TKnob

Source: source/classes/tknob.prg | Command: include/tknob.ch

Inherits from: TControl

Contributed by Silvio Falconi.

TKnob is a modern custom rotary knob control for FiveWin / Harbour, designed for audio, MIDI and synthesizer style applications (mixers, drum machines, VST-like interfaces and touch screens). It is a pure Harbour/FiveWin implementation built on TControl — all drawing is done with GDI primitives, so no extra DLL is required.

Features

Modern rotary knob design with compact control area and correct clipping.
Transparent / themed background support (IsAppThemed()).
Two indicator modes: LED (dot) or LINE.
External illuminated ring with soft glow, plus optional external ticks (lTicks).
Unipolar mode (0..127) and Bipolar mode (-30..+30, shows signed value).
Mouse drag (vertical) and mouse wheel control; hold CTRL for a finer wheel step.
Double click resets to the default value.
Enable / disable state with dimmed visual feedback (Toggle()).
Internal value display and external label, with separate fonts (oFontInner / oFont).
bSetGet variable binding, bChanged and bAction callbacks.

Key DATA Members

DATA	Type	Default	Description
`nValue`	Numeric	`64`	Current value (clamped to nMin..nMax)
`nMin`	Numeric	`0`	Minimum value
`nMax`	Numeric	`127`	Maximum value
`nDefault`	Numeric	`64`	Value restored on double click
`cIndicator`	Char	`"LED"`	Indicator style: `"LED"` or `"LINE"`
`cMode`	Char	`"UNIPOLAR"`	Range mode: `"UNIPOLAR"` or `"BIPOLAR"`
`lTicks`	Logical	`.F.`	Draw external tick marks around the ring
`lActive`	Logical	`.T.`	Enabled state (dimmed when .F.)
`nWheelStep` / `nCtrlStep`	Numeric	`1`	Wheel step, and finer step while CTRL is held
`oFont` / `oFontInner`	Object		Fonts for the external label and the inner value text
`bSetGet`	Block		SetGet codeblock for variable binding (read/write)
`bChanged`	Block		Fired when the value changes; receives `( Self, nValue )`
`bAction`	Block		Fired on toggle; receives `( Self, lActive )`

Methods

Method	Description
`New( nTop, nLeft, bSetGet, oWnd, nWidth, nHeight, cMsg, nMin, nMax, cIndicator, cMode, lTicks, bAction, lDesign, oFont, oFontInner )`	Create a new knob control
`SetValue( nValue )`	Set the value (clamped), fire bSetGet/bChanged and repaint
`GetValue()`	Return the current `nValue`
`SetMode( cMode )`	Switch between `"UNIPOLAR"` (0..127) and `"BIPOLAR"` (-30..+30) and reset range/default
`Toggle()`	Flip the enabled state and fire `bAction`
`Display()` / `Paint()`	Render the knob (ring, glow arc, body, indicator, value, label)
`Destroy()`	Destroy the control

The @ ... KNOB Command

Include tknob.ch to use the declarative command:

@ <nRow>, <nCol> KNOB <oKnob>            ;
   VAR <nVar>                            ;
   OF <oWnd>                             ;
   SIZE <nWidth>, <nHeight>              ;
   LABEL <cMsg>                          ;
   MIN <nMin> MAX <nMax>                 ;
   [ LED | LINE ]                        ;
   [ UNIPOLAR | BIPOLAR ]                ;
   [ TICKS | NOTICKS ]                   ;
   FONT <oFont> FONTINNER <oFontInner>   ;
   [ ON CHANGE <uChange> ]               ;
   [ ACTION <uAction> ]

Example: Volume & Modulation Knobs

#include "FiveWin.ch"
#include "tknob.ch"

function Main()

   local oDlg, oFont, oFontInner
   local oKnobVol, oKnobMod, oSayVol, oSayMod
   local nVol := 0, nMod := 64

   DEFINE FONT oFont      NAME "Segoe UI" SIZE 0, -11 BOLD
   DEFINE FONT oFontInner NAME "Segoe UI" SIZE 0, -14 BOLD

   DEFINE DIALOG oDlg TITLE "TKnob" SIZE 780, 280 PIXEL

   @ 35, 150 SAY oSayVol PROMPT "VOL: " + AllTrim( Str( nVol ) ) ;
      SIZE 40, 10 PIXEL OF oDlg

   @ 35, 40 KNOB oKnobVol VAR nVol OF oDlg SIZE 76, 86 ;
      LABEL "VOL" MIN -30 MAX 30 LED BIPOLAR NOTICKS ;
      FONT oFont FONTINNER oFontInner ;
      ON CHANGE { |o,n| oSayVol:SetText( "VOL: " + AllTrim( Str( n ) ) ) }

   @ 35, 370 SAY oSayMod PROMPT "MOD: " + AllTrim( Str( nMod ) ) ;
      SIZE 50, 10 PIXEL OF oDlg

   @ 35, 200 KNOB oKnobMod VAR nMod OF oDlg SIZE 76, 86 ;
      LABEL "MOD" MIN 0 MAX 200 LINE UNIPOLAR TICKS ;
      FONT oFont FONTINNER oFontInner ;
      ON CHANGE { |o,n| oSayMod:SetText( "MOD: " + AllTrim( Str( n ) ) ) }

   ACTIVATE DIALOG oDlg CENTERED ;
      VALID ( oFont:End(), oFontInner:End(), .T. )

return nil

Notes

Drag the knob vertically to change the value; the mouse wheel also works, and holding CTRL uses the finer nCtrlStep.
A single click (no drag) toggles the enabled state via Toggle(); a double click resets to nDefault.
In BIPOLAR mode the inner value is shown signed (e.g. +12) and the green arc starts from the center (zero) position.
Bind a variable with VAR (the command wraps it in a bSetGet block) or set bSetGet manually; use ON CHANGE for UI updates.
Demos: samples/knobtst1.prg (direct New) and samples/knobtst2.prg (command syntax).