kitepdf-compose-viewer/io.github.yuroyami.kitepdf.compose/ComposeCanvas

ComposeCanvas

class ComposeCanvas(drawScope: DrawScope, textMeasurer: TextMeasurer, hairlineWidthPx: Float = 1.0f, skipSystemFontText: Boolean = false) : KiteCanvas

KiteCanvas backed by a Compose Multiplatform DrawScope.

Three rendering paths:

Embedded outlines: when hasOutlines is true, each byte/CID becomes a Compose Path filled at the right position.
System-font fallback: when no outlines are available, decode to text and hand to Compose's TextMeasurer.
Transparency groups: open a saveLayer on the underlying Canvas when the renderer requests one; later restore composites the layer back with the requested blend mode + alpha.

Clipping uses Compose's clipPath inside a recursive scope; transparency groups use the lower-level Canvas.saveLayer so they can span multiple DrawScope operations.

Constructors

ComposeCanvas

constructor(drawScope: DrawScope, textMeasurer: TextMeasurer, hairlineWidthPx: Float = 1.0f, skipSystemFontText: Boolean = false)

Properties

resolvesGlyphOutlines

open val resolvesGlyphOutlines: Boolean

Functions

applySoftMask

open override fun applySoftMask(kind: SoftMask.Kind, maskBBox: KiteRectangle, maskCtm: KiteMatrix, render: () -> Unit, renderMask: (KiteCanvas) -> Unit)

open override fun applySoftMask(kind: SoftMask.Kind, maskBBox: KiteRectangle, maskCtm: KiteMatrix, transfer: KiteMaskTransfer?, render: () -> Unit, renderMask: (KiteCanvas) -> Unit)

Soft-mask compositing (ISO 32000-1 §11.6.5). We open a saveLayer for the content, render it, then over-paint the mask group with ComposeBlendMode.DstIn so the mask's alpha clips the content.

beginPage

open override fun beginPage(widthPt: Double, heightPt: Double, deviceCtm: KiteMatrix)

beginTransparencyGroup

open override fun beginTransparencyGroup(bbox: KiteRectangle, ctm: KiteMatrix, isolated: Boolean, knockout: Boolean, alpha: Double, blendMode: KiteBlendMode)

Transparency groups: open a Compose saveLayer on the active Canvas with a Paint that carries the requested alpha + blend mode. Subsequent draws accumulate into the offscreen layer; matching endTransparencyGroup calls restore, which composites the layer onto the parent.

drawGlyphs

open override fun drawGlyphs(glyphs: List<TextGlyph>, fontSize: Double, unitsPerEm: Int, hasOutlines: Boolean, fontSpec: FontSpec, textToDevice: KiteMatrix, color: RgbColor, alpha: Double, blendMode: KiteBlendMode)

drawImage

open override fun drawImage(image: KiteImageData, ctm: KiteMatrix, alpha: Double)

open override fun drawImage(image: KiteImageData, ctm: KiteMatrix, alpha: Double, blendMode: KiteBlendMode)

endPage

open override fun endPage()

endTransparencyGroup

open override fun endTransparencyGroup()

fillPath

open override fun fillPath(path: KitePath, ctm: KiteMatrix, color: RgbColor, evenOdd: Boolean, alpha: Double, blendMode: KiteBlendMode)

fillShading

open override fun fillShading(shading: KiteShading, ctm: KiteMatrix, clipPath: KitePath?, alpha: Double, blendMode: KiteBlendMode)

hostGlyphOutline

open override fun hostGlyphOutline(text: String, fontSpec: FontSpec): KitePath?

The outline of text in the host face drawGlyphs draws a font without embedded outlines in, at 1000 units per em with y up (#85). Off the main thread it only records the run, as the system-font path does, so the page renders again on Main.

popClip

open override fun popClip()

pushClip

open override fun pushClip(path: KitePath, ctm: KiteMatrix, evenOdd: Boolean)

strokePath

open override fun strokePath(path: KitePath, ctm: KiteMatrix, color: RgbColor, lineWidth: Double, alpha: Double, blendMode: KiteBlendMode, dashArray: List<Double>?, dashPhase: Double, lineCap: Int, lineJoin: Int, miterLimit: Double)