Slider Widgets

Slider widgets provide continuous control over values in QLC+. They can control fixture intensity, function playback, or act as submasters. Sliders are implemented in ui/src/virtualconsole/vcslider.h and vcslider.cpp, and inherit from both VCWidget and DMXSource.

Overview

Slider widgets support three distinct modes:

Level Mode: Control individual fixture channels (intensity, color, etc.)
Playback Mode: Control function intensity and playback
Submaster Mode: Act as a master intensity control for other widgets

Sliders can be displayed as traditional linear sliders or rotary knobs, making them versatile for different interface layouts.

Slider Modes

Level Mode

Direct control of DMX channel values:

enum SliderMode
{
    Level,
    Playback,
    Submaster
};

Source: vcslider.h:147-152 Level mode allows you to:

Control specific fixture channels directly
Set DMX values between low and high limits
Monitor current channel values from other functions
Override temporary values (useful for manual control)

Level mode bypasses the function system and writes directly to DMX universes through the DMXSource interface. This provides immediate, low-latency control of fixtures.

Playback Mode

Control function intensity during playback:

Start/stop assigned function
Adjust function intensity in real-time
Flash button for temporary full intensity
Monitor function state and intensity

Playback mode is ideal for:

Controlling chaser speed and intensity
Adjusting scene brightness
Fading effects in and out during performances

Submaster Mode

Act as a master control for other widgets:

Control intensity of multiple widgets simultaneously
No function assignment needed
Widgets listen for submasterValueChanged() signal
Common in professional lighting setups

Level Mode Configuration

Level Channels

Level mode controls specific fixture channels:

class LevelChannel
{
public:
    quint32 fixture;  // Fixture ID
    quint32 channel;  // Channel within fixture
};

void addLevelChannel(quint32 fixture, quint32 channel);
void removeLevelChannel(quint32 fixture, quint32 channel);
void clearLevelChannels();
QList<VCSlider::LevelChannel> levelChannels();

Source: vcslider.h:224-284 Example: Control the intensity channel of multiple fixtures with one slider.

Level Limits

Set minimum and maximum values for controlled channels:

void setLevelLowLimit(uchar value);   // 0-255
uchar levelLowLimit() const;
void setLevelHighLimit(uchar value);  // 0-255
uchar levelHighLimit() const;

Source: vcslider.h:287-308 Use cases:

Park dimmer at minimum: Set low limit to 10-20 to prevent complete darkness
Limit maximum brightness: Set high limit to 200 to protect fixtures
Restricted range: Control only a portion of the channel range

Channel Monitoring

Monitor current channel values from other functions:

void setChannelsMonitorEnabled(bool enable);
bool channelsMonitorEnabled() const;

Source: vcslider.h:312-318 When enabled:

Slider displays current DMX value from other sources
Visual feedback shows actual output level
Useful for seeing what other functions are doing
Can override monitored value by moving slider

The monitoring is implemented through slotUniverseWritten() which receives universe data updates.

Playback Mode Configuration

Playback Function

Assign a function to control:

void setPlaybackFunction(quint32 fid);
quint32 playbackFunction() const;
uchar playbackValue() const;
void setPlaybackValue(uchar value);

Source: vcslider.h:364-392 The slider:

Starts function when moved from zero
Adjusts function intensity as slider moves
Stops function when returned to zero
Monitors function state from other sources

Flash Button

Optional button for temporary full intensity:

bool playbackFlashEnable() const;
void setPlaybackFlashEnable(bool enable);

Source: vcslider.h:397-399 When enabled:

Button appears next to slider
Press to temporarily set function to full intensity
Release to return to slider value
Keyboard shortcut support

Flash button state is tracked through:

protected:
    bool m_playbackFlashEnable;
    bool m_playbackIsFlashing;
    uchar m_playbackFlashPreviousValue;

Source: vcslider.h:416-418 Sliders can be displayed in two styles:

enum SliderWidgetStyle
{
    WSlider,  // Traditional linear slider
    WKnob     // Rotary knob
};

void setWidgetStyle(SliderWidgetStyle mode);
SliderWidgetStyle widgetStyle() const;

Source: vcslider.h:474-489

Linear Slider

Traditional vertical or horizontal bar
Shows current value visually
Easy to see at a glance
Better for precise value setting

Rotary Knob

Space-saving circular control
Familiar to audio engineers
Good for dense control surfaces
Implemented via KnobWidget class

Value Display

Sliders can display values in different formats:

enum ValueDisplayStyle
{
    ExactValue,        // DMX value (0-255)
    PercentageValue    // Percentage (0-100%)
};

void setValueDisplayStyle(ValueDisplayStyle style);
ValueDisplayStyle valueDisplayStyle() const;

Source: vcslider.h:189-199 The value is displayed in labels above and below the slider showing the current position.

Inverted Appearance

Reverse the slider direction:

bool invertedAppearance() const;
void setInvertedAppearance(bool invert);

Source: vcslider.h:206-209 Useful for:

Matching hardware controller layouts
Ergonomic improvements
Visual organization

Value Catching

Smooth transition when moving slider:

bool catchValues() const;
void setCatchValues(bool enable);

Source: vcslider.h:213-216 When enabled:

Slider “catches” current value before responding
Prevents jumps when monitoring is active
Smooth takeover from monitored values
Common in professional lighting consoles

Click & Go

Quick value selection through popup interfaces:

void setClickAndGoType(ClickAndGoWidget::ClickAndGo type);
ClickAndGoWidget::ClickAndGo clickAndGoType() const;
ClickAndGoWidget* getClickAndGoWidget();

Source: vcslider.h:533-554 Click & Go types:

None: Disabled
Preset: Choose from preset values
RGB: Color picker for RGB fixtures
CMY: Color picker for CMY fixtures
RGBW/RGBA/RGBAW: Extended color pickers

Click the button next to the slider to open the Click & Go widget for quick value selection.

Override Reset

Return to monitored value after override:

void setOverrideResetKeySequence(const QKeySequence& keySequence);
QKeySequence overrideResetKeySequence() const;

Source: vcslider.h:576-580 Workflow:

Slider monitors channel value from function
User moves slider (override)
User presses reset key
Slider returns to monitoring current value

The reset button appears when monitoring is enabled and an override is active.

DMX Source Implementation

Sliders write directly to DMX universes:

class VCSlider : public VCWidget, public DMXSource
{
    void writeDMX(MasterTimer *timer, QList<Universe*> universes) override;
    
protected:
    void writeDMXLevel(MasterTimer *timer, QList<Universe*> universes);
    void writeDMXPlayback(MasterTimer *timer, QList<Universe*> universes);
};

Source: vcslider.h:75, vcslider.h:439-447 The writeDMX() method is called every timer tick:

Level Mode: Writes slider value to configured channels
Playback Mode: Adjusts running function’s intensity
Uses GenericFader: Smooth value transitions

Faders are managed per-universe:

private:
    QMap<quint32, QSharedPointer<GenericFader>> m_fadersMap;

Source: vcslider.h:451

External Control

Multiple Input Sources

Sliders support multiple input sources:

static const quint8 sliderInputSourceId;        // Main slider input
static const quint8 overrideResetInputSourceId; // Reset button input  
static const quint8 flashButtonInputSourceId;   // Flash button input

Source: vcslider.h:83-85 Each input source can be mapped independently to different MIDI/OSC controls.

Keyboard Control

Playback flash button supports keyboard shortcuts:

QKeySequence playbackFlashKeySequence() const;
void setPlaybackFlashKeySequence(const QKeySequence& keySequence);

Source: vcslider.h:603-604

Slider Matrix

Create multiple sliders at once:

Access via “Add Slider Matrix” menu
Creates a grid of sliders
Batch configure level channels
Map to fixture capabilities
Implemented in addvcslidermatrix.cpp

Slider matrices are particularly useful when you need to create manual control for multiple fixtures with similar capabilities, such as a bank of RGB color mixing sliders.

Layout Components

Slider UI consists of several components:

protected:
    QHBoxLayout *m_hbox;              // Main layout
    QAbstractSlider *m_slider;        // Slider or knob widget
    QLabel *m_topLabel;               // Value display above
    QLabel *m_bottomLabel;            // Caption below
    QToolButton *m_resetButton;       // Override reset
    QToolButton *m_cngButton;         // Click & Go
    QToolButton *m_flashButton;       // Flash (playback mode)

Source: vcslider.h:467-468, vcslider.h:507-510, vcslider.h:527, vcslider.h:592, vcslider.h:620 Each component is optional and appears based on slider configuration.

Common Use Cases

Master Dimmer

Level mode slider controlling intensity of all stage fixtures

Chaser Speed

Playback mode slider adjusting chaser playback speed

RGB Color Mix

Three level mode sliders for red, green, and blue channels

Scene Intensity

Playback mode with flash button for scene control

XML Persistence

Slider configuration example:

<Slider ID="1" WidgetStyle="Slider">
    <WindowState X="100" Y="10" Width="60" Height="200"/>
    <Appearance>
        <Font>Arial,10</Font>
    </Appearance>
    <SliderMode ValueDisplayStyle="Percentage">Level</SliderMode>
    <Level LowLimit="0" HighLimit="255" Monitor="true">
        <Channel Fixture="0">0</Channel>
        <Channel Fixture="1">0</Channel>
    </Level>
    <CatchValues>true</CatchValues>
    <Input Universe="0" Channel="1"/>
</Slider>

Key XML elements:

SliderMode: Level, Playback, or Submaster
Level: Channel mappings and limits
Playback: Function ID and flash button settings
ValueDisplayStyle: Exact or Percentage
WidgetStyle: Slider or Knob
CatchValues: Enable value catching

Next Steps

Choose Slider Mode

Decide between Level, Playback, or Submaster based on your needs

Configure Channels

In Level mode, add fixture channels to control

Set Value Limits

Define low and high limits for safe operation

Add External Control

Map MIDI faders or OSC controls to the slider

Get Started

Core Concepts

Functions

Fixture Management

Virtual Console

Input/Output

Advanced Features

​Overview

​Slider Modes

​Level Mode

​Playback Mode

​Submaster Mode

​Level Mode Configuration

​Level Channels

​Level Limits

​Channel Monitoring

​Playback Mode Configuration

​Playback Function

​Flash Button

​Widget Style

​Linear Slider

​Rotary Knob

​Value Display

​Inverted Appearance

​Value Catching

​Click & Go

​Override Reset

​DMX Source Implementation

​External Control

​Multiple Input Sources

​Keyboard Control

​Slider Matrix

​Layout Components

​Common Use Cases

Master Dimmer

Chaser Speed

RGB Color Mix

Scene Intensity

​XML Persistence

​Next Steps

Build docs developers (and LLMs) love

Overview

Slider Modes

Level Mode

Playback Mode

Submaster Mode

Level Mode Configuration

Level Channels

Level Limits

Channel Monitoring

Playback Mode Configuration

Playback Function

Flash Button

Widget Style

Linear Slider

Rotary Knob

Value Display

Inverted Appearance

Value Catching

Click & Go

Override Reset

DMX Source Implementation

External Control

Multiple Input Sources

Keyboard Control

Slider Matrix

Layout Components

Common Use Cases

XML Persistence

Next Steps