Brush & ShaderUniforms — Prowl.Quill Fill-State Types

The Brush struct is the fill-state record that every DrawCall carries. It describes how geometry is painted: a solid colour from vertex data, a linear or radial gradient, a box gradient with rounded corners, an optional texture overlay, or a fully custom shader. When you call SetLinearBrush, SetRadialBrush, SetBoxBrush, SetBrushTexture, or SetCustomShader on a Canvas, the canvas writes into this struct and snaps a hash so that consecutive draw operations with the same state are batched into a single DrawCall automatically.

Fields

Transform

Transform2D

The 2D transformation applied to gradient coordinates. For linear and radial brushes, Canvas automatically copies the current canvas transform here so gradients follow world-space geometry. Modify directly only when you need an independent gradient coordinate system.

TextureTransform

Transform2D

The 2D transformation applied to texture coordinates. By default the canvas sets this so that one logical unit equals one texel. Override with Canvas.SetBrushTextureTransform to tile, offset, or rotate the texture.

Type

BrushType

Selects the gradient mode. See BrushType for the full description of each value and how Point1, Point2, CornerRadii, and Feather are interpreted under each mode.

Color1

Color32

The primary (inner / start) colour of the gradient.

Linear — colour at Point1 (the start of the line).
Radial — colour at the centre (Point1), blending outward to Color2.
Box — colour inside the rounded box.
None — ignored; colour comes from per-vertex data.

Colours stored here are premultiplied by the canvas before the struct is snapped into a draw call.

Color2

Color32

The secondary (outer / end) colour of the gradient. Premultiplied, same as Color1.

Point1

Float2

Gradient anchor — interpretation depends on Type:

BrushType	Meaning of Point1
`Linear`	Start point of the gradient line
`Radial`	Centre of the radial gradient
`Box`	Centre of the rounded box
`None`	Unused

Point2

Float2

Second gradient parameter — interpretation depends on Type:

BrushType	Meaning of Point2
`Linear`	End point of the gradient line
`Radial`	X = inner radius, Y = outer radius
`Box`	X = half-width, Y = half-height of the box
`None`	Unused

CornerRadii

float

Corner radius for BrushType.Box gradients. Controls how rounded the corners of the box are. Has no effect for other brush types.

Feather

float

Edge-softness amount for BrushType.Box gradients. Larger values create a wider, softer fade between the inner and outer colour. Has no effect for other brush types.

BackdropBlur

float

Backdrop blur radius in pixels. When greater than zero, any shape painted with this brush is composited over a blurred copy of the framebuffer behind it, creating a frosted-glass effect. The shape’s own fill (solid, gradient, or texture) is layered on top as a tint — use a translucent fill colour for a glass look. This flag is orthogonal to Type; it combines with any brush mode. Backends that do not implement ICanvasRenderer.SupportsBackdropBlur degrade gracefully to a flat fill.

Texture

object?

The backend-specific texture object to sample during rendering, or null for no texture. Set via Canvas.SetBrushTexture. When present, the renderer samples the texture using TextureMatrix and multiplies the result against the gradient colour and vertex colour.

Shader

object?

A backend-specific custom shader object, or null to use the built-in default shader. When non-null the renderer skips all default uniform uploads; your code is responsible for providing every uniform the shader requires via Canvas.SetShaderUniform / Canvas.SetShaderUniforms.

Uniforms

ShaderUniforms?

The collection of custom uniform values forwarded to Shader. null when no custom shader is active. The canvas clones this object when a new draw call is created so that later mutations cannot retroactively change already-emitted draw calls.

Computed Properties

BrushMatrix

Float4x4

Returns Transform.Inverse().ToMatrix(). The shader multiplies fragment world-space coordinates by this matrix to arrive at gradient-local coordinates before sampling the gradient function.

TextureMatrix

Float4x4

Returns TextureTransform.Inverse().ToMatrix(). Used by the shader to map fragment world-space coordinates into UV space for texture sampling.

Point1 / Point2 / CornerRadii / Feather by BrushType

Understanding how the four geometric parameters are packed into Point1 and Point2 lets you create brush structs directly or debug gradient artefacts.

BrushType.Linear

Color1 ───────────────── Color2
Point1                   Point2

The gradient transitions linearly along the axis from Point1 to Point2. CornerRadii and Feather are ignored.

BrushType.Radial

         Color1
       ┌───────┐
   ─ ─ │  •    │ ─ ─   Color2 begins at inner radius, ends at outer
       └───────┘

Point1 is the centre. Point2.X is the inner radius (at which Color1 ends) and Point2.Y is the outer radius (at which Color2 begins). CornerRadii and Feather are ignored.

BrushType.Box

Point1 is the centre of the box. Point2 stores the half-extents (X = half-width, Y = half-height). CornerRadii rounds the corners. Feather controls how wide the soft transition is between inner and outer colour.

┌──────────────────┐
│   Color1         │  ← interior
│         ╭──╮     │
│         │  │     │  ← CornerRadii rounds corners
│         ╰──╯     │
└──────────────────┘  ← Color2 outside, feathered by Feather

ShaderUniforms

ShaderUniforms is a mutable dictionary of named values passed verbatim to a custom shader. It supports a fixed set of types that map cleanly to GPU primitives: float, int, Float2, Float3, Float4, and Float4x4. The canvas uses the dictionary’s content hash for draw-call batching; shapes that share the same shader reference and the same uniform values are batched together automatically.

Fields

Values

IReadOnlyDictionary<string, object>

Read-only view over the current uniform name-to-value map. Iterate this to upload uniforms inside a custom ICanvasRenderer.RenderCalls implementation.

Methods

Set(string name, object value)

void

Adds or overwrites a uniform entry. Invalidates the hash cache.Supported value types: float, int, Float2, Float3, Float4, Float4x4. Passing an unsupported type will not throw at the ShaderUniforms layer, but the renderer backend is responsible for handling (or rejecting) it.

Remove(string name)

void

Removes the uniform with the given name, if it exists. Invalidates the hash cache only if the entry was present.

Clear()

void

Removes all uniform entries and invalidates the hash cache.

Usage Examples

Linear gradient brush

canvas.SetLinearBrush(
    x1: 0,   y1: 0,
    x2: 200, y2: 0,
    color1: Color32.FromArgb(255, 255, 80, 0),
    color2: Color32.FromArgb(255, 80, 0, 255));

canvas.Rect(0, 0, 200, 60);
canvas.FillComplex();

Radial gradient brush

canvas.SetRadialBrush(
    centerX: 100, centerY: 100,
    innerRadius: 10, outerRadius: 80,
    innerColor: Color32.FromArgb(255, 255, 255, 0),
    outerColor: Color32.FromArgb(0,   255, 255, 0));

canvas.CircleFilled(100, 100, 80, Color32.White);

Box gradient brush (frosted panel)

canvas.SetBoxBrush(
    centerX: 150, centerY: 100,
    width: 260, height: 160,
    radi: 12, feather: 20,
    innerColor: Color32.FromArgb(200, 255, 255, 255),
    outerColor: Color32.FromArgb(0,   200, 200, 200));

canvas.RoundedRectFilled(20, 20, 260, 160, 12, Color32.White);

Custom shader with uniforms

canvas.SetCustomShader(myGlowShader);
canvas.SetShaderUniform("u_GlowRadius", 8.0f);
canvas.SetShaderUniform("u_GlowColor", new Float4(1, 0.8f, 0, 1));

canvas.CircleFilled(200, 200, 60, Color32.White);

canvas.ClearCustomShader(); // revert to default shader

Backdrop blur (frosted glass)

canvas.SetBackdropBlur(16f);
canvas.SetFillColor(Color32.FromArgb(80, 255, 255, 255)); // translucent tint
canvas.RoundedRectFilled(50, 50, 300, 180, 16, Color32.White);
canvas.ClearBackdropBlur();

Canvas

Types

Renderer Interface

Brush & ShaderUniforms — Prowl.Quill Fill-State Types

Fields

Computed Properties

Point1 / Point2 / CornerRadii / Feather by BrushType

BrushType.Linear

BrushType.Radial

BrushType.Box

ShaderUniforms

Fields

Methods

Usage Examples

Linear gradient brush

Radial gradient brush

Box gradient brush (frosted panel)

Custom shader with uniforms

Backdrop blur (frosted glass)

Build docs developers (and LLMs) love

Canvas

Types

Renderer Interface

Documentation Index

​Fields

​Computed Properties

​Point1 / Point2 / CornerRadii / Feather by BrushType

​BrushType.Linear

​BrushType.Radial

​BrushType.Box

​ShaderUniforms

​Fields

​Methods

​Usage Examples

​Linear gradient brush

​Radial gradient brush

​Box gradient brush (frosted panel)

​Custom shader with uniforms

​Backdrop blur (frosted glass)

Build docs developers (and LLMs) love

Fields

Computed Properties

Point1 / Point2 / CornerRadii / Feather by BrushType

BrushType.Linear

BrushType.Radial

BrushType.Box

ShaderUniforms

Fields

Methods

Usage Examples

Linear gradient brush

Radial gradient brush

Box gradient brush (frosted panel)

Custom shader with uniforms

Backdrop blur (frosted glass)