance method must be called to handle the change.
DynamicReport report = dependencyObject as DynamicReport;
report.OnSourceChanged();
}
/// <summary>
/// Handles a change to the Split dependency property.
/// </summary>
/// <param name="dependencyObject">The object that owns the property.</param>
/// <param name="dependencyPropertyChangedEventArgs">A description of the changed property.</param>
private static void OnSplitChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
{
// The 'Scale' property is just a convinient way to generate a command that is used to set the scale factor. The
// commands are the only way to register events with the Undo manager.
DynamicReport report = dependencyObject as DynamicReport;
report.reportGrid.Split = (Size)dependencyPropertyChangedEventArgs.NewValue;
}
/// <summary>
/// Handles a change to the content of the report.
/// </summary>
/// <param name="dependencyObject">The object that owns the property.</param>
/// <param name="dependencyPropertyChangedEventArgs">A description of the changed property.</param>
private static void OnContentChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
{
// Load the new content into the core report.
DynamicReport report = dependencyObject as DynamicReport;
IContent iContent = dependencyPropertyChangedEventArgs.NewValue as IContent;
if (report.reportGrid != null)
{
report.reportGrid.reportRowCollection.Load(iContent);
}
}
/// <summary>
/// Handles a change to the IsHeaderFrozen dependency property.
/// </summary>
/// <param name="dependencyObject">The object that owns the property.</param>
/// <param name="dependencyPropertyChangedEventArgs">A description of the changed property.</param>
private static void OnIsHeaderFrozenChanged(DependencyObject dependencyObject, DependencyPropertyChangedEventArgs dependencyPropertyChangedEventArgs)
{
// The headers can be frozen to prevent any changes to the position, sort order, visibility, etc.
DynamicReport report = dependencyObject as DynamicReport;
Boolean isHeaderFrozen = (Boolean)dependencyPropertyChangedEventArgs.NewValue;
if (report.reportGrid != null)
{
report.reportGrid.IsColumnHeaderFrozen = isHeaderFrozen;
report.reportGrid.IsRowHeaderFrozen = isHeaderFrozen;
}
}
/// <summary>
/// Brings all the cells in a given column to the top of the Z axis.
/// </summary>
/// <param name="frontColumn">The column to be moved in front of the other columns.</param>
internal void SetZIndex(List <ReportRow> reportRows)
{
// Each visual element that matches the specified report row will be recycled and the data connection to the underlying
// cell severed.
foreach (UIElement uiElement in this.Children)
{
ReportCell reportCell = DynamicReport.GetCell(uiElement);
if (reportCell != null)
{
Canvas.SetZIndex(uiElement, reportCell.ReportRow.ZIndex);
}
}
}
/// <summary>
/// Removes all elements from a canvas.
/// </summary>
internal void Clear()
{
// This will reset the canvas and reclaim all the visual elements associated with virtual cells.
foreach (UIElement uiElement in this.Children)
{
if (uiElement is FrameworkElement)
{
FrameworkElement frameworkElement = uiElement as FrameworkElement;
ReportCell reportCell = DynamicReport.GetCell(frameworkElement);
if (reportCell != null)
{
this.Remove(reportCell);
}
}
}
}
/// <summary>
/// Removes a ReportCell from the canvas.
/// </summary>
/// <param name="frameworkElement"></param>
/// <param name="reportCell"></param>
private void Remove(ReportCell reportCell)
{
// The visual element associated with this cell can be found using the mapping table. Once the element is found
// it is reclaimed for use later on and the data connection is severed.
FrameworkElement frameworkElement;
if (this.elementTable.TryGetValue(reportCell, out frameworkElement))
{
// This recycles the element by putting it back in the cache associated with the cell's datatype. This visual element
// can be used again when another cell with the same data type needs to be instantiated.
Type contentType = reportCell.Content.GetType();
Stack <FrameworkElement> elementStack;
if (!this.elementCache.TryGetValue(contentType, out elementStack))
{
elementStack = new Stack <FrameworkElement>();
this.elementCache.Add(contentType, elementStack);
}
elementStack.Push(frameworkElement);
// The association between the visual element and the abstract cell is removed when the element is removed from the
// canvas.
DynamicReport.SetCell(frameworkElement, ReportCell.Empty);
this.elementTable.Remove(reportCell);
// When a virtual cell is removed from the report -- as opposed to simply being made invisible -- the virtual focus
// is reset. Resetting the virtual focus is a problem because the FocusScope of the parent focus scope (as well as
// the current focus scope) maintains a link to the last visual element that had the focus. When that visual
// element goes away, there's no good way to tell the parent focus scope to change. If you sent a FocusScope's
// FocusedElement to anything other than 'null', the handler tries to set the keyboard focus as well. This has the
// undesireable effect of stealing the keyboard focus away from some other window (there's no guarantee that the
// keyboard focus is on this canvas when removing rows). Resetting the current and parent focus scopes is the best
// of some bad options.
if (reportCell.IsFocused)
{
this.ReportGrid.ClearFocusedCell();
FocusManager.SetFocusedElement(this.ReportGrid, null);
FocusManager.SetFocusedElement(FocusManager.GetFocusScope(this.ReportGrid.Parent), null);
if (frameworkElement.IsKeyboardFocusWithin)
{
Keyboard.Focus(this.ReportGrid);
}
}
// The visual element can now be safely removed from the window.
this.Children.Remove(frameworkElement);
}
}
/// <summary>
/// Brings all the cells in a given column to the top of the Z axis.
/// </summary>
/// <param name="frontColumn">The column to be moved in front of the other columns.</param>
internal void BringToFront(List <ReportColumn> reportColumns)
{
// Each visual element that matches the specified report row will be recycled and the data connection to the underlying
// cell severed.
foreach (UIElement uiElement in this.Children)
{
if (uiElement is FrameworkElement)
{
FrameworkElement frameworkElement = uiElement as FrameworkElement;
ReportCell reportCell = DynamicReport.GetCell(frameworkElement);
if (reportCell != null)
{
Canvas.SetZIndex(frameworkElement, reportColumns.Contains(reportCell.ReportColumn) ? 1 : 0);
}
}
}
}
/// <summary>
/// Returns List of currently selectedCells
/// </summary>
/// <returns></returns>
public List <FrameworkElement> GetSelectedCells()
{
List <FrameworkElement> selectedCells = new List <FrameworkElement>();
foreach (UIElement uiElement in this.Children)
{
if (uiElement is FrameworkElement)
{
FrameworkElement frameworkElement = uiElement as FrameworkElement;
ReportCell reportCell = DynamicReport.GetCell(frameworkElement);
if (reportCell != null)
{
if (reportCell.IsSelected)
{
selectedCells.Add(frameworkElement);
}
}
}
}
return(selectedCells);
}
/// <summary>
/// Removes a ReportRow from the canvas.
/// </summary>
/// <param name="columnDefinition">The description of the column to be removed.</param>
internal void Remove(ReportRow reportRow)
{
// Each visual element that matches the specified report row will be recycled and the data connection to the underlying
// cell severed.
for (int childIndex = 0; childIndex < this.Children.Count;)
{
UIElement uiElement = this.Children[childIndex];
if (uiElement is FrameworkElement)
{
FrameworkElement frameworkElement = uiElement as FrameworkElement;
ReportCell reportCell = DynamicReport.GetCell(frameworkElement);
if (reportCell != null && reportCell.ReportRow == reportRow)
{
this.Remove(reportCell);
}
else
{
childIndex++;
}
}
}
}
/// <summary>
/// Handles the mouse button being pressed.
/// </summary>
/// <param name="e">The event arguments.</param>
protected override void OnMouseDown(System.Windows.Input.MouseButtonEventArgs e)
{
// The sort order is maintained in this structure.
this.sortOrder = new List <SortItem>();
// This gets the location of the mouse in document coordinates.
Mouse.Capture(this);
// This state variable will control how the 'Mouse Move' and 'Mouse Up' event handlers interpret the user action. The
// 'selectedRow' field is used as the starting point for any drag-and-drop type of operation.
this.mouseState = MouseState.ButtonDown;
// Evaluate the state of the keyboard. Key combinations involving the shift and control keys will alter the areas that
// are selected.
bool isShiftKeyPressed = ((Keyboard.Modifiers & ModifierKeys.Shift) == ModifierKeys.Shift);
bool isControlKeyPressed = ((Keyboard.Modifiers & ModifierKeys.Control) == ModifierKeys.Control);
// This will use the current position for an anchor unless the shift key is pressed.
this.mouseDownLocation = e.GetPosition(this);
if (!isShiftKeyPressed)
{
this.anchorPoint = this.mouseDownLocation;
}
// The mouse indicates which column has been selected and the anchor indicates the starting point of the selection in
// an extended selection operation.
ReportRow selectedRow = this.ReportGrid.Rows.FindRowAt(this.mouseDownLocation.Y);
ReportRow anchorRow = this.ReportGrid.Rows.FindRowAt(this.anchorPoint.Y);
Point mouseDownLocation = e.GetPosition(this);
if (!isShiftKeyPressed)
{
IInputElement iInputElement = this.InputHitTest(mouseDownLocation);
DependencyObject dependencyObject = iInputElement as DependencyObject;
while (dependencyObject != null)
{
if (DynamicReport.GetCell(dependencyObject) != null)
{
Keyboard.Focus(dependencyObject as IInputElement);
break;
}
dependencyObject = VisualTreeHelper.GetParent(dependencyObject);
}
}
// Every cell that appears in the header canvas is considered part of the selectable header. This will collect all the
// selected cells in a list while creating a rectangle that is the union of all those selected cells.
this.headerCells.Clear();
foreach (ReportColumn reportColumn in this.ReportGrid.Columns)
{
ReportCell reportCell = selectedRow[reportColumn];
if (reportColumn.Left < this.ActualWidth)
{
this.headerCells.Add(reportCell);
}
}
// If a row is selected then the position and movement of the mouse will suggest one of several gestures that need
// to be interpreted: is a row being moved, is it being resized, is it being deleted or selected? The code below
// will begin to interpret the input gesture.
if (selectedRow != null)
{
// The header has two modes: when the headers are frozen, only selection operations are enabled with the mouse.
// When not frozen, the rows can be moved, resized, resorted and removed.
if (this.IsHeaderFrozen)
{
// The shift and control key extend the selection operation in the same way as Microsoft Excel.
if (isShiftKeyPressed || isControlKeyPressed)
{
// When the shift key is pressed during row selection, every row between the last row selected
// and the current row is selected.
if (isShiftKeyPressed)
{
// In the unlikely event that the shift key was down during the setting of the anchor point, this will
// create a dummy entry in the list of selected row ranges.
if (this.selectedRanges.Count == 0)
{
List <ReportRow> reportRows = new List <ReportRow>();
reportRows.Add(selectedRow);
this.selectedRanges.Add(reportRows);
}
// The most recent range will be replaced with a new range when the mouse is dragged around the row
// headers. This has the effect of clearing the rows that are no longer selected and selecting only
// the rows between the anchor and the currently selected row.
List <ReportRow> lastRange = this.selectedRanges[this.selectedRanges.Count - 1];
// This will select each row between the last selected row and the one just selected. Note that the
// list of rows is distinct, so duplicate rows are ignored.
ReportRow firstRow = anchorRow.Top < selectedRow.Top ? anchorRow : selectedRow;
ReportRow secondRow = anchorRow.Top < selectedRow.Top ? selectedRow : anchorRow;
lastRange.Clear();
foreach (ReportRow reportRow in this.ReportGrid.Rows)
{
if (firstRow.Top <= reportRow.Top && reportRow.Top <= secondRow.Top)
{
lastRange.Add(reportRow);
}
}
}
// When the control key is pressed a single row is added to the range of rows selected.
if (isControlKeyPressed)
{
// This removes any previous instance of this row in the selection.
foreach (List <ReportRow> rowRange in this.selectedRanges)
{
if (rowRange.Contains(selectedRow))
{
rowRange.Remove(selectedRow);
}
}
// The row is added (or re-added) at the start of the range of selected rows.
List <ReportRow> reportRows = new List <ReportRow>();
reportRows.Add(selectedRow);
this.selectedRanges.Add(reportRows);
}
}
else
{
// The row is added at the start of a new range of selected rows.
List <ReportRow> reportRows = new List <ReportRow>();
// The if condition below fixes issue that allows the right click to not clear the selected rows.
// Hence it allows every other condition to clear the state.
if (e.RightButton != MouseButtonState.Pressed)
{
// A simple selection that doesn't involve the modifier keys will clear out any previously selected ranges.
this.selectedRanges.Clear();
}
else
{
// This removes any previous instance of this row in the selection.
foreach (List <ReportRow> rowRange in this.selectedRanges)
{
if (rowRange.Contains(selectedRow))
{
rowRange.Remove(selectedRow);
}
}
}
reportRows.Add(selectedRow);
this.selectedRanges.Add(reportRows);
}
// This will select all the rows in the selected ranges of rows and remove the selection from all the
// rest of the cells.
SelectRows();
// This instructs the event handlers how the mouse movement is to be interpreted.
this.mouseState = MouseState.Selecting;
}
else
{
// The top mouse button can either select the row or begin a resizing operation. This will perform a 'Hit
// Test' to see which operation should be performed.
if (e.LeftButton == MouseButtonState.Pressed)
{
// This is a 'Hit Test' for the bottom edge of the row header tile to see if the user is trying to change
// the size of the row. If the mouse is close to the bottom edge, then the drag operation to change the
// size of the tile is begun.
if (selectedRow.Bottom - DynamicReport.splitBorder <= this.mouseDownLocation.Y &&
this.mouseDownLocation.Y < selectedRow.Bottom)
{
this.resizeStart = selectedRow.Bottom;
this.mouseState = MouseState.ResizingRow;
this.destinationRow = null;
}
else
{
// This is a 'Hit Test' for the top edge of the row header tile to see if the user is trying to change
// the size of the row. Note that because the top edge really belongs to the previous row header when
// resizing, that the previous row is selected for the operation.
if (selectedRow.Top <= this.mouseDownLocation.Y &&
this.mouseDownLocation.Y < selectedRow.Top + DynamicReport.splitBorder)
{
this.resizeStart = selectedRow.Top;
this.mouseState = MouseState.ResizingRow;
foreach (ReportRow reportRow in this.ReportGrid.Rows)
{
if (reportRow.Bottom == selectedRow.Top)
{
selectedRow = reportRow;
}
}
this.destinationRow = null;
}
}
}
// At this point, a resizing operation has been selected from the input gesture of the mouse.
if (this.mouseState == MouseState.ResizingRow)
{
// The parent window will watch for this event to tell it how to draw the row width indicator lines. The
// dimension and location of those lines are outside of this window and must be handled by the parent.
if (this.ResizeMouseMove != null)
{
this.ResizeMouseMove(this, new ResizeRowEventArgs(selectedRow, selectedRow.Height,
false));
}
// This window provides quantitative feedback for the new width of the row. The offsets were arrived at
// empirically from reverse engineering Excel.
this.rowHeightPopup.VerticalOffset = this.mouseDownLocation.Y - 2.0;
this.rowHeightPopup.Content = selectedRow.Height;
this.rowHeightPopup.IsOpen = true;
}
else
{
// This will select the button momentarily for drag-and-drop and sorting operations.
foreach (ReportCell reportCell in this.headerCells)
{
reportCell.IsSelected = true;
}
}
}
}
}
/// <summary>
/// Handles the mouse button being pressed.
/// </summary>
/// <param name="e">The event arguments.</param>
protected override void OnMouseDown(System.Windows.Input.MouseButtonEventArgs e)
{
// This state variable will control how the 'Mouse Move' and 'Mouse Up' event handlers interpret the user action. The
// 'selectedColumn' field is used as the starting point for any drag-and-drop type of operation.
this.mouseState = MouseState.ButtonDown;
// Evaluate the state of the keyboard. Key combinations involving the shift and control keys will alter the areas that
// are selected.
bool isShiftKeyPressed = ((Keyboard.Modifiers & ModifierKeys.Shift) == ModifierKeys.Shift);
bool isControlKeyPressed = ((Keyboard.Modifiers & ModifierKeys.Control) == ModifierKeys.Control);
// The mouse selected with the mouse button is used as an anchor point unless the shift key is pressed. The anchor
// point allows for ranges of columns to be selected. Everything between the anchor and the currently selected column
// will be selected when the shift key is down. This is modeled after the Excel extended range selection keys.
Point mouseDownLocation = e.GetPosition(this);
// Do not clear the select cells in the Report Grid if the right mouse button is pressed.
if (e.RightButton != MouseButtonState.Pressed)
{
//Since the user is selecting a cell, it will invalidate any row selection that there may be.
foreach (List <ReportRow> block in this.ReportGrid.SelectedRowBlocks)
{
foreach (ReportRow row in block)
{
foreach (ReportCell cell in row.Cells)
{
cell.IsSelected = false;
}
}
}
this.ReportGrid.SelectedRowBlocks.Clear();
this.ReportGrid.SelectedRowHeaderBlocks.Clear();
}
if (!isShiftKeyPressed)
{
IInputElement iInputElement = this.InputHitTest(mouseDownLocation);
DependencyObject dependencyObject = iInputElement as DependencyObject;
while (dependencyObject != null)
{
ReportCell reportCell = DynamicReport.GetCell(dependencyObject);
if (reportCell != null)
{
Keyboard.Focus(dependencyObject as IInputElement);
currentSelectedCell = reportCell;
break;
}
dependencyObject = VisualTreeHelper.GetParent(dependencyObject);
}
this.anchorPoint = mouseDownLocation;
}
// The shift and control key extend the selection operation in the same way as Microsoft Excel.
if (isShiftKeyPressed || isControlKeyPressed)
{
// When the shift key is pressed during column selection, every column between the last column selected
// and the current column is selected.
if (isShiftKeyPressed)
{
// This is an ordered rectangle that encompasses all the selected cells.
Rect selectedRectangle = GetSelectionRectangle(mouseDownLocation);
SetSelectedRectangle(selectedRectangle);
}
// When the control key is pressed a single column is added to the range of columns selected.
if (isControlKeyPressed)
{
// A point marks the range when the control key is pressed. This is almost identical to pressing the mouse
// button except the previous ranges are not cleared. This is part of the extended selection algorithm that is
// modeled after Excel.
Rect selectedRange = new Rect(mouseDownLocation, new Size(0, 0));
// This removes any previous instance of this column in the selection.
foreach (Rect existingRange in this.selectedRanges)
{
if (selectedRange == existingRange)
{
this.selectedRanges.Remove(existingRange);
break;
}
}
// The new range becomes the starting point for any further extended selection operations.
this.selectedRanges.Add(selectedRange);
}
// This instructs the event handlers how the mouse movement is to be interpreted.
this.mouseState = MouseState.Selecting;
}
else
{
// Evaluate if we need to be able to determine the when we right click within the currently selected range then do not clear the selectedRanges.
if (!((e.RightButton == MouseButtonState.Pressed) && (CurrentSelectedCell != null) && (CurrentSelectedCell.IsSelected))) //MIGHT try this --> if (reportCell.Rect.IntersectsWith(selectedRange))
{
// Clear the selected ranges as we do not have a right mouse button pressed with the currently Selected ranges.
// A simple selection that doesn't involve the modifier keys will clear out any previously selected ranges.
this.selectedRanges.Clear();
// The column is added at the start of a new range of selected columns.
this.selectedRanges.Add(new Rect(mouseDownLocation, new Size(0, 0)));
}
}
// Evaluate if we need to be able to determine the when we right click within the currently selected range then do not clear the selectedRanges.
if (!((e.RightButton == MouseButtonState.Pressed) && (CurrentSelectedCell != null) && (CurrentSelectedCell.IsSelected))) //MIGHT try this --> if (reportCell.Rect.IntersectsWith(selectedRange))
{
// This will select all the columns in the selected ranges of columns and remove the selection from all the rest of the cells.
SelectCells();
}
}
/// <summary>
/// Overrides the default arrangement of a Canvas.
/// </summary>
/// <param name="arrangeSize">The largest possible size for the canvas.</param>
/// <returns>The actual size used by this canvas.</returns>
protected override Size MeasureOverride(Size constraint)
{
// This calculates the visible area of the virtual canvas. Note that the 'MeasureOverride' is called before the
// 'OnRenderSizeChanged' so the rectangle used for clipping can't be used here because it hasn't been calclated
// properly yet.
Rect viewport = new Rect(this.rectangleGeometry.Rect.Location, constraint);
// IMPORTANT CONCEPT: The FrameworkElements are recycled for performance. Creating the user interface elements and
// adding and removing them from the canvas are very time consuming tasks. The XAML for the reports contains templates
// used to create FrameworkElements for a given CLR type. It turns out that any CLR object of a given type can use any
// FrameworkElement created for that given type. So a factory of sorts is created for building and reusing the
// framework elements based on a CLR type. A screen is drawn by first reclaiming all the elements that are no longer
// visible. These elements are not removed from the screen in the first pass. The secod pass draws the visible area
// of the report using reclaimed elements when it can, creating new FrameworkElements when it can't. The important
// performance kick here is that the elements are not actually removed from the screen during the reclaimation pass and
// the drawing pass. All elements are put into this list when during the reclaimation cycle. If they are still in
// this list after the drawing pass, then they are not visible and can be removed from the canvas. This is the
// reclamation cycle. All the user interface elements that have become invisible are pushed back into the element
// cache where they can be used again when the viewport is updated.
foreach (UIElement uiElement in this.Children)
{
if (uiElement is FrameworkElement)
{
// This element will be examined to see if it needs to be recycled.
FrameworkElement frameworkElement = uiElement as FrameworkElement;
// The 'ReportCell' is the virtual information behind the user interface element and is attached to all the
// visual elements in the canvas. It is used here to indicate whether the associated FrameworkElement is
// invisible.
ReportCell reportCell = DynamicReport.GetCell(frameworkElement);
try
{
if (reportCell != null)
{
// This will test the virtual cell to see if it is invisible. Note that any cell that touches the right or
// bottom edge of the viewport is considered to be invisible. There is no part of these cells that can
// actually be seen, whereas the left and top edges are visible.
Rect rect = reportCell.ActualRect;
if (((viewport.Top > rect.Top || rect.Top >= viewport.Bottom) &&
(viewport.Top >= rect.Bottom || rect.Bottom > viewport.Bottom)) ||
((viewport.Left > rect.Left || rect.Left >= viewport.Right) &&
(viewport.Left >= rect.Right || rect.Right > viewport.Right)))
{
// When the framework element has become invisible, it is placed back in the cache based on the CLR
// type of the object it can display. It can be recycled for use with similar types when the new
// viewport is constructed in the second pass.
Type contentType = reportCell.Content.GetType();
Stack <FrameworkElement> elementStack;
if (!this.elementCache.TryGetValue(contentType, out elementStack))
{
elementStack = new Stack <FrameworkElement>();
this.elementCache.Add(contentType, elementStack);
}
elementStack.Push(frameworkElement);
// This disconnects the visual element from the virtual ReportCell and the virtual ReportCell from the
// visual element.
DynamicReport.SetCell(frameworkElement, ReportCell.Empty);
this.elementTable.Remove(reportCell);
// The focus scope for this canvas must be cleared when the element that had the focus is recycled.
// This method 'virtualizes' the handling of the focus. The virtual focus is saved in the 'IsFocused'
// property of the ReportCell while the cell is invisible. When this virtual cell becomes visible
// again, the keyboard focus will be given back to to user interface element used to instantiate the
// virtual cell.
if (reportCell.IsFocused)
{
FocusManager.SetFocusedElement(this.ReportGrid, null);
if (frameworkElement.IsKeyboardFocusWithin)
{
Keyboard.Focus(this.ReportGrid);
}
}
// All these bindings need to be released when a cell is no longer visible. There seems to be a very
// practical limitation to how many binding updates can be done by the operating system. Failure to
// release a binding when a user element is no longer visible will quickly result all the resources
// being used.
BindingOperations.ClearBinding(frameworkElement, Canvas.LeftProperty);
BindingOperations.ClearBinding(frameworkElement, Canvas.TopProperty);
BindingOperations.ClearBinding(frameworkElement, FrameworkElement.WidthProperty);
BindingOperations.ClearBinding(frameworkElement, FrameworkElement.HeightProperty);
BindingOperations.ClearBinding(frameworkElement, DynamicReport.IsEvenProperty);
BindingOperations.ClearBinding(frameworkElement, DynamicReport.IsSelectedProperty);
}
}
}
catch (Exception exception)
{
String message = reportCell.ReportColumn == null ? "ReportColumn is null" : reportCell.ReportRow == null ? "ReportRow is null" : "not sure why";
EventLog.Error("{0}: {1} ({2})\n{3}", exception.GetType(), exception.Message, message, exception.StackTrace);
}
}
}
// This pass will construct the visible part of the canvas. The main idea is to find the virtual cells that appear in
// the viewport and associate the cell with a visual element. If a visual element can be found in the cache, it is
// used, otherwise one is created from a template.
foreach (ReportRow reportRow in this.ReportGrid.Rows)
{
if (reportRow.IsEmpty)
{
continue;
}
// Only rows that appear in the visible part of the canvas are considered. Evaluating the rows this way quickly
// removes the number of cells that need to be checked.
if (((viewport.Top <= reportRow.Top && reportRow.Top < viewport.Bottom) ||
(viewport.Top < reportRow.Bottom && reportRow.Bottom <= viewport.Bottom)))
{
// At this point we have a row that is part of the visible canvas. This will see which of the columns are
// visible.
foreach (ReportColumn reportColumn in this.ReportGrid.Columns)
{
// Note that columns that fall on the right edge are excluded. Even though they appear to intersect with
// the viewport, there is no part of these columns that's actally visible.
if ((viewport.Left <= reportColumn.Left && reportColumn.Left < viewport.Right) ||
(viewport.Left < reportColumn.Right && reportColumn.Right <= viewport.Right))
{
// The cell exists at a virtual location in the document coordinate system. They are instantiated and
// added to the canvas when the become visible and are remove from the canvas when not visible. This
// is how a very large document can be viewed with a relatively small number of visual elements and
// bindings.
ReportCell reportCell = reportRow[reportColumn];
// If this cell doesn't have a framework element associated with it, then one is either recycled
// from the cache or created from a template.
FrameworkElement frameworkElement;
if (!this.elementTable.TryGetValue(reportCell, out frameworkElement))
{
// Each Framework element will work with one and only one CLR type. The content of the
// ReportCell determines what kind of FrameworkElement instance is used to display the data in
// that cell.
Type contentType = reportCell.Content.GetType();
// The CLR type of the content is used to find a stack of FrameworkElements that can be used to
// display that content.
Stack <FrameworkElement> elementStack;
if (!this.elementCache.TryGetValue(contentType, out elementStack))
{
elementStack = new Stack <FrameworkElement>();
this.elementCache.Add(contentType, elementStack);
}
// If there are no instances of a visual element that can be used to display the content of
// this ReportCell, then one is generated from the template. Otherwise, a recycled element is
// used. Note that all default focus styles are removed from visual elements on the canvas as
// there these elements have a custom style applied which functions like the Microsoft Excel
// focus and selection.
if (elementStack.Count == 0)
{
DataTemplateKey dataTemplateKey = new DataTemplateKey(reportCell.Content.GetType());
DataTemplate dataTemplate = this.ReportGrid.Resources[dataTemplateKey] as DataTemplate;
if (dataTemplate != null)
{
frameworkElement = dataTemplate.LoadContent() as FrameworkElement;
frameworkElement.FocusVisualStyle = null;
}
}
else
{
frameworkElement = elementStack.Pop();
}
// This associates the visual element with the ReportCell that contains the information about
// the location of that element in the virtual document coordinate space. The 'elementTable'
// contains the reciprocal relation.
DynamicReport.SetCell(frameworkElement, reportCell);
this.elementTable.Add(reportCell, frameworkElement);
// The data context for the XAML elements is the content of the cell, not the ReportCell.
// This is done intensionally to hide the implementation details of how elements are positioned
// on the screen. It is also done to simplify the programming model for the XAML code.
frameworkElement.DataContext = reportCell.Content;
// Bind the element's 'Left' property of the element to the column's position.
Binding leftBinding = new Binding("ActualLeft");
leftBinding.Source = reportCell.ReportColumn;
BindingOperations.SetBinding(frameworkElement, Canvas.LeftProperty, leftBinding);
// Bind the element's 'Top' property of the element to the row's position.
Binding topBinding = new Binding("ActualTop");
topBinding.Source = reportCell.ReportRow;
BindingOperations.SetBinding(frameworkElement, Canvas.TopProperty, topBinding);
// Bind the element's 'Width' property of the element to the column's width.
Binding widthBinding = new Binding("ActualWidth");
widthBinding.Source = reportCell.ReportColumn;
BindingOperations.SetBinding(frameworkElement, FrameworkElement.WidthProperty, widthBinding);
// Bind the element's 'Height' property of the element to the row's height.
Binding heightBinding = new Binding("ActualHeight");
heightBinding.Source = reportCell.ReportRow;
BindingOperations.SetBinding(frameworkElement, FrameworkElement.HeightProperty, heightBinding);
// Bind the element's 'IsSelected' property to the cell's property. This property is used to
// highlight the selected cells.
Binding isSelectedBinding = new Binding("IsSelected");
isSelectedBinding.Source = reportCell;
BindingOperations.SetBinding(frameworkElement, DynamicReport.IsSelectedProperty, isSelectedBinding);
// Bind the 'Height' property of the element to the row's 'IsEven' property. This property is
// generally used to shade every other line to make it easier to follow the information on a
// row.
Binding evenBinding = new Binding("IsEven");
evenBinding.Source = reportCell.ReportRow;
BindingOperations.SetBinding(frameworkElement, DynamicReport.IsEvenProperty, evenBinding);
}
// New and recycled elements need to be added to the canvas to become part of the visible report.
if (frameworkElement.Parent == null)
{
this.Children.Add(frameworkElement);
}
// The logical (and keyboard) focus is restored to the element that has the virtual focus when the
// virtual cell is made visible again. Note that the logical focus is only moved when the canvas
// has the keyboard focus. This prevents a scenario where the canvas grabs the input focus away
// from another window when the input focus is made visible again.
if (reportCell.IsFocused)
{
if (this.IsKeyboardFocusWithin)
{
if (FocusManager.GetFocusedElement(this.ReportGrid) != frameworkElement)
{
FocusManager.SetFocusedElement(this.ReportGrid, frameworkElement);
}
}
}
}
}
}
}
// At this point, all the elements that can be recycled have been recycled. The remaining elements on the canvas that
// are not associated with a virtual report element need to be removed.
for (int index = 0; index < this.Children.Count;)
{
UIElement uiElement = this.Children[index];
if (DynamicReport.GetCell(uiElement) == ReportCell.Empty)
{
this.Children.RemoveAt(index);
}
else
{
index++;
}
}
// The base class takes care of the hard work of measuring the visible user interface elements on the canvas.
return(base.MeasureOverride(constraint));
}
