IGraphics

Core graphics context class for rendering UI in iPlug2

IGraphics

The IGraphics class is the lowest level base class of an IGraphics context. It manages the drawing canvas, controls, and all UI interactions for audio plugins built with iPlug2.

Overview

IGraphics provides:

• Cross-platform drawing API (NanoVG, Skia)
• Control management and rendering
• Mouse and keyboard event handling
• Layer and bitmap management
• Platform-specific windowing integration

Constructor

IGraphics(IGEditorDelegate& dlg, int w, int h, int fps = DEFAULT_FPS, float scale = 1.)

dlg · IGEditorDelegate& · required

The delegate that handles communication between IGraphics and the plugin

w · int · required

Width of the graphics context in pixels (1:1 screen)

h · int · required

Height of the graphics context in pixels (1:1 screen)

fps · int · default: "DEFAULT_FPS"

Target frame rate for redrawing

scale · float · default: "1.0"

Initial draw scale factor

Core Drawing Methods

BeginFrame

virtual void BeginFrame()

Called at the beginning of drawing. Override to perform pre-frame setup. Always call the base implementation.

EndFrame

virtual void EndFrame()

Called after drawing to blit the draw bitmap onto the screen or perform cleanup.

Shape Drawing

DrawLine

virtual void DrawLine(const IColor& color, float x1, float y1, float x2, float y2, 
                     const IBlend* pBlend = 0, float thickness = 1.f)

Draw a line to the graphics context.

color · const IColor& · required

The color to draw the line with

x1 · float · required

X coordinate of the line start

y1 · float · required

Y coordinate of the line start

x2 · float · required

X coordinate of the line end

y2 · float · required

Y coordinate of the line end

pBlend · const IBlend* · default: "nullptr"

Optional blend method

thickness · float · default: "1.0"

Line thickness in pixels

Example

g.DrawLine(COLOR_RED, 10, 10, 100, 100, nullptr, 2.f);

DrawRect

virtual void DrawRect(const IColor& color, const IRECT& bounds, 
                     const IBlend* pBlend = 0, float thickness = 1.f)

Draw a rectangle outline.

FillRect

virtual void FillRect(const IColor& color, const IRECT& bounds, const IBlend* pBlend = 0)

Fill a rectangular region with a color.

Example

IRECT rect(10, 10, 110, 60);
g.FillRect(COLOR_BLUE, rect);

DrawRoundRect

virtual void DrawRoundRect(const IColor& color, const IRECT& bounds, float cornerRadius = 5.f,
                          const IBlend* pBlend = 0, float thickness = 1.f)

Draw a rounded rectangle outline.

FillRoundRect

virtual void FillRoundRect(const IColor& color, const IRECT& bounds, float cornerRadius = 5.f,
                          const IBlend* pBlend = 0)

Fill a rounded rectangle with a color.

DrawCircle

virtual void DrawCircle(const IColor& color, float cx, float cy, float r,
                       const IBlend* pBlend = 0, float thickness = 1.f)

Draw a circle outline.

cx · float · required

X coordinate of the circle center

cy · float · required

Y coordinate of the circle center

r · float · required

Radius of the circle in pixels

FillCircle

virtual void FillCircle(const IColor& color, float cx, float cy, float r, const IBlend* pBlend = 0)

Fill a circle with a color.

DrawArc

virtual void DrawArc(const IColor& color, float cx, float cy, float r, float a1, float a2,
                    const IBlend* pBlend = 0, float thickness = 1.f)

Draw an arc.

a1 · float · required

Start angle in degrees clockwise (0 = up)

a2 · float · required

End angle in degrees clockwise (0 = up)

FillArc

virtual void FillArc(const IColor& color, float cx, float cy, float r, float a1, float a2,
                    const IBlend* pBlend = 0)

Fill an arc segment.

DrawTriangle

virtual void DrawTriangle(const IColor& color, float x1, float y1, float x2, float y2,
                         float x3, float y3, const IBlend* pBlend = 0, float thickness = 1.f)

Draw a triangle outline.

FillTriangle

virtual void FillTriangle(const IColor& color, float x1, float y1, float x2, float y2,
                         float x3, float y3, const IBlend* pBlend = 0)

Fill a triangle with a color.

DrawEllipse

virtual void DrawEllipse(const IColor& color, const IRECT& bounds,
                        const IBlend* pBlend = 0, float thickness = 1.f)

Draw an ellipse within a rectangular region.

FillEllipse

virtual void FillEllipse(const IColor& color, const IRECT& bounds, const IBlend* pBlend = 0)

Fill an ellipse.

Text Drawing

DrawText

void DrawText(const IText& text, const char* str, const IRECT& bounds, const IBlend* pBlend = 0)

Draw text to the graphics context in a specific rectangle.

text · const IText& · required

IText struct containing font and text properties

str · const char* · required

The text string to draw

bounds · const IRECT& · required

The rectangular region to draw the text in

Example

IText text(16, COLOR_BLACK, "Roboto-Regular", EAlign::Center, EVAlign::Middle);
g.DrawText(text, "Hello iPlug2", mRECT);

MeasureText

virtual float MeasureText(const IText& text, const char* str, IRECT& bounds) const

Measure the rectangular region that text will occupy.

return · float

The width of the measured text

Bitmap Drawing

DrawBitmap

virtual void DrawBitmap(const IBitmap& bitmap, const IRECT& bounds, int srcX, int srcY,
                       const IBlend* pBlend = 0) = 0

Draw a bitmap image to the graphics context.

bitmap · const IBitmap& · required

The bitmap image to draw

bounds · const IRECT& · required

The rectangular region to draw the image in

srcX · int · required

X offset in the source image

srcY · int · required

Y offset in the source image

LoadBitmap

virtual IBitmap LoadBitmap(const char* fileNameOrResID, int nStates = 1,
                          bool framesAreHorizontal = false, int targetScale = 0)

Load a bitmap from disk or Windows resource.

fileNameOrResID · const char* · required

File name or resource ID

nStates · int · default: "1"

Number of frames in a multi-frame bitmap

framesAreHorizontal · bool · default: "false"

True if frames are stacked horizontally

targetScale · int · default: "0"

Explicit scale (e.g., 2 for @2x.png). 0 = auto-detect

return · IBitmap

An IBitmap representing the loaded image

DrawSVG

virtual void DrawSVG(const ISVG& svg, const IRECT& bounds, const IBlend* pBlend = 0,
                    const IColor* pStrokeColor = nullptr, const IColor* pFillColor = nullptr)

Draw an SVG image to the graphics context.

pStrokeColor · const IColor* · default: "nullptr"

Optional color to override all SVG stroke commands

pFillColor · const IColor* · default: "nullptr"

Optional color to override all SVG fill commands

LoadSVG

virtual ISVG LoadSVG(const char* fileNameOrResID, const char* units = "px", float dpi = 72.f)

Load an SVG from disk or Windows resource.

Layer Management

StartLayer

void StartLayer(IControl* pOwner, const IRECT& r, bool cacheable = false)

Create an IGraphics layer for offscreen drawing.

pOwner · IControl* · required

The control that owns the layer

r · const IRECT& · required

The bounds of the layer

cacheable · bool · default: "false"

Make bitmap shareable between plugin instances

EndLayer

ILayerPtr EndLayer()

End drawing to a layer and return a pointer to it.

return · ILayerPtr

Pointer to the layer that should be kept to draw it later

DrawLayer

void DrawLayer(const ILayerPtr& layer, const IBlend* pBlend = nullptr)

Draw a layer to the main IGraphics context.

Control Management

AttachControl

IControl* AttachControl(IControl* pControl, int ctrlTag = kNoTag, const char* group = "")

Attach an IControl to the graphics context.

pControl · IControl* · required

Pointer to the control to attach

ctrlTag · int · default: "kNoTag"

Integer tag to identify the control

group · const char* · default: "empty string"

Group name for batch operations

return · IControl*

Pointer to the attached control

Example

auto* knob = new IVKnobControl(bounds, kGain);
knob = g.AttachControl(knob, kCtrlTagGainKnob, "mainControls");

GetControl

IControl* GetControl(int idx)

Get the control at a specific index.

GetControlWithTag

IControl* GetControlWithTag(int ctrlTag) const

Get a control by its tag.

RemoveControl

void RemoveControl(IControl* pControl)

Remove a control and free its memory.

NControls

int NControls() const

Get the number of controls in the context.

return · int

Number of controls

Context Properties

Width / Height

int Width() const
int Height() const

Get the dimensions of the graphics context in 1:1 pixels.

GetDrawScale

float GetDrawScale() const

Get the current draw scale factor.

return · float

The scale applied to the graphics context

GetScreenScale

float GetScreenScale() const

Get the screen/display scaling factor (e.g., 2 for Retina).

FPS

int FPS() const

Get the target frame rate.

Resize

void Resize(int w, int h, float scale, bool needsPlatformResize = true)

Resize the graphics context.

w · int · required

New width in pixels

h · int · required

New height in pixels

scale · float · required

New scale ratio

needsPlatformResize · bool · default: "true"

Set false when called from OnParentWindowResize to avoid feedback

Font Management

LoadFont

virtual bool LoadFont(const char* fontID, const char* fileNameOrResID)

Load a font to be used by the graphics context.

fontID · const char* · required

String identifier for the font

fileNameOrResID · const char* · required

Absolute path or resource ID

return · bool

True on success

Path Drawing

PathClear

virtual void PathClear() = 0

Clear the stack of path drawing commands.

PathMoveTo

virtual void PathMoveTo(float x, float y) = 0

Move the current point in the path.

PathLineTo

virtual void PathLineTo(float x, float y) = 0

Add a line to the current path from the current point.

PathArc

virtual void PathArc(float cx, float cy, float r, float a1, float a2,
                    EWinding winding = EWinding::CW) = 0

Add an arc to the current path.

PathStroke

virtual void PathStroke(const IPattern& pattern, float thickness,
                       const IStrokeOptions& options = IStrokeOptions(),
                       const IBlend* pBlend = 0) = 0

Stroke the current path.

pattern · const IPattern& · required

Pattern for color or gradient

thickness · float · required

Line thickness

options · const IStrokeOptions& · default: "IStrokeOptions()"

Dash, join, and preserve options

PathFill

virtual void PathFill(const IPattern& pattern,
                     const IFillOptions& options = IFillOptions(),
                     const IBlend* pBlend = 0) = 0

Fill the current path.

Example Usage

Complete Example

class MyPlugin : public Plugin {
public:
  MyPlugin(const InstanceInfo& info) : Plugin(info, MakeConfig(kNumParams, kNumPrograms)) {
    auto* pGraphics = MakeGraphics(*this, PLUG_WIDTH, PLUG_HEIGHT, PLUG_FPS);
    
    pGraphics->AttachPanelBackground(COLOR_GRAY);
    pGraphics->LoadFont("Roboto-Regular", "Roboto-Regular.ttf");
    
    const IRECT bounds = pGraphics->GetBounds().GetPadded(-20);
    
    // Attach controls
    pGraphics->AttachControl(new IVKnobControl(bounds.GetGridCell(0, 2, 1), kGain));
    pGraphics->AttachControl(new IVSliderControl(bounds.GetGridCell(1, 2, 1), kCutoff));
    
    SetUI(pGraphics);
  }
};

See Also

IControl

Base class for all UI controls

IGraphics Structs

Supporting data structures