Widget Overview

Common widgets

AutomatableModelView.cpp	Base class for anything that can be automated
AutomatableButton.cpp	Base class for PixmapButton and LedCheckBox
AutomatableSlider.cpp
CaptionMenu.cpp
ComboBox.cpp
CPULoadWidget.cpp
CustomTextKnob.cpp	Used by VST, based on Knob
Fader.cpp
Graph.cpp
GroupBox.cpp
Knob.cpp
LedCheckBox.cpp
LcdFloatSpinBox.cpp
LcdSpinBox.cpp
LcdWidget.cpp	Does not support interaction
LeftRightNav.cpp	Used in instrument window
MeterDialog.cpp	Same widget, two looks
MixerLineLcdSpinBox.cpp	Used in SampleTrackWindow and InstrumentTrackWindow
NStateButton.cpp	Alternates between icons when clicked
Oscilloscope.cpp
PixmapButton.cpp
RowTableView.cpp
StringPairDrag.cpp	Floating image when dragging knobs etc
TabBar.cpp
TabWidget.cpp
TempoSyncKnob.cpp
TextFloat.cpp
TimeDisplayWidget.cpp
ToolButton.cpp

Main window

FileBrowser.cpp
MainWindow.cpp
PluginBrowser.cpp
RecentProjectsMenu.cpp
SideBar.cpp
SideBarWidget.cpp	Base class for PluginBrowser and FileBrowser
SubWindow.cpp	All windows inside the LMMS main window
TemplatesMenu.cpp

Controllers

ControllerDialog.cpp	Base class for LfoControllerDialog and PeakControllerDialog
ControllerRackView.cpp
ControllerView.cpp
LfoControllerDialog.cpp
PeakControllerDialog.cpp

Dialogs (separate window)

AboutDialog.cpp
ColorChooser.cpp	OS native (?) color picker
ControllerConnectionDialog.cpp
EffectSelectDialog.cpp
ExportProjectDialog.cpp
FileDialog.cpp	Open/export
VersionedSaveDialog.cpp	For saving project files
RenameDialog.cpp

Editors

AutomationEditor.cpp
Editor.cpp	Base class that provides a toolbar and playback control
PatternEditor.cpp
PianoRoll.cpp
PositionLine.cpp
ProjectNotes.cpp	not an Editor but still and "editor"
Rubberband.cpp
SongEditor.cpp
StepRecorderWidget.cpp	The red stuff drawn on top of Piano Roll
TimeLineWidget.cpp

Effects

EffectControlDialog.cpp	Window for native effects
EffectView.cpp
EffectRackView.cpp
LadspaControlView.cpp

Instrument (InstrumentTrackWindow)

EnvelopeAndLfoView.cpp
InstrumentView.cpp
InstrumentFunctionViews.cpp
InstrumentMidiIOView.cpp
InstrumentMiscView.cpp
InstrumentSoundShapingView.cpp
InstrumentTrackWindow.cpp
PianoView.cpp

Midi

MidiCCRackView.cpp
MidiPortMenu.cpp	Used both by TrackOperationsWidget and InstrumentMidiIOView

Mixer

MixerView.cpp
MixerLine.cpp
SendButtonIndicator.cpp

Settings

AudioDeviceSetupWidget.cpp
AudioAlsaSetupWidget.cpp
MidiSetupWidget.cpp
SetupDialog.cpp	exception, it's a Dialog

Tracks and Clips (TrackContainerView)

AutomationClipView.cpp
AutomationTrackView.cpp
ClipView.cpp	Base class
FadeButton.cpp	The thing that blinks
InstrumentTrackView.cpp
MidiClipView.cpp
PatternClipView.cpp
PatternTrackView.cpp
SampleClipView.cpp
SampleTrackView.cpp
TrackContainerView.cpp
TrackContentWidget.cpp
TrackLabelButton.cpp
TrackOperationsWidget.cpp
TrackRenameLineEdit.cpp
TrackView.cpp	Base class

Other subwindows

MicrotunerConfig.cpp
SampleTrackWindow.cpp	very similar to InstrumentTrackWindow
ToolPluginView.cpp	Used by plugins found in the Tool menu

Non-widget classes

ActionGroup.cpp	Used to group buttons like these
embed.cpp	Loading of external pixmaps and text files
GuiApplication.cpp	Holds pointers to the main components of the GUI
LmmsPalette.cpp	Theme colors
LmmsStyle.cpp	Widget styling
MainApplication.cpp	Used to catch events
ModelView.cpp	Base class for anything that can be connected to a backend Model
ToolTip.cpp	Adds the ability to disable tool tips

LV2

I don't understand these

ControlLayout.cpp	QLayout used by LinkedModelGroupView
Controls.cpp	Subclasses of common LMMS widgets, used by LinkedModelGroupView
LinkedModelGroupViews.cpp	QWidget used by Lv2ViewBase
Lv2ViewBase.cpp	Base class for Lv2Instrument