Default Trackbar Message Processing
This section describes the window message processing performed by a trackbar.
Message
| Processing performed
|
WM_CAPTURECHANGED
| Kills the timer if one was set during WM_LBUTTONDOWN processing and sends the TB_THUMBPOSITION notification message, if necessary.
It always sends the TB_ENDTRACK notification message.
|
WM_CREATE
| Performs additional initialization. It sets the initial tick frequency to 1,
the line size to 1, and the page size to  1.
|
WM_DESTROY
| Frees resources.
|
WM_ENABLE
| Repaints the trackbar window.
|
WM_ERASEBKGND
| Erases the window background, using the current background color for the
trackbar.
|
WM_GETDLGCODE
| Returns the DLGC_WANTARROWS value.
|
WM_KEYDOWN
| Processes the direction keys and sends the TB_TOP, TB_BOTTOM, TB_PAGEUP,
TB_PAGEDOWN, TB_LINEUP, and TB_LINEDOWN notification messages, as appropriate.
|
WM_KEYUP
| Sends the TB_ENDTRACK notification message if the key was one of the direction
keys.
|
WM_KILLFOCUS
| Repaints the trackbar window.
|
WM_LBUTTONDOWN
| Sets the focus and the mouse capture to the trackbar. When necessary, it sets
a timer that determines how quickly the slider moves toward the mouse cursor
when the user holds down the mouse button in the window.
|
WM_LBUTTONUP
| Releases the mouse capture and kills the timer if one was set during WM_LBUTTONDOWN processing. It sends the TB_THUMBPOSITION notification message, if necessary.
It always sends the TB_ENDTRACK notification message.
|
WM_MOUSEMOVE
| Moves the slider and sends the TB_THUMBTRACK notification message when
tracking the mouse (see WM_TIMER).
|
WM_PAINT
| Paints the trackbar. If the wParam parameter is non-NULL, the control assumes that the value is an HDC and
paints using that device context.
|
WM_SETFOCUS
| Repaints the trackbar window.
|
WM_SIZE
| Sets the dimensions of the trackbar, removing the slider if there is not
enough room to display it.
|
WM_TIMER
| Retrieves the mouse position and updates the position of the slider. (It is
received only when the user is dragging the slider.)
|
WM_WININICHANGE
| Initializes slider dimensions.
|
- Software for developers
-
Delphi Components
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Software for Android Developers
- More information resources
-
MegaDetailed.Net
Unix Manual Pages
Delphi Examples
