OwnerDraw decription

A rendering mode in which you take responsibility for drawing a control, rather than relying on the control’s default rendering behavior.

Typically, Windows handles painting automatically by using property settings such as BackColor to determine the appearance of a control. With owner drawing, you take over the painting process, changing elements of appearance that are not available by using properties. For example, many controls let you set the color of the text that is displayed, but you are limited to a single color. Owner drawing enables you to do things like display part of the text in black and part in red.

In practice, owner drawing is similar to drawing graphics on a form. For example, you could use graphics methods in a handler for the form's Paint event to emulate a ListBox control, but you would have to write your own code to handle all user interaction. With owner drawing, the control uses your code to draw its contents but otherwise retains all its intrinsic capabilities. You can use DRAW methods to draw each item in the control or to customize some aspects of each item while you use the default appearance for other aspects of each item.  DRAW methods based on Device context API methods and GDI Plus methods. Please, feel free for ask to add new methods if need.

To perform owner drawing in controls that support it, you will typically set one property and write OnerDraw context script.

Most controls that support owner drawing have an OwnerDraw property that indicates whether the control will raise its drawing-related event or events when it paints itself.

There are many different kinds of drawing events, but a typical drawing event occurs in order to draw a single item within a control. BRIZ provides automaticaly binding of Your OnerDraw context script when receives an OwnerDraw events. BRIZ sets variables to drawing. For example, variables typically contains the item's index number, a Rectangle that indicates the item's display boundaries and for some objects provides additional information about the item such as the background or a focus rectangle.

OnerDraw context script is reusable (You can use one context with many objects).

The following Objects support owner drawing:

• BUTTON
• CHECKLISTBOX
• COMBOBOX
• DRAGLISTBOX
• LISTBOX
• LISTCTRL
• STATIC
• TABCTRL
• TREECTRL
• MENUITEM

How it works

BRIZ handles Windows messages WM_DRAWITEM and WM_MEASUREITEM . BRIZ executes OwnerDrawContext script on each message. You can manage OwnerDrawContext by sytem methods through subroutines GP.SystemSub( SubStr ) and GP.SystemFn( SubStr, Ret )

Setting the Owner-Drawn Flag

For menu You should use the Menu subroutines to specify an owner-drawn menu item, just add option 'O' to flag and define OwnerDrawContext name after flag. For example "EO;CONTEXT=MyMenu"

For objects You should specify ownerdraw style and define OwnerDrawContext name with help of method "SetDrawContext ContextName" or DRAWCONTEXT=xxxxx; option in intial string.

OwnerDraw styles for objects:

• BUTTON - _OWENERDRAW
• LISTBOX - LBS_OWNERDRAWFIXED  or LBS_OWNERDRAWVARIABLE 
• DRAGLISTBOX - LBS_OWNERDRAWFIXED  or LBS_OWNERDRAWVARIABLE 
• CHECKLISTBOX - LBS_OWNERDRAWFIXED  or LBS_OWNERDRAWVARIABLE 
• COMBOBOX - CBS_OWNERDRAWFIXED or CBS_OWNERDRAWVARIABLE 
• HEADER - HDF_OWNERDRAW for item
• LISTCTRL - LVS_OWNERDRAWFIXED
• TABCTRL - TCS_OWNERDRAWFIXED
• STATIC - SS_OWNERDRAW

Owner-Drawn Menus and the WM_MEASUREITEM Message

Before the system displays an owner-drawn menu item for the first time, it sends the WM_MEASUREITEM message to the window procedure of the window that owns the item's menu. BRIZ automaticaly calls DrawContext that  must fill the itemWidth and itemHeight members before returning. The system uses the information in these members when creating the bounding rectangle in which an application draws the menu item. It also uses the information to detect when the user chooses the item.

Owner-Drawn Menus and the DRAWITEM

Whenever the item must be drawn (for example, when it is first displayed or when the user selects it), the system calls the DrawContext. DrawContext contains flags that indicate the state of the item (such as whether it is grayed or selected) as well as a bounding rectangle and a device context that the application uses to draw the item.

An application must do the following while processing the DRAWITEM:

• Determine the type of drawing that is necessary. To do so, check the itemAction member.
• Draw the menu item appropriately, using the bounding rectangle. The application must draw only within the bounding rectangle. For performance reasons, the system does not clip portions of the image that are drawn outside the rectangle.  

If the user selects the menu item, the system sets the itemAction member to the ODA_SELECT value and sets the ODS_SELECTED value in the itemState member. This is an application's cue to redraw the menu item to indicate that it is selected.

DrawContext script predefined values

• Array of integer values:
  • 0 - Dialog ID (zero based)
  • 1 - Object ID
  • 2 - reserved
  • 3 - ControlType
    The control type. The values for control types are as follows:

    • ODT_BUTTON    (4) Owner-drawn button
    • ODT_COMBOBOX    (3) Owner-drawn combo box
    • ODT_LISTBOX (2)  Owner-drawn list box
    • ODT_MENU    (1) Owner-drawn menu
    • ODT_LISTVIEW (102)  List view control
    • ODT_STATIC (5)  Owner-drawn static control
    • ODT_TAB    (101) Tab control
    • ODT_HEADER  (100) Tab control  
  • 4 - ControlID (Windows ID) The control ID for a combo box, list box, or button. This member is not used for a menu.
  • 5 - The menu-item ID for a menu or the index of the item in a list box or combo box. For an empty list box or combo box, this member is a negative value, which allows the application to draw only the focus rectangle at the coordinates specified by the rcItem member even though there are no items in the control. The user can thus be shown whether the list box or combo box has the input focus. The setting of the bits in the itemAction member determines whether the rectangle is to be drawn as though the list box or combo box has input focus.
  • 6 - Item Action
    Defines the drawing action required. This will be one or more of the following bits:

    • ODA_DRAWENTIRE (0x1)  This bit is set when the entire control needs to be drawn.
    • ODA_FOCUS (0x4)  This bit is set when the control gains or loses input focus. The itemState member should be checked to determine whether the control has focus.
    • ODA_SELECT  (0x2)  This bit is set when only the selection status has changed. The itemState member should be checked to determine the new selection state.
  • 7 - Item State
    Specifies the visual state of the item after the current drawing action takes place. That is, if a menu item is to be dimmed, the state flag ODS_GRAYED will be set. The state flags are as follows:

    • ODS_CHECKED    (0x0008) This bit is set if the menu item is to be checked. This bit is used only in a menu.
    • ODS_DISABLED    (0x0004) This bit is set if the item is to be drawn as disabled.
    • ODS_FOCUS    (0x0010) This bit is set if the item has input focus.
    • ODS_GRAYED    (0x0002) This bit is set if the item is to be dimmed. This bit is used only in a menu.
    • ODS_SELECTED    (0x0001) This bit is set if the item's status is selected.
    • ODS_COMBOBOXEDIT    (0x1000) The drawing takes place in the selection field (edit control) of an ownerdrawn combo box.
    • ODS_DEFAULT    (0x0020) The item is the default item.
    • ODS_HOTLIGHT    (0x0040) Windows 98/Me, Windows 2000/XP: The item is being hot-tracked, that is, the item will be highlighted when the mouse is on the item.
    • ODS_INACTIVE    (0x0080) Windows 98/Me, Windows 2000/XP: The item is inactive and the window associated with the menu is inactive.
    • ODS_NOACCEL    (0x0100) Windows 2000/XP: The control is drawn without the keyboard accelerator cues.
    • ODS_NOFOCUSRECT    (0x0200) Windows 2000/XP: The control is drawn without focus indicator cues.  
  • 8 - Specifies the window handle of the control for combo boxes, list boxes, and buttons. Specifies the handle of the menu (HMENU) that contains the item for menus.
  • 9 - Identifies a device context. This device context must be used when performing drawing operations on the control.
  • 10 - Item DATA 
  • 11 - Measure mode flag (0-WM_DRAWITEM, 1-WM_MEASUREITEM)
  • 12 - Specifies the width of a menu item. The DrawContext script of the owner-draw menu item must fill this member when measure mode flag equal to 1.
  • 13 - Specifies the height of an individual item in a list box or a menu. Before it returns from the message, the owner of the owner-draw combo box, list box, or menu item must fill out this member. The maximum height of a list box item is 255.
  • 14 - Subitem ID
  • 15-29 - Reserved
  • 30-49 - Object data
  • 50-59 - integer representation of strings 50-59
  • 60-99 - Reserved
• Array of string values:
  • 0 - Full text of item
  • 1 - top
  • 2-49 - Reserved
  • 50-59 - strings extracted from Full text of item using delimiter char(3)
  • 60-99 - Reserved
• Array of double values (You can use union syntax). Values 0-3 is a rectangle in the device context specified by the hDC member that defines the boundaries of the control to be drawn. Windows automatically clips anything the owner draws in the device context for combo boxes, list boxes, and buttons, but it does not clip menu items. When drawing menu items, the owner must not draw outside the boundaries of the rectangle:
  • 0-49 - Reserved
  • 50-59 - double representation of strings 50-59
  • 60-99 - Reserved
• Array of rectangles:
  • 0 - window rect of control (undefined for menus)
  • 1 - client rect of control (undefined for menus)
  • 2-9 - Reserved

Specific predefine values by ControlType