TScrollPanel

Fuente: source/classes/scrlpanl.prg

Inherits from: TPanel

TScrollPanel is a scrollable container panel with automatic vertical and horizontal scrollbars that track the extent of child controls. It supports mouse-wheel scrolling, click-and-drag scroll, touch panning via gesture handling, page-based navigation, and helper methods to bring any child control into view. Created by G.N. Rao.

Key DATA Members

DATA	Type	Description
`vStep`	Numeric	Vertical scroll step in pixels (default 20)
`hStep`	Numeric	Horizontal scroll step in pixels (default 20)
`nScrollRange`	Numeric	Vertical scroll range calculated from child controls
`nHScrollRange`	Numeric	Horizontal scroll range calculated from child controls
`aSays`	Array	Array of static text rectangles scrolled with the panel
`aPages`	Array	Array of { cPageName, nRow } bookmarks for page navigation
`lScrollDrag`	Logical	Drag-to-scroll mode flag
`nRightMargin`	Numeric	Right margin preserved when parent resizes
`nBottomMargin`	Numeric	Bottom margin preserved when parent resizes
`oCtrlTop`	Object	Topmost child control (for scroll range)
`oCtrlBot`	Object	Bottommost child control (for scroll range)

Methods

Method	Description
`New( nTop, nLeft, nBottom, nRight, oWnd, lNoBorder )`	Create a new TScrollPanel
`SetRange()`	Scan child controls and set scroll range. Call after adding all controls.
`ScrollBy( nV, nH )`	Scroll the panel by nV pixels vertically and nH pixels horizontally
`GoTop()`	Scroll to the top of the panel
`GoBottom()`	Scroll to the bottom of the panel
`GoLeft()`	Scroll to the left edge
`GoRight()`	Scroll to the right edge
`GoUp( nPix )`	Scroll up by nPix pixels (default vStep)
`GoDown( nPix )`	Scroll down by nPix pixels (default vStep)
`ControlIntoView( oControl )`	Scroll the panel to ensure oControl is visible
`SetPage( cPage, nRow )`	Bookmark the current row with a page name
`GoToPage( cPage )`	Scroll to a previously bookmarked page
`AddText( nRow, nCol, nW, nH, cbText, oFont, nClrText )`	Add scrolling text that moves with the panel content

Example: Scroll Panel with Controls

#include "FiveWin.ch"

function Main()

   local oWnd, oPanel, oGet, oBtn, cText := ""

   DEFINE WINDOW oWnd TITLE "Scroll Panel" SIZE 400, 300

   oPanel := TScrollPanel():New( 10, 10, 290, 390, oWnd )

   @ 10, 10 GET oGet VAR cText OF oPanel SIZE 200, 20 PIXEL
   @ 40, 10 BUTTON oBtn PROMPT "Button" OF oPanel SIZE 100, 30 PIXEL ;
      ACTION MsgInfo( "Clicked" )

   // Add more controls below the visible area to test scrolling
   @ 400, 10 SAY "This is far down" OF oPanel SIZE 200, 20 PIXEL

   oPanel:SetRange()   // Recalculate scroll range

   ACTIVATE WINDOW oWnd CENTERED

return nil

Notes

Call SetRange() after adding all child controls to calculate the scroll range and enable the scrollbars.
The panel creates both vertical and horizontal scrollbars automatically via WS_VSCROLL and WS_HSCROLL styles.
Drag-to-scroll is enabled by holding the left mouse button and dragging. Touch panning is supported via HandleGesture() for WM_GESTURE messages.
Use ControlIntoView() in bGotFocus blocks of child controls to automatically scroll the panel when tabbing through controls.
AddText() creates scrolling text labels that move with the panel content, unlike standard SAY controls which stay fixed unless scrolled manually.
The nRightMargin and nBottomMargin DATA members allow the panel to auto-resize when its parent window is resized.

TScrollPanel

Key DATA Members

Methods

Example: Scroll Panel with Controls

Notes

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