Grids Reference Page/de

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Die Zielsetzung

Dieser Text will versuchen, dem Benutzer einige Aspekte der Grid-Komponenten in Lazarus zu zeigen. Es ist auch vorgesehen, als ein Handbuch für Benutzer zu dienen, die noch nie zuvor Grids benutzt haben (während erfahrene Benutzer im Allgemeinen nur eine Referenz benötigen für neue Funktionalitäten). Daher will dieser Text versuchen, die folgenden Ziele zu erreichen:

1. Die Grid-Komponenten den Menschen mit geringem oder gar keinem Delphi Kontakt vorzustellen.
2. Die Unterschiede hinsichtlich der Delphi Grid-Komponenten zu dokumentieren.
3. Die neuen Funktionalitäten in Lazarus Grids zu dokumentieren.
4. Referenzen und Beispiele für die Komponenten zu erstellen.

Überblick

Ein Grid ist eine Komponente, die a mean zur Anzeige von Daten in einem tabellarischen Format bietet. Die offensichtlichste Charakteristik von Grids ist, daß sie aus Zellen bestehen, Zeilen und Spalten bildend.

Der Informationstyp, der in einem Grid angezeigt werden kann, ist sehr weitläufig, hauptsächlich abhängig von dem, was der Benutzer anzeigen möchte. Gewöhnlich wird diese Information in Text, Farben, Bilder oder eine Kombination daraus übersetzt.

In Anbetracht der großen Vielfalt von Informationen, die representiert werden können, existiert eine Reihe von Grids, deren Zweck darin besteht, den Benutzer zu unterstützen, eine spezifische Art von Informationen zu zeigen.

Vererbungsbaum

                      [TCustomControl]           
                              |                    
                              |                    
                         TCustomGrid               
                              |                    
                +-------------+------------+       
                |                          |       
          TCustomDrawGrid             TCustomDbGrid
                |                          |       
       +--------+--------+                 |       
       |                 |              TDbGrid    
   TDrawGrid      TCustomStringGrid                
                         |                         
                         |                         
                    TStringGrid                    

Ein Anfangsbeispiel

As one of the objectives of this is to be nice with people with little or no previous lazarus knowledge lets do a quick starting example of grids in action. Why not, lets make a traditional "hello world" Beispiel unter Verwendung der TStringGrid Komponente.

1. Erstellen sie eine neue Anwendung.
   • Im Hauptmenü wählen sie: Projekt -> Neues Projekt
   • Im Erzeuge neues Projekt Dialog drücken sie den "Erzeuge Button"
   • Ein neues leeres Formular wird angezeigt.
2. Platzieren sie ein Grid auf dem Formular.
   • In der Komponentenpalette wählen sie den "Additional" Tab.
   • Klicken sie auf das TStringGrid Icon [].
   • Klicken sie auf das Formular, in der Nähe der oberen linken Ecke. Ein neues leeres Grid erscheint.
3. Platzieren sie einen Button auf dem Formular.
   • In der Komponentenpalette wählen sie den "Standard" Tab.
   • Klicken sie auf das TButton Icon [].
   • Klicken sie auf einen freien Bereich im Formular. Ein neuer Button erscheint.
4. Klicken sie doppelt auf den Button von Schritt 3, und schreiben sie den folgenden Code in den click button handler:
   • Stringgrid1.Cells[1,1] := 'Hi World!';
5. Starten sie das Programm durch klicken auf das Start Icon [].
   • Durch Drücken von Button1, sollte der hello world Text in der Zelle Spalte 1, Zeile 1 erscheinen.

Unterschiede zwischen Lazarus und Delphi Grids

The current grids components present several differences with respect to delphi grids. This is mainly because the lazarus grids were created from scratch primarily without trying to make them fully compatible.

At a later stage, compatibility with delphi's grids became a desired objective and the grids starting to conform more closely the delphi grid's interface, but even then this was done without a strong effort to make every single property or method match it's delphi counterpart. Also, because the grid's internals are very different some things are not possible or need to be done in a different way in the lazarus' grids. As the grids have evolved, greater compatibility has been achieved and this is desireable.

Unterschiede

An dieser Stelle werden die bekannten Unterschiede aufgeführt ohne spezielle Reihenfolge.

• Cell Editors
• Designtime Behaviour
• Cell Drawing has some differences, see customizing grid section.

Neue Funktionsweise

• Spalten
• Ereignisse
• Grid Editor

Anpassungen zur Verbesserung der Delphi grids Kompatibilität

Hier ist eine Liste von Eigenschaften und Anpassungen die vorgenommen werden können, damit Lazarus grids wie Delphi grids aussehen oder sich so verhalten. This adjustments are based in a newly created grid. Einträge mit [Code] müssen im Quellcode gesetzt werden, [Design] Einträge können zur Entwicklungszeit geändert werden.

• [Design] TitleStyle:=tsStandard;
• [Design] DefaultRowHeight:=24;
• [Code] EditorBorderStyle:=bsNone; // dies dürfte nur unter Windows funktionieren.
• [Code] UseXORFatures:=true;
• [Code] AllowOutBoundClicks:=False; (r10992 oder später)
• [Code] FastEditing:=False; (unterstützt in dbgrid. StringGrid benötigt r10992 oder später)
• [Design] AutoAdvance:=aaNone;

Grids Referenz

Information

Der Ausgangspunkt für eine Referenz über TCustomGrid, TDrawGrid, TCustomDrawGrid, TCustomStringGrid und TStringGrid ist die Unit grids.pas Referenz.

Für TCustomDBGrid und TDBgrid ist es die Unit dbgrids.pas Referenz.

Gegenwärtig enthalten diese Links noch nicht viel Inhalt, teilweise wegen des Fehlens eines Werkzeugs, das eine einfache Wartung ihres Inhalts erlaubt. Aber ein solches Werkzeug is under construction and eventually the gaps will be filled.

Im Allgemeinen, jede Delphi Referenz über Grids sollte helfen, die Lazarus Grids zu verwenden (don't forget that there are several differences between Delphi and Lazarus grids being documented), with this in mind and as a temporal place for reference information, wird dieser Ort genutzt, um Dinge zu dokumentieren, die nicht wie in Delphi funktionieren oder die eine neue Funktionalität darstellen.

[TODO: the rest of this section will dissapear, it's content will be moved to unit grids.pas reference

TCustomGrid

See the full TCustomGrid Reference

TCustomStringGrid

TCustomStringGrid serves as the base for TStringGrid. It can be used for derived TStringGrid components that want to hide published properties. See new intermediate grids for more information.

These properties or methods are public and are also available to TStringGrid.

See the full TCustomStringGrid Reference

procedure AutoSizeColumn(aCol: Integer);

This procedure sets the column width to the size of the widest text it finds in all rows for the column aCol. Tip: see the goDblClickAutoSize option to allow columns to be automatically resized when doubleClicking the column border.

procedure AutoSizeColumns;

Automatically resizes all columns by adjusting them to fit in the longest text in each column. This is a quick method of applying AutoSizeColumn() for every column in the grid.

procedure Clean; overload;

Cleans all cells in the grid, fixed or not.

procedure Clean(CleanOptions: TCleanOptions); overload;

Cleans all cells in the grid subject to the given CleanOptions. see TCleanOptions for more information. Some examples:

• Clean all cells: grid.Clean([]); (the same as grid.clean)
• Clean all non fixed cells: grid.Clean([gzNormal]);
• Clean all cells but don't touch grid column headers: Grid.Clean[gzNormal, gzFixedRows]);

procedure Clean(StartCol,StartRow,EndCol,EndRow: integer; CleanOptions:TCleanOptions); overload;

does the same as Clean(CleanOptions:TCleanOptions) but restricted to the given StartCol,StartRow,EndCol and EndRow. Examples:

• Clean column index 4 to 6 but don't touch grid column headers: many variations, Grid.Clean(4,Grid.FixedRows,6,Grid.RowCount-1,[]); Grid.Clean(4,0,6,Grid,RowCount-1, [gzNormal]); etc.

procedure Clean(aRect: TRect; CleanOptions: TCleanOptions); overload;

The same as Clean(StartCol,StartRow,EndCol,EndRow, CleanOptions), just taking a TRect instead of individual cell coordinates. Useful to clean the selection: grid.Clean(Grid.Selection,[]);

property Cols[index: Integer]: TStrings read GetCols write SetCols;

Get/set a list of strings from/to the given grid's column index starting from row index 0 to RowCount-1.

Beispiele

• Set Example: Set the content of the third column in the grid from a ListBox:

Grid.Cols[2] := ListBox1.Items;

• Get Example: Set the content of a Listbox from the grid's column index 4:

procedure TForm1.FillListBox1;
var 
  StrTempList: TStringList;
begin
  StrTempList := TStringList(Grid.Cols[4]);
  if StrTempList<>nil then begin
    ListBox1.Items.Assign(StrTempList);
    StrTempList.Free;
  end;
end;   

Anmerkungen

This property works in a different way in Lazarus than in Delphi when getting the data from the grid. In Lazarus a temporary TStringList object is created for retrieving the column content. It is the responsibility of the user to free this object after use.

This means also that changes in the returned list will not affect the grids content or layout.

See the Get Example.

property Rows[index: Integer]: TStrings read GetRows write SetRows;

Get/set a list of strings from/to the given grid's row index starting from column index 0 to column ColCount-1.

Anmerkungen

This property works in a different way in Lazarus than in Delphi when getting the data from the grid. In Lazarus a temporary TStringList object is created for retrieving the row content. It is the responsibility of the user to free this object after use.

This means also that changes in the returned list will not affect the grids content or layout.

Beispiele

• Set Example: Set the content of the third row in the grid from a ListBox:

Grid.Rows[2] := ListBox1.Items;

• Get Example: Set the content of a Listbox from the grid's row index 4:

procedure TForm1.FillListBox1;
var 
  StrTempList: TStringList;
begin
  StrTempList := TStringList(Grid.Rows[4]);
  if StrTempList<>nil then begin
    ListBox1.Items.Assign(StrTempList);
    StrTempList.Free;
  end;
end;  

• Not Working Example and Fix: Retrieved string list is read only

// this will not work and will cause memory leak
// because returned StringList is not being freed
Grid.Rows[1].CommaText := '1,2,3,4,5';
Grid.Rows[2].Text := 'a'+#13#10+'s'+#13#10+'d'+#13#10+'f'+#13#10+'g'; 

// fixing the first case
Lst:=TStringList.Create;
Lst.CommaText := '1,2,3,4,5';
Grid.Rows[1] := Lst;
Lst.Free;

property UseXORFeatures;

Boolean property, default value: false;

This property controls how the dotted focus rectangle appears in the grid. When true, the rectangle is painted using the XOR raster operation. This allow us to see the focus rectangle no matter what the cells' background color is. When false, the user can control the color of the dotted focus rectangle using the FocusColor property

It also controls the look of the column/row resizing. When true, a line shows visually the size that the the column or row will have if the user ends the operation. When false, the column or row resizing takes effect just as the user drags the mouse.

Grids Howto

Customizing grids

Grid are components derived from TCustomControl class, and don't have a native widget associated to them which means that grids are not restricted by the look of current interface theme. This can be equally considered an advantage but also a disadvantage because usually programmers want to create a uniform-look application. The good news is that Lazarus grids are flexible enough to get something from both worlds, programmers can easily make grids to look like other native controls or they can customize the grid to the finest detail so they can obtain almost the same look in any platform or widget interface, that is, with the exception of scrollbars because their look is still determined by current theme.

Properties and Events for customizing grids

Some properties can affect the way the grid looks by acting when the cell is about to be painted in PrepareCanvas/OnPrepareCanvas by changing default canvas properties like brush color or font. Following is a list of such properties:

• AlternateColor. With this the user can change the background color appears on alternated rows. This is to allow easy reading off of grid rows data.
• Color. This sets the primary color used to draw non fixed cells background.
• FixedColor. This is the color used to draw fixed cells background.
• Flat. this eliminates the 3d look of fixed cells.
  
• TitleFont. Font used to draw the text in fixed cells.
  
• TitleStyle. This property changes the 3D look of fixed cells, there are 3 settings:
  • tsLazarus. This is the default look
  • tsNative. This tries to set a look that is in concordance with current widgetset theme.
  • tsStandard. This style is a more contrasted look, like delphi grids.
• AltColorStartNormal. boolean, if true alternate color is always in the second row after fixed rows, the first row after fixed rows will be always color, if false default color is set to the first row as if there were no fixed rows.
• BorderColor. This sets the grid's border color used when Flat:=True and BorderStyle:=bsSingle;
• EditorBorderStyle. If set to bsNone under windows the cell editors will not have the border, like in delphi, set to bsSingle by default because the border can be theme specific in some widgetsets and to allow a uniform look.
  
• FocusColor. The color used to draw the current focused cell if UseXORFeatures is not set, by default this is clRed.
• FocusRectVisible. turns on/off the drawing of focused cell.
• GridLineColor. color of grid lines in non fixed area.
• GridLineStyle. Pen style used to draw lines in non fixed area, possible choices are: psSolid, psDash, psDot, psDashDot, psDashDotDot, psinsideFrame, psPattern,psClear. default is psSolid.
• SelectedColor. Color used to draw cell background on selected cells.
• UseXORFeatures. If set, focus rect is drawn using XOR mode so it should make visible the focus rect in combination with any cell color ackground. It also affects the moving columns look.
• DefaultDrawing. boolean. Normally the grids prepare the grid canvas using some properties according to the kind of cell is being painted. If user write an OnDrawCell event handler, DefaultDrawing if set also paints the cell background, if user is drawing fully the cell is better turn off this property so painting is not duplicated. In a StringGrid if DefaultDrawing is set it draws the text in each cell.
• AutoAdvance. where the cell cursor will go when pressing enter or tab/shift tab, or after editing.
• ExtendedColSizing. If true user can resize columns not just at the headers but along the columns height.

(write me)

Description of grid's drawing process

Like other custom controls, the grid draws itself in the paint method, in general terms the grid is drawn by painting all rows, and each row by painting it's individual cells. The process is as follow:

• First the range of visible area is determined, each row is tested to see if it intersects the canvas clipping region, if it's ok, then visible area is painted by drawing columns of each row. The column and row values are used to identify the cell that is about to be painted and again each column is tested for intersection with clippling region, if everything is ok, some additional properties like it's rectangualar extent and visual state are feed to DrawCell method.
• DrawCell. The DrawCell method is virtual and may be overriden in descendant grids to do custom drawing. The information passed to DrawCell method helps to identify the particular cell is being painted, the physical area ocuppied in screen and it's visible status. See DrawCell reference for details. For each cell following occurs:
• PrepareCanvas. PrepareCanvas method is called, in this method, If DefaultDrawing property es set, the grid canvas is setup with default properties for brush and font based on current visual state and on several design and runtime properties, the text alignment is set to match programmer selection in custom columns if they exists. If DefaultDrawing is false, brush color is set to clWindow and Font color to clWindowText, the text alignment is set with grids defaultTextStyle property value.
• OnPrepareCanvas. If programmer wrote a event handler for OnPrepareCanvas event, it's called at this point. This event can be used for doing simple customization like changing cell's background color, font's properties like color, fontface and style, Text layout like different combinations of left, center, top, bottom, right alignment, etc. Any change made to the canvas in this event would be lost, because the next cell drawing will reset canvas again to a default state. So it's safe doing changes only for particular cell or cells and forget about it for the rest. Using this event sometimes helps to avoid uusing OnDrawCell grid event where users would be forced to duplicate the grid's drawing code. todo: samples of what can be made and what to leave for OnDrawCell?...
• OnDrawCell. Next if no handler for OnDrawCell event was specified, the grid calls the DefaultDrawCell method which simply paints the cell background using current canvas brush color and style, if OnDrawCell handler exists, the grid first paints the cell background but only if DefaultDrawing property was set, then it calls OnDrawCell event to do custom cell painting. Usually programmers want to do custom drawing only for particular cells, but standard drawing for others, in this case, they can restrict custom operation to certain cell or cells by looking into ACol,ARow and AState arguments, and for other cells simply call DefaultDrawCell method and let the grid to take care of it.
• Text. At this point (only for TStringGrid) if DefaultDrawing property is true, the cell's text content is painted.
• Grid lines. The last step for each cell is to paint the grid lines if grid options goVertLine,goHorzLine, goFixedVertLine and goFixedHorzLine are specified the cell grid is drawn at this point. Grids with only rows or only cols can be obtained by changing these options. If programmer elected to have a "themed" look it's done at this point also (see property TitleStyle).
• FocusRect. When all columns of current row have been painted it's time to draw the focus rectangle for current selected cell or for the whole row if goRowSelect option is set.

Several differences with delphi have been identified

• In Lazarus TCustomGrid.DrawCell method is not abstract and it's default implementation do basic cell background filling.
• In delphi, the cell's text is drawn before entering the OnDrawCell event see bug report #9619).

When above customizaton is not enough, derived grids

Derivd grids usually have to override following methods:
DrawAllRows: Draws all visible rows.
DrawRow: Draw All Cells in a Row.
DrawRow draws all cells in the row by first checking if cell is withing clipping region, and only draws the cell if it is.
DrawCell:
DrawCellGrid:
DrawCellText:
DrawFocusRect:
(write me).

Operationen

Save and Retrieve Grid Content

The SaveToFile procedure allows you save the TStringGrid format, attributes & values to a XML file. Previously you must set the SaveOptios property as follow:

soDesign:     Save & Load ColCount,RowCount,FixedCols,FixedRows,
              ColWidths, RowHeights and Options (TCustomGrid)
soPosition:   Save & Load Scroll Position, Row, Col and Selection (TCustomGrid)
soAttributes: Save & Load Colors, Text Alignment & Layout, etc. (TCustomDrawGrid)
soContent:    Save & Load Text (TCustomStringGrid)

The LoadFromFile procedure allows you to load into a StringGrid instance, attributes, formats & values, from a XML file. First, you must set some of this options of the SaveOptios property (on your TStringGrid instance) SaveOptions

 soDesign:     Save & Load ColCount,RowCount,FixedCols,FixedRows,
               ColWidths, RowHeights and Options (TCustomGrid)
 soPosition:   Save & Load Scroll Position, Row, Col and Selection (TCustomGrid)
 soAttributes: Save & Load Colors, Text Alignment & Layout, etc. (TCustomDrawGrid)
 soContent:    Save & Load Text (TCustomStringGrid)

---

Example: 1) First Open a new project "Application". 2) Put an empty TStringGrid. 3) Put a TButton. 4) Put a TOpenDialog 5) Add the event OnCreate for the Form 5) Add the event OnClick for the Button <delphi> unit Unit1;

{$mode objfpc}{$H+}

interface

uses

 Classes, SysUtils, LResources, Forms, Controls, Graphics, Dialogs, Grids,
 Buttons, StdCtrls, XMLCfg;

type

 { TForm1 }
 TForm1 = class(TForm)
   StringGrid1: TStringGrid;
   Button1: TButton;
   OpenDialog1: TOpenDialog;
   procedure Button1Click(Sender: TObject);
   procedure Form1Create(Sender: TObject);
 private
   { private declarations }
 public
   { public declarations }
 end; 

var

 Form1: TForm1; 

implementation

{ TForm1 }

procedure TForm1.Form1Create(Sender: TObject); begin

//sets the SaveOptions at creation time of the form 
stringgrid1.SaveOptions := [soDesign,soPosition,soAttributes,soContent];

end;

procedure TForm1.Button1Click(Sender: TObject); begin

//Ask if thew Execute method of the OpenDialog was launched 
//when this occurs, the user selects an XML file to Load
//wich name was stored in the FileName prop.

if opendialog1.Execute then
Begin
  //Clear the grid 
  StringGrid1.Clear;
  //Load the XML
  StringGrid1.LoadFromFile(OpenDialog1.FileName);
  //Refresh the Grid
  StringGrid1.Refresh;
End;

end;

initialization

 {$I unit1.lrs}

end. </delphi>

---

The sample xml file: (Copy the text below into a txt file Don't forget put the xml header :-)) <xml> <?xml version="1.0"?> <CONFIG>

 <grid version="3">
   <saveoptions create="True" position="True" content="True"/>
   <design columncount="2" rowcount="5" fixedcols="1" fixedrows="1" defaultcolwidth="64" defaultRowHeight="20">
     <options>
       <goFixedVertLine value="True"/>
       <goFixedHorzLine value="True"/>
       <goVertLine value="True"/>
       <goHorzLine value="True"/>
       <goRangeSelect value="True"/>
       <goDrawFocusSelected value="False"/>
       <goRowSizing value="False"/>
       <goColSizing value="False"/>
       <goRowMoving value="False"/>
       <goColMoving value="False"/>
       <goEditing value="False"/>
       <goTabs value="False"/>
       <goRowSelect value="False"/>
       <goAlwaysShowEditor value="False"/>
       <goThumbTracking value="False"/>
       <goColSpanning value="False"/>
       <goRelaxedRowSelect value="False"/>
       <goDblClickAutoSize value="False"/>
       <goSmoothScroll value="True"/>
     </options>
   </design>
   <position topleftcol="1" topleftrow="1" col="1" row="1">
     <selection left="1" top="1" right="1" bottom="1"/>
   </position>
   <content>
     <cells cellcount="10">
       <cell1 column="0" row="0" text="Title Col1"/>
       <cell2 column="0" row="1" text="value(1.1)"/>
       <cell3 column="0" row="2" text="value(2.1)"/>
       <cell4 column="0" row="3" text="value(3.1)"/>
       <cell5 column="0" row="4" text="value(4.1)"/>
       <cell6 column="1" row="0" text="Title Col2"/>
       <cell7 column="1" row="1" text="value(1.2)"/>
       <cell8 column="1" row="2" text="value(2.2)"/>
       <cell9 column="1" row="3" text="value(3.2)"/>
       <cell10 column="1" row="4" text="value(4.2)"/>
     </cells>
   </content>
 </grid>

</CONFIG> </xml>

---

--Raditz 21:06, 11 Jan 2006 (CET) from ARGENTINA

Grid Cell Editors

The grid uses cell editors to change the content of cells. For a specilized grid like TStringGrid, the editor is the habitual single line text editor control, sometimes it's desireable to have other means to enter information. For example,

to call the open file dialog to find the location of a file so the user doesn't have to type the full path manually, if 

the text in the cell represents a date, it would be more friendly if we could popup a calendar so we can choose a specific date easily. Sometimes the information the user should enter in a cell is restricted to a limited list of words, in this case typing the information directly might introduce errors and validating routines might need to be implemented, we can avoid this by using a cell editor that present the user a list with only the legal values. This is also the case of generic grids like TDrawGrid where user have to have some kind of structure to hold the data that will be shown in the grid, in this situation, the information that is entered in the cell editor updates the internal structure to reflect the changes in the grid.

Builtin cell editors

The grids.pas unit already include some of the most used cell editors ready for use in grids, there is also the posibility to create new cell editors (custom cell editors) if the builtin editors are not appropiated for a specific tasks.

The builtin cell editors are Button, Edit, and Picklist.

Using cell editors

Users can specify what editor will be used for a cell using one of two methods.

1. Using a custom column and selecting the ButtonStyle property of column. In this method the user can select the style of

the editor that will be shown. Available values are: cbsAuto, cbsEllipsis, cbsNone, cbsPickList, cbsCheckboxColumn

1. Using OnSelectEditor grid event, here the user specify in the Editor parameter which editor to use for a cell identified

for column aCol and row ARow in a TCustomDrawGrid derived grid or TColumn in TCustomDBGrid. For this purpose there is a useful public function of grids, EditorByStyle() that takes as parameter one of the following values: cbsAuto, cbsEllipsis, cbsNone, cbsPickList, cbsCheckboxColumn. This method takes precedence over the first one using custom columns. A Custom cell editor can be specified here. This event is also the place to setup the editor with values specific to the cell, row or column.

Description of editor styles

The following is the description of each editor style, they are enumeated values of type TColumnButtonStyle and so they are prefixed by 'cbs'. This type was used so it remains compatible with delphi's dbgrid.

• cbsAuto

This is the default editor style for TCustomGrid derived grids. The actual editor class that will be used to edit the

cell content, depends on several factors. For TCustomGrids it uses a TStringCelleditor class derived from TCustomMaskEdit,

this editor is speciallized to edit single line strings. It is then used in TStringGrid and TDrawGrid by default. When 

using Custom Columns and programmer filled the Column's PickList property, this behaves as if cbsPickList editor style was set. For a TCustomDBGrid that have a field of type boolean, behaves as if cbsCheckBoxColumn editor style was specified. This is the recomended value for Custom Cell Editors TODO: related OnEditingDone.

• cbsEllipsis

This editor style is the most generic one. When used, a button appears in the editing cell, programmers could use the

OnEditButtonClick grid event to detect when user has pressed the button and take any action was programmed for such cell. For example a programmer could use this editor style to pop up a calendar dialog so user can easily pick a specific date, another could be to show a file open dialog to find files, a calculator so user can enter the numeric result of calcs, etc.

OnEditButtonClick is just a notification, so to find out which cell a button has been clicked, take a look at grid.Row

and grid.Col properties.

A DbGrid has specific properties to retrieve the active column or field and because this event occurs in active record,

it could update the information in active field.

This editor style is implemented using TButtonCellEditor a direct descendant of TButton.

• cbsNone

This editor style instruct the grid to not use any editor for a specific cell or column, it behaves then, as if the grid

is readonly for such cell or column.

• cbsPickList

Used to present the user a list of values that can be entered, this editor style is implemented using

TPickListCellEditor a component derived from TCustomComboBox. The list of values that are shown, are filled in two ways depending of the method used to select the editor style.

1. When using custom columns, programmers can enter a list of values using the column's PickList property. [FOR BEGINNERS:

TODO: exact procedure to edit the list]

1. In OnSelectEditor, programmers get the TPickListCellEditor instance using the function EditorByStyle(cbsPickList), an

example would be: var Lst:TPickListCellEditor; begin [...] Lst:=TPickListCellEditor(EditorByStyle(cbsPickList)); Lst.clear; Lst.Items.add('One');lst.items.add('Two'); Editor:=Lst; end;

The value in a TStringGrid grid will automatically reflect the value selected, if necessary the programmer could detect

the moment the value is selected by writing an event handler for grid's OnPickListSelect event, so additional steps can be taken for example, to process the new value. TODO: related OnEditingDone.

• cbsCheckboxColumn

This editor style is at the moment only available in TDbGrid. This editor style can be useful when field content

associated with the column are restricted to a pair of values, for example, yes-no, true-false, on-off, 1-0, etc. Instead of forcing the user to type the values for this kind of field in a StringCellEditor or to choose one from a list, cbsCheckboxColumn is used to modify the field content of a column by using a checkbox representation that user can toggle by using a mouse click or pressing the SPACE key.

If columns' ButtonStyle property is set to cbsAuto and DbGrid detects that the field associated to the column is a

boolean field, then the grid use this editor style automatically, this automatic selection can be disabled or enabled using dbgrid's OptionsExtra property, setting dgeCheckboxColumn element to false disable this feature.

The values that are used to recognize the checked or unchecked states are set in column's properties ValueChecked and

ValueUnchecked.

In any moment, the field value can be in one to three states: Unchecked, checked or grayed. Internally this states are

identified by the following values of type TDBGridCheckBoxState: gcbpUnChecked, gcbpChecked and gcbpGrayed.

This editor style doesn't use real TCheckbox components to handle user interaction, the visual representation is given

by three builtin bitmap images that corresponds to the possible states of checkbox. The used bitmaps can be customized by writing a handler for DBGrid event OnUserCheckboxBitmap, the handler of this event gets the state of the checkbox in parameter CheckedState of type TDbGridCheckboxState and a bitmap parameter that programmer could use to specify custom bitmaps.

Beispiel: How to set a custom cell editor

Siehe lazarus/examples/gridcelleditor/gridcelleditor.lpi

Todo

• TInplaceEditor Support

Bekannte Probleme

29-marzo-2005:

• mouse autoedit
  • linux: clicking a selected cell doesn't trigger the autoedit function (the editor lost focus inmmediatelly)
  • windows: it should work only if the grid has the focus, if not it should focus and a second click should autoedit (cannot detect if the grid was previously focused or not)
• ColumnWidths: linux, windows: dbgrid start with default column widths instead of calculated ones (it's disabled because early canvas creation causes strange effects if the parent is a notebook page)
• Resizing Columns: linux, windows. Resizing a column should not hide the editor (specially in dbgrid if we are inserting)
• MouseWheel:
  • linux: mousewheel doesn't work as it should, (seems it's calling the default mousewheel handler)
  • windows: patch was sent.
• Double painting: Apparently dbgrid paints the cell background twice (once with fillrect and once in textRect)
• AutoFillColumns: sometimes the clientwidth is evaluated incorrectly (sometimes there are phantom scrollbars)