Canvas State Management — Prowl.Quill API Reference

Every drawing operation in Prowl.Quill reads from a mutable draw state object. The state bundles fill color, stroke style, active brush, scissor rectangle, and transform into a single unit that can be saved and restored atomically. Understanding state management is key to writing correct, efficient rendering code: the canvas batches draw calls together whenever the state hash is identical, so minimising unnecessary state changes directly reduces draw call count.

Save and Restore

The state stack lets you apply temporary changes — a transform, a clip rectangle, a gradient brush — and then revert cleanly without manually tracking every property you touched.

`SaveState`

public void SaveState()

Pushes a snapshot of the current state (transform, stroke, fill, scissor, brush, miter limit, tessellation tolerance, and rounding distance) onto an internal stack.

`RestoreState`

public void RestoreState()

Pops the most recently saved state from the stack and restores it. Does nothing if the stack is empty.

`ResetState`

public void ResetState()

Resets all state properties to their defaults without touching the saved-state stack. Equivalent to starting fresh without a BeginFrame.

// Typical save/restore pattern
canvas.SaveState();
canvas.SetFillColor(Color32.Red);
canvas.TransformBy(Transform2D.CreateRotate(0.5f));
canvas.CircleFilled(100, 100, 40, Color32.Red);
canvas.RestoreState(); // color and transform are restored

Default state values:

Property	Default
Stroke color	Black (`#000000FF`)
Fill color	Black (`#000000FF`)
Stroke width	`1.0`
Stroke scale	`1.0`
Joint style	`Bevel`
Start/end cap	`Butt`
Miter limit	`4.0`
Tessellation tolerance	`0.5`
Rounding min distance	`3.0`
Winding mode	`OddEven`
Scissor	Disabled
Brush type	`None` (solid color)

Fill

`SetFillColor`

public void SetFillColor(Color32 color)

Sets the solid fill color used by Fill(), FillComplex(), FillComplexAA(), and all filled primitive methods when no gradient brush is active.

`SetGlobalAlpha`

public void SetGlobalAlpha(float alpha)

Applies a global opacity multiplier (0–1) to every vertex written after this call. This is multiplicative with any per-vertex alpha already in the color.

SetGlobalAlpha is not part of the saved state stack. Calling SaveState and RestoreState will not undo a SetGlobalAlpha call — you must restore it manually.

canvas.SetGlobalAlpha(0.5f); // all subsequent draws are 50% transparent
canvas.RectFilled(0, 0, 200, 100, Color32.Blue);
canvas.SetGlobalAlpha(1.0f); // restore full opacity manually — SaveState/RestoreState won't do this

Stroke

`SetStrokeColor`

public void SetStrokeColor(Color32 color)

Sets the color used for Stroke() and FillAndStroke().

`SetStrokeWidth`

public void SetStrokeWidth(float width = 2f)

Sets the stroke width in logical units.

`SetStrokeScale`

public void SetStrokeScale(float scale)

Applies an additional scale factor to the stroke width. The effective pixel width is (strokeWidth × strokeScale) × FramebufferScale.

`SetStrokeJoint`

public void SetStrokeJoint(JointStyle joint)

Controls how corners between path segments are joined.

`JointStyle`	Description
`Bevel`	Flat edge connecting the outer corners (default).
`Miter`	Sharp extension of outer edges until they meet. Falls back to bevel when the miter length exceeds the miter limit.
`Round`	Circular arc connecting the outer edges.

`SetStrokeCap`

public void SetStrokeCap(EndCapStyle cap)

Sets the same cap style for both the start and end of open paths.

`SetStrokeStartCap` / `SetStrokeEndCap`

public void SetStrokeStartCap(EndCapStyle cap)
public void SetStrokeEndCap(EndCapStyle cap)

Sets the cap style for the start or end of open paths independently.

`EndCapStyle`	Description
`Butt`	No cap; stroke ends exactly at the endpoint (default).
`Square`	Square cap extending by half the stroke width beyond the endpoint.
`Round`	Semicircular cap with radius equal to half the stroke width.
`Bevel`	Triangular beveled cap.

`SetMiterLimit`

public void SetMiterLimit(float limit = 4)

When JointStyle.Miter is active, joints whose miter length exceeds limit × strokeWidth fall back to bevel. The default of 4 matches the SVG specification.

`SetTessellationTolerance`

public void SetTessellationTolerance(float tolerance = 0.5f)

Controls how finely Bézier curves and arcs are approximated. Lower values produce smoother curves with more triangles; higher values are faster but may look faceted at large sizes.

`SetRoundingMinDistance`

public void SetRoundingMinDistance(float distance = 3)

Minimum distance in logical units between consecutive points when approximating curves and arcs. Increasing this value reduces vertex count for very large radii.

Dash Patterns

`SetStrokeDash`

public void SetStrokeDash(List<float> pattern, float offset = 0.0f)

Applies a dash pattern to all subsequent Stroke() calls. The pattern is a flat list of alternating dash and gap lengths in logical units: [dash1, gap1, dash2, gap2, ...]. If the list has an odd number of elements it is duplicated and concatenated to make it even, matching SVG behaviour.

pattern

List<float>

required

Alternating dash and gap lengths. Pass null or an empty list for a solid line.

offset

float

default:"0.0"

Phase offset into the dash pattern at path start, in logical units.

// 10-unit dash, 5-unit gap, starting 3 units into the pattern
canvas.SetStrokeDash(new List<float> { 10f, 5f }, offset: 3f);
canvas.BeginPath();
canvas.MoveTo(0, 50);
canvas.LineTo(400, 50);
canvas.Stroke();

`ClearStrokeDash`

public void ClearStrokeDash()

Reverts the stroke to a solid line and resets the dash offset to zero.

Scissor Clipping

The scissor rectangle clips all geometry to an axis-aligned rectangular region. Unlike many APIs, Prowl.Quill’s scissor is transform-aware: it is stored in the coordinate space of the current transform at the time Scissor() is called.

`Scissor`

public void Scissor(float x, float y, float w, float h)

Sets the scissor rectangle in logical units relative to the current transform. Any geometry outside the rectangle is discarded at the shader level.

`IntersectScissor`

public void IntersectScissor(float x, float y, float w, float h)

Computes the intersection of the existing scissor rectangle with the new rectangle and uses the result as the new scissor. If no scissor is currently active, this behaves like Scissor().

`ResetScissor`

public void ResetScissor()

Disables clipping by invalidating the scissor region.

canvas.Scissor(50, 50, 300, 200);
canvas.CircleFilled(100, 100, 200, Color32.Teal); // clipped to 50,50–350,250
canvas.ResetScissor();

Gradient Brushes

Brushes override solid fill color with gradient or pattern fills. When a brush is active, its colors replace SetFillColor for all filled shapes.

`SetLinearBrush`

public void SetLinearBrush(
    float x1, float y1,
    float x2, float y2,
    Color32 color1, Color32 color2)

Sets a linear gradient from (x1, y1) to (x2, y2). Colors are premultiplied-alpha encoded internally.

x1, y1

float

Start point of the gradient in logical units.

x2, y2

float

End point of the gradient in logical units.

color1

Color32

Color at the start point.

color2

Color32

Color at the end point.

canvas.SetLinearBrush(0, 0, 200, 0,
    Color32.FromArgb(255, 255, 80, 0),
    Color32.FromArgb(255, 80, 0, 255));
canvas.RoundedRectFilled(0, 0, 200, 60, 12, Color32.White);
canvas.ClearBrush();

`SetRadialBrush`

public void SetRadialBrush(
    float centerX, float centerY,
    float innerRadius, float outerRadius,
    Color32 innerColor, Color32 outerColor)

Sets a radial gradient centred at (centerX, centerY). The innerColor fills from the origin to innerRadius; the gradient feathers to outerColor by outerRadius.

centerX, centerY

float

Center of the gradient in logical units.

innerRadius

float

Radius at which the inner color ends.

outerRadius

float

Radius at which the outer color begins.

innerColor

Color32

Color at the center.

outerColor

Color32

Color at the outer edge.

`SetBoxBrush`

public void SetBoxBrush(
    float centerX, float centerY,
    float width, float height,
    float radi, float feather,
    Color32 innerColor, Color32 outerColor)

Sets a box gradient: innerColor fills a rounded rectangle of size width × height centred at (centerX, centerY) with corner radius radi; the transition to outerColor is spread over feather logical units.

radi

float

Corner radius of the inner box.

feather

float

Softness of the box edge in logical units. Larger values produce a more blurred transition.

`ClearBrush`

public void ClearBrush()

Removes any active gradient brush, reverting fills to the solid SetFillColor color.

Texture Brush

A texture brush maps an image onto filled shapes using world-space UV coordinates.

`SetBrushTexture`

public void SetBrushTexture(object? texture)

Applies a texture to all subsequent fills. When texture is non-null and no explicit SetBrushTextureTransform has been called, a default transform is computed so that one logical unit maps to one texel.

`SetBrushTextureTransform`

public void SetBrushTextureTransform(Transform2D transform)

Controls how world-space coordinates map to texture UV space. The supplied transform is composed with the current canvas transform so the texture follows any active rotation or scale.

`ClearBrushTexture`

public void ClearBrushTexture()

Removes the active texture and resets the texture transform to identity.

Backdrop Blur

Backdrop blur turns any filled shape into a frosted-glass panel by blending the shape’s fill over a blurred copy of the framebuffer content behind it.

`SetBackdropBlur`

public void SetBackdropBlur(float radius)

Enables backdrop blur for subsequent filled shapes. radius is the blur radius in physical pixels. A translucent fill tints the blurred background; a fully opaque fill completely obscures it. Backends that do not support backdrop blur draw the fill normally.

canvas.SetBackdropBlur(12f);
canvas.SetFillColor(Color32.FromArgb(120, 255, 255, 255)); // semi-transparent white
canvas.RoundedRectFilled(20, 20, 400, 200, 16, Color32.White);
canvas.ClearBackdropBlur();

`ClearBackdropBlur`

public void ClearBackdropBlur()

Disables backdrop blur (radius set to 0).

Custom Shaders

Custom shaders allow backend-specific shader programs to be bound for individual draw calls. When a shader is active, the default Prowl.Quill uniforms are not set — the application is responsible for supplying all required uniforms.

`SetCustomShader`

public void SetCustomShader(object? shader)

Binds a backend-specific shader object. Pass null to revert to the default shader.

`SetShaderUniform`

public void SetShaderUniform(string name, object value)

Sets a single named uniform. Supported value types: float, int, Float2, Float3, Float4, Float4x4.

`SetShaderUniforms`

public void SetShaderUniforms(Dictionary<string, object> uniforms)

Sets multiple uniforms in a single call.

`ClearCustomShader`

public void ClearCustomShader()

Removes the custom shader and clears all associated uniforms.

canvas.SetCustomShader(myGlowShader);
canvas.SetShaderUniform("u_GlowRadius", 8.0f);
canvas.SetShaderUniform("u_GlowColor", new Float4(1f, 0.5f, 0f, 1f));
canvas.CircleFilled(200, 200, 60, Color32.White);
canvas.ClearCustomShader();

Canvas

Types

Renderer Interface

Documentation Index

​Save and Restore

​SaveState

​RestoreState

​ResetState

​Fill

​SetFillColor

​SetGlobalAlpha

​Stroke

​SetStrokeColor

​SetStrokeWidth

​SetStrokeScale

​SetStrokeJoint

​SetStrokeCap

​SetStrokeStartCap / SetStrokeEndCap

​SetMiterLimit

​SetTessellationTolerance

​SetRoundingMinDistance

​Dash Patterns

​SetStrokeDash

​ClearStrokeDash

​Scissor Clipping

​Scissor

​IntersectScissor

​ResetScissor

​Gradient Brushes

​SetLinearBrush

​SetRadialBrush

​SetBoxBrush

​ClearBrush

​Texture Brush

​SetBrushTexture

​SetBrushTextureTransform

​ClearBrushTexture

​Backdrop Blur

​SetBackdropBlur

​ClearBackdropBlur

​Custom Shaders

​SetCustomShader

​SetShaderUniform

​SetShaderUniforms

​ClearCustomShader

Build docs developers (and LLMs) love

Save and Restore

`SaveState`

`RestoreState`

`ResetState`

Fill

`SetFillColor`

`SetGlobalAlpha`

Stroke

`SetStrokeColor`

`SetStrokeWidth`

`SetStrokeScale`

`SetStrokeJoint`

`SetStrokeCap`

`SetStrokeStartCap` / `SetStrokeEndCap`

`SetMiterLimit`

`SetTessellationTolerance`

`SetRoundingMinDistance`

Dash Patterns

`SetStrokeDash`

`ClearStrokeDash`

Scissor Clipping

`Scissor`

`IntersectScissor`

`ResetScissor`

Gradient Brushes

`SetLinearBrush`

`SetRadialBrush`

`SetBoxBrush`

`ClearBrush`

Texture Brush

`SetBrushTexture`

`SetBrushTextureTransform`

`ClearBrushTexture`

Backdrop Blur

`SetBackdropBlur`

`ClearBackdropBlur`

Custom Shaders

`SetCustomShader`

`SetShaderUniform`

`SetShaderUniforms`

`ClearCustomShader`